rfc9583.original   rfc9583.txt 
QIRG C. Wang Internet Research Task Force (IRTF) C. Wang
Internet-Draft InterDigital Communications, LLC Request for Comments: 9583 InterDigital Communications, LLC
Intended status: Informational A. Rahman Category: Informational A. Rahman
Expires: 18 April 2024 Ericsson ISSN: 2070-1721 Ericsson
R. Li R. Li
Kanazawa University Kanazawa University
M. Aelmans M. Aelmans
Juniper Networks Juniper Networks
K. Chakraborty K. Chakraborty
The University of Edinburgh The University of Edinburgh
16 October 2023 June 2024
Application Scenarios for the Quantum Internet Application Scenarios for the Quantum Internet
draft-irtf-qirg-quantum-internet-use-cases-19
Abstract Abstract
The Quantum Internet has the potential to improve application The Quantum Internet has the potential to improve application
functionality by incorporating quantum information technology into functionality by incorporating quantum information technology into
the infrastructure of the overall Internet. This document provides the infrastructure of the overall Internet. This document provides
an overview of some applications expected to be used on the Quantum an overview of some applications expected to be used on the Quantum
Internet and categorizes them. Some general requirements for the Internet and categorizes them. Some general requirements for the
Quantum Internet are also discussed. The intent of this document is Quantum Internet are also discussed. The intent of this document is
to describe a framework for applications, and describe a few selected to describe a framework for applications and to describe a few
application scenarios for the Quantum Internet.This document is a selected application scenarios for the Quantum Internet. This
product of the Quantum Internet Research Group (QIRG). document is a product of the Quantum Internet Research Group (QIRG).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Research Task Force
and may be updated, replaced, or obsoleted by other documents at any (IRTF). The IRTF publishes the results of Internet-related research
time. It is inappropriate to use Internet-Drafts as reference and development activities. These results might not be suitable for
material or to cite them other than as "work in progress." deployment. This RFC represents the consensus of the QIRG Research
Group of the Internet Research Task Force (IRTF). Documents approved
for publication by the IRSG are not candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on 18 April 2024. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9583.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Terms and Acronyms List . . . . . . . . . . . . . . . . . . . 4 2. Terms and Acronyms List
3. Quantum Internet Applications . . . . . . . . . . . . . . . . 6 3. Quantum Internet Applications
3.1. Quantum Cryptography Applications . . . . . . . . . . . . 7 3.1. Quantum Cryptography Applications
3.2. Quantum Sensing/Metrology Applications . . . . . . . . . 8 3.2. Quantum Sensing and Metrology Applications
3.3. Quantum Computing Applications . . . . . . . . . . . . . 9 3.3. Quantum Computing Applications
4. Selected Quantum Internet Application Scenarios . . . . . . . 9 4. Selected Quantum Internet Application Scenarios
4.1. Secure Communication Setup . . . . . . . . . . . . . . . 9 4.1. Secure Communication Setup
4.2. Blind Quantum Computing . . . . . . . . . . . . . . . . . 13 4.2. Blind Quantum Computing
4.3. Distributed Quantum Computing . . . . . . . . . . . . . . 16 4.3. Distributed Quantum Computing
5. General Requirements . . . . . . . . . . . . . . . . . . . . 19 5. General Requirements
5.1. Operations on Entangled Qubits . . . . . . . . . . . . . 21 5.1. Operations on Entangled Qubits
5.2. Entanglement Distribution . . . . . . . . . . . . . . . . 22 5.2. Entanglement Distribution
5.3. The Need for Classical Channels . . . . . . . . . . . . . 22 5.3. The Need for Classical Channels
5.4. Quantum Internet Management . . . . . . . . . . . . . . . 22 5.4. Quantum Internet Management
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 22 6. Conclusion
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 7. IANA Considerations
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. Security Considerations
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 9. Informative References
10. Informative References . . . . . . . . . . . . . . . . . . . 25 Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses
1. Introduction 1. Introduction
The Classical, i.e., non-quantum, Internet has been constantly The Classical, i.e., non-quantum, Internet has been constantly
growing since it first became commercially popular in the early growing since it first became commercially popular in the early
1990's. It essentially consists of a large number of end nodes 1990s. It essentially consists of a large number of end nodes (e.g.,
(e.g., laptops, smart phones, network servers) connected by routers laptops, smart phones, and network servers) connected by routers and
and clustered in Autonomous Systems. The end nodes may run clustered in Autonomous Systems. The end nodes may run applications
applications that provide service for the end users such as that provide service for the end users such as processing and
processing and transmission of voice, video or data. The connections transmission of voice, video, or data. The connections between the
between the various nodes in the Internet include backbone links various nodes in the Internet include backbone links (e.g., fiber
(e.g., fiber optics) and access links (e.g., fiber optics, WiFi, optics) and access links (e.g., fiber optics, Wi-Fi, cellular
cellular wireless, Digital Subscriber Lines (DSLs)). Bits are wireless, and Digital Subscriber Lines (DSLs)). Bits are transmitted
transmitted across the Classical Internet in packets. across the Classical Internet in packets.
Research and experiments have picked up over the last few years for Research and experiments have picked up over the last few years for
developing the Quantum Internet [Wehner]. End nodes will also be developing the Quantum Internet [Wehner]. End nodes will also be a
part of the Quantum Internet, in that case called quantum end nodes part of the Quantum Internet; in that case, they are called "quantum
that may be connected by quantum repeaters/routers. These quantum end nodes" and may be connected by quantum repeaters and/or routers.
end nodes will also run value-added applications which will be These quantum end nodes will also run value-added applications, which
discussed later. will be discussed later.
The physical layer quantum channels between the various nodes in the The physical layer quantum channels between the various nodes in the
Quantum Internet can be either waveguides such as optical fibers or Quantum Internet can be either waveguides, such as optical fibers, or
free space. Photonic channels are particularly useful because light free space. Photonic channels are particularly useful because light
(photons) is very suitable for physically realizing qubits. The (photons) is very suitable for physically realizing qubits. The
Quantum Internet will operate according to quantum physical Quantum Internet will operate according to quantum physical
principles such as quantum superposition and entanglement [RFC9340]. principles such as quantum superposition and entanglement [RFC9340].
The Quantum Internet is not anticipated to replace, but rather to The Quantum Internet is not anticipated to replace but rather to
enhance the Classical Internet and/or provide breakthrough enhance the Classical Internet and/or provide breakthrough
applications. For instance, quantum key distribution can improve the applications. For instance, Quantum Key Distribution can improve the
security of the Classical Internet; quantum computing can expedite security of the Classical Internet, and quantum computing can
and optimize computation-intensive tasks in the Classical Internet. expedite and optimize computation-intensive tasks in the Classical
The Quantum Internet will run in conjunction with the Classical Internet. The Quantum Internet will run in conjunction with the
Internet. The process of integrating the Quantum Internet with the Classical Internet. The process of integrating the Quantum Internet
Classical Internet is similar to the process of introducing any new with the Classical Internet is similar to the process of introducing
communication and networking paradigm into the existing Internet, but any new communication and networking paradigm into the existing
with more profound implications. Internet but with more profound implications.
The intent of this document is to provide a common understanding and The intent of this document is to provide a common understanding and
framework of applications and application scenarios for the Quantum framework of applications and application scenarios for the Quantum
Internet. It is noted that ITU-T SG13-TD158/WP3 [ITUT] briefly Internet. It is noted that ITU-T SG13-TD158/WP3 [ITUT] briefly
describes four kinds of use cases of quantum networks beyond quantum describes four kinds of use cases of quantum networks beyond Quantum
key distribution networks: quantum time synchronization use cases, Key Distribution networks: quantum time synchronization use cases,
quantum computing use cases, quantum random number generator use quantum computing use cases, quantum random number generator use
cases, and quantum communication use cases (e.g., quantum digital cases, and quantum communication use cases (e.g., quantum digital
signatures, quantum anonymous transmission, and quantum money). This signatures, quantum anonymous transmission, and quantum money). This
document focuses on quantum applications that have more impact on document focuses on quantum applications that have more impact on
networking such as secure communication setup, blind quantum networking, such as secure communication setup, blind quantum
computing, and distributed quantum computing; although these computing, and distributed quantum computing; although these
applications were mentioned in [ITUT], this document gives more applications were mentioned in [ITUT], this document gives more
details and derives some requirements from networking perspective. details and derives some requirements from a networking perspective.
This document was produced by the Quantum Internet Research This document was produced by the Quantum Internet Research Group
Group(QIRG). It was discussed on the QIRG mailing list and several (QIRG). It was discussed on the QIRG mailing list and during several
meetings of the Research Group. It has been reviewed extensively by meetings of the research group. It has been reviewed extensively by
the QIRG members with expertise in both quantum physics and classical the QIRG members with expertise in both quantum physics and Classical
Internet operation. This document represents the consensus of the Internet operation. This document represents the consensus of the
QIRG members, of both experts in the subject matter (from the quantum QIRG members, of both experts in the subject matter (from the quantum
and networking domains) and newcomers who are the target audience. and networking domains) and newcomers, who are the target audience.
It is not an IETF product and is not a standard. It is not an IETF product and is not a standard.
2. Terms and Acronyms List 2. Terms and Acronyms List
This document assumes that the reader is familiar with the quantum This document assumes that the reader is familiar with the terms and
information technology related terms and concepts that are described concepts that relate to quantum information technology described in
in [RFC9340]. In addition, the following terms and acronyms are [RFC9340]. In addition, the following terms and acronyms are defined
defined herein for clarity: herein for clarity:
* Bell Pairs – A special type of two-qubits quantum state. The two Bell Pairs: A special type of quantum state that is two qubits. The
qubits show a correlation that cannot be observed in classical two qubits show a correlation that cannot be observed in classical
information theory. We refer to such correlation as quantum information theory. We refer to such correlation as quantum
entanglement. Bell pairs exhibit the maximal quantum entanglement. Bell pairs exhibit the maximal quantum
entanglement. One example of a Bell pair is entanglement. One example of a Bell pair is
(|00>+|11>)/(Sqrt(2)). The Bell pairs are a fundamental resource (|00>+|11>)/(Sqrt(2)). The Bell pairs are a fundamental resource
for quantum communication. for quantum communication.
* Bit - Binary Digit (i.e., fundamental unit of information in Bit: Binary digit (i.e., fundamental unit of information in
classical communications and classical computing). Bit is used in classical communications and classical computing). Bit is used in
Classical Internet where the state of a bit is deterministic. In the Classical Internet where the state of a bit is deterministic.
contrast, Qubit is used in Quantum Internet where the state of a In contrast, qubit is used in the Quantum Internet where the state
qubit is uncertain before it is measured. of a qubit is uncertain before it is measured.
* Classical Internet - The existing, deployed Internet (circa 2020) Classical Internet: The existing, deployed Internet (circa 2020)
where bits are transmitted in packets between nodes to convey where bits are transmitted in packets between nodes to convey
information. The Classical Internet supports applications which information. The Classical Internet supports applications that
may be enhanced by the Quantum Internet. For example, the end-to- may be enhanced by the Quantum Internet. For example, the end-to-
end security of a Classical Internet application may be improved end security of a Classical Internet application may be improved
by secure communication setup using a quantum application. by a secure communication setup using a quantum application.
Classical Internet is a network of classical network nodes which Classical Internet is a network of classical network nodes that do
do not support quantum information technology. In contrast, not support quantum information technology. In contrast, Quantum
Quantum Internet consists of quantum nodes based on quantum Internet consists of quantum nodes based on quantum information
information technology. technology.
* Entanglement Swapping: It is a process of sharing an entanglement Entanglement Swapping: It is a process of sharing an entanglement
between two distant parties via some intermediate nodes. For between two distant parties via some intermediate nodes. For
example, suppose there are three parties A, B, C, and each of the example, suppose that there are three parties (A, B, and C) and
parties (A, B) and (B, C) share Bell pairs. B can use the qubits that each of the parties (A, B) and (B, C) share Bell pairs. B
it shares with A and C to perform entanglement swapping can use the qubits it shares with A and C to perform entanglement-
operations, and as a result, A and C share Bell pairs. swapping operations, and as a result, A and C share Bell pairs.
Entanglement swapping essentially realizes entanglement Entanglement swapping essentially realizes entanglement
distribution (i.e., two nodes in distance can share a Bell pair). distribution (i.e., two nodes separated in distance can share a
Bell pair).
* Fast Byzantine Negotiation - A Quantum-based method for fast Fast Byzantine Negotiation: A quantum-based method for fast
agreement in Byzantine negotiations [Ben-Or] [Taherkhani]. agreement in Byzantine negotiations [Ben-Or] [Taherkhani].
* Local Operations and Classical Communication (LOCC) - A method Local Operations and Classical Communication (LOCC): A method where
where nodes communicate in rounds, in which (1) they can send any nodes communicate in rounds, in which (1) they can send any
classical information to each other; (2) they can perform local classical information to each other, (2) they can perform local
quantum operations individually; and (3) the actions performed in quantum operations individually, and (3) the actions performed in
each round can depend on the results from previous rounds. each round can depend on the results from previous rounds.
* Noisy Intermediate-Scale Quantum (NISQ) - NISQ was defined in Noisy Intermediate-Scale Quantum (NISQ): NISQ was defined in
[Preskill] to represent a near-term era in quantum technology. [Preskill] to represent a near-term era in quantum technology.
According to this definition, NISQ computers have two salient According to this definition, NISQ computers have two salient
features: (1) The size of NISQ computers range from 50 to a few features: (1) the size of NISQ computers range from 50 to a few
hundred physical qubits (i.e., intermediate-scale); and (2) Qubits hundred physical qubits (i.e., intermediate-scale) and (2) qubits
in NISQ computers have inherent errors and the control over them in NISQ computers have inherent errors and the control over them
is imperfect (i.e., noisy). is imperfect (i.e., noisy).
* Packet - A self-identified message with in-band addresses or other Packet: A self-identified message with in-band addresses or other
information that can be used for forwarding the message. The information that can be used for forwarding the message. The
message contains an ordered set of bits of determinate number. message contains an ordered set of bits of determinate number.
The bits contained in a packet are classical bits. The bits contained in a packet are classical bits.
* Prepare-and-Measure - A set of Quantum Internet scenarios where Prepare and Measure: A set of Quantum Internet scenarios where
quantum nodes only support simple quantum functionalities (i.e., quantum nodes only support simple quantum functionalities (i.e.,
prepare qubits and measure qubits). For example, BB84 [BB84] is a prepare qubits and measure qubits). For example, BB84 [BB84] is a
prepare-and-measure quantum key distribution protocol. prepare-and-measure quantum key distribution protocol.
* Quantum Computer (QC) - A quantum end node that also has quantum Quantum Computer (QC): A quantum end node that also has quantum
memory and quantum computing capabilities is regarded as a full- memory and quantum computing capabilities is regarded as a full-
fledged quantum computer. fledged quantum computer.
* Quantum End Node - An end node that hosts user applications and Quantum End Node: An end node that hosts user applications and
interfaces with the rest of the Internet. Typically, an end node interfaces with the rest of the Internet. Typically, an end node
may serve in a client, server, or peer-to-peer role as part of the may serve in a client, server, or peer-to-peer role as part of the
application. A quantum end node must also be able to interface to application. A quantum end node must also be able to interface to
the Classical Internet for control purposes and thus also be able the Classical Internet for control purposes and thus be able to
to receive, process, and transmit classical bits/packets. receive, process, and transmit classical bits and/or packets.
* Quantum Internet - A network of Quantum Networks. The Quantum Quantum Internet: A network of quantum networks. The Quantum
Internet is expected to be merged into the Classical Internet. Internet is expected to be merged into the Classical Internet.
The Quantum Internet may either improve classical applications or The Quantum Internet may either improve classical applications or
may enable new quantum applications. enable new quantum applications.
* Quantum Key Distribution (QKD) - A method that leverages quantum Quantum Key Distribution (QKD): A method that leverages quantum
mechanics such as no-cloning theorem to let two parties create the mechanics such as a no-cloning theorem to let two parties create
same arbitrary classical key. the same arbitrary classical key.
* Quantum Network - A new type of network enabled by quantum Quantum Network: A new type of network enabled by quantum
information technology where quantum resources such as qubits and information technology where quantum resources, such as qubits and
entanglement are transferred and utilized between quantum nodes. entanglement, are transferred and utilized between quantum nodes.
The Quantum Network will use both quantum channels, and classical The quantum network will use both quantum channels and classical
channels provided by the Classical Internet, referred to as a channels provided by the Classical Internet, referred to as a
hybrid implementation. "hybrid implementation".
* Quantum Teleportation - A technique for transferring quantum Quantum Teleportation: A technique for transferring quantum
information via local operations and classical communication information via Local Operations and Classical Communication
(LOCC). If two parties share a Bell pair, then using quantum (LOCC). If two parties share a Bell pair, then by using quantum
teleportation a sender can transfer a quantum data bit to a teleportation, a sender can transfer a quantum data bit to a
receiver without sending it physically via a quantum channel. receiver without sending it physically via a quantum channel.
* Qubit - Quantum Bit (i.e., fundamental unit of information in Qubit: Quantum bit (i.e., fundamental unit of information in quantum
quantum communication and quantum computing). It is similar to a communication and quantum computing). It is similar to a classic
classic bit in that the state of a qubit is either "0" or "1" bit in that the state of a qubit is either "0" or "1" after it is
after it is measured, and is denoted as its basis state vector |0> measured and denotes its basis state vector as |0> or |1> using
or |1> using Dirac's ket notation. However, the qubit is Dirac's ket notation. However, the qubit is different than a
different than a classic bit in that the qubit can be in a linear classic bit in that the qubit can be in a linear combination of
combination of both states before it is measured and termed to be both states before it is measured and termed to be in
in superposition. Any of several Degrees of Freedom (DOF) of a superposition. Any of several Degrees of Freedom (DOF) of a
photon (e.g., polarization, time bib, and/or frequency) or an photon (e.g., polarization, time bib, and/or frequency) or an
electron (e.g., spin) can be used to encode a qubit. electron (e.g., spin) can be used to encode a qubit.
* Transmit a Qubit - An operation of encoding a qubit into a mobile Teleport a Qubit: An operation on two or more carriers in succession
carrier (i.e., typically photon) and passing it through a quantum to move a qubit from a sender to a receiver using quantum
channel from a sender (a transmitter) to a receiver. teleportation.
* Teleport a Qubit - An operation on two or more carriers in
succession to move a qubit from a sender to a receiver using
quantum teleportation.
* Transfer a Qubit - An operation to move a qubit from a sender to a Transfer a Qubit: An operation to move a qubit from a sender to a
receiver without specifying the means of moving the qubit, which receiver without specifying the means of moving the qubit, which
could be “transmit” or “teleport”. could be "transmit" or "teleport".
Transmit a Qubit: An operation to encode a qubit into a mobile
carrier (i.e., typically photon) and pass it through a quantum
channel from a sender (a transmitter) to a receiver.
3. Quantum Internet Applications 3. Quantum Internet Applications
The Quantum Internet is expected to be beneficial for a subset of The Quantum Internet is expected to be beneficial for a subset of
existing and new applications. The expected applications for the existing and new applications. The expected applications for the
Quantum Internet are still being developed as we are in the formative Quantum Internet are still being developed as we are in the formative
stages of the Quantum Internet [Castelvecchi] [Wehner]. However, an stages of the Quantum Internet [Castelvecchi] [Wehner]. However, an
initial (and non-exhaustive) list of the applications to be supported initial (and non-exhaustive) list of the applications to be supported
on the Quantum Internet can be identified and classified using two on the Quantum Internet can be identified and classified using two
different schemes. Note, this document does not include quantum different schemes. Note that this document does not include quantum
computing applications that are purely local to a given node. computing applications that are purely local to a given node.
Applications may be grouped by the usage that they serve. Applications may be grouped by the usage that they serve.
Specifically, applications may be grouped according to the following Specifically, applications may be grouped according to the following
categories: categories:
* Quantum cryptography applications - Refer to the use of quantum Quantum cryptography applications: Refer to the use of quantum
information technology for cryptographic tasks (e.g., quantum key information technology for cryptographic tasks (e.g., Quantum Key
distribution [Renner]). Distribution [Renner]).
* Quantum sensors applications - Refer to the use of quantum Quantum sensor applications: Refer to the use of quantum information
information technology for supporting distributed sensors (e.g., technology for supporting distributed sensors (e.g., clock
clock synchronization [Jozsa2000] [Komar] [Guo] ). synchronization [Jozsa2000] [Komar] [Guo]).
* Quantum computing applications - Refer to the use of quantum Quantum computing applications: Refer to the use of quantum
information technology for supporting remote quantum computing information technology for supporting remote quantum computing
facilities (e.g., distributed quantum computing [Denchev]). facilities (e.g., distributed quantum computing [Denchev]).
This scheme can be easily understood by both a technical and non- This scheme can be easily understood by both a technical and non-
technical audience. The next sections describe the scheme in more technical audience. The next sections describe the scheme in more
detail. detail.
3.1. Quantum Cryptography Applications 3.1. Quantum Cryptography Applications
Examples of quantum cryptography applications include quantum-based Examples of quantum cryptography applications include quantum-based
secure communication setup and fast Byzantine negotiation. secure communication setup and fast Byzantine negotiation.
1. Secure communication setup - Refers to secure cryptographic key Secure communication setup: Refers to secure cryptographic key
distribution between two or more end nodes. The most well-known distribution between two or more end nodes. The most well-known
method is referred to as Quantum Key Distribution (QKD) [Renner]. method is referred to as "Quantum Key Distribution (QKD)"
[Renner].
2. Fast Byzantine negotiation - Refers to a Quantum-based method for Fast Byzantine negotiation: Refers to a quantum-based method for
fast agreement in Byzantine negotiations [Ben-Or], for example, fast agreement in Byzantine negotiations [Ben-Or], for example, to
to reduce the number of expected communication rounds and in turn reduce the number of expected communication rounds and, in turn,
achieve faster agreement, in contrast to classical Byzantine to achieve faster agreement, in contrast to classical Byzantine
negotiations. A quantum aided Byzantine agreement on quantum negotiations. A quantum-aided Byzantine agreement on quantum
repeater networks as proposed in [Taherkhani] includes repeater networks as proposed in [Taherkhani] includes
optimization techniques to greatly reduce the quantum circuit optimization techniques to greatly reduce the quantum circuit
depth and the number of qubits in each node. Quantum-based depth and the number of qubits in each node. Quantum-based
methods for fast agreement in Byzantine negotiations can be used methods for fast agreement in Byzantine negotiations can be used
for improving consensus protocols such as practical Byzantine for improving consensus protocols such as practical Byzantine
Fault Tolerance(pBFT), as well as other distributed computing Fault Tolerance (pBFT) as well as other distributed computing
features which use Byzantine negotiations. features that use Byzantine negotiations.
3. Quantum money - The main security requirement of money is Quantum money: Refers to the main security requirement of money is
unforgeability. A quantum money scheme aims to fulfill by unforgeability. A quantum money scheme aims to exploit the no-
exploiting the no-cloning property of the unknown quantum states. cloning property of the unknown quantum states. Though the
Though the original idea of quantum money dates back to 1970, original idea of quantum money dates back to 1970, these early
these early protocols allow only the issuing bank to verify a protocols allow only the issuing bank to verify a quantum
quantum banknote. However, the recent protocols such as public- banknote. However, the recent protocols such as public key
key quantum money [Zhandry] allow anyone to verify the banknotes quantum money [Zhandry] allow anyone to verify the banknotes
locally. locally.
3.2. Quantum Sensing/Metrology Applications 3.2. Quantum Sensing and Metrology Applications
The entanglement, superposition, interference, squeezing properties The entanglement, superposition, interference, and squeezing of
can enhance the sensitivity of the quantum sensors and eventually can properties can enhance the sensitivity of the quantum sensors and
outperform the classical strategies. Examples of quantum sensor eventually can outperform the classical strategies. Examples of
applications include network clock synchronization, high sensitivity quantum sensor applications include network clock synchronization,
sensing, etc. These applications mainly leverage a network of high-sensitivity sensing, etc. These applications mainly leverage a
entangled quantum sensors (i.e. quantum sensor networks) for high- network of entangled quantum sensors (i.e., quantum sensor networks)
precision multi-parameter estimation [Proctor]. for high-precision, multiparameter estimation [Proctor].
1. Network clock synchronization - Refers to a world wide set of Network clock synchronization: Refers to a world wide set of high-
high-precision clocks connected by the Quantum Internet to precision clocks connected by the Quantum Internet to achieve an
achieve an ultra precise clock signal [Komar] with fundamental ultra precise clock signal [Komar] with fundamental precision
precision limits set by quantum theory. limits set by quantum theory.
2. High sensitivity sensing - Refers to applications that leverage High-sensitivity sensing: Refers to applications that leverage
quantum phenomena to achieve reliable nanoscale sensing of quantum phenomena to achieve reliable nanoscale sensing of
physical magnitudes. For example, [Guo] uses an entangled physical magnitudes. For example, [Guo] uses an entangled quantum
quantum network for measuring the average phase shift among network for measuring the average phase shift among multiple
multiple distributed nodes. distributed nodes.
3. Interferometric Telescopes using Quantum Information - Interferometric telescopes using quantum information: Refers to inte
Interferometric techniques are used to combine signals from two rferometric techniques that are used to combine signals from two
or more telescopes to obtain measurements with higher resolution or more telescopes to obtain measurements with higher resolution
than what could be obtained with either telescope individually. than what could be obtained with either telescope individually.
It can make measurements of very small astronomical objects if It can make measurements of very small astronomical objects if the
the telescopes are spread out over a wide area. However, the telescopes are spread out over a wide area. However, the phase
phase fluctuations and photon loss introduced by the fluctuations and photon loss introduced by the communication
communication channel between the telescopes put a limitation on channel between the telescopes put a limitation on the baseline
the baseline lengths of the optical interferometers. This lengths of the optical interferometers. This limitation can
limitation can be potentially avoided using quantum potentially be avoided using quantum teleportation. In general,
teleportation. In general, by sharing EPR-pairs using quantum by sharing Einstein-Podolsky-Rosen pairs using quantum repeaters,
repeaters, the optical interferometers can communicate photons the optical interferometers can communicate photons over long
over long distances, providing arbitrarily long baselines distances, providing arbitrarily long baselines [Gottesman2012].
[Gottesman2012].
3.3. Quantum Computing Applications 3.3. Quantum Computing Applications
In this section, we include the applications for the quantum In this section, we include the applications for the quantum
computing. It's anticipated that quantum computers as a cloud computing. It's anticipated that quantum computers as a cloud
service will become more available in future. Sometimes, to run such service will become more available in future. Sometimes, to run such
applications in the cloud while preserving the privacy, a client and applications in the cloud while preserving the privacy, a client and
a server need to exchange qubits (e.g., in blind quantum computation a server need to exchange qubits (e.g., in blind quantum computation
[Fitzsimons] as described below). Therefore, such privacy preserving [Fitzsimons] as described below). Therefore, such privacy preserving
quantum computing applications require a Quantum Internet to execute. quantum computing applications require a Quantum Internet to execute.
Examples of quantum computing include distributed quantum computing Examples of quantum computing include distributed quantum computing
and blind quantum computing, which can enable new types of cloud and blind quantum computing, which can enable new types of cloud
computing. computing.
1. Distributed quantum computing - Refers to a collection of remote Distributed quantum computing: Refers to a collection of small-
small-capacity quantum computers (i.e., each supporting a capacity, remote quantum computers (i.e., each supporting a
relatively small number of qubits) that are connected and work relatively small number of qubits) that are connected and work
together in a coordinated fashion so as to simulate a virtual together in a coordinated fashion so as to simulate a virtual
large capacity quantum computer [Wehner]. large capacity quantum computer [Wehner].
2. Blind quantum computing - Refers to private, or blind, quantum Blind quantum computing: Refers to private, or blind, quantum
computation, which provides a way for a client to delegate a computation, which provides a way for a client to delegate a
computation task to one or more remote quantum computers without computation task to one or more remote quantum computers without
disclosing the source data to be computed over [Fitzsimons]. disclosing the source data to be computed [Fitzsimons].
4. Selected Quantum Internet Application Scenarios 4. Selected Quantum Internet Application Scenarios
The Quantum Internet will support a variety of applications and The Quantum Internet will support a variety of applications and
deployment configurations. This section details a few key deployment configurations. This section details a few key
application scenarios which illustrates the benefits of the Quantum application scenarios that illustrate the benefits of the Quantum
Internet. In system engineering, an application scenario is Internet. In system engineering, an application scenario is
typically made up of a set of possible sequences of interactions typically made up of a set of possible sequences of interactions
between nodes and users in a particular environment and related to a between nodes and users in a particular environment and related to a
particular goal. This will be the definition that we use in this particular goal. This will be the definition that we use in this
section. section.
4.1. Secure Communication Setup 4.1. Secure Communication Setup
In this scenario, two nodes (e.g., quantum node A and quantum node B) In this scenario, two nodes (e.g., quantum node A and quantum node B)
need to have secure communications for transmitting confidential need to have secure communications for transmitting confidential
information (see Figure 1). For this purpose, they first need to information (see Figure 1). For this purpose, they first need to
securely share a classic secret cryptographic key (i.e., a sequence securely share a classic secret cryptographic key (i.e., a sequence
of classical bits), which is triggered by an end user with local of classical bits), which is triggered by an end user with local
secure interface to quantum node A. This results in a quantum node A secure interface to quantum node A. This results in a quantum node A
to securely establish a classical secret key with a quantum node B. securely establishing a classical secret key with a quantum node B.
This is referred to as a secure communication setup. Note that This is referred to as a "secure communication setup". Note that
quantum nodes A and B may be either a bare-bone quantum end node or a quantum nodes A and B may be either a bare-bone quantum end node or a
full-fledged quantum computer. This application scenario shows that full-fledged quantum computer. This application scenario shows that
the Quantum Internet can be leveraged to improve the security of the Quantum Internet can be leveraged to improve the security of
Classical Internet applications. Classical Internet applications.
One requirement for this secure communication setup process is that One requirement for this secure communication setup process is that
it should not be vulnerable to any classical or quantum computing it should not be vulnerable to any classical or quantum computing
attack. This can be realized using QKD which is unbreakable in attack. This can be realized using QKD, which is unbreakable in
principle. QKD can securely establish a secret key between two principle. QKD can securely establish a secret key between two
quantum nodes, using a classical authentication channel and insecure quantum nodes, using a classical authentication channel and insecure
quantum channel without physically transmitting the key through the quantum channel without physically transmitting the key through the
network and thus achieving the required security. However, care must network and thus achieving the required security. However, care must
be taken to ensure that the QKD system is safe against physical side be taken to ensure that the QKD system is safe against physical side-
channel attacks which can compromise the system. An example of a channel attacks that can compromise the system. An example of a
physical side channel attack is to surreptitiously inject additional physical side-channel attack is to surreptitiously inject additional
light into the optical devices used in QKD to learn side information light into the optical devices used in QKD to learn side information
about the system such as the polarization. Other specialized about the system such as the polarization. Other specialized
physical attacks against QKD also use a classical authentication physical attacks against QKD also use a classical authentication
channel and insecure quantum channel such as the phase-remapping channel and an insecure quantum channel such as the phase-remapping
attack, photon number splitting attack, and decoy state attack attack, photon number splitting attack, and decoy state attack
[Zhao2018]. QKD can be used for many other cryptographic [Zhao2018]. QKD can be used for many other cryptographic
communications, such as IPSec and Transport Layer Security (TLS) communications, such as IPsec and Transport Layer Security (TLS),
where involved parties need to establish a shared security key, where involved parties need to establish a shared security key,
although it usually introduces a high latency. although it usually introduces a high latency.
QKD is the most mature feature of the quantum information technology, QKD is the most mature feature of quantum information technology and
and has been commercially released in small-scale and short-distance has been commercially released in small-scale and short-distance
deployments. More QKD use cases are described in ETSI documents deployments. More QKD use cases are described in the ETSI document
[ETSI-QKD-UseCases]; in addition, the ETSI document [ETSI-QKD-UseCases]; in addition, interfaces between QKD users and
[ETSI-QKD-Interfaces] specifies interfaces between QKD users and QKD QKD devices are specified in the ETSI document [ETSI-QKD-Interfaces].
devices.
In general, the prepare and measure QKD protocols (e.g., [BB84]) In general, the prepare-and-measure QKD protocols (e.g., [BB84])
without using entanglement work as follows: without using entanglement work as follows:
1. The quantum node A encodes classical bits to qubits. Basically, 1. The quantum node A encodes classical bits to qubits. Basically,
the node A generates two random classical bit strings X, Y. the node A generates two random classical bit strings X and Y.
Among them, it uses the bit string X to choose the basis and uses Among them, it uses the bit string X to choose the basis and uses
Y to choose the state corresponding to the chosen basis. For Y to choose the state corresponding to the chosen basis. For
example, if X=0 then in case of BB84 protocol Alice prepares the example, if X=0, then in case of the BB84 protocol, Alice
state in {|0>, |1>}-basis; otherwise she prepares the state in prepares the state in {|0>, |1>}-basis; otherwise, she prepares
{|+>, |->}-basis. Similarly, if Y=0 then Alice prepares the the state in {|+>, |->}-basis. Similarly, if Y=0, then Alice
qubit either |0> or |+> (depending on the value of X), and if Y prepares the qubit as either |0> or |+> (depending on the value
=1, then Alice prepares the qubit either |1> or |->. of X); and if Y =1, then Alice prepares the qubit as either |1>
or |->.
2. The quantum node A sends qubits to the quantum node B via quantum 2. The quantum node A sends qubits to the quantum node B via a
channel. quantum channel.
3. The quantum node B receives qubits and measures each of them in 3. The quantum node B receives qubits and measures each of them in
one of the two basis at random. one of the two bases at random.
4. The quantum node B informs the quantum node A of its choice of 4. The quantum node B informs the quantum node A of its choice of
basis for each qubit. bases for each qubit.
5. The quantum node A informs the quantum node B which random 5. The quantum node A informs the quantum node B which random
quantum basis is correct. quantum basis is correct.
6. Both nodes discard any measurement bit under different quantum 6. Both nodes discard any measurement bit under different quantum
basis and remaining bits could be used as the secret key. Before bases, and the remaining bits could be used as the secret key.
generating the final secret key, there is a post-processing Before generating the final secret key, there is a post-
procedure over authenticated classical channels. The classical processing procedure over authenticated classical channels. The
post-processing part can be subdivided into three steps, namely classical post-processing part can be subdivided into three
parameter estimation, error-correction, and privacy steps, namely parameter estimation, error correction, and privacy
amplification. In the parameter estimation phase, both Alice and amplification. In the parameter estimation phase, both Alice and
Bob use some of the bits to estimate the channel error. If it is Bob use some of the bits to estimate the channel error. If it is
larger than some threshold value, they abort the protocol larger than some threshold value, they abort the protocol or
otherwise move to the error-correction phase. Basically, if an otherwise move to the error-correction phase. Basically, if an
eavesdropper tries to intercept and read qubits sent from node A eavesdropper tries to intercept and read qubits sent from node A
to node B, the eavesdropper will be detected due to the entropic to node B, the eavesdropper will be detected due to the entropic
uncertainty relation property theorem of quantum mechanics. As a uncertainty relation property theorem of quantum mechanics. As a
part of the post-processing procedure, both nodes usually also part of the post-processing procedure, both nodes usually also
perform information reconciliation [Elkouss] for efficient error perform information reconciliation [Elkouss] for efficient error
correction and/or conduct privacy amplification [Tang] for correction and/or conduct privacy amplification [Tang] for
generating the final information-theoretical secure keys. generating the final information-theoretical secure keys.
7. The post-processing procedure needs to be performed over an 7. The post-processing procedure needs to be performed over an
authenticated classical channel. In other words, the quantum authenticated classical channel. In other words, the quantum
node A and the quantum node B need to authenticate the classical node A and the quantum node B need to authenticate the classical
channel to make sure there is no eavesdroppers or man-in-the- channel to make sure there is no eavesdroppers or on-path
middle attacks, according to certain authentication protocols attacks, according to certain authentication protocols such as
such as [Kiktenko]. In [Kiktenko], the authenticity of the that described in [Kiktenko]. In [Kiktenko], the authenticity of
classical channel is checked at the very end of the post- the classical channel is checked at the very end of the post-
processing procedure instead of doing it for each classical processing procedure instead of doing it for each classical
message exchanged between the quantum node A and the quantum node message exchanged between the quantum node A and the quantum node
B. B.
It is worth noting that: It is worth noting that:
1. There are many enhanced QKD protocols based on [BB84]. For 1. There are many enhanced QKD protocols based on [BB84]. For
example, a series of loopholes have been identified due to the example, a series of loopholes have been identified due to the
imperfections of measurement devices; there are several solutions imperfections of measurement devices; there are several solutions
to take into account these attacks such as measurement-device- to take into account concerning these attacks such as
independent QKD [Zhang2019]. These enhanced QKD protocols can measurement-device-independent QKD [Zheng2019]. These enhanced
work differently than the steps of BB84 protocol [BB84]. QKD protocols can work differently than the steps of BB84
protocol [BB84].
2. For large-scale QKD, QKD Networks (QKDN) are required, which can 2. For large-scale QKD, QKD Networks (QKDNs) are required, which can
be regarded as a subset of a Quantum Internet. A QKDN may be regarded as a subset of a Quantum Internet. A QKDN may
consist of a QKD application layer, a QKD network layer, and a consist of a QKD application layer, a QKD network layer, and a
QKD link layer [Qin]. One or multiple trusted QKD relays QKD link layer [Qin]. One or multiple trusted QKD relays
[Zhang2018] may exist between the quantum node A and the quantum [Zhang2018] may exist between the quantum node A and the quantum
node B, which are connected by a QKDN. Alternatively, a QKDN may node B, which are connected by a QKDN. Alternatively, a QKDN may
rely on entanglement distribution and entanglement-based QKD rely on entanglement distribution and entanglement-based QKD
protocols; as a result, quantum-repeaters/routers instead of protocols; as a result, quantum repeaters and/or routers instead
trusted QKD relays are needed for large-scale QKD. Entanglement of trusted QKD relays are needed for large-scale QKD.
swapping can be leveraged to realize entanglement distribution. Entanglement swapping can be leveraged to realize entanglement
distribution.
3. QKD provides an information-theoretical way to share secret keys 3. QKD provides an information-theoretical way to share secret keys
between two parties (i.e., a transmitter and a receiver) in the between two parties (i.e., a transmitter and a receiver) in the
presence of an eavesdropper. However, this is true in theory, presence of an eavesdropper. However, this is true in theory,
and there is a significant gap between theory and practice. By and there is a significant gap between theory and practice. By
exploiting the imperfection of the detectors Eve can gain exploiting the imperfection of the detectors, Eve can gain
information about the shared key [Xu]. To avoid such side- information about the shared key [Xu]. To avoid such side-
channel attacks in [Lo], the researchers provide a QKD protocol channel attacks in [Lo], the researchers provide a QKD protocol
called Measurement Device-Independent (MDI) QKD that allows two called "Measurement Device-Independent (MDI)" QKD that allows two
users (a transmitter “Alice” and a receiver “Bob”) to communicate users (a transmitter "Alice" and a receiver "Bob") to communicate
with perfect security, even if the (measurement) hardware they with perfect security, even if the (measurement) hardware they
are using has been tampered with (e.g., by an eavesdropper) and are using has been tampered with (e.g., by an eavesdropper) and
thus is not trusted. It is achieved by measuring correlations thus is not trusted. It is achieved by measuring correlations
between signals from Alice and Bob rather than the actual signals between signals from Alice and Bob, rather than the actual
themselves. signals themselves.
4. QKD protocols based on Continuous Variable (CV-QKD) have recently 4. QKD protocols based on Continuous Variable QKD (CV-QKD) have
seen plenty of interest as they only require telecommunications recently seen plenty of interest as they only require
equipment that is readily available and is also in common use telecommunications equipment that is readily available and is
industry-wide. This kind of technology is a potentially high- also in common use industry-wide. This kind of technology is a
performance technique for secure key distribution over limited potentially high-performance technique for secure key
distances. The recent demonstration of CV-QKD shows distribution over limited distances. The recent demonstration of
compatibility with classical coherent detection schemes that are CV-QKD shows compatibility with classical coherent detection
widely used for high bandwidth classical communication systems schemes that are widely used for high-bandwidth classical
[Grosshans]. Note that we still do not have a quantum repeater communication systems [Grosshans]. Note that we still do not
for the continuous variable systems; hence, this kind of QKD have a quantum repeater for the continuous variable systems;
technologies can be used for the short distance communications or hence, these kinds of QKD technologies can be used for the short
trusted relay-based QKD networks. distance communications or trusted relay-based QKD networks.
5. Secret sharing can be used to distribute a secret key among 5. Secret sharing can be used to distribute a secret key among
multiple nodes by letting each node know a share or a part of the multiple nodes by letting each node know a share or a part of the
secret key, while no single node can know the entire secret key. secret key, while no single node can know the entire secret key.
The secret key can only be re-constructed via collaboration from The secret key can only be reconstructed via collaboration from a
a sufficient number of nodes. Quantum Secret Sharing (QSS) sufficient number of nodes. Quantum Secret Sharing (QSS)
typically refers to the scenario: The secret key to be shared is typically refers to the following scenario: the secret key to be
based on quantum states instead of classical bits. QSS enables shared is based on quantum states instead of classical bits. QSS
to split and share such quantum states among multiple nodes. enables splitting and sharing such quantum states among multiple
nodes.
6. There are some entanglement-based QKD protocols, such as 6. There are some entanglement-based QKD protocols, such as that
[Treiber][E91][BBM92], which work differently than the above described in [Treiber], [E91], and [BBM92], which work
steps. The entanglement-based schemes, where entangled states differently than the above steps. The entanglement-based
are prepared externally to the quantum node A and the quantum schemes, where entangled states are prepared externally to the
node B, are not normally considered "prepare-and-measure" as quantum node A and the quantum node B, are not normally
defined in [Wehner]; other entanglement-based schemes, where considered "prepare and measure" as defined in [Wehner]. Other
entanglement is generated within the source quantum node can entanglement-based schemes, where entanglement is generated
still be considered "prepare-and-measure"; send-and-return within the source quantum node, can still be considered "prepare
schemes can still be "prepare-and-measure", if the information and measure". Send-and-return schemes can still be "prepare and
content, from which keys will be derived, is prepared within the measure" if the information content, from which keys will be
quantum node A before being sent to the quantum node B for derived, is prepared within the quantum node A before being sent
measurement. to the quantum node B for measurement.
As a result, the Quantum Internet in Figure 1 contains quantum As a result, the Quantum Internet in Figure 1 contains quantum
channels. And in order to support secure communication setup channels. And in order to support secure communication setup,
especially in large-scale deployment, it also requires entanglement especially in large-scale deployment, it also requires entanglement
generation and entanglement distribution generation and entanglement distribution [QUANTUM-CONNECTION],
[I-D.van-meter-qirg-quantum-connection-setup], quantum repeaters/ quantum repeaters and/or routers, and/or trusted QKD relays.
routers, and/or trusted QKD relays.
+---------------+ +---------------+
| End User | | End User |
+---------------+ +---------------+
^ ^
| Local Secure Interface | Local Secure Interface
| (e.g., the same physical hardware | (e.g., the same physical hardware
| or a local secure network) | or a local secure network)
V V
+-----------------+ /--------\ +-----------------+ +-----------------+ /--------\ +-----------------+
skipping to change at page 13, line 45 skipping to change at line 602
| |<-->( Internet )<-->| | | |<-->( Internet )<-->| |
+-----------------+ \--------/ +-----------------+ +-----------------+ \--------/ +-----------------+
Figure 1: Secure Communication Setup Figure 1: Secure Communication Setup
4.2. Blind Quantum Computing 4.2. Blind Quantum Computing
Blind quantum computing refers to the following scenario: Blind quantum computing refers to the following scenario:
1. A client node with source data delegates the computation of the 1. A client node with source data delegates the computation of the
source data to a remote computation node (i.e. a server). source data to a remote computation node (i.e., a server).
2. Furthermore, the client node does not want to disclose any source 2. Furthermore, the client node does not want to disclose any source
data to the remote computation node, which preserves the source data to the remote computation node, which preserves the source
data privacy. data privacy.
3. Note that there is no assumption or guarantee that the remote 3. Note that there is no assumption or guarantee that the remote
computation node is a trusted entity from the source data privacy computation node is a trusted entity from the source data privacy
perspective. perspective.
As an example illustrated in Figure 2, a terminal node can be a small As an example illustrated in Figure 2, a terminal node can be a small
quantum computer with limited computation capability compared to a quantum computer with limited computation capability compared to a
remote quantum computation node (e.g., a remote mainframe quantum remote quantum computation node (e.g., a remote mainframe quantum
computer), but the terminal node needs to run a computation-intensive computer), but the terminal node needs to run a computation-intensive
task (e.g., Shor’s factoring algorithm). The terminal node can task (e.g., Shor's factoring algorithm). The terminal node can
create individual qubits and send them to the remote quantum create individual qubits and send them to the remote quantum
computation node. Then, the remote quantum computation node can computation node. Then, the remote quantum computation node can
entangle the qubits, calculate on them, measure them, generate entangle the qubits, calculate on them, measure them, generate
measurement results in classical bits, and return the measurement measurement results in classical bits, and return the measurement
results to the terminal node. It is noted that those measurement results to the terminal node. It is noted that those measurement
results will look like purely random data to the remote quantum results will look like purely random data to the remote quantum
computation node because the initial states of the qubits were chosen computation node because the initial states of the qubits were chosen
in a cryptographically secure fashion. in a cryptographically secure fashion.
As a new client/server computation model, Blind Quantum Computation As a new client and server computation model, Blind Quantum
(BQC) generally enables: 1) The client delegates a computation Computation (BQC) generally enables the following process:
function to the server; 2) The client does not send original qubits
to the server, but send transformed qubits to the server; 3) The 1. The client delegates a computation function to the server.
computation function is performed at the server on the transformed
qubits to generate temporary result qubits, which could be quantum- 2. The client does not send original qubits to the server but does
circuit-based computation or measurement-based quantum computation. send transformed qubits to the server.
The server sends the temporary result qubits to the client; 4) The
client receives the temporary result qubits and transforms them to 3. The computation function is performed at the server on the
the final result qubits. During this process, the server can not transformed qubits to generate temporary result qubits, which
figure out the original qubits from the transformed qubits. Also, it could be quantum-circuit-based computation or measurement-based
will not take too much efforts on the client side to transform the quantum computation. The server sends the temporary result
original qubits to the transformed qubits, or transform the temporary qubits to the client.
result qubits to the final result qubits. One of the very first BQC
protocols such as [Childs] follows this process, although the client 4. The client receives the temporary result qubits and transforms
them to the final result qubits.
During this process, the server cannot figure out the original qubits
from the transformed qubits. Also, it will not take too much effort
on the client side to transform the original qubits to the
transformed qubits or transform the temporary result qubits to the
final result qubits. One of the very first BQC protocols, such as
that described in [Childs], follows this process, although the client
needs some basic quantum features such as quantum memory, qubit needs some basic quantum features such as quantum memory, qubit
preparation and measurement, and qubit transmission. Measurement- preparation and measurement, and qubit transmission. Measurement-
based quantum computation is out of the scope of this document and based quantum computation is out of the scope of this document, and
more details about it can be found in [Jozsa2005]. more details about it can be found in [Jozsa2005].
It is worth noting that: It is worth noting that:
1. The BQC protocol in [Childs] is a circuit-based BQC model, where 1. The BQC protocol in [Childs] is a circuit-based BQC model, where
the client only performs simple quantum circuit for qubit the client only performs simple quantum circuit for qubit
transformation, while the server performs a sequence of quantum transformation, while the server performs a sequence of quantum
logic gates. Qubits are transmitted back and forth between the logic gates. Qubits are transmitted back and forth between the
client and the server. client and the server.
2. Universal BQC in [Broadbent] is a measurement-based BQC model, 2. Universal BQC (UBQC) in [Broadbent] is a measurement-based BQC
which is based on measurement-based quantum computing leveraging model, which is based on measurement-based quantum computing
entangled states. The principle in UBQC is based on the fact the leveraging entangled states. The principle in UBQC is based on
quantum teleportation plus a rotated Bell measurement realizes a the fact that the quantum teleportation plus a rotated Bell
quantum computation, which can be repeated multiple times to measurement realize a quantum computation, which can be repeated
realize a sequence of quantum computation. In this approach, the multiple times to realize a sequence of quantum computation. In
client first prepares transformed qubits and sends them to the this approach, the client first prepares transformed qubits and
server and the server needs first to prepare entangled states sends them to the server, and the server needs to first prepare
from all received qubits. Then, multiple interaction and entangled states from all received qubits. Then, multiple
measurement rounds happen between the client and the server. For interaction and measurement rounds happen between the client and
each round, the client computes and sends new measurement the server. For each round:
instructions or measurement adaptations to the server; then, the
server performs the measurement according to the received
measurement instructions to generate measurement results (qubits
or in classic bits); the client receives the measurement results
and transforms them to the final results.
3. A hybrid universal BQC is proposed in [Zhang2009], where the i. the client computes and sends new measurement instructions
server performs both quantum circuits like [Childs] and quantum or measurement adaptations to the server;
measurements like [Broadbent] to reduce the number of required
entangled states in [Broadbent]. Also, the client is much
simpler than the client in [Childs]. This hybrid BQC is a
combination of circuit-based BQC model and measurement-based BQC
model.
4. It will be ideal if the client in BQC is a purely classical ii. the server performs the measurement according to the
client, which only needs to interact with the server using received measurement instructions to generate measurement
classical channel and communications. [Huang] demonstrates such results (in qubits or classic bits); and
an approach, where a classical client leverages two entangled
servers to perform BQC, with the assumption that both servers iii. then the client receives the measurement results and
cannot communicate with each other; otherwise, the blindness or transforms them to the final results.
privacy of the client cannot be guaranteed. The scenario as
demonstrated in [Huang] is essentially an example of BQC with 3. A hybrid UBQC is proposed in [Zhang2009], where the server
multiple servers. performs both quantum circuits like that demonstrated in [Childs]
and quantum measurements like that demonstrated in [Broadbent] to
reduce the number of required entangled states in [Broadbent].
Also, the client is much simpler than the client in [Childs].
This hybrid BQC is a combination of a circuit-based BQC model and
a measurement-based BQC model.
4. It is ideal if the client in BQC is a purely classical client,
which only needs to interact with the server using classical
channels and communications. [Huang] demonstrates such an
approach where a classical client leverages two entangled servers
to perform BQC with the assumption that both servers cannot
communicate with each other; otherwise, the blindness or privacy
of the client cannot be guaranteed. The scenario as demonstrated
in [Huang] is essentially an example of BQC with multiple
servers.
5. How to verify that the server will perform what the client 5. How to verify that the server will perform what the client
requests or expects is an important issue in many BQC protocols, requests or expects is an important issue in many BQC protocols,
referred to as verifiable BQC. [Fitzsimons] discusses this issue referred to as "verifiable BQC". [Fitzsimons] discusses this
and compares it in various BQC protocols. issue and compares it in various BQC protocols.
In Figure 2, the Quantum Internet contains quantum channels and In Figure 2, the Quantum Internet contains quantum channels and
quantum repeaters/routers for long-distance qubits transmission quantum repeaters and/or routers for long-distance qubits
[RFC9340]. transmission [RFC9340].
+----------------+ /--------\ +-------------------+ +----------------+ /--------\ +-------------------+
| |--->( Quantum )--->| | | |--->( Quantum )--->| |
| | ( Internet ) | Remote Quantum | | | ( Internet ) | Remote Quantum |
| Terminal | \--------/ | Computation | | Terminal | \--------/ | Computation |
| Node | | Node | | Node | | Node |
| (e.g., A Small| /--------\ | (e.g., Remote | | (e.g., a small| /--------\ | (e.g., a remote |
| Quantum | ( Classical) | Mainframe | | quantum | ( Classical) | mainframe |
| Computer) |<-->( Internet )<-->| Quantum Computer)| | computer) |<-->( Internet )<-->| quantum computer) |
+----------------+ \--------/ +-------------------+ +----------------+ \--------/ +-------------------+
Figure 2: Bind Quantum Computing Figure 2: Bind Quantum Computing
4.3. Distributed Quantum Computing 4.3. Distributed Quantum Computing
There can be two types of distributed quantum computing [Denchev]: There can be two types of distributed quantum computing [Denchev]:
1. Leverage quantum mechanics to enhance classical distributed 1. Leverage quantum mechanics to enhance classical distributed
computing. For example, entangled quantum states can be computing. For example, entangled quantum states can be
exploited to improve leader election in classical distributed exploited to improve leader election in classical distributed
computing, by simply measuring the entangled quantum states at computing by simply measuring the entangled quantum states at
each party (e.g., a node or a device) without introducing any each party (e.g., a node or a device) without introducing any
classical communications among distributed parties [Pal]. classical communications among distributed parties [Pal].
Normally, pre-shared entanglement needs first be established Normally, pre-shared entanglement first needs to be established
among distributed parties, followed by LOCC operations at each among distributed parties, followed by LOCC operations at each
party. And it generally does not need to transfer qubits among party. And it generally does not need to transfer qubits among
distributed parties. distributed parties.
2. Distribute quantum computing functions to distributed quantum 2. Distribute quantum computing functions to distributed quantum
computers. A quantum computing task or function (e.g., quantum computers. A quantum computing task or function (e.g., quantum
gates) is split and distributed to multiple physically separate gates) is split and distributed to multiple physically separate
quantum computers. And it may or may not need to transmit qubits quantum computers. And it may or may not need to transmit qubits
(either inputs or outputs) among those distributed quantum (either inputs or outputs) among those distributed quantum
computers. Entangled states will be needed and actually consumed computers. Entangled states will be needed and actually consumed
to support such distributed quantum computing tasks. It is worth to support such distributed quantum computing tasks. It is worth
noting that: 1)Entangled states can be created beforehand and noting that:
stored or buffered; 2) The rate of entanglement creation will
limit the performance of practical quantum internet applicaitons a. Entangled states can be created beforehand and stored or
including distributed quantum computing, although entangled buffered;
states could be buffered. For example, [Gottesman1999] and
[Eisert] have proved that a CNOT gate can be realized jointly by b. The rate of entanglement creation will limit the performance
and distributed to multiple quantum computers. The rest of this of practical Quantum Internet applications including
distributed quantum computing, although entangled states
could be buffered.
For example, [Gottesman1999] and [Eisert] have demonstrated that
a Controlled NOT (CNOT) gate can be realized jointly by and
distributed to multiple quantum computers. The rest of this
section focuses on this type of distributed quantum computing. section focuses on this type of distributed quantum computing.
As a scenario for the second type of distributed quantum computing, As a scenario for the second type of distributed quantum computing,
Noisy Intermediate-Scale Quantum (NISQ) computers distributed in Noisy Intermediate-Scale Quantum (NISQ) computers distributed in
different locations are available for sharing. According to the different locations are available for sharing. According to the
definition in [Preskill], a NISQ computer can only realize a small definition in [Preskill], a NISQ computer can only realize a small
number of qubits and has limited quantum error correction. This number of qubits and has limited quantum error correction. This
scenario is referred to as distributed quantum computing [Caleffi] scenario is referred to as "distributed quantum computing" [Caleffi]
[Cacciapuoti2020] [Cacciapuoti2019]. This application scenario [Cacciapuoti2020] [Cacciapuoti2019]. This application scenario
reflects the vastly increased computing power which quantum computers reflects the vastly increased computing power that quantum computers
as a part of the Quantum Internet can bring, in contrast to classical can bring as a part of the Quantum Internet, in contrast to classical
computers in the Classical Internet, in the context of distributed computers in the Classical Internet, in the context of a distributed
quantum computing ecosystem [Cuomo]. According to [Cuomo], quantum quantum computing ecosystem [Cuomo]. According to [Cuomo], quantum
teleportation enables a new communication paradigm, referred to as teleportation enables a new communication paradigm, referred to as
teledata [VanMeter2006-01], which moves quantum states among qubits "teledata" [VanMeter2006-01], which moves quantum states among qubits
to distributed quantum computers. In addition, distributed quantum to distributed quantum computers. In addition, distributed quantum
computation also needs the capability of remotely performing quantum computation also needs the capability of remotely performing quantum
computation on qubits on distributed quantum computers, which can be computation on qubits on distributed quantum computers, which can be
enabled by the technique called telegate [VanMeter2006-02]. enabled by the technique called "telegate" [VanMeter2006-02].
As an example, a user can leverage these connected NISQ computers to As an example, a user can leverage these connected NISQ computers to
solve highly complex scientific computation problems, such as solve highly complex scientific computation problems, such as
analysis of chemical interactions for medical drug development [Cao] analysis of chemical interactions for medical drug development [Cao]
(see Figure 3). In this case, qubits will be transmitted among (see Figure 3). In this case, qubits will be transmitted among
connected quantum computers via quantum channels, while the user's connected quantum computers via quantum channels, while the user's
execution requests are transmitted to these quantum computers via execution requests are transmitted to these quantum computers via
classical channels for coordination and control purpose. Another classical channels for coordination and control purpose. Another
example of distributed quantum computing is secure Multi-Party example of distributed quantum computing is secure Multi-Party
Quantum Computation (MPQC) [Crepeau], which can be regarded as a Quantum Computation (MPQC) [Crepeau], which can be regarded as a
skipping to change at page 18, line 25 skipping to change at line 798
In a secure MPQC protocol, multiple participants jointly perform In a secure MPQC protocol, multiple participants jointly perform
quantum computation on a set of input quantum states, which are quantum computation on a set of input quantum states, which are
prepared and provided by different participants. One of the primary prepared and provided by different participants. One of the primary
aims of the secure MPQC is to guarantee that each participant will aims of the secure MPQC is to guarantee that each participant will
not know input quantum states provided by other participants. Secure not know input quantum states provided by other participants. Secure
MPQC relies on verifiable quantum secret sharing [Lipinska]. MPQC relies on verifiable quantum secret sharing [Lipinska].
For the example shown in Figure 3, we want to move qubits from one For the example shown in Figure 3, we want to move qubits from one
NISQ computer to another NISQ computer. For this purpose, quantum NISQ computer to another NISQ computer. For this purpose, quantum
teleportation can be leveraged to teleport sensitive data qubits from teleportation can be leveraged to teleport sensitive data qubits from
one quantum computer A to another quantum computer B. Note that one quantum computer (A) to another quantum computer (B). Note that
Figure 3 does not cover measurement-based distributed quantum Figure 3 does not cover measurement-based distributed quantum
computing, where quantum teleportation may not be required. When computing, where quantum teleportation may not be required. When
quantum teleportation is employed, the following steps happen between quantum teleportation is employed, the following steps happen between
A and B. In fact, LOCC [Chitambar] operations are conducted at the A and B. In fact, LOCC [Chitambar] operations are conducted at the
quantum computers A and B in order to achieve quantum teleportation quantum computers A and B in order to achieve quantum teleportation
as illustrated in Figure 3. as illustrated in Figure 3.
1. The quantum computer A locally generates some sensitive data 1. The quantum computer A locally generates some sensitive data
qubits to be teleported to the quantum computer B. qubits to be teleported to the quantum computer B.
2. A shared entanglement is established between the quantum computer 2. A shared entanglement is established between the quantum computer
A and the quantum computer B (i.e., there are two entangled A and the quantum computer B (i.e., there are two entangled
qubits: q1 at A and q2 at B). For example, the quantum computer qubits: q1 at A and q2 at B). For example, the quantum computer
A can generate two entangled qubits (i.e., q1 and q2) and sends A can generate two entangled qubits (i.e., q1 and q2) and send q2
q2 to the quantum computer B via quantum communications. to the quantum computer B via quantum communications.
3. Then, the quantum computer A performs a Bell measurement of the 3. Then, the quantum computer A performs a Bell measurement of the
entangled qubit q1 and the sensitive data qubit. entangled qubit q1 and the sensitive data qubit.
4. The result from this Bell measurement will be encoded in two 4. The result from this Bell measurement will be encoded in two
classical bits, which will be physically transmitted via a classical bits, which will be physically transmitted via a
classical channel to the quantum computer B. classical channel to the quantum computer B.
5. Based on the received two classical bits, the quantum computer B 5. Based on the received two classical bits, the quantum computer B
modifies the state of the entangled qubit q2 in the way to modifies the state of the entangled qubit q2 in the way to
generate a new qubit identical to the sensitive data qubit at the generate a new qubit identical to the sensitive data qubit at the
quantum computer A. quantum computer A.
In Figure 3, the Quantum Internet contains quantum channels and In Figure 3, the Quantum Internet contains quantum channels and
quantum repeaters/routers [RFC9340]. This application scenario needs quantum repeaters and/or routers [RFC9340]. This application
to support entanglement generation and entanglement distribution (or scenario needs to support entanglement generation and entanglement
quantum connection) setup distribution (or quantum connection) setup [QUANTUM-CONNECTION] in
[I-D.van-meter-qirg-quantum-connection-setup] in order to support order to support quantum teleportation.
quantum teleportation.
+-----------------+ +-----------------+
| End User | | End User |
| | | |
+-----------------+ +-----------------+
^ ^
| Local Secure Interface | Local Secure Interface
| (e.g., the same phyical hardware | (e.g., the same physical hardware
| or a local secure network) | or a local secure network)
| |
+------------------+-------------------+ +------------------+-------------------+
| | | |
| | | |
V V V V
+----------------+ /--------\ +----------------+ +----------------+ /--------\ +----------------+
| |--->( Quantum )--->| | | |--->( Quantum )--->| |
| | ( Internet ) | | | | ( Internet ) | |
| Quantum | \--------/ | Quantum | | Quantum | \--------/ | Quantum |
| Computer A | | Computer B | | Computer A | | Computer B |
| (e.g., Site #1)| /--------\ | (e.g., Site #2)| | (e.g., Site #1)| /--------\ | (e.g., Site #2)|
| | ( Classical) | | | | ( Classical) | |
| |<-->( Internet )<-->| | | |<-->( Internet )<-->| |
+----------------+ \--------/ +----------------+ +----------------+ \--------/ +----------------+
Figure 3: Distributed Quantum Computing Figure 3: Distributed Quantum Computing
5. General Requirements 5. General Requirements
Quantum technologies are steadily evolving and improving. Therefore, Quantum technologies are steadily evolving and improving. Therefore,
it is hard to predict the timeline and future milestones of quantum it is hard to predict the timeline and future milestones of quantum
technologies as pointed out in [Grumbling] for quantum computing. technologies as pointed out in [Grumbling] for quantum computing.
Currently, a NISQ computer can achieve fifty to hundreds of qubits Currently, a NISQ computer can achieve fifty to hundreds of qubits
with some given error rate. with some given error rate.
On the network level, six stages of Quantum Internet development are On the network level, six stages of Quantum Internet development are
described in [Wehner] as Quantum Internet technology roadmap as described in [Wehner] as a Quantum Internet technology roadmap as
follows: follows:
1. Trusted repeater networks (Stage-1) 1. Trusted repeater networks (Stage-1)
2. Prepare and measure networks (Stage-2)
2. Prepare-and-measure networks (Stage-2)
3. Entanglement distribution networks (Stage-3) 3. Entanglement distribution networks (Stage-3)
4. Quantum memory networks (Stage-4) 4. Quantum memory networks (Stage-4)
5. Fault-tolerant few qubit networks (Stage-5) 5. Fault-tolerant few qubit networks (Stage-5)
6. Quantum computing networks (Stage-6) 6. Quantum computing networks (Stage-6)
The first stage is simple trusted repeater networks, while the final The first stage is simple trusted repeater networks, while the final
stage is the quantum computing networks where the full-blown Quantum stage is the quantum computing networks where the full-blown Quantum
Internet will be achieved. Each intermediate stage brings with it Internet will be achieved. Each intermediate stage brings with it
new functionality, new applications, and new characteristics. new functionality, new applications, and new characteristics.
Figure 4 illustrates Quantum Internet application scenarios as Table 1 illustrates Quantum Internet application scenarios as
described in Section 3 and Section 4 mapped to the Quantum Internet described in Sections 3 and 4 mapped to the Quantum Internet stages
stages described in [Wehner]. For example, secure communication described in [Wehner]. For example, secure communication setup can
setup can be supported in Stage-1, Stage-2, or Stage-3, but with be supported in Stage-1, Stage-2, or Stage-3 but with different QKD
different QKD solutions. More specifically: solutions. More specifically:
In Stage-1, basic QKD is possible and can be leveraged to support * In Stage-1, basic QKD is possible and can be leveraged to support
secure communication setup but trusted nodes are required to provide secure communication setup, but trusted nodes are required to
end-to-end security. The primary requirement is the trusted nodes. provide end-to-end security. The primary requirement is the
trusted nodes.
In Stage-2, the end users can prepare and measure the qubits. In * In Stage-2, the end users can prepare and measure the qubits. In
this stage, the users can verify classical passwords without this stage, the users can verify classical passwords without
revealing it. revealing them.
In Stage-3, end-to-end security can be enabled based on quantum * In Stage-3, end-to-end security can be enabled based on quantum
repeaters and entanglement distribution, to support the same secure repeaters and entanglement distribution to support the same secure
communication setup application. The primary requirement is communication setup application. The primary requirement is
entanglement distribution to enable long-distance QKD. entanglement distribution to enable long-distance QKD.
In Stage-4, the quantum repeaters gain the capability of storing and * In Stage-4, the quantum repeaters gain the capability of storing
manipulating entangled qubits in the quantum memories. Using these and manipulating entangled qubits in the quantum memories. Using
kind of quantum networks, one can run sophisticated applications like these kinds of quantum networks, one can run sophisticated
blind quantum computing, leader election, quantum secret sharing. applications like blind quantum computing, leader election, and
quantum secret sharing.
In Stage-5, quantum repeaters can perform error correction; hence * In Stage-5, quantum repeaters can perform error correction; hence,
they can perform fault-tolerant quantum computations on the received they can perform fault-tolerant quantum computations on the
data. With the help of these repeaters, it is possible to run received data. With the help of these repeaters, it is possible
distributed quantum computing and quantum sensor applications over a to run distributed quantum computing and quantum sensor
smaller number of qubits. applications over a smaller number of qubits.
Finally, in Stage-6, distributed quantum computing relying on more * Finally, in Stage-6, distributed quantum computing relying on more
qubits can be supported. qubits can be supported.
+---------+----------------------------+------------------------+ +================+==========================+=====================+
| Quantum | Example Quantum | | | Quantum | Example Quantum Internet | Characteristic |
| Internet| Internet Use | Characteristic | | Internet Stage | Use Cases | |
| Stage | Cases | | +================+==========================+=====================+
+---------+----------------------------+------------------------+ | Stage-1 | Secure communication | Trusted nodes |
| Stage-1 | Secure comm setup | Trusted nodes | | | setup using basic QKD | |
| | using basic QKD | | +----------------+--------------------------+---------------------+
|---------------------------------------------------------------| | Stage-2 | Secure communication | Prepare-and-measure |
| Stage-2 | Secure comm setup | Prepare-and-measure | | | setup using the QKD with | capability |
| | using the QKD with | capability | | | end-to-end security | |
| | end-to-end security | | +----------------+--------------------------+---------------------+
|---------------------------------------------------------------| | Stage-3 | Secure communication | Entanglement |
| Stage-3 | Secure comm setup | Entanglement | | | setup using | distribution |
| | using entanglement-enabled | distribution | | | entanglement-enabled QKD | |
| | QKD | | +----------------+--------------------------+---------------------+
|---------------------------------------------------------------| | Stage-4 | Blind quantum computing | Quantum memory |
| Stage-4 | Blind quantum | Quantum memory | +----------------+--------------------------+---------------------+
| | computing | | | Stage-5 | Higher-accuracy clock | Fault tolerance |
|---------------------------------------------------------------| | | synchronization | |
| Stage-5 | Higher-Accuracy Clock | Fault tolerance | +----------------+--------------------------+---------------------+
| | synchronization | | | Stage-6 | Distributed quantum | More qubits |
|---------------------------------------------------------------| | | computing | |
| Stage-6 | Distributed quantum | More qubits | +----------------+--------------------------+---------------------+
| | computing | |
+---------------------------------------------------------------+
Figure 4: Example Application Scenarios in Different Quantum Table 1: Example Application Scenarios in Different Quantum
Internet Stages Internet Stages
Some general and functional requirements on the Quantum Internet from Some general and functional requirements on the Quantum Internet from
the networking perspective, based on the above application scenarios the networking perspective, based on the above application scenarios
and Quantum Internet technology roadmap [Wehner], are identified and and Quantum Internet technology roadmap [Wehner], are identified and
described in next sections. described in next sections.
5.1. Operations on Entangled Qubits 5.1. Operations on Entangled Qubits
Methods for facilitating quantum applications to interact efficiently Methods for facilitating quantum applications to interact efficiently
with entangled qubits are necessary in order for them to trigger with entangled qubits are necessary in order for them to trigger
distribution of designated entangled qubits to potentially any other distribution of designated entangled qubits to potentially any other
quantum node residing in the Quantum Internet. To accomplish this, quantum node residing in the Quantum Internet. To accomplish this,
specific operations must be performed on entangled qubits (e.g., specific operations must be performed on entangled qubits (e.g.,
entanglement swapping, entanglement distillation). Quantum nodes may entanglement swapping or entanglement distillation). Quantum nodes
be quantum end nodes, quantum repeaters/routers, and/or quantum may be quantum end nodes, quantum repeaters and/or routers, and/or
computers. quantum computers.
5.2. Entanglement Distribution 5.2. Entanglement Distribution
Quantum repeaters/routers should support robust and efficient Quantum repeaters and/or routers should support robust and efficient
entanglement distribution in order to extend and establish high- entanglement distribution in order to extend and establish a high-
fidelity entanglement connection between two quantum nodes. For fidelity entanglement connection between two quantum nodes. For
achieving this, it is required to first generate an entangled pair on achieving this, it is required to first generate an entangled pair on
each hop of the path between these two nodes, and then perform each hop of the path between these two nodes and then perform
entanglement swapping operations at each of the intermediate nodes. entanglement-swapping operations at each of the intermediate nodes.
5.3. The Need for Classical Channels 5.3. The Need for Classical Channels
Quantum end nodes must send additional information on classical Quantum end nodes must send additional information on classical
channels to aid in transferring and understanding qubits across channels to aid in transferring and understanding qubits across
quantum repeaters/receivers. Examples of such additional information quantum repeaters and/or receivers. Examples of such additional
include qubit measurements in secure communication setup Section 4.1, information include qubit measurements in secure communication setup
and Bell measurements in distributed quantum computing Section 4.3. (Section 4.1) and Bell measurements in distributed quantum computing
In addition, qubits are transferred individually and do not have any (Section 4.3). In addition, qubits are transferred individually and
associated packet header which can help in transferring the qubit. do not have any associated packet header, which can help in
Any extra information to aid in routing, identification, etc., of the transferring the qubit. Any extra information to aid in routing,
qubit(s) must be sent via classical channels. identification, etc. of the qubit(s) must be sent via classical
channels.
5.4. Quantum Internet Management 5.4. Quantum Internet Management
Methods for managing and controlling the Quantum Internet including Methods for managing and controlling the Quantum Internet including
quantum nodes and their quantum resources are necessary. The quantum nodes and their quantum resources are necessary. The
resources of a quantum node may include quantum memory, quantum resources of a quantum node may include quantum memory, quantum
channels, qubits, established quantum connections, etc. Such channels, qubits, established quantum connections, etc. Such
management methods can be used to monitor network status of the management methods can be used to monitor the network status of the
Quantum Internet, diagnose and identify potential issues (e.g. Quantum Internet, diagnose and identify potential issues (e.g.,
quantum connections), and configure quantum nodes with new actions quantum connections), and configure quantum nodes with new actions
and/or policies (e.g. to perform a new entanglement swapping and/or policies (e.g., to perform a new entanglement-swapping
operation). New management information model for the Quantum operation). A new management information model for the Quantum
Internet may need to be developed. Internet may need to be developed.
6. Conclusion 6. Conclusion
This document provides an overview of some expected application This document provides an overview of some expected application
categories for the Quantum Internet, and then details selected categories for the Quantum Internet and then details selected
application scenarios. The applications are first grouped by their application scenarios. The applications are first grouped by their
usage which is easy to understand classification scheme. This set of usage, which is an easy-to-understand classification scheme. This
applications may, of course, expand over time as the Quantum Internet set of applications may, of course, expand over time as the Quantum
matures. Finally, some general requirements for the Quantum Internet Internet matures. Finally, some general requirements for the Quantum
are also provided. Internet are also provided.
This document can also serve as an introductory text to readers This document can also serve as an introductory text to readers
interested in learning about the practical uses of the Quantum interested in learning about the practical uses of the Quantum
Internet. Finally, it is hoped that this document will help guide Internet. Finally, it is hoped that this document will help guide
further research and development of the Quantum Internet further research and development of the Quantum Internet
functionality required to implement the application scenarios functionality required to implement the application scenarios
described herein. described herein.
7. IANA Considerations 7. IANA Considerations
This document requests no IANA actions. This document has no IANA actions.
8. Security Considerations 8. Security Considerations
This document does not define an architecture nor a specific protocol This document does not define an architecture nor a specific protocol
for the Quantum Internet. It focuses instead on detailing for the Quantum Internet. It focuses instead on detailing
application scenarios, requirements, and describing typical Quantum application scenarios and requirements and describing typical Quantum
Internet applications. However, some salient observations can be Internet applications. However, some salient observations can be
made regarding security of the Quantum Internet as follows. made regarding security of the Quantum Internet as follows.
It has been identified in [NISTIR8240] that once large-scale quantum It has been identified in [NISTIR8240] that, once large-scale quantum
computing becomes reality that it will be able to break many of the computing becomes reality, it will be able to break many of the
public-key (i.e., asymmetric) cryptosystems currently in use. This public key (i.e., asymmetric) cryptosystems currently in use. This
is because of the increase in computing ability with quantum is because of the increase in computing ability with quantum
computers for certain classes of problems (e.g., prime factorization, computers for certain classes of problems (e.g., prime factorization
optimizations). This would negatively affect many of the security and optimizations). This would negatively affect many of the
mechanisms currently in use on the Classical Internet which are based security mechanisms currently in use on the Classical Internet that
on public-key (Diffie-Hellman) encryption. This has given strong are based on public key (Diffie-Hellman (DH)) encryption. This has
impetus for starting development of new cryptographic systems that given strong impetus for starting development of new cryptographic
are secure against quantum computing attacks [NISTIR8240]. systems that are secure against quantum computing attacks
[NISTIR8240].
Interestingly, development of the Quantum Internet will also mitigate Interestingly, development of the Quantum Internet will also mitigate
the threats posed by quantum computing attacks against Diffie-Hellman the threats posed by quantum computing attacks against DH-based
based public-key cryptosystems. Specifically, the secure public key cryptosystems. Specifically, the secure communication
communication setup feature of the Quantum Internet as described in setup feature of the Quantum Internet, as described in Section 4.1,
Section 4.1 will be strongly resistant to both classical and quantum will be strongly resistant to both classical and quantum computing
computing attacks against Diffie-Hellman based public-key attacks against Diffie-Hellman based public key cryptosystems.
cryptosystems.
A key additional threat consideration for the Quantum Internet is A key additional threat consideration for the Quantum Internet is
pointed to by [RFC7258], which warns of the dangers of pervasive addressed in [RFC7258], which warns of the dangers of pervasive
monitoring as a widespread attack on privacy. Pervasive monitoring monitoring as a widespread attack on privacy. Pervasive monitoring
is defined as a widespread, and usually covert, surveillance through is defined as a widespread, and usually covert, surveillance through
intrusive gathering of application content or protocol metadata such intrusive gathering of application content or protocol metadata, such
as headers. This can be accomplished through active or passive as headers. This can be accomplished through active or passive
wiretaps, traffic analysis, or subverting the cryptographic keys used wiretaps, through traffic analysis, or by subverting the
to secure communications. cryptographic keys used to secure communications.
The secure communication setup feature of the Quantum Internet as The secure communication setup feature of the Quantum Internet, as
described in Section 4.1 will be strongly resistant to pervasive described in Section 4.1, will be strongly resistant to pervasive
monitoring based on directly attacking (Diffie-Hellman) encryption monitoring based on directly attacking (Diffie-Hellman) encryption
keys. Also, Section 4.2 describes a method to perform remote quantum keys. Also, Section 4.2 describes a method to perform remote quantum
computing while preserving the privacy of the source data. Finally, computing while preserving the privacy of the source data. Finally,
the intrinsic property of qubits to decohere if they are observed, the intrinsic property of qubits to decohere if they are observed,
albeit covertly, will theoretically allow detection of unwanted albeit covertly, will theoretically allow detection of unwanted
monitoring in some future solutions. monitoring in some future solutions.
Modern networks are implemented with zero trust principles where Modern networks are implemented with zero trust principles where
classical cryptography is used for confidentiality, integrity classical cryptography is used for confidentiality, integrity
protection, and authentication on many of the logical layers of the protection, and authentication on many of the logical layers of the
network stack, often all the way from device to software in the cloud network stack, often all the way from device to software in the cloud
[NISTSP800-207]. The cryptographic solutions in use today are based [NISTSP800-207]. The cryptographic solutions in use today are based
on well-understood primitives, provably secure protocols and state- on well-understood primitives, provably secure protocols, and state-
of-the-art implementations that are secure against a variety of side- of-the-art implementations that are secure against a variety of side-
channel attacks. channel attacks.
In contrast to conventional cryptography and Post-Quantum In contrast to conventional cryptography and Post-Quantum
Cryptography (PQC), the security of QKD is inherently tied to the Cryptography (PQC), the security of QKD is inherently tied to the
physical layer, which makes the threat surfaces of QKD and physical layer, which makes the threat surfaces of QKD and
conventional cryptography quite different. QKD implementations have conventional cryptography quite different. QKD implementations have
already been subjected to publicized attacks [Zhao2008] and the already been subjected to publicized attacks [Zhao2008], and the
National Security Agency (NSA) notes that the risk profile of National Security Agency (NSA) notes that the risk profile of
conventional cryptography is better understood [NSA]. The fact that conventional cryptography is better understood [NSA]. The fact that
conventional cryptography and PQC are implemented at a higher layer conventional cryptography and PQC are implemented at a higher layer
than the physical one means PQC can be used to securely send than the physical one means PQC can be used to securely send
protected information through untrusted relays. This is in stark protected information through untrusted relays. This is in stark
contrast with QKD, which relies on hop-by-hop security between contrast with QKD, which relies on hop-by-hop security between
intermediate trusted nodes. The PQC approach is better aligned with intermediate trusted nodes. The PQC approach is better aligned with
the modern technology environment, in which more applications are the modern technology environment, in which more applications are
moving toward end-to-end security and zero-trust principles. It is moving toward end-to-end security and zero-trust principles. It is
also important to note that while PQC can be deployed as a software also important to note that, while PQC can be deployed as a software
update, QKD requires new hardware. In addition, IETF has a working update, QKD requires new hardware. In addition, the IETF has a
group on Post-Quantum Use In Protocols (PQUIP) that is studying PQC working group on Post-Quantum Use In Protocols (PQUIP) that is
transition issues. studying PQC transition issues.
Regarding QKD implementation details, the NSA states that Regarding QKD implementation details, the NSA states that
communication needs and security requirements physically conflict in communication needs and security requirements physically conflict in
QKD and that the engineering required to balance them has extremely QKD and that the engineering required to balance them has extremely
low tolerance for error. While conventional cryptography can be low tolerance for error. While conventional cryptography can be
implemented in hardware in some cases for performance or other implemented in hardware in some cases for performance or other
reasons, QKD is inherently tied to hardware. The NSA points out that reasons, QKD is inherently tied to hardware. The NSA points out that
this makes QKD less flexible with regard to upgrades or security this makes QKD less flexible with regard to upgrades or security
patches. As QKD is fundamentally a point-to-point protocol, the NSA patches. As QKD is fundamentally a point-to-point protocol, the NSA
also notes that QKD networks often require the use of trusted relays, also notes that QKD networks often require the use of trusted relays,
which increases the security risk from insider threats. which increases the security risk from insider threats.
The UK’s National Cyber Security Centre cautions against reliance on The UK's National Cyber Security Centre cautions against reliance on
QKD, especially in critical national infrastructure sectors, and QKD, especially in critical national infrastructure sectors, and
suggests that PQC as standardized by the NIST is a better solution suggests that PQC, as standardized by NIST, is a better solution
[NCSC]. Meanwhile, the National Cybersecurity Agency of France has [NCSC]. Meanwhile, the National Cybersecurity Agency of France has
decided that QKD could be considered as a defense-in-depth measure decided that QKD could be considered as a defense-in-depth measure
complementing conventional cryptography, as long as the cost incurred complementing conventional cryptography, as long as the cost incurred
does not adversely affect the mitigation of current threats to IT does not adversely affect the mitigation of current threats to IT
systems [ANNSI]. systems [ANNSI].
9. Acknowledgments 9. Informative References
The authors want to thank Michele Amoretti, Mathias Van Den Bossche,
Xavier de Foy, Patrick Gelard, Álvaro Gómez Iñesta, Mallory Knodel,
Wojciech Kozlowski, John Mattsson, Rodney Van Meter, Colin Perkins,
Joey Salazar, and Joseph Touch, Brian Trammell, and the rest of the
QIRG community as a whole for their very useful reviews and comments
to the document.
10. Informative References
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Acknowledgments
The authors want to thank Michele Amoretti, Mathias Van Den Bossche,
Xavier de Foy, Patrick Gelard, Álvaro Gómez Iñesta, Mallory Knodel,
Wojciech Kozlowski, John Preuß Mattsson, Rodney Van Meter, Colin
Perkins, Joey Salazar, Joseph Touch, Brian Trammell, and the rest of
the QIRG community as a whole for their very useful reviews and
comments on the document.
Authors' Addresses Authors' Addresses
Chonggang Wang Chonggang Wang
InterDigital Communications, LLC InterDigital Communications, LLC
1001 E Hector St 1001 E Hector St
Conshohocken, 19428 Conshohocken, PA 19428
United States of America United States of America
Email: Chonggang.Wang@InterDigital.com Email: Chonggang.Wang@InterDigital.com
Akbar Rahman Akbar Rahman
Ericsson Ericsson
349 Terry Fox Drive 349 Terry Fox Drive
Ottawa Ontario K2K 2V6 Ottawa Ontario K2K 2V6
Canada Canada
Email: Akbar.Rahman@Ericsson.Com Email: Akbar.Rahman@Ericsson.Com
Ruidong Li Ruidong Li
Kanazawa University Kanazawa University
Kakuma-machi, Kakumamachi, Kanazawa, Ishikawa
Ishikawa Prefecture 920-1192 920-1192
Japan Japan
Email: lrd@se.kanazawa-u.ac.jp Email: lrd@se.kanazawa-u.ac.jp
Melchior Aelmans Melchior Aelmans
Juniper Networks Juniper Networks
Boeing Avenue 240 Boeing Avenue 240
Schiphol-Rijk 1119 PZ Schiphol-Rijk
Netherlands
Email: maelmans@juniper.net Email: maelmans@juniper.net
Kaushik Chakraborty Kaushik Chakraborty
The University of Edinburgh The University of Edinburgh
10 Crichton Street 10 Crichton Street
Edinburgh Edinburgh, Scotland
EH8 9AB, Scotland EH8 9AB
United Kingdom United Kingdom
Email: kchakrab@exseed.edu.ac.uk Email: kaushik.chakraborty9@gmail.com
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