Applications and Use Cases for the Quantum Internet
draft-irtf-qirg-quantum-internet-use-cases-07

Document Type Active Internet-Draft (qirg RG)
Authors Chonggang Wang  , Akbar Rahman  , Ruidong Li  , Melchior Aelmans  , Kaushik Chakraborty 
Last updated 2021-07-12
Replaces draft-wang-qirg-quantum-internet-use-cases
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QIRG                                                             C. Wang
Internet-Draft                                                 A. Rahman
Intended status: Informational          InterDigital Communications, LLC
Expires: January 13, 2022                                          R. Li
                                                     Kanazawa University
                                                              M. Aelmans
                                                        Juniper Networks
                                                          K. Chakraborty
                                             The University of Edinburgh
                                                           July 12, 2021

          Applications and Use Cases for the Quantum Internet
             draft-irtf-qirg-quantum-internet-use-cases-07

Abstract

   The Quantum Internet has the potential to improve application
   functionality by incorporating quantum information technology into
   the infrastructure of the overall Internet.  This document provides
   an overview of some applications expected to be used on the Quantum
   Internet, and then categorizes them using various classification
   schemes.  Some general requirements for the Quantum Internet are also
   discussed.  The intent of this document is to describe a framework
   for applications, and describe use cases for the Quantum Internet.
   This document is a product of the Quantum Internet Research Group
   (QIRG).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on January 13, 2022.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms and Acronyms List . . . . . . . . . . . . . . . . . . .   3
   3.  Quantum Internet Applications . . . . . . . . . . . . . . . .   6
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Classification by Application Usage . . . . . . . . . . .   6
       3.2.1.  Quantum Cryptography Applications . . . . . . . . . .   6
       3.2.2.  Quantum Sensor Applications . . . . . . . . . . . . .   7
       3.2.3.  Quantum Computing Applications  . . . . . . . . . . .   8
     3.3.  Control vs Data Plane Classification  . . . . . . . . . .   8
   4.  Selected Quantum Internet Use Cases . . . . . . . . . . . . .  10
     4.1.  Secure Communication Setup  . . . . . . . . . . . . . . .  10
     4.2.  Secure Quantum Computing with Privacy Preservation  . . .  14
     4.3.  Distributed Quantum Computing . . . . . . . . . . . . . .  17
   5.  General Requirements  . . . . . . . . . . . . . . . . . . . .  20
     5.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .  20
     5.2.  Requirements  . . . . . . . . . . . . . . . . . . . . . .  22
   6.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  22
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  24
   10. Informative References  . . . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   The Classical Internet has been constantly growing since it first
   became commercially popular in the early 1990's.  It essentially
   consists of a large number of end-nodes (e.g., laptops, smart phones,
   network servers) connected by routers and clustered in Autonomous
   Systems.  The end-nodes may run applications that provide service for
   the end-users such as processing and transmission of voice, video or

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   data.  The connections between the various nodes in the Internet
   include backbone links (e.g., fiber optics) and access links (e.g.,
   WiFi, cellular wireless, Digital Subscriber Lines (DSLs)).  Bits are
   transmitted across the Classical Internet in packets.

   Research and experiments have picked up over the last few years for
   developing the Quantum Internet [Wehner].  End-nodes will also be
   part of the Quantum Internet, in that case called quantum end-nodes
   that may be connected by quantum repeaters/routers.  These quantum
   end-nodes will also run value-added applications which will be
   discussed later.

   The connections between the various nodes in the Quantum Internet are
   expected to be primarily fiber optics and free-space optical lasers.
   Photonic connections are particularly useful because light (photons)
   is very suitable for physically realizing qubits.  Qubits are
   expected to be transmitted across the Quantum Internet.  The Quantum
   Internet will operate according to quantum physical principles such
   as quantum superposition and entanglement [I-D.irtf-qirg-principles].

   The Quantum Internet is not anticipated to replace, but rather to
   enhance the Classical Internet.  For instance, quantum key
   distribution can improve the security of the Classical Internet; the
   powerful computation capability of quantum computing can expedite and
   optimize computation-intensive tasks (e.g., routing modelling) in the
   Classical Internet.  The Quantum Internet will run in conjunction
   with the Classical Internet to form a new Hybrid Internet.  The
   process of integrating the Quantum Internet with the Classical
   Internet is similar to, but with more profound implications, as the
   process of introducing any new communication and networking paradigm
   into the existing Internet.  The intent of this document is to
   provide a common understanding and framework of applications and use
   cases for the Quantum Internet.

   This document represents the consensus of the Quantum Internet
   Research Group (QIRG).  It has been reviewed extensively by Research
   Group (RG) members with expertise in both quantum physics and
   Classical Internet operation.

2.  Terms and Acronyms List

   This document assumes that the reader is familiar with the quantum
   information technology related terms and concepts that are described
   in [I-D.irtf-qirg-principles].  In addition, the following terms and
   acronyms are defined herein for clarity:

   o  Bit - Binary Digit (i.e., fundamental unit of information in
      classical communications and classical computing).

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   o  Classical Internet - The existing, deployed Internet (circa 2020)
      where bits are transmitted in packets between nodes to convey
      information.  The Classical Internet supports applications which
      may be enhanced by the Quantum Internet.  For example, the end-to-
      end security of a Classical Internet application may be improved
      by secure communication setup using a quantum application.

   o  Entanglement Swapping: It is a process of sharing an entanglement
      between two distant parties via some intermediate nodes.  For
      example, suppose there are three parties A, B, C, and each of the
      parties (A, B) and (B, C) share EPR-pairs.  B can use the qubits
      it shares with A and C to perform entanglement swapping
      operations, and as a result, A and C share EPR-pairs.

   o  EPR-Pairs - A special type of two-qubits quantum states.  The two
      qubits show a correlation that cannot be observed in classical
      information theory.  We refer to such correlation as quantum
      entanglement.  EPR-pairs exhibit the maximal quantum entanglement.
      One example of an EPR-pair is (|00>+|11>)/(Sqrt(2)).  The EPR-
      pairs are a fundamental resource for quantum communication.

   o  Fast Byzantine Negotiation - A Quantum-based method for fast
      agreement in Byzantine negotiations [Ben-Or] [Taherkhani].

   o  Hybrid Internet - The "new" or evolved Internet to be formed due
      to a merger of the Classical Internet and the Quantum Internet.

   o  Local Operations and Classical Communication (LOCC) - A method
      where nodes communicate in rounds, in which (1) they can send any
      classical information to each other; (2) they can perform local
      quantum operations individually; and (3) the actions performed in
      each round can depend on the results from previous rounds.

   o  Noisy Intermediate-Scale Quantum (NISQ) - NISQ was defined in
      [Preskill] to represent a near-term era in quantum technology.
      According to this definition, NISQ computers have two salient
      features: (1) The size of NISQ computers range from 50 to a few
      hundred physical qubits (i.e., intermediate-scale); and (2) Qubits
      in NISQ computers have inherent errors and the control over them
      is imperfect (i.e., noisy).

   o  Packet - Formatted unit of multiple related bits.  The bits
      contained in a packet may be classical bits, or the measured state
      of qubits expressed in classical bits.

   o  Prepare-and-Measure - A set of Quantum Internet scenarios where
      quantum nodes only support simple quantum functionalities (i.e.,

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      prepare qubits and measure qubits).  For example, BB84 [BB84] is a
      prepare-and-measure quantum key distribution protocol.

   o  Quantum Computer (QC) - A quantum end-node that also has quantum
      memory and quantum computing capabilities is regarded as a full-
      fledged quantum computer.

   o  Quantum End-node - An end-node hosts user applications and
      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
      application.  If the end-node is part of a Quantum Network (i.e,
      is a quantum end-node), it must be able to generate/transmit and
      receive/process qubits.  A quantum end-node must also be able to
      interface to the Classical Internet for control purposes and thus
      also be able to receive, process, and transmit classical bits/
      packets.

   o  Quantum Key Distribution (QKD) - A method that leverages quantum
      mechanics such as no-cloning theorem to let two parties (e.g., a
      sender and a receiver) securely establish/agree on a key.

   o  Quantum Internet - A network of Quantum Networks.  The Quantum
      Internet is expected to be merged into the Classical Internet to
      form a new Hybrid Internet.  The Quantum Internet may either
      improve classical applications or may enable new quantum
      applications.

   o  Quantum Network - A new type of network enabled by quantum
      information technology where qubits are transmitted between nodes
      to convey information.  (Note: qubits must be sent individually
      and not in packets).  The Quantum Network will use both quantum
      channels, and classical channels provided by the Classical
      Internet.

   o  Quantum Teleportation - A technique for transferring quantum
      information via local operations and classical communication
      (LOCC).  If two parties share an EPR-pair, then using quantum
      teleportation a sender can transfer a quantum data bit to a
      receiver without sending it physically via a quantum communication
      channel.

   o  Qubit - Quantum Bit (i.e., fundamental unit of information in
      quantum communication and quantum computing).  It is similar to a
      classic bit in that the state of a qubit is either "0" or "1"
      after it is measured, and is denoted as its basis state vector |0>
      or |1>.  However, the qubit is different than a classic bit in
      that the qubit can be in a linear combination of both states
      before it is measured and termed to be in superposition.  The

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      Degrees of Freedom (DOF) of a photon (e.g., polarization) or an
      electron (e.g., spin) can be used to encode a qubit.

3.  Quantum Internet Applications

3.1.  Overview

   The Quantum Internet is expected to be beneficial for a subset of
   existing and new applications.  The expected applications for the
   Quantum Internet are still being developed as we are in the formative
   stages of the Quantum Internet [Castelvecchi] [Wehner].  However, an
   initial (and non-exhaustive) list of the applications to be supported
   on the Quantum Internet can be identified and classified using two
   different schemes.  Note, this document does not include quantum
   computing applications that are purely local to a given node (e.g.,
   quantum random number generator).

3.2.  Classification by Application Usage

   Applications may be grouped by the usage that they serve.
   Specifically, applications may be grouped according to the following
   categories:

   o  Quantum cryptography applications - Refers to the use of quantum
      information technology for cryptographic tasks such as quantum key
      distribution and quantum commitment.

   o  Quantum sensors applications - Refers to the use of quantum
      information technology for supporting distributed sensors (e.g.,
      clock synchronization).

   o  Quantum computing applications - Refers to the use of quantum
      information technology for supporting remote quantum computing
      facilities (e.g., distributed quantum computing).

   This scheme can be easily understood by both a technical and non-
   technical audience.  The next sections describe the scheme in more
   detail.

3.2.1.  Quantum Cryptography Applications

   Examples of quantum cryptography applications include quantum-based
   secure communication setup and fast Byzantine negotiation.

   1.  Secure communication setup - Refers to secure cryptographic key
       distribution between two or more end-nodes.  The most well-known
       method is referred to as Quantum Key Distribution (QKD) [Renner],
       which has been mathematically proven to be unbreakable.

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   2.  Fast Byzantine negotiation - Refers to a Quantum-based method for
       fast agreement in Byzantine negotiations [Ben-Or], for example,
       to reduce the number of expected communication rounds and in turn
       achieve faster agreement, in contrast to classical Byzantine
       negotiations.  A quantum aided Byzantine agreement on quantum
       repeater networks as proposed in [Taherkhani] includes
       optimization techniques to greatly reduce the quantum circuit
       depth and the number of qubits in each node.  Quantum-based
       methods for fast agreement in Byzantine negotiations can be used
       for improving consensus protocols such as practical Byzantine
       Fault Tolerance(pBFT), as well as other distributed computing
       features which use Byzantine negotiations.

   3.  Quantum money - The main security requirement of money is
       unforgeability.  A quantum money scheme aims to fulfill by
       exploiting the no-cloning property of the unknown quantum states.
       Though the original idea of quantum money dates back to 1970,
       these early protocols allow only the issuing bank to verify a
       quantum banknote.  However, the recent protocols that are called
       public-key quantum money [Zhandry] allow anyone to verify the
       banknotes locally.

3.2.2.  Quantum Sensor Applications

   The entanglement, superposition, interference, squeezing properties
   can enhance the sensitivity of the quantum sensors and eventually can
   outperform the classical strategies.  Examples of quantum sensor
   applications include network clock synchronization, high sensitivity
   sensing, quantum imaging, etc.  These applications mainly leverage a
   network of entangled quantum sensors (i.e. quantum sensor networks)
   for high-precision multi-parameter estimation [Proctor].

   1.  Network clock synchronization - Refers to a world wide set of
       atomic clocks connected by the Quantum Internet to achieve an
       ultra precise clock signal [Komar] with fundamental precision
       limits set by quantum theory.

   2.  High sensitivity sensing - Refers to applications that leverage
       quantum phenomena to achieve reliable nanoscale sensing of
       physical magnitudes.  For example, [Guo] uses an entangled
       quantum network for measuring the average phase shift among
       multiple distributed nodes.

   3.  Quantum imaging - The highly sensitive quantum sensors show great
       potential in improving the domain of magnetoencephalography.
       Unlike the current classical strategies, with the help of a
       network of quantum sensors, it is possible to measure the
       magnetic fields generated by the flow of current through neuronal

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       assemblies in the brain while the subject is moving.  It reveals
       the dynamics of the networks of neurons inside the human brain on
       a millisecond timescale.  This kind of imaging capability could
       improve the diagnosis and monitoring the conditions like
       attention-deficit-hyperactivity disorder [Hill].

3.2.3.  Quantum Computing Applications

   Examples of quantum computing include distributed quantum computing
   and secure quantum computing with privacy preservation, which can
   enable new types of cloud computing.

   1.  Distributed quantum computing - Refers to a collection of remote
       small capacity quantum computers (i.e., each supporting a
       relatively small number of qubits) that are connected and working
       together in a coordinated fashion so as to simulate a virtual
       large capacity quantum computer [Wehner].

   2.  Secure quantum computing with privacy preservation - Refers to
       private, or blind, quantum computation, which provides a way for
       a client to delegate a computation task to one or more remote
       quantum computers without disclosing the source data to be
       computed over [Fitzsimons].

   3.  Quantum chemistry - Quantum chemistry is one of the most
       promising quantum computing applications that can outperform the
       classical strategy using only a few hundred qubits quantum
       computers.  Using the NISQ devices, the quantum algorithms manage
       to determine the molecular energies of the small molecules within
       chemical accuracy [YudongCao].  However, due to the short
       coherence time of the quantum devices, it is still difficult to
       simulate larger molecules.

3.3.  Control vs Data Plane Classification

   The majority of routers currently used in the Classical Internet
   separate control plane functionality and data plane functionality
   for, amongst other reasons, stability, capacity and security.  In
   order to classify applications for the Quantum Internet, a somewhat
   similar distinction can be made.  Specifically some applications can
   be classified as being responsible for initiating sessions and
   performing other control plane functionality (including management
   functionalities too).  Other applications carry application or user
   data and can be classified as data plane functionality.

   Some examples of what may be called control plane applications in the
   Classical Internet are Domain Name Server (DNS), Session Information
   Protocol (SIP), and Internet Control Message Protocol (ICMP).

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   Furthermore, examples of data plane applications are E-mail, web
   browsing, and video streaming.  Note that some applications may
   require both control plane and data plane functionality.  For
   example, a Voice over IP (VoIP) application may use SIP to set up the
   call and then transmit the VoIP user packets over the data plane to
   the other party.

   Similarly, nodes in the Quantum Internet applications may also use
   the classification paradigm of control plane functionality versus
   data plane functionality where:

   o  Control Plane - Network functions and processes that operate on
      (1) control bits/packets or qubits (e.g., to setup up end-user
      encryption); or (2) management bits/packets or qubits (e.g., to
      configure nodes).  For example, a quantum ping could be
      implemented as a control plane application to test and verify if
      there is a quantum connection between two quantum nodes.  Another
      example is quantum superdense coding (which is used to transmit
      two classical bits by sending only one qubit).  This approach does
      not need classical channels.  Quantum superdense coding can be
      leveraged to implement a secret sharing application to share
      secrets between two parties [ChuanWang].  This secret sharing
      application based on quantum superdense encoding can be classified
      as control plane functionality.

   o  Data Plane - Network functions and processes that operate on end-
      user application bits/packets or qubits (e.g., voice, video,
      data).  Sometimes also referred to as the user plane.  For
      example, a data plane application can be video conferencing, which
      uses QKD-based secure communication setup (which is a control
      plane function) to share a classical secret key for encrypting and
      decrypting video frames.

   As shown in the table in Figure 1, control and data plane
   applications vary for different types of networks.  For a standalone
   Quantum Network (i.e., that is not integrated into the Internet),
   entangled qubits are its "data" and thus entanglement distribution
   can be regarded as its data plane application, while the signalling
   for controlling entanglement distribution be considered as control
   plane.  However, looking at the Quantum Internet, QKD-based secure
   communication setup, which may be based on and leverage entanglement
   distribution, is in fact a control plane application, while video
   conference using QKD-based secure communication setup is a data plane
   application.  In the future, two data planes may exist, respectively
   for Quantum Internet and Classical Internet, while one control plane
   can be leveraged for both Quantum Internet and Classical Internet.

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     +----------+-----------+----------------+----------------------+
     |          |           |                |                      |
     |          | Classical |    Quantum     |      Hybrid          |
     |          | Internet  |    Internet    |      Internet        |
     |          | Examples  |    Examples    |      Examples        |
     +----------+-----------+----------------+----------------------+
     |  Control | ICMP;     | Quantum ping;  | QKD-based secure     |
     |  Plane   | DNS       | Signalling for | communication        |
     |          |           | controlling    | setup                |
     |          |           | entanglement   |                      |
     |          |           | distribution;  |                      |
     ---------------------------------------------------------------|
     |  Data    | Video     | QKD;           | Video conference     |
     |  Plane   | conference| Entanglement   | using QKD-based      |
     |          |           | distribution   | secure communication |
     |          |           |                | setup                |
     +--------------------------------------------------------------+

        Figure 1: Examples of Control vs Data Plane Classification

4.  Selected Quantum Internet Use Cases

   The Quantum Internet will support a variety of applications and
   deployment configurations.  This section details a few key use cases
   which illustrates the benefits of the Quantum Internet.  In system
   engineering, a use case is typically made up of a set of possible
   sequences of interactions between nodes and users in a particular
   environment and related to a particular goal.  This will be the
   definition that we use in this section.

4.1.  Secure Communication Setup

   In this scenario, two banks (i.e., Bank #1 and Bank #2) need to have
   secure communications for transmitting important financial
   transaction records (see Figure 2).  For this purpose, they first
   need to securely share a classic secret cryptographic key (i.e., a
   sequence of classical bits), which is triggered by an end-user banker
   at Bank #1.  This results in a source quantum node A at Bank #1 to
   securely establish a classical secret key with a destination quantum
   node B at Bank #2.  This is referred to as a secure communication
   setup.  Note that the quantum node A and B may be either a bare-bone
   quantum end-node or a full-fledged quantum computer.  This use case
   shows that the Quantum Internet can be leveraged to improve the
   security of Classical Internet applications of which the financial
   application shown in Figure 2 is an example.

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   One requirement for this secure communication setup process is that
   it should not be vulnerable to any classical or quantum computing
   attack.  This can be realized using QKD which has been mathematically
   proven to be information-theoretically secureand unbreakable.  QKD
   can securely establish a secret key between two quantum nodes, using
   a classical authentication channel and insecure quantum communication
   channel without physically transmitting the key through the network
   and thus achieving the required security.  However, care must be
   taken to ensure that the QKD system is safe against physical side
   channel attacks which can compromise the system.  An example of a
   physical side channel attack is when an attacker is able to
   surreptitiously inject additional light into the optical devices used
   in QKD to learn side information about the system such as the
   polarization.  Other specialized physical attacks against QKD have
   also beusing a classical authentication channel and insecure quantum
   communication channelen developed such as the phase-remapping attack,
   photon number splitting attack, and decoy state attack [Zhao].

   QKD is the most mature feature of the quantum information technology,
   and has been commercially released in small-scale and short-distance
   deployments.  More QKD use cases are described in ETSI documents
   [ETSI-QKD-UseCases]; in addition, the ETSI document
   [ETSI-QKD-Interfaces] specifies interfaces between QKD users and QKD
   devices.

   In general, the prepare and measure QKD protocols (e.g., [BB84])
   without using entanglement works as follows:

   1.  The source quantum node A encodes classical bits to qubits.
       Basically, the source node A generates two random classical bit
       strings X, Y.  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 example, if X=0 then in case of BB84 protocol Alice
       prepares the state in {|0>, |1>}-basis; otherwise she prepares
       the state in {|+>, |->}-basis.  Similarly, if Y=0 then Alice
       prepares the qubit either |0> or |+> (depending on the value of
       X), and if Y =1, then Alice prepares the qubit either |1> or |->.

   2.  The source quantum node A sends qubits to the destination quantum
       node B via quantum channel.

   3.  The destination quantum node receives qubits and measures each of
       them in one of the two basis at random.

   4.  The destination quantum node informs the source node of its
       choice of basis for each qubit.

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   5.  The source quantum node informs the destination node which random
       quantum basis is correct.

   6.  Both nodes discard any measurement bit under different quantum
       basis and remaining bits could be used as the secret key.  Before
       generating the final secret key, there is a post-processing
       procedure over authenticated classical channels.  The classical
       post-processing part can be subdivided into three steps, namely
       parameter estimation, error-correction, and privacy
       amplification.  In the parameter estimation phase, both Alice and
       Bob use some of the bits to estimate the channel error.  If it is
       larger than some threshold value, then they abort the protocol
       otherwise move to the error-correction phase.  Basically, if an
       eavesdropper tries to intercept and read qubits sent from node A
       to node B, the eavesdropper will be detected due to the entropic
       uncertainty relation property theorem of quantum mechanics.  As a
       part of the post-processing procedure, both nodes usually also
       perform information reconciliation [Elkouss] for efficient error
       correction and/or conduct privacy amplification [BTang] for
       generating the final information-theoretical secure keys.

   7.  The post-processing procedure needs to be performed over an
       authenticated classical channel.  In other words, the source
       quantum node and the destination quantum node need to
       authenticate the classical channel to make sure there is no
       eavesdroppers or man-in-the-middle attacks, according to certain
       authentication protocols such as [Kiktenko].  In [Kiktenko], the
       authenticity of the classical channel is checked at the very end
       of the post-processing procedure instead of doing it for each
       classical message exchanged between the quantum source node and
       the quantum destination node.

   It is worth noting that:

   1.  There are some entanglement-based QKD protocols such as
       [Treiber], which work differently than above steps.  The
       entanglement-based schemes, where entangled states are prepared
       externally to the source quantum node and the destination quantum
       node, are not normally considered "prepare-and-measure" as
       defined in [Wehner]; other entanglement-based schemes, where
       entanglement is generated within the source quantum node can
       still be considered "prepare-and-measure"; send-and-return
       schemes can still be "prepare-and-measure", if the information
       content, from which keys will be derived, is prepared within the
       source quantum node the source quantum node before being sent to
       the destination quantum node for measurement.

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   2.  There are many enhanced QKD protocols based on [BB84].  For
       example, a series of loopholes have been identified due to the
       imperfections of measurement devices; there are several solutions
       to take into account these attacks such as measurement-device-
       independent QKD [PZhang].  These enhanced QKD protocols can work
       differently than the steps of BB84 protocol [BB84].

   3.  For large-scale QKD, QKD Networks (QKDN) are required, which can
       be regarded as a subset of a Quantum Internet.  A QKDN may
       consist of a QKD application layer, a QKD network layer, and a
       QKD link layer [Qin].  One or multiple trusted QKD relays
       [QZhang] may exist between the source quantum node A and the
       destination quantum node B, which are connected by a QKDN.
       Alternatively, a QKDN may rely on entanglement distribution and
       entanglement-based QKD protocols; as a result, quantum-repeaters/
       routers instead of trusted QKD relays are needed for large-scale
       QKD.

   4.  Although the addresses of Source Quantum Node A and Destination
       Quantum Node B could be identified and exposed, the identity of
       users, who will use the secret cryptographic key for secure
       communications, will not necessarily be exposed during QKD
       process.  In other words, there is no direct mapping from the
       addresses of quantum nodes to the user identity; as a result, QKD
       protocols do not disclose user identities.

   5.  QKD provides an information-theoretical way to share secret keys
       between two parties in the presence of Eve. However, this is true
       in theory, and there is a significant gap between theory and
       practice.  By exploiting the imperfection of the detectors Eve
       can gain information about the shared key [FeihuXu].  To avoid
       such side-channel attacks in [Lo], the researchers provide a QKD
       protocol called Measurement Device-Independent (MDI) QKD that
       allows two users (a transmitter "Alice" and a receiver "Bob") to
       communicate with perfect security, even if the (measurement)
       hardware they are using has been tampered with (e.g., by an
       eavesdropper) and thus is not trusted.  It is achieved by
       measuring correlations between signals from Alice and Bob rather
       than the actual signals themselves.

   6.  QKD protocols based on Continuous Variable (CV-QKD) have recently
       seen plenty of interest as it only requires telecommunications
       equipment that is readily available and is also in common use
       industry-wide.  This kind of technology is a potentially high-
       performance technique for secure key distribution over limited
       distances.  The recent demonstration of CV-QKD shows
       compatibility with classical coherent detection schemes that are

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       widely used for high bandwidth classical communication systems
       [Grosshans].

   As a result, the Quantum Internet in Figure 2 contains quantum
   channels.  And in order to support secure communication setup
   especially in large-scale deployment, it also requires entanglement
   generation and entanglement distribution
   [I-D.van-meter-qirg-quantum-connection-setup], quantum repeaters/
   routers, and/or trusted QKD relays.

        +---------------+
        |   End User    |
        |(e.g., Banker) |
        +---------------+
              ^
              | User Interface
              | (e.g., GUI)
              V
        +-----------------+     /--------\     +-----------------+
        |                 |--->( Quantum  )--->|                 |
        |     Source      |    ( Internet )    |  Destination    |
        |     Quantum     |     \--------/     |    Quantum      |
        |     Node A      |                    |     Node B      |
        | (e.g., Bank #1) |     /--------\     | (e.g., Bank #2) |
        |                 |    ( Classical)    |                 |
        |                 |<-->( Internet )<-->|                 |
        +-----------------+     \--------/     +-----------------+

                   Figure 2: Secure Communication Setup

4.2.  Secure Quantum Computing with Privacy Preservation

   Secure computation with privacy preservation refers to the following
   scenario:

   1.  A client node with source data delegates the computation of the
       source data to a remote computation node (i.e. a server).

   2.  Furthermore, the client node does not want to disclose any source
       data to the remote computation node and thus preserve the source
       data privacy.

   3.  Note that there is no assumption or guarantee that the remote
       computation node is a trusted entity from the source data privacy
       perspective.

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   As an example illustrated in Figure 3, a terminal node such as a home
   gateway has collected lots of data and needs to perform computation
   on the data.  The terminal node could be a classical node without any
   quantum capability, a bare-bone quantum end-node or a full-fledged
   quantum computer.  The terminal node has insufficient computing power
   and needs to offload data computation to some remote nodes.  Although
   the terminal node can upload the data to the cloud to leverage cloud
   computing without introducing local computing overhead, to upload the
   data to the cloud can cause privacy concerns.  In this particular
   case, there is no privacy concern since the source data will not be
   sent to the remote computation node which could be compromised.  Many
   protocols as described in [Fitzsimons] for delegated quantum
   computing or Blind Quantum Computation (BQC) can be leveraged to
   realize secure delegated computation and guarantee privacy
   preservation simultaneously.

   As a new client/server computation model, BQC generally enables: 1)
   The client delegates a computation function to the server; 2) The
   client does not send original qubits to the server, but send
   transformed qubits to the server; 3) The computation function is
   performed at the server on the transformed qubits to generate
   temporary result qubits, which could be quantum-circuit-based
   computation or measurement-based quantum computation.  The server
   sends the temporary result qubits to the client; 4) The client
   receives the temporary result qubits and transform them to the final
   result qubits.  During this process, the server can not figure out
   the original qubits from the transformed qubits.  Also, it will not
   take too much efforts 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 [Childs] follows this process, although the client
   needs some basic quantum features such as quantum memory, qubit
   preparation and measurement, and qubit transmission.  Measurement-
   based quantum computation is out of the scope of this document and
   more details about it can be found in [Jozsa].

   It is worth noting that:

   1.  The BQC protocol in [Childs] is a circuit-based BQC model, where
       the client only performs simple quantum circuit for qubit
       transformation, while the server performs a sequence of quantum
       logic gates.  Qubits are transmitted back and forth between the
       client and the server.

   2.  Universal BQC in [Broadbent] is a measurement-based BQC model,
       which is based on measurement-based quantum computing leveraging
       entangled states.  The principle in UBQC is based on the fact the
       quantum teleportation plus a rotated Bell measurement realizes a

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       quantum computation, which can be repeated multiple times to
       realize a sequence of quantum computation.  In this approach, the
       client first prepares transformed qubits and send them to the
       server and the server needs first to prepare entangled states
       from all received qubits.  Then, multiple interaction and
       measurement rounds happen between the client and the server.  For
       each round, the client computes and sends new measurement
       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 transform them to the final results.

   3.  A hybrid universal BQC is proposed in [XZhang], where the server
       performs both quantum circuits like [Childs] and quantum
       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
       client, which only needs to interact with the server using
       classical channel and communications.  [HHuang] demonstrates such
       an approach, where a classical client leverages two entangled
       servers to perform BQC, with the assumption that both servers can
       not communicate with each other; otherwise, the blindness or
       privacy of the client can not be guaranteed.  The scenario as
       demonstrated in [HHuang] is essentially an example of BQC with
       multiple servers.

   5.  How to verify that the server will perform what the client
       requests or expects is an important issue in many BQC protocols,
       referred to as verifiable BQC.  [Fitzsimons] discusses this issue
       and compares it in various BQC protocols.

   In Figure 3, the Quantum Internet contains quantum channels and
   quantum repeaters/routers for long-distance qubits transmission
   [I-D.irtf-qirg-principles].

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         +----------------+     /--------\     +----------------+
         |                |--->( Quantum  )--->|                |
         |                |    ( Internet )    |   Remote       |
         |   Terminal     |     \--------/     |   Computation  |
         |   Node         |                    |   Node         |
         |  (e.g., Home   |     /--------\     |   (e.g., QC    |
         |   Gateway)     |    ( Classical)    |   in Cloud)    |
         |                |<-->( Internet )<-->|                |
         +----------------+     \--------/     +----------------+

       Figure 3: Secure Quantum Computing with Privacy Preservation

4.3.  Distributed Quantum Computing

   There can be two types of distributed quantum computing [Denchev]:

   1.  Leverage quantum mechanics to enhance classical distributed
       computing problems.  For example, entangled quantum states can be
       exploited to improve leader election in classical distributed
       computing, by simply measuring the entangled quantum states at
       each party (e.g., a node or a device) without introducing any
       classical communications among distributed parties [Pal].
       Normally, pre-shared entanglement needs first be established
       among distributed parties, followed by LOCC operations at each
       party.  And it generally does not need to transmit qubits among
       distributed parties.

   2.  Distribute quantum computing functions to distributed quantum
       computers.  A quantum computing task or function (e.g., quantum
       gates) is split and distributed to multiple physically separate
       quantum computers.  And it may or may not need to transmit qubits
       (either inputs or outputs) among those distributed quantum
       computers.  Pre-shared entangled states may be needed to transmit
       quantum states among distributed quantum computers without using
       quantum communications, similar to quantum teleportation.  For
       example, [Yimsiriwattana] has proved that a 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.

   As a scenario for the second type of distributed quantum computing,
   Noisy Intermediate-Scale Quantum (NISQ) computers distributed in
   different locations are available for sharing.  According to the
   definition in [Preskill], a NISQ computer can only realize a small
   number of qubits and has limited quantum error correction.  In order
   to gain higher computation power before fully-fledged quantum
   computers become available, NISQ computers can be connected via

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   classic and quantum channels.  This scenario is referred to as
   distributed quantum computing [Caleffi] [Cacciapuoti01]
   [Cacciapuoti02].  This use case reflects the vastly increased
   computing power which quantum computers as a part of the Quantum
   Internet can bring, in contrast to classical computers in the
   Classical Internet, in the context of distributed quantum computing
   ecosystem [Cuomo].  According to [Cuomo], quantum teleportation
   enables a new communication paradigm, referred to as teledata
   [VanMeter01], which moves quantum states among qubits to distributed
   quantum computers.  In addition, distributed quantum computation also
   needs the capability of remotely performing quantum computation on
   qubits on distributed quantum computers, which can be enabled by the
   technique called telegate [VanMeter02].

   As an example, scientists can leverage these connected NISQ computer
   to solve highly complex scientific computation problems such as
   analysis of chemical interactions for medical drug development [Cao]
   (see Figure 4).  In this case, qubits will be transmitted among
   connected quantum computers via quantum channels, while classic
   control messages will be transmitted among them via classical
   channels for coordination and control purpose.  Another example of
   distributed quantum computing is secure Multi-Party Quantum
   Computation (MPQC) [Crepeau], which can be regarded as a quantum
   version of classical secure Multi-Party Computing (MPC).  In secure
   MPQC, multiple participants jointly perform quantum computation on a
   set of input quantum states, which are prepared and provided by
   different participants.  One of primary aims of secure MPQC is to
   guarantee that each participant will not know input quantum states
   provided by other participants.  Secure MPQC relies on verifiable
   quantum secret sharing [Lipinska].

   For the example shown in Figure 4, qubits from one NISQ computer to
   another NISQ computer are very sensitive and should not be lost.  For
   this purpose, quantum teleportation can be leveraged to teleport
   sensitive data qubits from one quantum computer A to another quantum
   computer B.  Note that Figure 4 does not cover measurement-based
   distributed quantum computing, where quantum teleportation may not be
   required.  When quantum teleportation is employed, the following
   steps happen between A and B.  In fact, LOCC [Chitambar] operations
   are conducted at the quantum computer A and B in order to achieve
   quantum teleportation as illustrated in Figure 4.

   1.  The quantum computer A locally generates some sensitive data
       qubits to be teleported to the quantum computer B.

   2.  A shared entanglement is established between the quantum computer
       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

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       A can generate two entangled qubits (i.e., q1 and q2) and sends
       q2 to the quantum computer B via quantum communications.

   3.  Then, the quantum computer A performs a Bell measurement of the
       entangled qubit q1 and the sensitive data qubit.

   4.  The result from this Bell measurement will be encoded in two
       classical bits, which will be physically transmitted via a
       classical channel to 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
       generate a new qubit identical to the sensitive data qubit at the
       quantum computer A.

   In Figure 4, the Quantum Internet contains quantum channels and
   quantum repeaters/routers [I-D.irtf-qirg-principles].  This use case
   needs to support entanglement generation and entanglement
   distribution (or quantum connection) setup
   [I-D.van-meter-qirg-quantum-connection-setup] in order to support
   quantum teleportation.

                           +-----------------+
                           |     End-User    |
                           |(e.g., Scientist)|
                           +-----------------+
                                    ^
                                    |User Interface (e.g. GUI)
                                    |
                 +------------------+-------------------+
                 |                                      |
                 |                                      |
                 V                                      V
         +----------------+     /--------\     +----------------+
         |                |--->( Quantum  )--->|                |
         |                |    ( Internet )    |                |
         |   Quantum      |     \--------/     |   Quantum      |
         |   Computer A   |                    |   Computer B   |
         | (e.g., Site #1)|     /--------\     | (e.g., Site #2)|
         |                |    ( Classical)    |                |
         |                |<-->( Internet )<-->|                |
         +----------------+     \--------/     +----------------+

                  Figure 4: Distributed Quantum Computing

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5.  General Requirements

5.1.  Background

   Quantum technologies are steadily evolving and improving.  Therefore,
   it is hard to predict the timeline and future milestones of quantum
   technologies as pointed out in [Grumbling] for quantum computing.
   Currently, a NISQ computer can achieve fifty to hundreds of qubits
   with some given error rate.  In fact, the error rates of two-qubit
   quantum gates have decreased nearly in half every 1.5 years (for
   trapped ion gates) to 2 years (for superconducting gates).  The error
   rate also increases as the number of qubits increases.  For example,
   a current 20-physical-qubit machine has a total error rate which is
   close to the total error rate of a 7 year old two-qubit machine
   [Grumbling].

   On the network level, six stages of Quantum Internet development are
   described in [Wehner] as follows:

   1.  Trusted repeater networks (Stage-1)

   2.  Prepare and measure networks (Stage-2)

   3.  Entanglement distribution networks (Stage-3)

   4.  Quantum memory networks (Stage-4)

   5.  Fault-tolerant few qubit networks (Stage-5)

   6.  Quantum computing networks (Stage-6)

   The first stage are simple trusted repeater networks, while the final
   stage are quantum computing networks where the full-blown Quantum
   Internet will be achieved.  Each intermediate stage brings with it
   new functionality, new applications, and new characteristics.
   Figure 5 illustrates Quantum Internet use cases as described in this
   document mapped to the Quantum Internet stages described in [Wehner].
   For example, secure communication setup can be supported in Stage-1,
   Stage-2, or Stage-3, but with different QKD solutions.  More
   specifically:

   In Stage-1, basic QKD is possible and can be leveraged to support
   secure communication setup but trusted nodes are required to provide
   end-to-end security.  The primary requirement is trusted nodes.

   In Stage-2, the end users can prepare receive and measure qubits.  In
   this stage the users can verify classical passwords without revealing
   it.

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   In Stage-3, end-to-end security can be enabled based on quantum
   repeaters and entanglement distribution, to support the same secure
   communication setup application.  The primary requirement is
   entanglement distribution to enable long-distance QKD.

   In Stage-4, the quantum repeaters gain the capability of storing and
   manipulating entangled qubits in the quantum memories.  Using these
   kind of quantum networks one can run sophisticated applications like
   blind quantum computing, leader election, quantum secret sharing.

   In Stage-5, quantum repeaters can perform error correction; hence
   they can perform fault-tolerant quantum computations on the received
   data.  With the help of these repeaters, it is possible to run
   distributed quantum computing and quantum sensor applications over a
   smaller number of qubits.

   Finally, in Stage-6, distributed quantum computing relying on more
   qubits can be supported.

     +---------+----------------------------+------------------------+
     | Quantum |     Example Quantum        |                        |
     | Internet|      Internet Use          |   Characteristic       |
     | Stage   |         Cases              |                        |
     +---------+----------------------------+------------------------+
     | Stage-1 | Secure comm setup          |  Trusted nodes         |
     |         | using basic QKD            |                        |
     |---------------------------------------------------------------|
     | Stage-2 | Secure comm setup          |  Prepare-and-measure   |
     |         | using the QKD with         |       capability       |
     |         | end-to-end security        |                        |
     |---------------------------------------------------------------|
     | Stage-3 | Secure comm setup          |  Entanglement          |
     |         | using entanglement-enabled |  distribution          |
     |         | QKD                        |                        |
     |---------------------------------------------------------------|
     | Stage-4 | Secure/blind quantum       |  Quantum memory        |
     |         | computing                  |                        |
     |---------------------------------------------------------------|
     | Stage-5 | Higher-Accuracy Clock      |  Fault tolerance       |
     |         | synchronization            |                        |
     |---------------------------------------------------------------|
     | Stage-6 | Distributed quantum        |  More qubits           |
     |         | computing                  |                        |
     +---------------------------------------------------------------+

     Figure 5: Example Use Cases in Different Quantum Internet Stages

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5.2.  Requirements

   Some general and functional requirements on the Quantum Internet from
   the networking perspective, based on the above applications and use
   cases, are identified as follows:

   1.  Methods for facilitating quantum applications to interact
       efficiently with entanglement qubits are necessary in order for
       them to trigger distribution of designated entangled qubits to
       potentially any other quantum node residing in the Quantum
       Internet.  To accomplish this specific operations must be
       performed on entangled qubits (e.g., entanglement swapping,
       entanglement distillation).  Quantum nodes may be quantum end-
       nodes, quantum repeaters/routers, and/or quantum computers.

   2.  Quantum repeaters/routers should support robust and efficient
       entanglement distribution in order to extend and establish high-
       fidelity entanglement connection between two quantum nodes.  For
       achieving this, it is required to first generate an entangled
       pair on each hop of the path between these two nodes, and then
       perform entanglement swapping operations at each of the
       intermediate nodes.

   3.  Quantum end-nodes must send additional information on classical
       channels to aid in transmission of qubits across quantum
       repeaters/receivers.  This is because qubits are transmitted
       individually and do not have any associated packet overhead which
       can help in transmission of the qubit.  Any extra information to
       aid in routing, identification, etc., of the qubit(s) must be
       sent via classical channels.

   4.  Methods for managing and controlling the Quantum Internet
       including quantum nodes and their quantum resources are
       necessary.  The resources of a quantum node may include quantum
       memory, quantum channels, qubits, established quantum
       connections, etc.  Such management methods can be used to monitor
       network status of the Quantum Internet, diagnose and identify
       potential issues (e.g. quantum connections), and configure
       quantum nodes with new actions and/or policies (e.g. to perform a
       new entanglement swapping operation).  New management information
       model for the Quantum Internet may need to be developed.

6.  Conclusion

   This document provides an overview of some expected applications for
   the Quantum Internet, and then details selected use cases.  The
   applications are first grouped by their usage which is a natural and
   easy to understand classification scheme.  The applications are also

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   classified as either control plane or data plane functionality as
   typical for the Classical Internet.  This set of applications may, of
   course, naturally expand over time as the Quantum Internet matures.
   Finally, some general requirements for the Quantum Internet are also
   provided.

   This document can also serve as an introductory text to readers
   interested in learning about the practical uses of the Quantum
   Internet.  Finally, it is hoped that this document will help guide
   further research and development of the Quantum Internet
   functionality required to implement the applications and uses cases
   described herein.

7.  IANA Considerations

   This document requests no IANA actions.

8.  Security Considerations

   This document does not define an architecture nor a specific protocol
   for the Quantum Internet.  It focuses instead on detailing use cases,
   requirements, and describing typical Quantum Internet applications.
   However, some salient observations can be made regarding security of
   the Quantum Internet as follows.

   It has been identified in [NISTIR8240] that once large-scale quantum
   computing becomes reality that it will be able to break many of the
   public-key (i.e., asymmetric) cryptosystems currently in use.  This
   is because of the increase in computing ability with quantum
   computers for certain classes of problems (e.g., prime factorization,
   optimizations).  This would negatively affect many of the security
   mechanisms currently in use on the Classical Internet which are based
   on public-key (Diffie-Hellman) encryption.  This has given strong
   impetus for starting development of new cryptographic systems that
   are secure against quantum computing attacks [NISTIR8240].

   Interestingly, development of the Quantum Internet will also mitigate
   the threats posed by quantum computing attacks against Diffie-Hellman
   based public-key cryptosystems.  Specifically, the secure
   communication setup feature of the Quantum Internet as described in
   Section 4.1 will be strongly resistant to both classical and quantum
   computing attacks against Diffie-Hellman based public-key
   cryptosystems.

   A key additional threat consideration for the Quantum Internet is
   pointed to by [RFC7258], which warns of the dangers of pervasive
   monitoring as a widespread attack on privacy.  Pervasive monitoring
   is defined as a widespread, and usually covert, surveillance through

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   intrusive gathering of application content or protocol metadata such
   as headers.  This can be accomplished through active or passive
   wiretaps, traffic analysis, or subverting the cryptographic keys used
   to secure communications.

   The secure communication setup feature of the Quantum Internet as
   described in Section 4.1 will be strongly resistant to pervasive
   monitoring based on directly attacking (Diffie-Hellman) encryption
   keys.  Also, Section 4.2 describes a method to perform remote quantum
   computing while preserving the privacy of the source data.  Finally,
   the intrinsic property of qubits to decohere if they are observed,
   albeit covertly, will theoretically allow detection of unwanted
   monitoring in some future solutions.

9.  Acknowledgments

   The authors want to thank Michele Amoretti, Mathias Van Den Bossche,
   Xavier de Foy, Patrick Gelard, Alvaro Gomez Inesta, Wojciech
   Kozlowski, John Mattsson, Rodney Van Meter, Joey Salazar, and Joseph
   Touch, and the rest of the QIRG community as a whole for their very
   useful reviews and comments to the document.

10.  Informative References

   [BB84]     Bennett, C. and G. Brassard, "Quantum Cryptography: Public
              Key Distribution and Coin Tossing", 1984,
              <http://researcher.watson.ibm.com/researcher/files/us-
              bennetc/BB84highest.pdf>.

   [Ben-Or]   Ben-Or, M. and A. Hassidim, "Fast Quantum Byzantine
              Agreement", SOTC, ACM, 2005,
              <https://dl.acm.org/doi/10.1145/1060590.1060662>.

   [Broadbent]
              Broadbent, A. and et. al., "Universal Blind Quantum
              Computation", 50th Annual Symposium on Foundations of
              Computer Science, IEEE, 2009,
              <https://arxiv.org/pdf/0807.4154.pdf>.

   [BTang]    Tang, B. and et. al., "High-speed and Large-scale Privacy
              Amplification Scheme for Quantum Key Distribution",
              Scientific Reports, Nature Research, 2019,
              <https://doi.org/10.1038/s41598-019-50290-1>.

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   [Cacciapuoti01]
              Cacciapuoti, A. and et. al., "Quantum Internet: Networking
              Challenges in Distributed Quantum Computing", IEEE
              Network, January 2020, 2020,
              <https://ieeexplore.ieee.org/document/8910635>.

   [Cacciapuoti02]
              Cacciapuoti, A. and et. al., "When Entanglement meets
              Classical Communications: Quantum Teleportation for the
              Quantum Internet", 2019,
              <https://arxiv.org/abs/1907.06197>.

   [Caleffi]  Caleffi, M. and et. al., "Quantum internet: From
              Communication to Distributed Computing!", NANOCOM, ACM,
              2018, <https://dl.acm.org/doi/10.1145/3233188.3233224>.

   [Cao]      Cao, Y. and et. al., "Potential of Quantum Computing for
              Drug Discovery", Journal of Research and Development, IBM,
              2018, <https://doi.org/10.1147/JRD.2018.2888987>.

   [Castelvecchi]
              Castelvecchi, D., "The Quantum Internet has arrived (and
              it hasn't)", Nature 554, 289-292, 2018,
              <https://www.nature.com/articles/d41586-018-01835-3>.

   [Childs]   Childs, A., "Secure Assisted Quantum Computation", 2005,
              <https://arxiv.org/pdf/quant-ph/0111046.pdf>.

   [Chitambar]
              Chitambar, E. and et. al., "Everything You Always Wanted
              to Know About LOCC (But Were Afraid to Ask)",
              Communications in Mathematical Physics, Springer, 2014,
              <https://link.springer.com/article/10.1007/
              s00220-014-1953-9>.

   [ChuanWang]
              Wang, C. and et. al., "Quantum Secure Direct Communication
              with High-Dimension Quantum Superdense Coding", Physical
              Review A, American Physical Society, 2005,
              <https://doi.org/10.1103/PhysRevA.71.044305>.

   [Crepeau]  Crepeau, C. and et. al., "Secure Multi-party Quantum
              Computation", 34th Symposium on Theory of Computing
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Authors' Addresses

   Chonggang Wang
   InterDigital Communications, LLC
   1001 E Hector St
   Conshohocken  19428
   USA

   Email: Chonggang.Wang@InterDigital.com

   Akbar Rahman
   InterDigital Communications, LLC
   1000 Sherbrooke Street West
   Montreal  H3A 3G4
   Canada

   Email: rahmansakbar@yahoo.com

   Ruidong Li
   Kanazawa University
   4-2-1 Nukui-Kitamachi
   Kakuma-machi, Kanazawa City  920-1192
   Japan

   Email: lrd@se.kanazawa-u.ac.jp

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   Melchior Aelmans
   Juniper Networks
   Boeing Avenue 240
   Schiphol-Rijk  1119 PZ
   The Netherlands

   Email: maelmans@juniper.net

   Kaushik Chakraborty
   The University of Edinburgh
   10 Crichton Street
   Edinburgh  EH8 9AB, Scotland
   UK

   Email: kchakrab@exseed.ed.ac.uk

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