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QIRG                                                             C. Wang
Internet-Draft                                                 A. Rahman
Intended status: Informational          InterDigital Communications, LLC
Expires: July 18, 2020                                  January 15, 2020

          Applications and Use Cases for the Quantum Internet


   The Quantum Internet has the potential to improve Internet protocol
   and application functionality by incorporating quantum information
   technology into the infrastructure of the overall Internet.  In this
   document, we provide an overview of some applications expected to be
   used on the Quantum Internet, and then categorize them using the
   standard telecommunications classification of control plane versus
   data plane functionality.  We then provide detailed use cases for
   selected applications which can help steer the development of the
   requisite Quantum Internet functionality.

Status of This Memo

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   This Internet-Draft will expire on July 18, 2020.

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Terms and Acronyms List . . . . . . . . . . . . . . . . . . .   3
   4.  Overview of Quantum Internet Applications . . . . . . . . . .   4
   5.  Selected Quantum Internet Use Cases . . . . . . . . . . . . .   5
     5.1.  Secure Communication Setup  . . . . . . . . . . . . . . .   6
     5.2.  Distributed Quantum Computing . . . . . . . . . . . . . .   7
     5.3.  Secure Quantum Computing with Privacy Preservation  . . .   9
   6.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   10. Informative References  . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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.  The end-nodes run
   applications that provide some value added service for the end-users
   such as processing and transmission of voice, video or data.  The
   physical connections between the various nodes in the Internet
   include Digital Subscriber Lines (DSLs), fiber optics, etc.  Bits are
   transmitted across the classical Internet in packets.

   Research and experimentation have picked up over the last few years
   for developing a Quantum Internet [Wehner].  It is anticipated that
   the Quantum Internet will provide intrinsic benefits such as better
   end-user and network security.  The Quantum Internet will have end-
   nodes, which must be quantum computers, connected by quantum
   repeaters/routers.  These quantum computer end-nodes will also run
   value-added applications which will be discussed later.  The physical
   connections between the various nodes in the Quantum Internet are
   expected to be primarily fiber optics and free-space optics.  Unlike
   the classical Internet, qubits (and not classical bits or packets)
   are expected to be transmitted across the Quantum Internet due to the
   underlying physics [I-D.irtf-qirg-principles].

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   The Quantum Internet is not anticipated to replace the classical
   Internet.  Instead the Quantum Internet will be integrated into 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.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  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 here for clarity:

   o  Bit - Binary Digit (i.e., fundamental unit of information in a
      classical computer).

   o  Classical Internet - The existing, deployed Internet (circa 2020)
      where bits are transmitted in packets between nodes to convey

   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).

   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.

   o  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 the Quantum Internet it must be a
      quantum computer and be able to transmit and receive qubits.  It
      may optionally also interface to the classical Internet and thus
      be able to transmit and receive classical bits/packets.

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

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   o  NISQ - Noisy Intermediate-Scale Quantum

   o  Packet - Formatted unit of multiple related bits.

   o  Quantum Internet - 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 Internet will be merged into the
      classical Internet to form a new hybrid Internet.

   o  QC - Quantum Computer

   o  QKD - Quantum Key Distribution

   o  Qubit - Quantum Bit (i.e., fundamental unit of information in a
      quantum computer).  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 |0> or |1>.  However, the qubit is
      different than a classic bit in that the qubit is in a linear
      combination of both states before it is measured and termed to be
      in superposition.  A photon or an electron can be used to
      represent a qubit.

4.  Overview of Quantum Internet Applications

   The Quantum Internet is expected to be extremely beneficial for a
   subset of existing and new applications.  We use "applications" in
   the widest sense of the word and include functionality typically
   contained in Layers 4 (Transport) to Layers 7 (Application) of the
   Open System Interconnect (OSI) model.

   The expected applications are still being developed as we are in the
   formative stages of the Quantum Internet [Castelvecchi] [Wehner].
   However, a tentative (and non-exhaustive) list of the applications to
   be supported on the Quantum Internet can be identified and classified
   as below.  From the list it is clear that a variety of control plane
   and data plane applications will run on the Quantum Internet.

   Control Plane Applications using Quantum Internet:

   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 QKD [Renner].

   2.  Fast Byzantine negotiation - Refers to a quantum network based
       method for fast agreement in Byzantine negotiations [Fitzi].
       This can be used for the popular financial blockchain feature as

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       well as other distributed computing features which use Byzantine

   3.  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].

   4.  Position verification - Refers to a method for an end-node to
       prove that it is at a particular location to, for example, access
       a specific service [Unruh].

   Data Plane Applications using Quantum Internet:

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

   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].

   It is also important to understand which applications will not be
   supported on the Quantum Internet.  Many existing applications have
   no clear advantage if transmitted over the Quantum Internet and so
   are not expected to be migrated there.  Key examples are Voice over
   IP (VoIP) calls, streaming video sessions, and web browsing sessions.
   These applications usually have a real-time human end-user and/or
   involve high bandwidth content transmission.  These applications are
   better suited to remain on the classical Internet.

   A given end-node may need to support both a classical Internet
   interface and a Quantum Internet interface as will be illustrated in
   some of the use cases below.

5.  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.
   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.

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5.1.  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 1).  For this purpose, they first
   need to securely exchange 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 send a classic secret key to a destination quantum node B at
   Bank #2.  This is referred to as a secure communication setup.

   One requirement for this secure communication setup process is that
   it should not be vulnerable to any classic or quantum computing
   attack.  This can be realized using QKD [ETSI-QKD].  QKD can securely
   distribute a secret key between two quantum nodes, without physically
   transmitting it through the network and thus achieving the required
   security.  QKD is the most mature feature of the quantum information
   technology, and has been commercially deployed in small-scale and
   short-distance deployments.

   In general, QKD (e.g., [BB84]) without using entanglement works as

   1.  The source quantum node A transforms the secret key to qubits.
       Basically, for each classical bit in the secret key, the source
       quantum node A randomly selects one quantum computational basis
       and uses it to prepare/generate a qubit for the classical bit.

   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 them
       based on its random quantum basis.

   4.  The destination quantum node sends the measurement results (i.e.,
       classic bits) to the source quantum node via any public classic

   5.  Both the source node and the destination node inform each other's
       random quantum basis.

   6.  Both nodes discard any measurement bit under different quantum
       basis and store all remaining bits as the secret key.

   Note that there are some entanglement-based QKD protocols such as
   [Treiber], which work differently than above steps.  In addition, For
   large-scale QKD, one or multiple trusted QKD relays [Zhang] may exist
   between the source quantum node A and the destination quantum node B.

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   As a result, the Quantum Internet in Figure 1 may contain quantum
   channels, quantum repeaters/routers [I-D.irtf-qirg-principles], and/
   or trusted QKD relays.

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

                   Figure 1: Secure Communication Setup

5.2.  Distributed Quantum Computing

   In this scenario, 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 classic and quantum channels.

   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 (see
   Figure 2).  In this case, qubits will be transmitted among connected
   quantum computers via quantum channels, while classic control
   messages will be transmitted among them via classic channels for
   coordination and control purpose . Qubits from one NISQ computer to
   another NISQ computer are very sensitive and cannot be lost.  For
   this purpose, quantum teleportation can be leveraged to teleport

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   sensitive data qubits from one quantum computer A to another quantum
   computer B.

   Specifically, the following steps happen between A and B:

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

   2.  The quantum computer A first establishes a shared entanglement
       with the quantum computer B (i.e., there are two entangled
       bits: |q1> at A and |q2> at B).

   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
       classic bits, which will be physically transmitted via a classic
       channel to the quantum computer B.

   5.  Based on the received two classic 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 2, the Quantum Internet contains quantum channels and
   quantum repeaters/routers [I-D.irtf-qirg-principles].

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                           |     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 2: Distributed Quantum Computing

5.3.  Secure Quantum Computing with Privacy Preservation

   Secure computation with privacy preservation refers to the scenario:

   1.  A client node with source data delegates the computation of the
       source data to a remote computation node.

   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

   As an example illustrated in Figure 3, the client node could be a
   virtual voice-controlled home assistant device like Amazon's Alexa
   product.  The remote computation node could be a quantum computer in
   the cloud.  A resident as an end-user uses voice to control the home
   device.  The home device captures voice-based commands from the end-
   user.  Then, the home device interfaces to a home quantum terminal
   node (e.g., a home gateway), which interacts with the remote
   computation node to perform computation over the captured voice-based

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   In this particular case, there is no privacy concern since the source
   data (i.e., captured voice-based commands) will not be sent to the
   remote computation node which could be compromised.  Protocols
   [Fitzsimons] for delegated quantum computing or blind quantum
   computation can be leveraged to realize secure delegated computation
   and guarantee privacy preservation simultaneously.  Using delegated
   quantum computing protocols, the client node does not need send the
   source data but qubits with some measurement instructions to the
   remote computation node (e.g., a quantum computer).

   After receiving qubits and measurement instructions, the remote
   computation node performs the following actions:

   1.  It first performs certain quantum operations on received qubits
       and measure them according to received measurement instructions
       to generate computation results (in classic bits).

   2.  Then it sends the computation results back to the client node via
       classic channel.

   3.  In this process, the source data is not disclosed to the remote
       computation node and the privacy is preserved.

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

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         |   End-User     |
         |(e.g., Resident)|
                 | User Interface
                 | (e.g., voice commands)
         |   Home Device  |
                 | Classic
                 | Channel
         +----------------+     /--------\     +----------------+
         |                |--->( Quantum  )--->|                |
         |   Quantum      |    ( Internet )    |   Remote       |
         |   Terminal     |     \--------/     |   Computation  |
         |   Node         |                    |   Node         |
         |  (e.g., Home   |     /--------\     |   (e.g., QC    |
         |   Gateway)     |    ( Classical)    |   in Cloud)    |
         |                |<-->( Internet )<-->|                |
         +----------------+     \--------/     +----------------+

          Figure 3: Secure Computation with Privacy Preservation

6.  Conclusion

   This document provides an overview of some expected applications for
   the Quantum Internet and details selected use cases.  One key take
   away is that a variety of control plane applications will run on the
   Quantum Internet.  In contrast, the data plane applications running
   on the Quantum Internet will be focused on supporting different forms
   of remote quantum computing.  This set of applications may, of
   course, naturally expand over time as the Quantum Internet matures.

   This document can also serve as an introductory text to persons
   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 specific Quantum Internet
   functionality required to implement the applications and uses cases
   described herein.

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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 on detailing use cases and
   describing typical Quantum Internet applications.  However, some
   useful observations can be made regarding security as follows.

   It has been clearly identified that once large-scale quantum
   computing becomes reality it will be able to theoretically break many
   of the public-key (i.e., asymmetric) cryptosystems currently in use
   because of the exponential increase of computing power with quantum
   computing.  This would negatively affect many of the security
   mechanisms currently in use on the classic Internet.  This has given
   strong impetus for starting development of new cryptographic systems
   that are secure against quantum computing attacks [NISTIR8240].

   Paradoxically, development of a Quantum Internet will also mitigate
   the threats posed by quantum computing attacks against public-key
   cryptosystems.  Specifically, the secure communication setup feature
   of the Quantum Internet as described in Section 5.1 will be strongly
   resistant to both classical and quantum computing attacks.

   Finally, Section 5.3 provides a method to perform remote quantum
   computing while preserving the privacy of the source data.

9.  Acknowledgments

   The authors want to thank Xavier de Foy for his very useful review
   and comments to the document.

10.  Informative References

   [BB84]     Bennett, C. and G. Brassard, "Quantum Cryptography: Public
              Key Distribution and Coin Tossing", 1984,

              Castelvecchi, D., "The Quantum Internet has arrived (and
              it hasn't)", Nature 554, 289-292, 2018,

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              ETSI GR QKD 003 V2.1.1, "Quantum Key Distribution (QKD):
              Components and Internal Interfaces", 2018,

   [Fitzi]    Fitzi, M. and et. al., "A Quantum Solution to the
              Byzantine Agreement Problem", 2001,

              Fitzsimons, J., "Private Quantum Computation: An
              Introduction to Blind Quantum Computing and Related
              Protocols", 2017,

              Dahlberg, A., Skrzypczyk, M., and S. Wehner, "The Link
              Layer service in a Quantum Internet", draft-dahlberg-ll-
              quantum-03 (work in progress), October 2019.

              Kozlowski, W., Wehner, S., Meter, R., and B. Rijsman,
              "Architectural Principles for a Quantum Internet", draft-
              irtf-qirg-principles-02 (work in progress), November 2019.

              Meter, R. and T. Matsuo, "Connection Setup in a Quantum
              Network", draft-van-meter-qirg-quantum-connection-setup-01
              (work in progress), September 2019.

   [Komar]    Komar, P. and et. al., "A Quantum Network of Clocks",
              2013, <https://arxiv.org/pdf/1310.6045.pdf>.

              Alagic, G. and et. al., "Status Report on the First Round
              of the NIST Post-Quantum Cryptography Standardization
              Process", NISTIR 8240, 2019,

              Preskill, J., "Quantum Computing in the NISQ Era and
              Beyond", 2018, <https://arxiv.org/pdf/1801.00862>.

   [Renner]   Renner, R., "Security of Quantum Key Distribution", 2006,

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [Treiber]  Treiber, A. and et. al., "A Fully Automated Entanglement-
              based Quantum Cyptography System for Telecom Fiber
              Networks", New Journal of Physics, 11, 045013, 2009,

   [Unruh]    Unruh, D., "Quantum Position Verification in the Random
              Oracle Model", 2014, <https://link.springer.com/content/

              Van Meter, R. and S. Devitt, "Quantum internet: A vision
              for the road ahead", IEEE 49, 2016,

   [Wehner]   Wehner, S., Elkouss, D., and R. Hanson, "Quantum internet:
              A vision for the road ahead", Science 362, 2018,

   [Zhang]    Zhang, Q., Hu, F., Chen, Y., Peng, C., and J. Pan, "Large
              Scale Quantum Key Distribution: Challenges and Solutions",
              Optical Express, OSA, 2018,

Authors' Addresses

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

   Email: Chonggang.Wang@InterDigital.com

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

   Email: rahmansakbar@yahoo.com

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