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QIRG                                                             C. Wang
Internet-Draft                                                 A. Rahman
Intended status: Informational          InterDigital Communications, LLC
Expires: November 25, 2020                                         R. Li
                                                              M. Aelmans
                                                        Juniper Networks
                                                            May 24, 2020

          Applications and Use Cases for the Quantum Internet


   The Quantum Internet has the potential to improve Internet
   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 various
   classification schemes.  Some general requirements for the Quantum
   Internet are also discussed.  The intent of this document is to
   provide a common understanding and framework of applications and use
   cases for the Quantum Internet.

Status of This Memo

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   This Internet-Draft will expire on November 25, 2020.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Terms and Acronyms List . . . . . . . . . . . . . . . . . . .   3
   4.  Quantum Internet Applications . . . . . . . . . . . . . . . .   5
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  Classification by Application Usage . . . . . . . . . . .   5
       4.2.1.  Quantum Cryptography Applications . . . . . . . . . .   6
       4.2.2.  Quantum Sensor Applications . . . . . . . . . . . . .   6
       4.2.3.  Quantum Computing Applications  . . . . . . . . . . .   6
     4.3.  Control vs Data Plane Classification  . . . . . . . . . .   7
   5.  Selected Quantum Internet Use Cases . . . . . . . . . . . . .   8
     5.1.  Secure Communication Setup  . . . . . . . . . . . . . . .   8
     5.2.  Distributed Quantum Computing . . . . . . . . . . . . . .  11
     5.3.  Secure Quantum Computing with Privacy Preservation  . . .  12
   6.  General Requirements  . . . . . . . . . . . . . . . . . . . .  14
   7.  Conclusion  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  16
   11. Informative References  . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

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 may run
   applications that provide service for the end-users such as
   processing and transmission of voice, video or data.  The connections
   between the various nodes in the Internet include Digital Subscriber
   Lines (DSLs), fiber optics, coax cable and wireless that include
   Bluetooth, WiFi, cellular (e.g., 3G, 4G, 5G), and satellite, etc.
   Bits are transmitted across the Classical Internet in packets.

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   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-to-end and network security.  The Quantum Internet will also have
   end-nodes, termed quantum end-nodes.  Quantum end-nodes 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 optics.
   Photonic connections are particularly useful because light (photons)
   is very suitable for physically encoding qubits.  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.  The Quantum Internet will operate according to
   unique physical principles such as quantum superposition,
   entanglement and teleportation [I-D.irtf-qirg-principles].

   The Quantum Internet is not anticipated to replace the Classical
   Internet.  For instance, Local Operations and Classical Communication
   (LOCC) operations [Chitambar] even rely on classical communications.
   Instead 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.

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

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      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  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: 1) local quantum operations (e.g., quantum measurement) are
      performed at one quantum node A; 2) the quantum operation result
      is sent to another quantum node B via classical communications; 3)
      the quantum node B may also perform some local quantum operations
      dependent on the received operation result from the quantum node
      A.  For example, LOCC can be used to transform entangled states
      into other entangled states.

   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 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.

   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 the Quantum Network, it
      must be able to generate/transmit and/or receive/process qubits.
      A quantum end-node, if it has quantum memory and quantum computing
      capabilities, can be regarded as a quantum computer.  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 Computer (QC) - Compared to a quantum end-node, a QC has
      more capabilities such as quantum memory and quantum circuits,
      which are required for performing quantum computing tasks.

   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

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      channels, and classical channels provided by the Classical

   o  Quantum Internet - A network of quantum networks.  The Quantum
      Internet will 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  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.  The Degrees of Freedom (DOF) of a photon (e.g.,
      polarization) or an electron (e.g., spin) can be used to encode a

4.  Quantum Internet Applications

4.1.  Overview

   The Quantum Internet is expected to be extremely beneficial for a
   subset of existing and new applications.  The expected applications
   using 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.

4.2.  Classification by Application Usage

   Applications may also be grouped by the usage that they serve into a
   tripartite classification.  Specifically, applications may be
   classified according to the following usages:

   o  Quantum cryptography applications - Refers to the use of quantum
      information technology to ensure secure communications (e.g.,

   o  Quantum sensors applications - Refers to the use of quantum
      information technology for supporting distributed sensors or
      Internet of Things (IoT) devices (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).

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   This is a useful classification scheme as it can be easily understood
   by both a technical and non-technical audience.  Following are some
   more details.

4.2.1.  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].

   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
       well as other distributed computing features which use Byzantine

4.2.2.  Quantum Sensor Applications

   The main example of a quantum sensor applications is currently
   network clock synchronization.

   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].

4.2.3.  Quantum Computing Applications

   Examples of quantum computing include distributed quantum computing
   and secure quantum computing with privacy preservation.

   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 [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].

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4.3.  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.  Other applications
   carry application or user data and can be classified as data plane

   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).
   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 use the
   same 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).

   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.

   As shown in the table in Figure 1, control and data plane
   applications vary for different types of networks.  For quantum
   network (i.e. without integration with 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.
   But looking at 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.

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     |  Planes  | Classical |     Quantum    |       Quantum        |
     |          | Internet  |     Network    |       Internet       |
     |  Control | ICMP,     | Signalling for | QKD-based secure     |
     |  Plane   | DNS       | controlling    | communication        |
     |          |           | entanglement   | setup                |
     |          |           | distribution   |                      |
     |  Data    | Web       | Entanglement   | Video conference     |
     |  Plane   | Browsing  | distribution   | using QKD-based      |
     |          |           |                | secure communication |
     |          |           |                | setup                |

        Figure 1: Examples of Control vs Data Plane Classification

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
   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.

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 2).  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.  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.

   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 [ETSI-QKD-Interfaces].  QKD
   can securely establish a secret key between two quantum nodes,

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   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.  More QKD use
   cases have been described in ETSI GS QKD 002 [ETSI-QKD-UseCases].

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

   1.  The source quantum node A (e.g.  Alice) 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 (e.g.  Bob) via quantum channel.

   3.  The destination quantum node receives qubits and measures them
       based on its random quantum basis.

   4.  The destination node informs the source node of its random
       quantum basis.

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

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

   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 Alice and Bob, are not normally considered
       "prepare-and-measure" as defined in [Wehner]; other entanglement-
       based schemes, where entanglement is generated within Alice 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
       Alice before being sent to Bob for measurement.

   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-

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       independent QKD [ZhangPeiyu].  These enhanced QKD protocol 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 [QinHao].  One or multiple trusted QKD relays
       [ZhangQiang] 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

   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., 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 2: Secure Communication Setup

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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.  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.

   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 3).  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.  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
   sensitive data qubits from one quantum computer A to another quantum
   computer B.  Note that Figure 3 does not cover measurement-based
   distributed quantum computing, where quantum teleportation may not be

   Specifically, 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 3.

   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).

   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.

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   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 3, the Quantum Internet contains quantum channels and
   quantum repeaters/routers [I-D.irtf-qirg-principles].  This use case
   needs to support entanglement generation in order to enable quantum
   teleportation, entanglement distribution or quantum connection setup
   [I-D.van-meter-qirg-quantum-connection-setup] in order to support
   long-distance 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 3: 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.

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   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 4, 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
   commands.  The home quantum terminal could be either a bare-bone
   quantum end-node or a full-fledged quantum computer.

   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
       classical channel.

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

   In Figure 4, the Quantum Internet contains quantum channels and
   quantum repeaters/routers for long-distance qubits transmission

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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 4: Secure Computation with Privacy Preservation

6.  General Requirements

   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 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-qubit machine has a total error rate which is close to the total
   error rate of a 7-year old two-qubit machine [Grumbling].

   Although it is challenging to predict future progress of quantum
   technologies, 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

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       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
       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.

   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 must be sent
       via classical channels.

7.  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 then
   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

   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.  To this end, a few key requirements for the
   Quantum Internet are specified.

8.  IANA Considerations

   This document requests no IANA actions.

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9.  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.

10.  Acknowledgments

   The authors want to thank Mathias VAN DEN BOSSCHE, Xavier de Foy,
   Patrick Gelard, Wojciech Kozlowski, Rodney Van Meter, and Joseph
   Touch for their very useful reviews and comments to the document.

11.  Informative References

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

              Cacciapuoti, A. and et. al., "Quantum Internet: Networking
              Challenges in Distributed Quantum Computing", IEEE
              Network, (Early Access), 2019,

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              Cacciapuoti, A. and et. al., "When Entanglement meets
              Classical Communications: Quantum Teleportation for the
              Quantum Internet", 2019,

   [Caleffi]  Caleffi, M. and et. al., "Quantum internet: From
              Communication to Distributed Computing!", NANOCOM, ACM,
              2018, <https://arxiv.org/abs/1907.06197>.

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

              Chitambar, E. and et. al., "Everything You Always Wanted
              to Know About LOCC (But Were Afraid to Ask)",
              Communications in Mathematical Physics, Springer, 2014,

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

              ETSI GR QKD 002 V1.1.1, "Quantum Key Distribution (QKD);
              Use Cases", 2010, <https://www.etsi.org/deliver/etsi_gs/

   [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,

              Grumbling, E. and M. Horowitz, "Quantum Computing:
              Progress and Prospects", National Academies of Sciences,
              Engineering, and Medicine, The National Academies Press,
              2019, <https://doi.org/10.17226/25196>.

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              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., Rijsman, B.,
              Cacciapuoti, A., and M. Caleffi, "Architectural Principles
              for a Quantum Internet", draft-irtf-qirg-principles-03
              (work in progress), March 2020.

              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>.

   [QinHao]   Qin, H., "Towards Large-Scale Quantum Key Distribution
              Network and Its Applications", 2019,

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

   [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,

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

              Zhang, P. and et. al., "Integrated Relay Server for
              Measurement-Device-Independent Quantum Key Distribution",
              2019, <https://arxiv.org/abs/1912.09642>.

              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

   Ruidong Li
   4-2-1 Nukui-Kitamachi
   Koganei, Tokyo  184-8795

   Email: lrd@nict.go.jp

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

   Email: maelmans@juniper.net

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