draft-kaws-qirg-advent-01.txt

QIRG                                                         K. Kompella
Internet-Draft                                                M. Aelmans
Intended status: Standards Track                  Juniper Networks, Inc.
Expires: June 21, 2019                                         S. Wehner
                                                                  QuTech
                                                                C. Sirbu
                                                         Redbit Networks
                                                             A. Dahlberg
                                                                  QuTech
                                                       December 18, 2018


       Advertising Entanglement Capabilities in Quantum Networks
                       draft-kaws-qirg-advent-01

Abstract

   This document describes the use of link-state routing protocols on
   classical links in Quantum Networks.  It contains proposals for
   additions to the IS-IS and OSPF protocols in order for them to
   transport relevant information for a Quantum Network, specifically,
   for the creation and manipulation of entangled pairs.  The document
   will describe some of the necessary attributes and some suggestions
   of how this information may be used.

   No Schrodinger's cats were harmed in the creation of this document.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [2].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."




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   This Internet-Draft will expire on June 21, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Definitions and Notation  . . . . . . . . . . . . . . . .   4
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Theory of Operation . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Multihop Entanglement . . . . . . . . . . . . . . . . . .   8
     3.2.  Distillation  . . . . . . . . . . . . . . . . . . . . . .   9
     3.3.  Node Properties . . . . . . . . . . . . . . . . . . . . .   9
     3.4.  Link Properties . . . . . . . . . . . . . . . . . . . . .  10
   4.  The (Ab)use of Protocols  . . . . . . . . . . . . . . . . . .  10
     4.1.  A Brief Primer on Link-state Protocols  . . . . . . . . .  10
     4.2.  Node Properties . . . . . . . . . . . . . . . . . . . . .  12
     4.3.  Link Properties . . . . . . . . . . . . . . . . . . . . .  12
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Quantum networking is an emerging field using the strange (even
   counterintuitive) properties of quantum mechanics to bring new,
   useful capabilities to networking.  One of these is "entanglement"
   [8], where the state of a group of particles must be described as a
   unit -- it cannot be decomposed to the state of each particle
   independently.  Entangled pairs (often called EPR pairs, abbreviated




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   here as EP) of particles can be used for quantum teleportation [10]
   and for quantum key distribution (QKD) [14].

   A Quantum Network consists of quantum nodes and links.  Here, we will
   be concerned with controllable quantum nodes (CQN) that allow control
   decisions.  We posit a classical network parallel to the quantum
   network, with classical nodes (CN) and links.  A classical node is
   colocated with a quantum node; a classical link may be a fiber or
   wavelength parallel to the corresponding quantum link.  Such a
   classical link is required by most quantum methods to create EPs
   deterministically or in a heralded fashion, where the creation of EPs
   is deterministic conditioned on a specific signal.  To make useful
   decisions, it is desirable to augment this data to describe the
   capabilities and states of quantum nodes and links.

   This document proposes to carry entanglement capability data as Type
   Length Values (TLVs) over IS-IS or OSPF link-state advertisements
   over the corresponding classical network.  A subset of the CQNs may
   run quantum applications such as QKD; these nodes may want to
   initiate multihop EPs.

   Once an EP is created, the state of one particle ("quantum bit" or
   qubit) of an EP can be transferred to another qubit within the same
   QN by a process known as swapping or a SWAP gate ([12]).  Also,
   several pairs of imperfectly entangled qubits can be "distilled"
   ([13]) to fewer but "better entangled" qubits.

   Long distance entanglement can be produced from piecewise short
   distance entanglement: Given an EP between CQN A and CQN B, and
   another EP between CQN B and CQN C, one can create an EP between CQN
   A and CQN C by a process known as an "entanglement swap".  These
   operations can be used to manipulate EPs to improve their lifetimes
   or their quality, or to create multihop EPs.  Physically, qubits can
   be realized in many ways.  For example, they can be represented by
   the energy levels of Nitrogen Vacancy (NV) Centers in diamond ([16],
   [17]).  Logically, a qubit can be classified as a "communication
   qubit", a "traveling qubit" or a "storage qubit".

   This document primarily discusses the exchange of quantum
   capabilities over a classical network.  Some illustrative examples of
   how these capabilities can be used in a quantum network may be given,
   but this document should not be considered authoritative on these
   procedures.








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1.1.  Definitions and Notation

   The following terms are used in this document:

   Quantum link:  A quantum link is a connection transporting traveling
      qubits, typically photons.  This could be a physical link.  This
      document does not describe the usage of this link.

   Classical link:  A classical link is a connection transporting
      packets.  This could be a physical link.  The proposed extensions
      in this document use these links to exchange capabilities.

   Controllable Quantum Node (CQN):  A controllable quantum node is a
      quantum device consisting of at least one qubit, capable of
      performing (a subset of) the following operations described in
      detail below: storing qubits for some amount of time, performing
      quantum operations such as entanglement distillation and
      entanglement swapping, and producing entanglement between the
      nodes and traveling qubits.  The latter are generally realized
      using photons over fibers or through free space.

      The term controllable refers to the fact that external control in
      software is capable of selecting the desired operations and qubits
      to use.  Such nodes can be quantum repeaters that allow choices of
      operations to be made, as well as quantum end nodes capable of
      executing complex application protocols [14].  Quantum repeaters
      that merely allow timing control, such as automatic entanglement
      swapping whenever qubits arrive in a specific timing interval,
      will not be referred to as CQN.  Such automated repeaters can be
      seen as lying at the quantum physical layer and do not enter
      routing or other decision making, apart from being switched on or
      off, and hence are not relevant to advertisement protocols like
      the ones considered here.

   Quantum end node (QEN):  In this document, a quantum end node [14] is
      one of a pair of quantum nodes forming a entanglement via a
      sequence of zero or more CQNs.  Quantum end nodes typically run a
      higher-layer quantum application such as QKD.

   Entangled Pair (EP):  An entangled pair is a special state of two
      qubits, known as an EPR pair [8].  An entangled pair of qubits c@A
      and c@B is denoted [[c@A, c@B]].

      The process of entangling two particles c@A and c@B is denoted as
      follows:

   ent(c@A, c@B) -> [[c@A, c@B]]




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      ent(c@A, c@B) may take time T and succeed with probability P, and
      yield an entangled pair [[c@A, c@B]] of fidelity F.

   Fidelity:  A measure of the quality of the entanglement of an EP
      (xref target='QFid'/>).  Fidelity lies in the interval [0, 1]
      where a higher value indicates better quality; usable fidelity
      values lie in the half-open interval (0.5, 1].

   Communication qubit:  A qubit is called a communication qubit if it
      is possible to produce entanglement between this qubit and a
      traveling photon.  This can be done by emission from the quantum
      node, that is, entanglement is produced between the qubit and the
      photon which is emitted from the quantum node.  This process has
      been demonstrated in a number of physical systems that can be used
      as quantum nodes such as NV in diamond ([16], [17]), Ion Traps
      ([18]) and Neutral Atoms ([19]).  An example of a communication
      qubit is the electron spin of the NV in diamond system ([15]).
      Entanglement between a communication qubit and traveling photons
      can also be produced by absorption.  Examples include atomic
      ensemble memories ([20]).

      A communication qubit c at CQN A is denoted by c@A, or simply c
      (if the node A is understood).

   Storage qubit:  A qubit is called a storage qubit if the node has the
      capability to use this qubit as a (temporary) quantum memory, but
      the qubit cannot serve as a communication qubit.  To make storage
      qubits useful a node is required to possess the ability to
      transfer the state of a communication qubit to a storage qubit.
      An example of a storage qubit is the nuclear spin in the NV in
      diamond system [16].

      A storage qubit s at node B is denoted s@B.

   Swap:  Two qubits located in the same CQN can interchange states
      ([13]).  For example, the states of a communication qubit and a
      storage qubit at A can be swapped as follows:

   swap(c@A, s@A)

      If c@A was entangled with c@B, the result is that s@A is now
      entangled with c@B.

   Distillation:  Distillation is the process of turning a large number
      of weakly entangled states into a smaller number of highly
      entangled states ([13]).





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      For example, EPs [[c1@A, c1@B]] and [[c2@A, c2@B]] of fidelities
      F1 and F2 respectively may be distilled as follows:

   dist([[c1@A, c1@B]], [[c2@A, c2@B]]) -> [[c3@A, c3@B]]

      If distillation is successful, the fidelity F3 of [[c3@A, c3@B]]
      will be higher than F1 and F2.

   Entanglement Swap:  Given two EPs [[c@A, c1@B]] and [[c2@B, c@C]],
      one can perform an entanglement swap:

   entSwap([[c@A, c1@B]], [[c2@B, c@C]]) -> [[c@A, c@C]]

      to create a new EP between c@A and c@C.  This is how "multihop"
      EPs are created from a sequence of "single-hop" EPs.

      The swap operation can also be used within a CQN.  A possible use
      case is when there aren't enough communication qubits to create
      the needed EPs.  If, in the above example, B doesn't have two
      communication qubits c1 and c2, the following can be done:

   ent(c@A, c@B)  -> [[c@A, c@B]]  # entangle
   swap(c@B, s@B) -> [[c@A, s@B]]  # swap EP to storage qubit
   ent(c@B, c@C)  -> [[c@B, c@C]]  # use freed up qubit c@B
   entSwap(c@A, c@B) -> [[s@B, c@C]]       # create multihop EP

2.  Motivation

   Consider the following (very simple) quantum network consisting of
   QENs A and B, and CQNs X, Y, Z, U, V.  The goal is to create an EP
   between qubits at A and at B, perhaps for the high-level task of QKD
   between A and B.

                    X - Y - Z
                  .           .
               A                 B                A, B: QEN
                  .           .
                     U --- V             X, Y, Z, U, V: CQNs

   From A's point of view, here are a number of questions:

   1.  Is B reachable from A via quantum links that allow EP creation?

   2.  If so, along what sequence(s) of quantum nodes?

   3.  Can each pair of adjacent CQNs in this sequence form EPs?  If so,
       how long will it take, and what fidelity can be expected?




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   4.  If each pair of adjacent CQNs successfully forms EPs of
       sufficient fidelity, can these be swapped to form a multihop EP
       between A and B?

   5.  If a multihop EP between A and B were to be formed, would it be
       of good enough fidelity, or should a second multihop EP be formed
       and the two EPs distilled into one high fidelity EP?  How many
       times should this process be repeated?

   6.  If the overall answer is Yes, should A proceed via sequence A, X,
       Y, Z, B, or sequence A, U, V, B?

   This document aims to provide all CQNs in a quantum network with the
   information they need to answer such questions, and to create EPs at
   their desired fidelity and speed.

3.  Theory of Operation

   A CQN contains one or more communication qubits and one or more
   storage qubits.  Many proposals exist for producing EPs between
   remote quantum nodes (see for example [16], [17], [18], [20]).
   Abstractly, these result in the generation of EPs with fidelity F
   after an expected time t.  To give an example, we describe the
   generation of EPs that has been implemented in NV in diamond ([16]),
   and Ion Traps ([18]).  The largest distance for producing long-lived
   entanglement is presently 1.3kms ([17]).  To entangle a pair of
   communication qubits, the QNs send carefully timed photons towards
   the HS.  If the process is successful, HS sends an OK message to both
   QNs.

      +----------+                                      +----------+
      |          |  c-chan    +------------+    c-chan  |          |
      | Control- | <------->  | Heralding  |  <-------> |  Control-|
      | lable    |            |  Station   |            |    lable |
      | Quantum  | *~~~~~~~>  |            |  <~~~~~~~* |  Quantum |
      | Node     |  q-chan    +------------+    q-chan  |     Node |
      | A        |                                      |        B |
      |          | <----------------------------------> |          |
      +----------+    classical network control plane   +----------+

   The classical network control plane is of particular interest here as
   it would be used by the proposed protocol to advertise and exchange
   information about the capabilities of the CQNs to generate
   entanglement.  This classical channel exists between all CQNs and is
   shared with other application specific control and data plane
   traffic.





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3.1.  Multihop Entanglement

                    resulting entanglement
        *~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
      +-+                            +-+                            +-+
      |A+----------------------------+B+----------------------------+C|
      +-+   A-B Link properties      +-+                            +-+
                [(F1,t1), (F2,t2)]    Node B properties:
                                      - Number of Communication Qubits
                                      - Number of Storage Qubits
                                      Node capabilities (operations):
                                      - Swap comm <-> storage
                                      - Entanglement swap
                                      - [(Distillation scheme, time)...]

   In the figure above, an example request for an entangled pair between
   nodes A and B will be affected by the following properties:

   o  A chosen combination of F(idelity) and t(ime) duration to produce
      an entanglement at the respective Fidelity.  These parameters
      roughly equate to the quality of the link, the accuracy with which
      the nodes can use the link, and the delay in classical networking.

   o  The actual capability of nodes A and B to make use of the
      communication qubits.

   A new EP creation between CQNs B and C will similarly be affected by
   the same parameters as above.

                                           resulting entanglement
        *~~~~~~~~~~~~~~~~~~~~~~~~~~~~* *~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
      +-+                            +-+                            +-+
      |A+----------------------------+B+----------------------------+C|
      +-+                            +-+   B-C Link properties      +-+
                                               [(F1,t1), (F2,t2)]

   And finally, with an entanglement swap operation at node B (which is
   a node specific capability and has a specific duration) we end up
   with an A-C EP:

        *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
      +-+                            +-+                            +-+
      |A+----------------------------+B+----------------------------+C|
      +-+                            +-+                            +-+
                       Node B entanglement swap operation






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3.2.  Distillation

   If a pair of CQNs A and B share a number of EPs of insufficient
   quality, they may be combined into a single EP of higher quality by
   distillation.  To do so, these CQNs need to agree on which
   distillation scheme to use before distillation can proceed.  This
   does not necessarily need to be via communication between A and B, if
   one agrees upon a deterministic procedure of selecting one.  This
   document suggests the following procedure:

   1.  A and B look at the distillation schemes that both advertise in
       common.

   2.  If there is none in common, stop.  Distillation is not possible.

   3.  If there is a non-trivial subset in common, the first scheme in
       the node with the lower router ID is to be used by A and B.

   Given a chosen distillation scheme (S,t,p), an additional time delay
   will be added for the actual operation: For a 2:1 distillation scheme
   between nodes A and B, 2 EPs need to be produced followed by an
   operation on A and B that produces 1 EP.  This operation will take
   time some expected time t, and succeed with probability p.

        2:1 distillation (S,t,p)
     *~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
     *~~~~~~~~~~~~~~~~~~~~~~~~~~~~*
   +-+                            +-+                            +-+
   |A+----------------------------+B+----------------------------+C|
   +-+   A-B Link properties      +-+                            +-+
             [(F1,t1), (F2,t2)]

3.3.  Node Properties

   We are interested in exposing the properties of CQNs (including QENs)
   to allow sophisticated decision making, for example in the creation
   of entanglement.  These properties include:

   1.  Number of communication qubits.  The number of communication
       qubits determines the number of entangled pairs that the node can
       produce simultaneously.

   2.  Number of storage qubits

   3.  Possible operations, along with their execution time and
       probability of success:

       1.  Swap between communication and storage qubits



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       2.  Entanglement swap

       3.  List of supported distillation schemes (in order of
           preference).

   Note that several other parameters can be advertised, such as the T1
   and T2 times for a qubit's decoherence.  These are omitted for now,
   instead just giving the decay of the fidelity of an EP.  If deemed
   useful, T1 and T2 times can additionally be advertised.

3.4.  Link Properties

   A list of (Fn,tn) pairs describing the tradeoffs of a possible
   entanglement produced by two nodes (the ends of said link): tn is the
   time to produce an entangled pair with fidelity Fn.

4.  The (Ab)use of Protocols

   The routing protocols IS-IS and/or OSPF could be used in order to
   advertise entanglement capabilities.  This section describes the
   additional data fields needed in order to facilitate the objective.

4.1.  A Brief Primer on Link-state Protocols

   This document suggests the use of a link-state protocol to distribute
   the capabilities of CQNs to create entanglement.  This section offers
   a short introduction to link-state protocols for those not familiar
   with them.

   Consider a directed graph G=(V, E) with vertices (nodes) V and edges
   (links) E.  Consider also G'=(V', E'); there is a 1-1 mapping from V'
   to V and from E' to E such that e1' = (v1', v2') is in E' iff e1 =
   (v1, v2) is in E and v1' maps to v1 and v2' maps to v2.  G'
   represents the quantum network; V' represents the set of CQNs, and E'
   the set of quantum links between pairs of CQNs; G represents a
   classical network parallel to G'; that is, each CQN v' has a
   corresponding classical node v.  v plays a dual role: it is the
   control node for v', and proxies on behalf of v' in the link-state
   protocol.

   The basic objective of a link-state protocol is to "flood" properties
   of nodes and (directed) links to all nodes in the network.  This is
   accomplished by means of "link-state advertisements" (LSAs) that each
   node originates and sends to its immediate neighbors.  The neighbors
   in turn send received LSAs to their own neighbors; this process
   repeats until every node receives every LSA (hence the term
   "flooding").  The focus of LSAs is the link properties (hence _link-
   state_ advertisements), although node properties are also advertised.



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   There are mechanisms to prevent looping of LSAs, and for reliable
   flooding.  There is also a sequence number by which a more recent
   update of an LSA can be identified as such, and a mechanism for
   "aging out" LSAs belonging to nodes no longer in the network.  In
   what follows, quantum node and link properties are added to the link-
   state advertisements of the corresponding classical node.  Note that
   link properties need not be symmetric; that is, the link properties
   of (v, w) need not be the same as those of (w, v).

   The net result of flooding is that every node has the same picture of
   the network (modulo LSAs in flight); in particular, each node knows
   the overall topology and connectivity of the network, and can use
   this information to make decisions.  In a classical network, such a
   decision could be to compute a shortest path; for the quantum
   network, it could be choosing a feasible path (i.e., sequence of
   CQNs) for a multihop entanglement.  Note that a node doesn't really
   know when it has complete and up-to-date information about the
   network; LSA updates may be originated at any time.  Usually, this is
   okay: for example, if a node v learns enough of the network to have a
   path to another node w, it can compute a multihop entanglement to w.
   Subsequent updates may provide a more optimal (or higher probability)
   entanglement path.  There are heuristics one can apply to guess that
   the link-state database (LSDB) (i.e., the union of all LSAs) is
   complete-ish; however, as nodes (and links) can fail or disconnect,
   there really is no such thing as "the full LSDB".

   Each node v is identified by a "router ID" (an IP address uniquely
   allocated to v), denoted by rid(v).  A link L = (v, w) is identified
   by (rid(v), i) where i is an index allocated by v for L unique for
   each link emanating from v.  (L may also be identified by IP
   addresses, but we'll ignore that for now.)  It is generally expected
   that a directed link (v, w) is matched by a link (w, v); if not, (v,
   w) is ignored from subsequent consideration; in particular, no link
   properties are advertised for this link by v.  Note that a pair of
   nodes may have multiple links between them; for simplicity, the
   notation will not be extended to indicate this.  We'll assume rid(v')
   = rid(v) and the index allocated to a quantum link e' is the same as
   that of the corresponding classical link e.

   Let v, w be a pair of neighboring nodes, and let L1 = (v, w) and L2 =
   (w, v) in E be directed links in opposite directions between v and w
   with identifiers (rid(v), i1) and (rid(w), i2) respectively (where i1
   is the index allocated for L1 by v, and similarly for i2)).  As a
   first step in running a link-state protocol, v runs a "hello
   protocol" all its links; in particular, over L1.  Similarly, w will
   run the hello protocol over L2.  The hello protocol serves to
   exchange the indices i1 and i2, and thus identify (rid(v), i1) as the
   reverse link of (rid(w), i2).  This allows both v and w to correlate



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   the link properties of L1 and L2.  If the hello protocol fails
   between v and w, neither node includes link properties for the link
   in their LSAs.

   Once the hello protocol has been run on all links, v starts the
   process of generating and sending its own LSA over all its links, and
   of receiving the current LSDB from its neighbors.  Note that an LSA
   originated by v must propagate unchanged across the network; only v
   is allowed to change it (and such a change must be accompanied by
   updating the LSA's sequence number).  Such an update is triggered by
   a new link coming up, an existing link going down, or a node or link
   property changing.

   IS-IS and OSPF are in principle similar, although the details of the
   protocol mechanisms and encodings vary.  In both protocols, a Type-
   Length-Value (TLV) is used to encode most node and link properties.
   In IS-IS, TLVs are used for all properties, and a single type of LSA
   is used; in OSPF, there are several types of LSAs, and many (but not
   all) properties are encoded as TLVs.

   [1] has examples of "standard" LSAs for routing; [4] has the so-
   called Traffic Engineering LSAs.

4.2.  Node Properties

   Here, we give a protocol-independent description of quantum node
   properties; later documents will specify the encoding specifically
   for IS-IS and OSPF.

   Note that the following list of node properties is a strawman; all
   details are subject to change, and other properties may be added as
   needed.

   The following node properties are added to the appropriate LSA:

                   <Qubit-TLV><NCQ><NSQ>
                   <CS-Swap><Prob><ExecTime>
                   <Ent-Swap><Prob><ExecTime>
                   <Measure><Prob><ExecTime>
                   <NDistSch><DistScheme1><DistScheme2>

4.3.  Link Properties

   Only one link property is listed.  It gives the time-fidelity
   tradeoffs of an entanglement operation as a list:

                  <N-Ent-TO><time1><fid1><time2><fid2>...




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   This is interpreted as follows: an entanglement operation may be
   initiated between nodes v and w over link (v, w).  Depending on how
   fast one wants to complete (time-i), the list gives the corresponding
   fidelity of the resulting entanglement (fid-i).  time-i is given in
   nanoseconds; fid-i as a number between 0 and 999999.  THe denominator
   is 1000000.

   Note that this link property is symmetric, as entanglement is
   initiated simultaneously at v and w.

5.  Security Considerations

   It is not anticipated that adding these extensions to IS-IS and OSPF
   will present new security hazards to those protocols.  Since however
   a common application of entangled pairs is for security purposes
   (such as QKD), it is worth investigating whether this application
   places a higher burden of security on the underlying protocols.

6.  Acknowledgments

   The authors would like to thank the following people for their
   contributions and support to this document: Vesna Manojlovic (RIPE
   NCC) and Axel Dahlberg (QuTech).  Kompella would also like to thank
   Bruno Rijsman for encouraging him to learn about Quantum Computing
   and Networking.

   Also:

          _,'|             _.-''``-...___..--';)
          /_ \'.      __..-' ,      ,--...--'''
         <\    .`--'''       `     /'
          `-';'               ;   ; ;
    __...--''     ___...--_..'  .;.'
   (,__....----'''       (,..--''

7.  IANA Considerations

   There are no requests as yet to IANA for this document.

8.  References

8.1.  Normative References

   [1]        Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <https://www.rfc-editor.org/info/rfc1195>.





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   [2]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [3]        Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [4]        Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [5]        Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
              "Traffic Engineering Extensions to OSPF Version 3",
              RFC 5329, DOI 10.17487/RFC5329, September 2008,
              <https://www.rfc-editor.org/info/rfc5329>.

   [6]        Aggarwal, R. and K. Kompella, "Advertising a Router's
              Local Addresses in OSPF Traffic Engineering (TE)
              Extensions", RFC 5786, DOI 10.17487/RFC5786, March 2010,
              <https://www.rfc-editor.org/info/rfc5786>.

8.2.  Informative References

   [7]        "Qubit", <https://en.wikipedia.org/wiki/Qubit>.

   [8]        "Quantum Entanglement",
              <https://en.wikipedia.org/wiki/Quantum_entanglement>.

   [9]        "Quantum Network",
              <https://en.wikipedia.org/wiki/Quantum_network>.

   [10]       "Quantum Teleportation",
              <https://en.wikipedia.org/wiki/Quantum_teleportation>.

   [11]       "Quantum Fidelity", <https://en.wikipedia.org/wiki/
              Fidelity_of_quantum_states>.

   [12]       Wehner, S., Elkouss, D., and R. Hanson, "Quantum internet:
              A vision for the road ahead", Science 362, 6412, 2018.

   [13]       Rozpedek, F., Schiet, T., Thinh, L., Elkouss, D., Doherty,
              A., and S. Wehner, "Optimizing practical entanglement
              distillation", Phys. Rev. A 97, 062333, 2018,
              <https://arxiv.org/abs/1803.10111>.




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   [14]       "Quantum Key Distribution",
              <https://en.wikipedia.org/wiki/Quantum_key_distribution>.

   [15]       "Nitrogen-vacancy center",
              <https://en.wikipedia.org/wiki/Nitrogen-vacancy_center>.

   [16]       Humphreys, P., "Deterministic delivery of remote
              entanglement on a quantum network", Nature 558, 2018.

   [17]       Hensen, B. and others, "Loophole-free Bell inequality
              violation using electron spins separated by 1.3
              kilometres", Nature 526, 2015.

   [18]       Hucul, D. and others, "Modular entanglement of atomic
              qubits using photons and phonons", Nature Physics 11(1),
              2015.

   [19]       Noelleke, C. and others, "Efficient Teleportation Between
              Remote Single-Atom Quantum Memories", Physical Review
              Letters 110, 140403, 2013.

   [20]       Sangouard, N. and others, "Quantum repeaters based on
              atomic ensembles and linear optics", Reviews of Modern
              Physics 83, 33, 2011.

Authors' Addresses

   Kireeti Kompella
   Juniper Networks, Inc.
   1133 Innovation Way
   Sunnyvale, CA  94089
   USA

   Email: kireeti.kompella@gmail.com


   Melchior Aelmans
   Juniper Networks, Inc.
   Boeing Avenue 240
   Schipol-Rijk, PZ  1119
   The Netherlands

   Email: maelmans@juniper.net








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   Stephanie Wehner
   QuTech
   Van der Waalsweg 122
   Delft, LC  2611
   The Netherlands

   Email: s.d.c.wehner@tudelft.nl


   Cristian Sirbu
   Redbit Networks
   Dublin
   Republic of Ireland

   Email: cristian@redbit.network


   Axel Dahlberg
   QuTech
   Van der Waalsweg 122
   Delft, LC  2611
   The Netherlands

   Email: E.A.Dahlberg@tudelft.nl



























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