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Digital Switching in Quantum Domain I. –Ming Tsai and Sy-Yen Kuo. Presented by Chin-Yi Tsai. Outline. Introduction Notation and Preliminaries Digital Switching Networks Digital Quantum Switching Conclusions. Introduction.
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Digital Switching in Quantum DomainI. –Ming Tsai and Sy-Yen Kuo Presented by Chin-Yi Tsai
Outline • Introduction • Notation and Preliminaries • Digital Switching Networks • Digital Quantum Switching • Conclusions
Introduction • A switching architecture such that digital data can be switched in the quantum domain. • The proposed mechanism supports unicasting and multicasting. • (interface conversion) The quantum switch can be used to build classical and quantum information networks. • To define the connection digraph which can be used to describe the behavior of a switch at a given time. • The connection digraph can be implemented using elementary quantum gates.
Introduction (cont’d) • Compared with a traditional space or time domain switch, the proposed switching mechanism is much more scalable.
control target Notations and Preliminaries
Qubit Permutation and Replication • A typical permutation P is represented using the symbol • A cycle is basically an ordered list, which is represented as C=(e1, e2, …, en-1, en). • The number of elements in a cycle is called length. • Length 1:trivial cycle • Length 2:transposition • P = (a, d )(c )(b, e, f )=(a, d )(b, e, f )
Qubit Permutation and Replication (cont’d) (transposition circuit)
Qubit Permutation and Replication (cont’d) • For a general n-qubit cycle C=(q0, q1, q2, …, qn-1), it can be done by six layers of CN gates with ancillary qubits. • For an even n (n=2m, m=2, 3, …), we define the following nonoverlapping qubit transpositions as: • The cycle can be implemented using
For the odd n(n=2m+1, m=1, 2, 3, …) n=6 X=(2, 4)(1, 5) Y=(3, 4)(2, 5)(1, 2) n=5 X=(2, 3)(1, 4) Y=(2, 4)(1, 0)
Qubit Replication (FANOUT) • Qubit replication takes one bit as input and gives two copies of the same bit value as output.
Digital Switching Networks • In classical digital communication, switching is needed in order to avoid a fully meshed transmission network. • Digital switching technologies fall under two broad categories: • Circuit switching • Packet switching • In both circuit switching and packet switching, the control subsystem needs to specify the switching configuration
Digital Switching Networks (cont’d) • The switching configuration can be described using a connection digraph. • Definition 1: Given an n x n switch, the connection digraph at time t, Gt={V, Et }, is a digraph such that: • Each represents an I/O port • if and only if a connection exists from the input port vm to the output port vn at time t. • A digraph Gtdescribes the connection status of a switch at a specific time, and is called the connection digraph at time t
Elementary Topologies • The connection digraph can be built from a set of elementary topologies • null point, loopback, queue, cycle, tree, forest
Connection with null points and loopbacks Connection Connection digraph
Digital Quantum Switching • The proposed architecture for building a digital quantum switching 0 -> |0> 1 -> |1> |0> -> 0 |1> -> 1
Connection Digraph Implementation • A connection digraph can be implemented using CN gates. • Transformation guideline can be used to implement a connection digraph.
Transformation Guideline • Unicasting and multicasting have different types of connection digraphs • The digraph of a unicast connection has a connection of disjointed null points, loopbacks, queues, and/or cycles as subdigraphs. • However, in the digraph of a multicast connection, subdigraph such as trees and forests are possible.
tree forest Interrelated Connection Topologies Cycle U=YX
forest Cycle Extraction • The process of cycle extraction detaches all the null points, queues • This procedure transforms a forest into one cycle and a collection of null point, queues, and/or trees. • null point and queues loopback and cycles • Tree forest
Link Recovery • After each cycle has been implemented, the links that had been cut must be recovered.
Unicast Quantum Switching GC=(q3, q4, q6, q7, q5) GQ=[q0, q1, q2] GC’=(q0, q1, q2)
GC=(q3, q4, q6, q7, q5) X=(q6, q7)(q4, q5) Y=(q6, q5)(q4, q3) (q4, q5)=CN(q4, q5).CN(q5, q4).CN(q4, q5) GC’=(q0, q1, q2) X=(q1, q2) Y=(q1, q0)
Multicast Quantum Switching tree GT=[q0, q1][q1, q4][q1, q3][q3, q5, q2][q3, q6, q7]
Multicast Quantum Switching tree forest
Conclusions • An architecture of digital quantum switching. • The proposed mechanism allows digital data to be switched using a series of quantum operations. • Connection digraph • Null point, queue, cycle, tree, forest