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Rigidity of Superdense Coding

delete2023-07-25
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OA
AI
A
Ashwin Nayak *
H
Henry Yuen
DOI:10.1145/3593593delete
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Abstract

Abstract

En 中文
The famous superdense coding protocol of Bennett and Wiesner demonstrates that it is possible to communicate two bits of classical information by sending only one qubit and using a shared EPR pair. Our first result is that an arbitrary protocol for achieving this task (where there are no assumptions on the sender's encoding operations or the dimension of the shared entangled state) is locally equivalent to the canonical Bennett-Wiesner protocol. In other words, the superdense coding task is rigid. In particular, we show that the sender and receiver only use additional entanglement (beyond the EPR pair) as a source of classical randomness. We also investigate several questions about higher-dimensional superdense coding, where the goal is to communicate one of d(2) possible messages by sending a d-dimensional quantum state, for general dimensions d. Unlike the d = 2 case (i.e., sending a single qubit), there can be inequivalent superdense coding protocols for higher d. We present concrete constructions of inequivalent protocols, based on constructions of inequivalent orthogonal unitary bases for all d > 2. Finally, we analyze the performance of superdense coding protocols where the encoding operators are independently sampled from the Haar measure on the unitary group. Our analysis involves bounding the distinguishability of random maximally entangled states, which may be of independent interest.
Keywords:
Superdense coding
rigidity
shared entanglement
orthogonal unitary basis
random maximally entangled states
distinguishability
generalized Holevo-Curlander bounds
Marcenko-Pastur Law

Journal

A
ACM Transactions on Quantum Computing
IF:
6.8
Papers:
539
Citations:
508

Organization

C
Columbia University
Scholars:
7.1W
Papers: 6.4W
Citations: 263
U
University of Waterloo
Scholars:
2.2W
Papers: 2.3W
Citations: 3.3W