Fundamental Limits of Repeaterless Quantum Communications

Stefano Pirandola, Riccardo Laurenza, Carlo Ottaviani, Leonardo Banchi

Research output: Working paperPreprint

Abstract

Quantum communications promises reliable transmission of quantum information, efficient distribution of entanglement and generation of completely secure keys. For all these tasks there is a crucial question to answer: What are their optimal rates without quantum repeaters? Our work solves this basic question for any two parties connected by a quantum channel, without any restriction on their classical communication, which can be unlimited and two-way. We design a method which reduces the most general protocol of quantum communication to the computation of a novel quantity, identified as the channel's relative entropy of entanglement. In this way, we bound the ultimate rates that are achievable over the most important bosonic and qubit channels, computing a number of exact formulas for their two-way capacities. In particular, we determine the fundamental rate-loss scaling which affects any quantum optical communication. By setting these limits, we establish the most general and correct benchmarks for testing the performance of quantum repeaters.
Original languageEnglish
Pages1-34
Number of pages34
Publication statusPublished - 29 Oct 2015

Keywords

  • quant-ph

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