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 language | English |
---|---|
Pages | 1-34 |
Number of pages | 34 |
Publication status | Published - 29 Oct 2015 |
Keywords
- quant-ph