Fundamental limits of repeaterless quantum communications

By Stefano Pirandola, Riccardo Laurenza, Carlo Ottaviani, Leonardo Banchi. Nature Communications, 2015

1,343 citations recorded by the source corpus.

Quantum communications promises reliable transmission of quantum information, efficient distribution of entanglement and generation of completely secure keys. For all these tasks, we need to determine the optimal point-to-point rates that are achievable by two remote parties at the ends of a quantum channel, without restrictions on their local operations and classical communication, which can be unlimited and two-way. These two-way assisted capacities represent the ultimate rates that are reachable without quantum repeaters. Here, by constructing an upper bound based on the relative entropy of entanglement and devising a dimension-independent technique dubbed ‘teleportation stretching’, we establish these capacities for many fundamental channels, namely bosonic lossy channels, quantum-limited amplifiers, dephasing and erasure channels in arbitrary dimension. In particular, we exactly determine the fundamental rate-loss tradeoff affecting any protocol of quantum key distribution. Our findings set the limits of point-to-point quantum communications and provide precise and general benchmarks for quantum repeaters. Quantum communications will be used to transmit entanglement and secure keys, but it is important to estimate their optimal transfer rates. Here the authors compute the fundamental limit of repeaterless quantum communications for the most relevant practical scenario.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/7300132677fdf9cb5611068e81cca5b7d71492b7

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Citations in the corpus

Advances in quantum cryptography (2019, positive): “Given a lossy link with transmissivity η, two parties cannot distribute more than the secret key capacity of the channel, which is −log2(1 − η) [33], i.”
Overcoming the rate–distance limit of quantum key distribution without quantum repeaters (2018, background): “On the other hand, the scheme presented here can overcome the point-to-point SKC. 9 We anticipate the TF-QKD key rates in Fig.”
High‐Dimensional Quantum Communication: Benefits, Progress, and Future Challenges (2019, neutral): “between two parties, the so-called PLOB-repeaterless bound [37].”
End-to-end capacities of a quantum communication network (2019, methodology): “This limit is the Pirandola – Laurenza – Ottaviani – Banchi (PLOB) bound 15 and cannot be surpassed even by the most powerful strategies that exploit arbitrary local operations (LOs) assisted by two-way classical communication (CC), also known as adaptive LOCCs 16 .”
Quantum-enhanced measurements without entanglement (2017, positive): “…of bits per channel use at which we can transmit quantum information, distribute entanglement or generate secret keys through such a lossy channel are all equal to − log(1 − η) (Pirandola et al., 2017), a fundamental rate-loss tradeoff that only quantum repeaters may surpass (Pirandola, 2016).”