Transmission of classical information with quantum gaussian states = 量子ガウス状態を用いた古典情報の伝送

正宜 相馬

Masaki Sohma

Alessio Serafini

The theoretical toolbox has developed to describe a series of tasks, related to the transmission or extraction of information, which may be implemented with quantum continuous variable systems. This chapter opens with quantum teleportation, the transmission of a quantum state through shared quantum entanglement and classical communication, and determines certain thresholds it must attain to be considered genuinely quantum. It establishes the maximum classical communication capacity of a class of Gaussian channels and considers the optimal estimation of a dynamical parameter by using Gaussian states as probes. The chapter illustrates the fact that Gaussian states may be used for the secure distribution of a cryptographic key. Gaussian quantum key distribution has already been commercialised, and all the other techniques are gradually approaching the status of full-blown engineering technologies, which would arguably form the most convincing empirical evidence one may have in support of the underlying physical theory.

Alessandro Ferraro, Stefano Olivares, Matteo G. A. Paris

Felipe Gomes Lacerda, Joseph M. Renes, Volkher B. Scholz

We propose constellations of finitely-many coherent states for high-rate quantum and classical communication over the thermal noise Bosonic Gaussian channel. Our constructions are based on constellations for the classical additive white Gaussian noise (AWGN) channel, and we adapt the results of Wu and Verdú [Allerton 2010, pp. 620] for the AWGN to determine achievable rates of classical and quantum information transmission for the thermal noise channel. Several constellations allow classical rates approaching the classical capacity, recently determined by Giovannetti et al. [Nature Photonics 8, 796 (2014)], while in the quantum case the rates approach the Gaussian coherent information. The constellations can also be used for private transmission of classical information at the coherent information rate.

Joachim Sch