Reliability function for transmission of classical information with Gaussian states

正宜 相馬

Kyungjoo Noh, Victor V. Albert, Linshu Li +2 more

Masaki Sohma, Osamu Hirota

The main purpose of this paper is to derive the capacity of attenuated or amplified noisy quantum channel assisted by two-mode squeezed states. In our previous works, formulas for capacity and reliability function have been obtained for continuous variable communication channel in the case where the classical information is conveyed by unentangled quantum Gaussian states. This paper investigates how two-mode squeezed states can enhance classical communication over quantum Gaussian channel.

Masaki Sohma

Felipe Gomes Lacerda

Optical communication channels are ultimately quantum-mechanical in nature, and we must therefore look beyond classical information theory to determine their communication capacity as well as to find efficient encoding and decoding schemes of the highest rates. Thermal channels, which arise from linear coupling of the field to a thermal environment, are of particular practical relevance; their classical capacity has been recently established, but their quantum capacity remains unknown. While the capacity sets the ultimate limit on reliable communication rates, it does not promise that such rates are achievable by practical means. Here we construct efficiently-encodable codes for thermal channels which achieve the classical capacity and the so-called Gaussian coherent information for transmission of classical and quantum information, respectively. Our codes are based on combining polar codes with a discretization of the channel input into a finite constellation of coherent states. Encoding of classical information can be done using linear optics.

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

Optical communication channels are ultimately quantum mechanical in nature, and we must therefore look beyond classical information theory to determine their communication capacity as well as to find efficient encoding and decoding schemes of the highest rates. Thermal channels, which arise from linear coupling of the field to a thermal environment, are of particular practical relevance; their classical capacity has been recently established, but their quantum capacity remains unknown. While the capacity sets the ultimate limit on reliable communication rates, it does not promise that such rates are achievable by practical means. Here we construct efficiently encodable codes for thermal channels which achieve the classical capacity and the so-called Gaussian coherent information for transmission of classical and quantum information, respectively. Our codes are based on combining polar codes with a discretization of the channel input into a finite ``constellation'' of coherent states. Encoding of classical information can be done using linear optics.