A Survey on Quantum Channel Capacities

Abstract

Quantum information processing exploits the quantum nature of information. It offers fundamentally new solutions in the field of computer science and extends the possibilities to a level that cannot be imagined in classical communication systems. For quantum communication channels, many new capacity definitions were developed in comparison to classical counterparts. A quantum channel can be used to realize classical information transmission or to deliver quantum information, such as quantum entanglement. Here we review the properties of the quantum communication channel, the various capacity measures and the fundamental differences between the classical and quantum channels.Comment: 58 pages, Journal-ref: IEEE Communications Surveys and Tutorials (2018) (updated & improved version of arXiv:1208.1270

Secret key rates of free‐space optical continuous‐variable quantum key distribution

“…The complementary channel for a reverse reconciliation in the CVQKD case is defined as where is the noise variance for . Assuming that the parties have quantum memories and can perform joint measurement on their quantum registers in the QKD protocol run, the appropriate correlate measure functions for the logical channels , , and are the Holevo quantities χ AB , χ AE , and χ BE .…”

“…Free‐space optical (FSO) quantum links provide a tool to implement quantum communications via wireless telecommunication network infrastructures. As an integrated component of future quantum Internet and long‐distance quantum communications, the FSO quantum channels could play a significant role in the global‐scale practical implementations of quantum communications and quantum key distribution (QKD) .…”

“…QKD protocols can be decomposed into discrete‐variable (DV) and continuous‐variable (CV) counterparts . Continuous‐variable quantum key distribution (CVQKD) schemes enable parties to use standard telecommunication devices for experimental implementations . The multicarrier CVQKD has been recently introduced through the adaptive quadrature division modulation (AMQD) scheme .…”

“…Another important difference from traditional crypto systems is that the correlation measure functions are non‐traditional. In the theoretical analysis, it is assumed that the legal parties and the eavesdropper have quantum memories and can perform joint measurements, therefore the Holevo information is the appropriate correlation measure function for deriving the private classical capacity.…”

Theory of quantum gravity information processing

“…In our macroscopic world, events and processes are distinguishable in time and, thus, causally separable because the space‐time geometry has a deterministic causality structure. The meaning of time evolution is also nonvanishing and has an interpretable notion in the microscopic world of quantum mechanics . It is precisely the reason why classical and quantum computations are evolved by a sequence of time steps and why the term time has an interpretable and plausible meaning in the macroscopic and microscopic levels.…”