ﻻ يوجد ملخص باللغة العربية
Transmission and storage of quantum information are the fundamental building blocks for large-scale quantum communication networks. Reliable certification of quantum communication channels and quantum memories requires the estimation of their capacities to transmit and store quantum information. This problem is challenging for continuous variable systems, such as the radiation field, for which a complete characterization of processes via quantum tomography is practically unfeasible. Here we develop protocols for detecting lower bounds to the quantum capacity of continuous variable communication channels and memories. Our protocols work in the general scenario where the devices are used a finite number of times, can exhibit correlations across multiple uses, and can be under the control of an adversary. Our protocols are experimentally friendly and can be implemented using Gaussian input states (single-mode squeezed or coherent) and Gaussian quantum measurements (homodyne or heterodyne). These schemes can be used to certify the transmission and storage of continuous variable quantum information, and to detect communication paths in quantum networks.
The rates at which classical and quantum information can be simultaneously transmitted from two spatially separated senders to a single receiver over an arbitrary quantum channel are characterized. Two main results are proved in detail. The first des
We investigate the performance of several continuous-variable quantum key distribution protocols in the presence of fading channels. These are lossy channels whose transmissivity changes according to a probability distribution. This is typical in com
We investigate the entanglement dynamics of continuous-variable quantum channels in terms of an entangled squeezed state of two cavity fields in a general non-Markovian environment. Using the Feynman-Vernon influence functional theory in the coherent
The positivity and nonadditivity of the one-letter quantum capacity (maximum coherent information) $Q^{(1)}$ is studied for two simple examples of complementary quantum channel pairs $(B,C)$. They are produced by a process, we call it gluing, for com
Quantum channels, which break entanglement, incompatibility, or nonlocality, are not useful for entanglement-based, one-sided device-independent, or device-independent quantum information processing, respectively. Here, we show that such breaking cha