Speaker: Konrad Banaszek, Centre for Quantum Optical Technologies and Faculty of Physics, University of Warsaw, Poland
Abstract:
Quantum theory of electromagnetic radiation sets fundamental limits on the information capacity of optical communication links. Analysis of quantum mechanical capacity limits, which follow from Holevo's theorem, requires a change of paradigm from identifying noise inherent to measuring quantities well defined in classical systems, such as the amplitude or the phase of an optical field, to optimizing distinguishability of non-orthogonal quantum states. We discuss capacity limits in the context of deep-space optical communication, in particular downlink transfer of data collected by missions beyond the near-Earth region. The current standard for deep-space links is based on the high-order pulse position modulation (PPM) format. Such a format requires high peak-to-average power ratio of the optical signal, which may reduce the overall wall-plug efficiency of the transmitter subsystem. We describe a possible solution to this problem motivated by the quantum mechanical phenomenon of superadditivity of accessible information in classical communication.