Antidegradable quantum channel with additional entanglement for quantum transduction
Phys. Rev. Applied 24, 024065 – Published 27 August, 2025
DOI: https://doi.org/10.1103/4g6d-6cmg
Abstract
Quantum communication theory studies how quantum information is transmitted through quantum channels, with the transmission rate quantified by the quantum channel capacity. Quantum channels often exhibit rich and complex structures—such as nonadditivity—that make evaluating their capacities particularly challenging. In this work, we show that a type of quantum channel known as the antidegradable one-mode Gaussian channel—whose capacity is believed to be zero—can be “activated” to transmit quantum information with the assistance of quantum entanglement. Although the channel’s output alone cannot be used to retrieve the input signal, combining it with additional entanglement makes this possible. Beyond its theoretical implications, it can also be realized in practical systems. For example, in electro-optic systems used for quantum transduction in the two-mode squeezing interaction regime, the transduction channel is antidegradable. We demonstrate that this system can transmit microwave-optical quantum information with the assistance of entanglement with an ancillary mode. This results in a type of quantum transducer that exhibits positive quantum capacity over a wide parameter space.
