Joint-detection learning for optical communication at the quantum limit
Matteo Rosati, Albert Solana
Abstract
Optical communication technology can be enhanced by using quantum signals to transfer classical bits. This requires the message-carrying signals to interact coherently at the decoder via a joint-detection receiver (JDR). To date, the realization of a JDR using optical technologies has remained elusive: the only explicit design, called a Green–Hadamard receiver (GHR), increases distinguishability at the cost of reducing the code size. We introduce a supervised-learning framework for the systematic discovery of optical JDR designs based on parametrized photonic integrated circuits. We find JDR designs with higher decoding success probability than any single-symbol receiver, including homodyne, Kennedy, and Dolinar. Furthermore, our new receiver families surpass the GHR receiver for mean photon number >0.1, both in terms of code size and decoding probability, paving the way for practical applications of JDR in optical fiber networks and free-space.