A Joint-Detection Receiver for Deep-Space Communications Leveraging Intermediate Measurements on NISQ Hardware.

Decoding laser-light-modulated classical-communication codewords on quantum devices presents a promising direction towards demonstrating quantum advantage in the near term. Here we implement the quantum circuit of a quantum joint detection receiver for a 3-bit binary linear tree code based on the algorithm of belief propagation with quantum messages¹. Assuming ideal transduction from optical to trapped-ion domain, we provide the first experimental demonstration of the joint detection receiver circuit on the Honeywell LT-1.0 trapped ion quantum computer. Our approach has the ability to conclusively surpass the quantum limit on the minimum average decoding error probability in the low-photon limit. The implementation takes advantage of executing intermediate measurements on qubits and perform conditioning on outcomes without interrupting the quantum circuit, which makes trapped-ion quantum architectures ideal candidates for joint-detection receivers in the near future. Our work offers a clear path to demonstrating quantum advantage in quantum-enhanced communications.

1. Rengaswamy, N., Seshadreesan, K. P., Guha, S. & Pfister, H. D. Quantum-message-passing receiver for quantum-enhanced classical communications. arXiv e-prints(2020). 2003.04356