Abstract

Demonstrating quantum advantage using near-term, noisy intermediate-scale quantum (NISQ) processors is a topic of keen interest in quantum computing. In laser communication systems that operate in the quantum-limited weak signal regime, such as deep-space optical communications, it has been rigorously proven that there exists a fundamental gap in terms of capacity and decoding error probability between conventional receivers that detect received modulated optical pulses one at a time, and "joint detection" receivers that collectively process optical pulse sequences (codeword blocks) in the quantum domain before detecting the individual symbols. For the binary phase-shift keying (BPSK) modulated codewords of an exemplary 5-bit linear tree code, using a quantum belief propagation algorithm that works by passing quantum messages along with classical bits, we present a structured design of such a joint detection receiver. The receiver attains the quantum limit on the minimum average decoding error probability. The receiver design readily translates into a low-depth quantum circuit that can be realized using a NISQ processor.

Bio

Dr. Kaushik P. Seshadreesan is a Research Scientist at the College of Optical Sciences, University of Arizona, affiliated to the Quantum Photonic Applications Group of Prof. Saikat Guha, and working closely with the recently formed NSF Center for Quantum Networks. Previously, he held postdoctoral positions at the Quantum Photonic Applications Group, the University of Arizona and at the Quantum Information Processing Group, Max Planck Institute for the Science of Light. Kaushik obtained his Ph.D. from Louisiana State University, working at the Quantum Science and Technologies Group, Department of Physics and Astronomy, under the supervision of Prof. Jonathan P. Dowling and co-supervision of Prof. Mark M. Wilde. Kaushik’s research interests lie at the interface of quantum optics and quantum information processing, in developing quantum communication, sensing, and computation applications. Currently, his research is primarily focused on designing i) quantum repeaters for quantum communication networks, and ii) quantum joint detection receivers for quantum-enhanced reliable classical optical communications.

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