Superadditive Communication with the Green Machine: A Practical Demonstration of Nonlocality without Entanglement

• URL: http://arxiv.org/abs/2310.05889v4
• Date: Tue, 22 Apr 2025 19:12:05 GMT
• Title: Superadditive Communication with the Green Machine: A Practical Demonstration of Nonlocality without Entanglement
• Abstract summary: Superadditivity -- a higher communication rate than that achievable by symbol-by-symbol optical detection -- is a special case of the well-known nonlocality without entanglement.<n>We build this receiver and show that its capacity surpasses any symbol-by-symbol receivers in the photon-starved regime with binary-phase-shift-keying (BPSK)
• Score: 0.6384650391969042
• License: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Abstract: Achieving the ultimate Holevo limit of optical communication capacity requires a joint-detection receiver which makes a collective quantum measurement over multiple modulated symbols. Such superadditivity -- a higher communication rate than that achievable by symbol-by-symbol optical detection -- is a special case of the well-known nonlocality without entanglement and has yet to be demonstrated. In this article, we propose and demonstrate a design of joint-detection receivers, the Green Machine, that can achieve superadditivity. We build this receiver and show that its capacity surpasses any symbol-by-symbol receivers in the photon-starved regime with binary-phase-shift-keying (BPSK). Our Green Machine receiver can also significantly reduce the transmitter peak power requirement compared with the pulse-position modulation (the conventional modulation format used for deep space laser communication). We further show that the self-referenced phase makes it immune to phase noise, e.g., atmospheric turbulence or platform vibrations.

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