Year: 2026
Type: preprint
Abstract: Eve receives genuine average photon counts from two opaque devices, finds input-independent single-party report distributions, and sees little activity in a specified leakage monitor. Do these observations establish physical isolation? We construct a cavity-based counterexample. Independently operated controls activate a shared interaction after the inputs arrive. Internal block measurements yield a CHSH score $S=13/4$ for four repetitions, approaching $4$ for large blocks. A fresh shared random bit symmetrizes the binary results without changing their parity; local preparation of vacuum or one-photon output states then produces truthful photon-number reports with exactly non-signalling marginals. A dispersive-bus model also permits weak monitored leakage; an illustrative dissipative calculation gives $S\simeq3.1702$ with ideal output encoding. These scores exceed $2\sqrt2$ because the devices interact during their response, not because quantum mechanics is violated. The construction separates honest measurement, non-signalling reported statistics, and causal isolation, while making the additional randomness, preparation, and monitoring assumptions explicit.
Source: arXiv (Cornell University)
Author: Wu, Yueying
Institution: University of Illinois Urbana-Champaign
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220923581