Detector-Frame Quantum Limits for Heterodyne Timing in Relativistic Optical Links

Abstract:Long-baseline optical links for space interferometry and satellite quantum networks rely on heterodyne phase tracking under Doppler motion and gravitational frequency shifts. These relativistic shifts can generate large detector-frame beat-frequency offsets over finite readout windows and thereby constrain the temporal precision of front-end phase readout. We develop a detector-frame framework for this problem using an effective two-mode signal--local-oscillator model in which relativistic motion rescales the local-oscillator frequency. Within this setting we derive closed-form Mandelstam--Tamm and Margolus--Levitin bounds for representative Gaussian resources and connect global state distinguishability with the operational precision of heterodyne phase tracking. In the bright-local-oscillator regime we identify a geometric--operational mismatch: the joint optical state can evolve on arbitrarily short global timescales while the relevant information rate is set by the measured detector record. Combining this result with an open-loop transient-acquisition analysis, we show that white phase noise and relativistic beat-frequency drift that is approximately constant over the acquisition window generate a cube-root scaling benchmark for the optimal pre-lock open-loop integration window and the minimum residual phase error. These results establish detector-frame benchmarks for quantum-limited heterodyne timing in relativistic optical links and clarify how global dynamical bounds enter task-restricted continuous optical measurements.

36 pages, 1 figure. Published in Advanced Quantum Technologies

arXiv:2610.13963 [quant-ph]

(or arXiv:2610.13963v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.13963 Focus to learn more arXiv-issued DOI via DataCite

https://doi.org/10.1002/qute.70446 Focus to learn more DOI(s) linking to related resources

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