Speaker
Description
Continuous-wave interferometers are the sensing backbone of gravitational-wave detectors, but their precision is usually discussed in the regime of standard quantum-limit scaling. In quantum metrology, Heisenberg scaling means that phase-estimation uncertainty improves inversely with the total quantum resource—here, photon flux—rather than with the square root of that resource as in the best classical strategies. In this talk, I will present a continuous-wave Mach-Zehnder interferometer experiment based on two phase-synchronized squeezed-vacuum inputs to estimate a time-dependent phase signal. Our experiment achieves sub-shot-noise performance and demonstrates resource scaling that approaches the Heisenberg limit, in agreement with a model including measured optical loss. A notable feature is that the nonlinear estimation protocol enables quantum-enhanced phase sensing below 1 kHz even though the squeezing is observed at much higher frequencies, effectively separating the signal band from the squeezing band. I will discuss the operating principle, the present loss-limited performance, and the implications of this approach for quantum-noise-limited readout in next-generation gravitational-wave detectors and related continuous interferometric sensors.
Manuscript: https://arxiv.org/abs/2509.25384