Quantum-enhanced correlated interferometry for fundamental physics tests

Improvements in measurement precision have historically led to new scientific discoveries, with gravitational wave detection being a recent prime example. The research field of quantum metrology deals with improving the resolution of instruments that are otherwise limited by quantum shot-noise. Quantum metrology is therefore a promising avenue for enabling scientific breakthroughs. Here we present the first feasibility tests of quantum-enhanced correlated interferometry, which outperforms the sensitivity of a single interferometer in revealing faint stochastic noise by several orders of magnitude. Using quantum-enhanced correlation techniques we detected an injected signal,invisible to the single interferometer, reaching a sensitivity of 3 × 10⁻¹⁷ m/√Hz (1/20 of the shot-noise) at $13.5 MHz in a fewseconds of integration time. By injecting bipartite quantum correlated statesinto the interferometers we also demonstrated a noise reduction in the subtraction of the interferometer outputs. The experimental techniques employed here could potentially be applied to solve open questions in fundamental physics, such as the detection of the stochastic gravitational wave background or primordial black holes, or to test the predictions of particular Planckscale theories.