Squeezing enhanced homodyne weak force sensing in cavity optomechanics

Cavity optomechanical systems have emerged as a promising platform for quantum sensing. Quantum mechanics imposes a standard quantum limit (SQL) on the force-sensitivity for the standard homodyne phase quadrature measurement of the cavity's output field. In this paper, we investigate ways to enhance sensitivity beyond SQL for weak-force measurement by adopting a variational homodyne quadrature readout and quantum squeezing. Our study reveals a remarkable improvement in the force sensitivity of a cavity optomechanical sensor at a suitable homodyne angle, compared with standard phase quadrature detection of the cavity output field within a specific frequency band. We show that the force sensitivity can be further improved by intra-cavity squeezing (ICS) or injected external squeezing (IES) of the cavity mode. Both variational homodyne readout and quantum squeezing induce quantum correlation between the amplitude and phase quadratures of the cavity's output field, thereby improving the force sensitivity. The squeezing-enhanced variational homodyne detection scheme can enable high-precision sensing across various hybrid quantum platforms.