Quantum fisher information of an optomechanical force sensor driven by a squeezed vacuum field.

We investigate the enhancement in sensitivity when measuring a weak force through the optical response of an optomechanical oscillator driven by squeezed light. In the context of a quantum sensor based on cavity-optomechanics, the sensitivity scaling measured by the quantum Fisher information for a squeezed vacuum state pump is compared to that for a coherent state pump. We show that squeezed state inputs can produce noise levels below the standard quantum limit and even the Heisenberg limit in given regimes. This study shows that new pathways can be opened for enhanced quantum sensing with optomechanical systems conducive to measuring various physical quantities such as gravitational force, acceleration, and acoustics.

Band-edge lasers based on randomly mixed photonic crystals.

By employing two-dimensional InGaAsP photonic band-edge lasers, we have experimentally demonstrated that a random mixture of two different photonic crystals (PCs) possesses a new band structure that is intermediate to that of the two host PCs. The photonic band-edges shift monotonically, but with a strong bowing effect, as the mixed PC system is systematically transformed from one PC to the other. The experimental observations are in excellent agreement with finite-difference time-domain simulations and model calculations based on virtual-crystal approximation with compositional disorder effect included.

Squeezed-light-driven force detection with an optomechanical cavity in a Mach-Zehnder interferometer.

We analyze the performance of a force detector based on balanced measurements with a Mach-Zehnder interferometer incorporating a standard optomechanical cavity. The system is driven by a coherent superposition of coherent light and squeezed vacuum field, providing quantum correlation along with optical coherence in order to enhance the measurement sensitivity beyond the standard quantum limit. We analytically find the optimal measurement strength, squeezing direction, and squeezing strength at which the symmetrized power spectral density for the measurement noise is minimized below the standard quantum limit. This force detection scheme based on a balanced Mach-Zehnder interferometer provides better sensitivity compared to that based on balanced homodyne detection with a local oscillator in the low frequency regime.