Higher‐Order Spatially Squeezed Beam for Enhanced Spatial Measurements

Abstract

A scheme is proposed to realize high‐precision spatial measurement of laser beams beyond quantum limit using a novel quantum state called the mth$m{\text{th}}$ order spatially squeezed state, which is the combination of a bright HGm,0$\text{HG}_{m,0}$ mode coherent state and squeezed vacuum HGm+1,0$\text{HG}_{m+1,0}$ mode state. An effective technique for the generation of a rectangular shape higher‐order mode squeezed light with a maximum mode order of 5 is experimentally demonstrated using a doubling resonated optical parametric amplifier. Furthermore, the fourth order tilt‐ and displacement‐squeezed beams are constructed and used to perform spatial tilt and displacement measurements, thereby improving the signal‐to‐noise ratio by 10 and 8.6 dB compared to the HG0,0$\text{HG}_{0,0}$ mode. The results indicate that high‐order spatially squeezed states enhance measurement precision beyond the shot noise limit and are more prominent in back‐action noise reduction. High‐precision spatial measurement has potential practical applications in high‐sensitivity atomic force microscope and super‐resolution quantum imaging.

Tilt Measurement at the Quantum Cramer–Rao Bound Using a Higher-Order Hermite–Gaussian Mode

“…This quantum technique was also demonstrated in the biological measurement beyond the quantum limit [3] and in the spatial entanglement characterization [14]. Recently, there have been experimental demonstrations of higher-order spatially squeezed beams, showing that a higher-order spatially squeezed beam is an effective probe beam used to boost the precision of spatial tilt and displacement measurements [15].…”

Tripartite entanglement in a detuned non-degenerate optical parametric oscillator

“…Continuous variable (CV) entanglement is an important quantum resource in quantum communication, quantum computation and quantum precision measurement [1][2][3].…”