Beam focusing and reduction of quantum uncertainty in width at the few-photon level via multi-spatial-mode squeezing

TL;DR

This paper demonstrates that multi-spatial-mode squeezing enables laser beam focusing at the few-photon level while simultaneously reducing quantum uncertainty in width, surpassing classical and single-mode approaches.

Contribution

It introduces a novel method using multi-spatial-mode squeezing to achieve simultaneous beam focusing and width uncertainty reduction at the quantum level.

Findings

Successful realization of laser focusing at the few-photon level.

Significant suppression of local intensity fluctuations.

Potential applications in quantum-enhanced imaging and nanometer displacement measurements.

Abstract

We show for the first time that it is possible to realize laser beam focusing at the few-photon level in the four-wave-mixing process, and at the same time, reducing the quantum uncertainty in width. The reduction in quantum uncertainty results directly from the strong suppression of local intensity fluctuations. This surprising effect of simultaneous focusing and reduction of width uncertainty is enabled by multi-spatial-mode squeezing, and is not possible via any classical optical approach or single-spatial-mode squeezing. Our results open promising possibilities for quantum-enhanced imaging, bio-sensing and metrology including measurements of nanometer displacement.