High-bandwidth squeezed light at 1550 nm from a compact monolithic PPKTP cavity

TL;DR

This paper demonstrates broadband squeezed vacuum light at 1550 nm with up to 4.8 dB noise reduction over a wide frequency range, using a compact PPKTP cavity, advancing high-speed quantum communication capabilities.

Contribution

It introduces a novel, compact PPKTP cavity for GHz bandwidth squeezed light generation at 1550 nm, with potential for enhanced quantum key distribution.

Findings

Achieved up to 4.8 dB squeezing from 5 MHz to 100 MHz.

Squeezing of up to 3 dB from 100 MHz to 1.2 GHz.

Proposed detection improvements to reach 10 dB squeezing over 1 GHz.

Abstract

We report the generation of squeezed vacuum states of light at 1550 nm with a broadband quantum noise reduction of up to 4.8 dB ranging from 5 MHz to 1.2 GHz sideband frequency. We used a custom-designed 2.6 mm long biconvex periodically-poled potassium titanyl phosphate (PPKTP) crystal. It featured reflectively coated end surfaces, 2.26 GHz of linewidth and generated the squeezing via optical parametric amplification. Two homodyne detectors with different quantum efficiencies and bandwidths were used to characterize the non-classical noise suppression. We measured squeezing values of up to 4.8 dB from 5 to 100 MHz and up to 3 dB from 100 MHz to 1.2 GHz. The squeezed vacuum measurements were limited by detection loss. We propose an improved detection scheme to measure up to 10 dB squeezing over 1 GHz. Our results of GHz bandwidth squeezed light generation provide new prospects for high-speed quantum key distribution.