Experimental generation of 8.4 dB entangled state with an optical cavity involving a wedged type-II nonlinear crystal

TL;DR

This paper reports the design and experimental realization of a compact optical device that generates highly entangled light states with 8.4 dB quantum correlations, advancing practical quantum information applications.

Contribution

The authors developed a compact, efficient NOPA with a wedged type-II KTP crystal achieving high entanglement and dispersion compensation in a single device.

Findings

Achieved 8.4 dB entanglement in both quadratures.

Used a triple resonance NOPA with a wedged crystal.

Demonstrated effective dispersion compensation.

Abstract

Entangled state of light is one of the essential quantum resources in quantum information science and technology. Especially, when the fundamental principle experiments have been achieved in labs and the applications of continuous variable quantum information in the real world are considered, it is crucial to design and construct the generation devices of entangled states with high entanglement and compact configuration. We have designed and built an efficient and compact light source of entangled state, which is a non-degenerate optical parametric amplifier (NOPA) with the triple resonance of the pump and two subharmonic modes. A wedged type-II KTP crystal inside the NOPA is used for implementing frequency-down-conversion of the pump field to generate the optical entangled state and achieving the dispersion compensation between the pump and the subharmonic waves. The EPR entangled state of light with quantum correlations of 8.4 dB for both amplitude and phase quadratures are experimentally produced by a single NOPA under the pump power of 75 mW.