Schr\"odinger's cat in an optical sideband

TL;DR

This paper introduces a novel method for photon subtraction in optical sidebands using phase modulation, enabling the creation of Schr"odinger's cat states with measurable quantum negativity.

Contribution

It presents a new technique employing phase modulation as a frequency sideband beamsplitter for photon subtraction in continuous-wave light.

Findings

Successful creation of optical Schr"odinger's cat state at 500MHz sideband

Wigner function shows negativity of -0.088, confirming non-classicality

Method demonstrates direct homodyne measurement of quantum states in sidebands

Abstract

We propose a method to subtract a photon from a double sideband mode of continuous-wave light. The central idea is to use phase modulation as a frequency sideband beamsplitter in the heralding photon subtraction scheme, where a small portion of the sideband mode is downconverted to the carrier frequency to provide a trigger photon. An optical Schr\"odinger's cat state is created by applying the propesed method to a squeezed state at 500MHz sideband, which is generated by an optical parametric oscillator. The Wigner function of the cat state reconstructed from a direct homodyne measurement of the 500MHz sideband modes shows the negativity of $W(0,0) = -0.088\pm0.001$ without any loss corrections.