Efficient optical cat state generation using squeezed few-photon superposition states

TL;DR

This paper introduces a highly efficient method to generate high-fidelity optical Schr"{o}dinger cat states using squeezed superpositions of zero and two photons, with protocols tolerant to loss and feasible with current technology.

Contribution

Proposes a novel protocol utilizing squeezed superpositions for efficient, high-fidelity optical cat state generation with linear optics and photon detection.

Findings

Achieves >99% fidelity for cat states with size |α|^2=5

Success probability exceeds 50% with current technology

Protocol remains effective with 2% detection loss

Abstract

Optical Schr\"{o}dinger cat states are non-Gaussian states with applications in quantum technologies, such as for building error-correcting states in quantum computing. Yet the efficient generation of high-fidelity optical Schr\"{o}dinger cat states is an outstanding problem in quantum optics. Here, we propose using squeezed superpositions of zero and two photons, $|\theta\rangle = \cos{(\theta/2)}|0\rangle + \sin{(\theta/2)}|2\rangle$, as ingredients for protocols to efficiently generate high-fidelity cat states. We present a protocol using linear optics with success probability $P\gtrsim 50\%$ that can generate cat states of size $|\alpha|^2=5$ with fidelity $F>0.99$. The protocol relies only on detecting single photons and is remarkably tolerant of loss, with $2\%$ detection loss still achieving $F>0.98$ for cats with $|\alpha|^2=5$. We also show that squeezed $\theta$ states are ideal candidates for nonlinear photon subtraction using a two-level system with near deterministic success probability and fidelity $F>0.98$ for cat states of size $|\alpha|^2=5$. Schemes for generating $\theta$ states using quantum emitters are also presented. Our protocols can be implemented with current state-of-the-art quantum optics experiments.