Broadcasting quantum nonlinearity in hybrid systems

TL;DR

This paper proposes a method to broadcast nonlinear quantum operations to linear oscillators using light-mediated interactions with a nonlinear system, enabling advanced quantum processing capabilities.

Contribution

It introduces a scheme for broadcasting quantum nonlinearity to linear systems via light-mediated interactions with a highly nonlinear auxiliary system.

Findings

Verification through negative Wigner function values.

Observation of squeezing below Gaussian thresholds.

Feasibility demonstrated with optically levitated mechanical oscillators.

Abstract

Linear oscillators contribute to most branches of contemporary quantum science. They have already successfully served as quantum sensors and memories, found applications in quantum communication, and hold promise for cluster-state-based quantum computing. To master universal quantum processing with linear oscillators, an unconditional nonlinear operation is required. We propose such an operation using light-mediated interaction with another system that possesses a nonlinearity equivalent to more than a quadratic potential. Such a potential grants access to a nonlinear operation that can be broadcast to the target linear system. The nonlinear character of the operation can be verified by observing adequate negative values of the target system's Wigner function and the squeezing of the variance of a certain nonlinear combination of the quadratures below the thresholds attainable by Gaussian states. We explicitly evaluate an optically levitated mechanical oscillator as a flexible source of nonlinearity for a proof-of-principle demonstration of the nonlinearity broadcasting to linear systems, for example, mechanical oscillators or macroscopic atomic spin ensembles.