Two-mode Schrödinger-cat states with nonlinear optomechanics: generation and verification of non-Gaussian mechanical entanglement

Abstract

Cavity quantum optomechanics has emerged as a new platform for quantum science and technology with applications ranging from quantum-information processing to tests of the foundations of physics. Of crucial importance for optomechanics is the generation and verification of non-Gaussian states of motion and a key outstanding challenge is the observation of a canonical two-mode Schrödinger-cat state in the displacement of two mechanical oscillators. In this work, we introduce a pulsed approach that utilizes the nonlinearity of the radiation-pressure interaction combined with photon-counting measurements to generate this entangled non-Gaussian mechanical state, and, importantly, describe a protocol using subsequent pulsed interactions to verify the non-Gaussian entanglement generated. Our pulsed verification protocol allows quadrature moments of the two mechanical oscillators to be measured up to any finite order providing a toolset for experimental characterisation of bipartite mechanical quantum states and allowing a broad range of inseparability criteria to be evaluated. Key experimental factors, such as optical loss and mechanical decoherence, are carefully analyzed and we show that the scheme is feasible with only minor improvements to current experiments that operate outside the resolved-sideband regime. Our scheme provides a new avenue for quantum experiments with entangled mechanical oscillators and offers significant potential for further research and development that utilizes such non-Gaussian states for quantum-information and sensing applications, and for studying the quantum-to-classical transition.

Can the displacemon device test objective collapse models?

“…( 25) was proposed in Ref. 63, which suggests a twomode displacemon system could be used to test Furry's hypothesis.…”

Quantum manipulation of a two-level mechanical system

“…Improved design and quality of optical cavities [2][3][4], microwave resonators [5,6], and mechanical oscillators [7][8][9][10][11] have facilitated studies of radiation pressure effects in highly coherent regimes. These include mechanical ground state cooling [12][13][14][15][16][17], ultra precise sensing [18][19][20][21][22], generation of non-classical light and mechanical states [23][24][25][26][27][28][29][30][31][32][33], back action cancellation [34][35][36], and detection of gravitational waves [37,38]. The vast majority of these achievements works in a linearized optomechanical regime, where phonons are coupled to photons through bilinear coupling terms, so-called Gaussian interactions.…”

“…Despite these successes, non-Gaussian in-teractions are required to extend the range of opto-and electromechanical applications to the generation of non-classical states with negative Wigner functions [39]. Some proposals achieve this goal by post-selecting measurement results [28,31,32], but for several application it is desirable to have a deterministic protocol.…”