Nonclassical-state generation in macroscopic systems via hybrid discrete-continuous quantum measurements

Abstract

Nonclassical-state generation is an important component throughout experimental quantum science for quantum information applications and probing the fundamentals of physics. Here, we investigate permutations of quantum nondemolition quadrature measurements and single quanta addition or subtraction to prepare quantum superposition states in bosonic systems. The performance of each permutation is quantified and compared using several different nonclassicality criteria including Wigner negativity, nonclassical depth, and optimal fidelity with a coherent-state superposition. We also compare the performance of our protocol using squeezing instead of a quadrature measurement and find that the purification provided by the quadrature measurement can significantly increase the nonclassicality generated. Our approach is ideally suited for implementation in light-matter systems such as quantum optomechanics and atomic spin ensembles, and offers considerable robustness to initial thermal occupation.

Combining Floquet and Lyapunov techniques for time-dependent problems in optomechanics and electromechanics

“…A crucial obstacle for a more widespread application of these techniques is the explicit time dependence of the driving electromagnetic fields. Dissipative preparation of mechanical states [4,[9][10][11][12][13][18][19][20][21][22][23][24][25] and tomographic backactionevading measurements of mechanical motion [26][27][28][29][30][31][32][33][34] rely on driving the system with multiple fields at different frequencies while parametric squeezing requires modulation of the optical spring [5,[35][36][37]; both of these approaches result in time-dependent optomechanical Hamiltonians. The steady-state Lyapunov equation can then only be applied under the rotating wave approximation (RWA) which neglects fast oscillating terms in the interaction and only keeps those that are resonant.…”

Nonclassicality and decoherence of photon-added squeezed coherent Schrödinger kitten states in a Kerr medium

“…Another way of studying the nonclassicality of the state is advanced by the nonclassical depth [35,36] that smears a highly singular P -representation with a Gaussian function possessing a variable dispersion so that the smoothed phase space distribution R(t), for a restricted choice of the dispersion parameter, assumes nonnegative values. The nonclassical depth has recently been used [37] to assess the nonclassicality of superposition of quantum states prepared by permutations of nondemolition quadrature experiments and single quanta addition or subtraction. It has also been applied [38] in quantitatively determining the nonclassicality of the non-Gaussian states prepared by utilizing the multiphoton catalysis with coherent state input.…”

Wigner Function Reconstruction in Levitated Optomechanics

“…Those are typically based on noise-cancelling homodyne techniques or sideband-resolved heterodyne methods [1]. With such sensitive measurement tools at hand it is not unreasonable to even expect the observation of non-classical features in domains where one would typically not expect any quantum mechanics to be at work, such as at high temperatures [2] or for highly excited states [3].…”