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

TL;DR

This paper explores hybrid quantum measurement protocols combining quadrature measurements and quanta addition/subtraction to generate non-classical states in macroscopic bosonic systems, with potential applications in quantum information and fundamental physics.

Contribution

It introduces and compares new permutation protocols of quantum non-demolition measurements and quanta addition/subtraction for non-classical state generation, demonstrating their effectiveness and robustness.

Findings

Quadrature measurements significantly enhance non-classicality.

Protocols are robust to initial thermal occupation.

Comparison shows improved non-classicality with quadrature measurement over squeezing.

Abstract

Non-classical 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 non-demolition quadrature measurements and single quanta addition/subtraction to prepare quantum superposition states in bosonic systems. The performance of each permutation is quantified and compared using several different non-classicality criteria including Wigner negativity, non-classical 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 non-classicality 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.