Generation of macroscopic Schr\"odinger-cat states in qubit-oscillator systems

TL;DR

This paper proposes a method to generate macroscopic Schr"odinger-cat states in a qubit-oscillator system using a conditional displacement mechanism driven by a monochromatic qubit drive, applicable across various quantum platforms.

Contribution

It introduces a novel scheme for creating macroscopic superpositions in oscillators via qubit-driven conditional displacement, with detailed analysis for both closed and open systems.

Findings

Enhanced oscillator displacement exceeding zero-point fluctuations.

Feasible implementation in cavity-QED, circuit-QED, and electromechanical systems.

Effective state generation through near-resonant driving and small detuning.

Abstract

We propose a scheme to generate macroscopic Schr\"odinger-cat states in a quantum harmonic oscillator (electromagnetic field or mechanical resonator) coupled to a quantum bit (two-level system) via a conditional displacement mechanism. By driving the qubit monochromatically, the oscillation of the qubit state modifies the effective frequency of the driving force acting on the oscillator, and a resonant or near-resonant driving on the oscillator can be achieved. The displacement of the oscillator is then significantly enhanced due to the small detuning of the driving force and can exceed that of the zero-point fluctuation. This effect can be used to prepare quantum superpositions of macroscopically distinct coherent states in the oscillator. We present detailed studies on this state-generation scheme in both the closed- and open-system cases. This approach can be implemented in various experimental platforms, such as cavity- or circuit-QED systems, electromechanical systems, and spin-cantilever systems.