Creation and manipulation of Schr\"odinger cat states based on semiclassical predictions

TL;DR

This paper proposes a method to generate Schrödinger cat states using a quantum measurement-induced gate, employing semiclassical predictions to accurately model the output state with high fidelity.

Contribution

It introduces a semiclassical approach to predict and analyze the creation of Schrödinger cat states via a quantum measurement-induced gate, achieving high fidelity in the output state.

Findings

Semiclassical predictions match the exact quantum solution with fidelity over 0.99.

The method effectively generates minimally disturbed cat-like states.

The approach simplifies modeling of complex quantum states in this context.

Abstract

We consider the generation of Schr{\"o}dinger cat states using a quantum measurement-induced logical gate where entanglement between the input state of the target oscillator and the Fock state of the ancillary system produced by the quantum non-demolition entangling $\hat{C}_Z$ operation is combined with the homodyne measurement. We utilize the semiclassical approach to construct both the input-output mapping of the field variables in the phase space and the wave function of the output state. This approach is found to predict that the state at the gate output can be represented by a minimally disturbed cat-like state which is a superposition of two copies of the initial state symmetrically displaced by momentum variable. For the target oscillator prepared in the coherent state, we show that the fidelity between the exact solution for the gate output state and the ``perfect'' Schr{\"o}dinger cat reconstructed from the semiclassical theory can reach high values exceeding 0.99.