Generation of Schr\"odinger cat states through photon-assisted Landau-Zener-St\"uckelberg interferometry

TL;DR

This paper introduces a new method to generate Schr"odinger cat states using photon-assisted Landau-Zener-St"uckelberg interferometry in a qubit-cavity system, achieving high fidelity in state preparation.

Contribution

The authors propose a novel protocol involving three sweeps of qubit energy to produce high-fidelity Schr"odinger cat states from coherent photon states.

Findings

High-fidelity (∼0.99) cat states can be generated for coherent states with |α|^2 ≈ 10.

The protocol effectively purifies photon parity, creating states close to ideal Schr"odinger cats.

Potential for quantum information transfer between qubit and cat states.

Abstract

Schr\"odinger cat states are useful for many applications, ranging from quantum information processing to high-precision measurements. In this paper we propose a conceptually new method for creating such cat states, based on photon-assisted Landau-Zener-St\"uckelberg interferometry in a hybrid system consisting of a qubit coupled to a photon cavity. We show that by initializing the qubit in one of its basis states, performing three consecutive sweeps of the qubit energy splitting across the 1-photon resonance, and finally projecting the qubit to the same basis state, the parity of the photon field can be purified to very high degree; when the initial photon state is a coherent state, the final state will then be very close to a Schr\"odinger cat state. We present numerical simulations that confirm that our protocol could work with high fidelity ($\sim 0.99$) for coherent states of reasonable size ($|\alpha|^2 \sim 10$). Furthermore, we suggest that our protocol can also be used to transfer quantum information between the qubit and a superposition of orthogonal cat states in the cavity.