Photon-assisted Landau-Zener transition: Role of coherent superposition states

TL;DR

This paper explores how a quantum two-level system coupled to a photon field in superposition states undergoes Landau-Zener transitions, revealing how photon states influence transition probabilities and entanglement.

Contribution

It provides analytical and qualitative insights into the effects of photon superposition states on Landau-Zener transitions, including the role of the rotating-wave approximation.

Findings

Photon number increases can enhance LZ probability under RWA.

Differences in LZ dynamics emerge without RWA, affecting photon statistics.

Entanglement creation occurs during the LZ process.

Abstract

We investigate a Landau-Zener (LZ) transition process modeled by a quantum two-level system (TLS) coupled to a photon mode when the bias energy is varied linearly in time. The initial state of the photon field is assumed to be a superposition of coherent states, leading to a more intricate LZ transition. Applying the rotating-wave approximation (RWA), analytical results are obtained revealing the enhancement of the LZ probability by increasing the average photon number. We also consider the creation of entanglement and the change of photon statistics during the LZ process. Without the RWA, we find some qualitative differences of the LZ dynamics from the RWA results, e.g., the average photon number no longer monotonically enhances the LZ probability. The ramifications and implications of these results are explored.