Bloch-Siegert shift for multiphoton resonances

TL;DR

This paper introduces a new theoretical approach using a unitary transform and variational energy estimates to accurately analyze Bloch-Siegert shifts in multiphoton resonances, especially away from level anticrossings.

Contribution

It presents a novel unitary transform and a variational method for precise analysis of Bloch-Siegert shifts in multiphoton regimes, extending understanding beyond previous perturbative methods.

Findings

Accurate energy estimates for multiphoton Bloch-Siegert shifts

Effective analysis away from level anticrossings

Wide applicability across coupling constants

Abstract

Recently there has been theoretical and experimental interest in Bloch-Siegert shifts in an intense photon field. A perturbative treatment becomes difficult in this multiphoton regime. We present a unitary transform and rotated model, which allows us to get accurate results away from the level anticrossings. A simple variational energy estimate leads to a new expression for the dressed two-level system energy which is accurate, and useful over a wide range of the dimensionless coupling constant.