Quantum anti-Zeno effect without rotating wave approximation

TL;DR

This paper investigates the quantum Zeno and anti-Zeno effects in a two-level system without using the rotating wave approximation, revealing conditions under which each effect occurs or disappears.

Contribution

It provides a systematic analysis of the quantum Zeno and anti-Zeno effects without RWA, clarifying their dependence on spectral distributions and state renormalization.

Findings

QAZE can occur for bare excited states without RWA.

QAZE disappears for physical dressed states, leaving only QZE.

Transition from QZE to QAZE depends on measurement interval.

Abstract

In this paper, we systematically study the spontaneous decay phenomenon of a two-level system under the influences of both its environment and continuous measurements. In order to clarify some well-established conclusions about the quantum Zeno effect (QZE) and the quantum anti-Zeno effect (QAZE), we do not use the rotating wave approximation (RWA) in obtaining an effective Hamiltonian. We examine various spectral distributions by making use of our present approach in comparison with other approaches. It is found that with respect to a bare excited state even without the RWA, the QAZE can still happen for some cases, e.g., the interacting spectra of hydrogen. But for a physical excited state, which is a renormalized dressed state of the atomic state, the QAZE disappears and only the QZE remains. These discoveries inevitably show a transition from the QZE to the QAZE as the measurement interval changes.