Quantum Zeno and anti-Zeno effects induced by either frequent measurements, modulations, or a mix of them

TL;DR

This paper compares the effects of frequent measurements, modulations, and their combination on quantum spin transition probabilities, revealing conditions for transition suppression, freezing, and enhancement across different distributions.

Contribution

It provides a numerical comparison of quantum Zeno and anti-Zeno effects induced by measurements and modulations, highlighting their distinct impacts on transition probabilities.

Findings

Frequent modulations suppress transition probabilities most at short pulse delays.

Decoherence freezing occurs with frequent phase modulations.

Transition probabilities are enhanced under frequent modulations at large pulse delays.

Abstract

Using numerical calculations, we compare the collective transition probabilities of many spins in random magnetic fields, subject to either frequent projective measurements, frequent phase modulations, or a mix of modulations and measurements. For three different distribution functions (Gaussian, Lorentzian, and exponential) we consider here, the transition probability under frequent modulations is suppressed most if the pulse delay is short and the evolution time is larger than a critical value. Furthermore, decoherence freezing (with a transition rate equals to zero) occurs when there are frequent phase modulations, while the transition rate only decreases when there are frequent measurements and a mix of them, as the pulse delay approaches zero. In the large pulse-delay region, however, the transition probabilities under frequent modulations are enhanced more than those under either frequent measurements or a mix of modulations and measurements.