Freezing a Coherent Field Growth in a Cavity by Quantum Zeno Effect

TL;DR

This paper demonstrates that repeated quantum measurements can inhibit the evolution of a field in a cavity, illustrating the Quantum Zeno effect and its implications for quantum measurement and feedback.

Contribution

It introduces a method to freeze the coherent evolution of a cavity field using repeated photon number measurements with Rydberg atoms, showcasing a novel application of the Quantum Zeno effect.

Findings

Photon number measurements inhibit field growth in the cavity.

Residual field growth behaves as a random walk in phase space.

The experiment provides insights into measurement back action and quantum feedback.

Abstract

We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a Field injected in the cavity by a classical source. This manifestation of the Quantum Zeno effect illustrates the back action of the photon number determination onto the Field phase. The residual growth of the Field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback.