Unlike classical measurements, quantum measurements in general disturb the state of a quantum system. This back-action of measurements is a peculiar concept of quantum mechanics which gives rise to striking phenomena such as the quantum Zeno effect (QZE) and quantum anti-Zeno effect (QAZE). In the QZE, repeated measurements hinder the time evolution of the quantum system. However, if the measurements are not rapid enough, a reverse effect, known as a quantum anti-Zeno effect (QAZE), can occur whereby measurements accelerate the quantum evolution. What has been lacking is a rigorous general study of the QZE and QAZE in the presence of coherent driving fields. The idea of controlling the dynamics of a quantum system by an external time-dependent field has found widespread theoretical and experimental interest in many areas of physics and chemistry.


We present a general treatment of the quantum Zeno and anti-Zeno effects for arbitrary driven open quantum systems, assuming only that the system-environment coupling is weak. We start by deriving a general expression for the effective decay rate of a two-level system subjected to arbitrary driving fields as well as periodic measurements. In particular, we consider in detail both the population decay model and the pure dephasing model in the presence of different driving fields. We demonstrate that the driving fields change the decay rate, and hence the quantum Zeno and anti-Zeno behavior, both qualitatively and quantitatively. We also extend our results to systems consisting of more than one two-level system, as well as a two-level system strongly coupled to an environment of harmonic oscillators, to further illustrate the non-trivial effect of the driving fields on the quantum Zeno and anti-Zeno effects.