Fractional Quantum Zeno and Anti-Zeno Effects in Open Quantum Systems

Undergraduate quantum mechanics implicitly assumes that a quantum-mechanical system has no interaction with the outside. In reality, physical systems are constantly exchanging with their surroundings — receiving external noise, or being acted upon through measurement. The field of "open quantum systems" addresses such systems open to the outside. We have found that when an open quantum system interacting with an infinite-degree-of-freedom environment is measured repeatedly at short time intervals, its time evolution can be either suppressed (quantum Zeno effect) or accelerated (quantum anti-Zeno effect). Although Zeno/anti-Zeno effects have been discussed by many physicists, the effects we found arise from a physical mechanism distinct from the conventional ones. In this seminar I discuss these new phenomena — fractional quantum Zeno and anti-Zeno effects — which arise precisely because quantum systems are subject to "measurement" and "interaction with an infinite-degree-of-freedom environment".