Tunneling under Coherent Control by Sequences of Unitary Pulses

TL;DR

This paper explores how sequences of unitary pulses can control quantum tunneling, either suppressing or accelerating it, by affecting interference without causing decoherence, and compares different control protocols including dynamical decoupling and quantum Zeno effects.

Contribution

It introduces a unified framework for controlling quantum tunneling using deterministic and stochastic unitary pulse sequences, highlighting their effects on quantum interference phenomena.

Findings

Control sequences can suppress or accelerate tunneling.

Stochastic pulse sequences can mimic quantum Zeno and anti-Zeno effects.

Interplay between coherent and incoherent dynamics is crucial.

Abstract

A general coherent control scenario to suppress, or accelerate, tunneling of quantum states decaying into a continuum, is investigated. The method is based on deterministic, or stochastic, sequences of unitary pulses that affect the underlying interference phenomena responsible for quantum dynamics, without inducing decoherence, or collapsing the coherent evolution of the system. The influence of control sequences on the ensuing quantum dynamics is analyzed by using perturbation theory to first order in the control pulse fields and compared to dynamical decoupling (DD) protocols and sequences of pulses that collapse the coherent evolution and induce quantum Zeno (QZE) or quantum anti-Zeno effects (AZE). The analysis reveals a subtle interplay between coherent and incoherent phenomena and demonstrating that dynamics analogous to evolution due to QZE or AZE can be generated from stochastic sequences of unitary pulses when averaged over all possible realizations.