Tuning the initial phase to control the final state of a driven qubit

TL;DR

This paper explores how initial phase tuning in a driven qubit can control its final state, enabling quantum coherent control and transition suppression through interference effects in single-passage Landau-Zener-Stuckelberg-Majorana dynamics.

Contribution

It introduces a method to achieve complete localization in a target state by tuning initial phase and system parameters during single-passage LZSM processes.

Findings

Initial phase tuning can suppress or enhance state transitions.

Varying system parameters enables control over quantum state evolution.

Achieves transitionless driving in a driven qubit system.

Abstract

A driven quantum system can experience Landau-Zener-Stuckelberg-Majorana (LZSM) transitions between its states, when the respective energy levels quasi-cross. If this quasicrossing is traversed repeatedly under periodic driving, the trajectories can interfere either constructively or destructively. In the latter case, known as coherent destruction of tunneling, the transition between the energy states is suppressed. Even for the double-passage case, the accumulated phase difference (also referred to as the Stuckelberg phase) can lead to destructive interference, resulting in no transition. In this paper, we discuss a similar process for the single-passage dynamics. We study the LZSM single-passage problem starting from a superposition state. The phase difference of this initial state results in interference. When this results in either a zero or a unit transition probability, such a situation can be called single-passage complete localization in a target state. The phase can be chosen so that the occupation probabilities do not change after the transition, which is analogous to the problem of transitionless driving. We demonstrate how varying the system parameters (driving velocity, initial phase, initial detuning) can be used for quantum coherent control.