Quantum state driving: measurements versus pulses

TL;DR

This paper explores how dynamical measurements and pulses can be used to control quantum systems, providing bounds for success and analyzing their resilience against noise, with implications for adiabatic quantum computation.

Contribution

It introduces a framework for dynamical measurements and pulses, extending the quantum Zeno effect to moving bases and analyzing their effectiveness and noise resilience.

Findings

Systems remain in the dynamical eigenbasis with slow changes.

Explicit bounds for application rate ensure high success probability.

Both methods are resilient against non-Markovian noise.

Abstract

The quantum Zeno effect is well-known for fixing a system to an eigenstate by frequent measurements. It is also known that applying frequent unitary pulses induces a Zeno subspace that can also pin the system to an eigenspace. Both approaches have been studied as means to maintain a system in a certain subspace. Extending the two concepts, we consider making the measurements/pulses dynamical so that the state can move with the motion of the measurement axis/pulse basis. We show that the system stays in the dynamical eigenbasis when the measurements/pulses are slowly changing. Explicit bounds for the apply rate that guarantees a success probability are provided. In addition, both methods are inherently resilient against non-Markovian noise. Finally, we discuss the similarities and differences between the two methods and their connection to adiabatic quantum computation.