A signature of quantumness in pure decoherence control

TL;DR

This paper investigates a decoherence reduction method involving intermediate measurements on qubits, revealing conditions for coherence gain and highlighting quantum effects related to Hamiltonian non-commutation.

Contribution

It identifies when intermediate measurements always enhance coherence and demonstrates the quantum nature of coherence loss through non-commuting Hamiltonian terms.

Findings

The scheme generally increases coherence regardless of measurement timing.

Quantum effects emerge from non-commuting Hamiltonian components.

Coherence behavior varies, favoring gain over loss in certain models.

Abstract

We study a decoherence reduction scheme that involves an intermediate measurement on the qubit in an equal superposition basis, in the general framework of all qubit-environment interactions that lead to qubit pure decoherence. We show under what circumstances the scheme always leads to a gain of coherence on average, regardless of the time at which the measurement is performed, demonstrating its wide range of applicability. Furthermore, we find that observing an average loss of coherence is a highly quantum effect, resulting from non-commutation of different terms in the Hamiltonian. We show the diversity of behavior of coherence as effected by the application of the scheme, which is skewed towards gain rather than loss, on a variant of the spin-boson model that does not fulfill the commutation condition.