Quantumness and speedup limit of a qubit under transition frequency modulation

TL;DR

This paper investigates how frequency modulation of a qubit in a leaky cavity can enhance quantum coherence and speed up its evolution, revealing new insights into the relationship between quantum speed limits and non-Markovianity.

Contribution

It introduces a novel frequency modulation scheme for qubits, demonstrating improved quantum coherence protection and a generalized relation between quantum speed limit and non-Markovianity.

Findings

Optimized quantum witness detects coherence preservation.

Frequency modulation induces evolution speedup.

Relation between QSLT and non-Markovianity depends on initial state.

Abstract

Controlling and maintaining quantum properties of an open quantum system along its evolution is essential for both fundamental and technological aims. We assess the capability of a frequency-modulated qubit embedded in a leaky cavity to exhibit enhancement of its dynamical quantum features. The qubit transition frequency is sinusoidally modulated by an external driving field. We show that a properly optimized quantum witness effectively identifies quantum coherence protection due to frequency modulation while a standard quantum witness fails. We also find an evolution speedup of the qubit through proper manipulation of the modulation parameters of the driving field. Importantly, by introducing a new figure of merit Rg, we discover that the relation between Quantum Speed Limit Time (QSLT) and non-Markovianity depends on the system initial state, which generalizes previous connections between these two dynamical features. The frequency-modulated qubit model thus manifests insightful dynamical properties with potential utilization against decoherence.