Quantumness and speedup limit of a qubit under transition-frequency modulation
Amin Rajabalinia, Mahshid Khazaei Shadfar, Farzam Nosrati, Ali Mortezapour, Roberto Morandotti, Rosario Lo Franco · Physical Review A · 2022
The control and maintenance of the quantum properties of an open quantum system along its evolution are 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 figure of merit ${\mathfrak{R}}_{\mathfrak{g}}$, we discover that the relation between quantum speed limit time 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.