Controlling qubit-oscillator systems using linear parameter sweeps

• Published in: New journal of physics Vol. 25; no. 9; pp. 93011 - 93025
• Main Authors: Ashhab, Sahel, Fuse, Tomoko, Yoshihara, Fumiki, Kim, Sunmi, Semba, Kouichi
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.09.2023
• Subjects: Asymmetry; Circuits; Excitation; Ground state; Harmonic oscillators; Landau–Zener transitions; Parameters; Phase transitions; Physics; Quantum computing; quantum quench; quantum Rabi model; superradiance phase transition
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/acf2b9

Abstract We investigate the dynamics of a qubit-oscillator system under the influence of a linear sweep of system parameters. We consider two main cases. In the first case, we consider sweeping the parameters between the regime of a weakly correlated ground state and the regime of a strongly correlated ground state, a situation that can be viewed as a finite-duration quench between two phases of matter: the normal phase and the superradiant phase. Excitations are created as a result of this quench. We investigate the dependence of the excitation probabilities on the various parameters. We find a qualitative asymmetry in the dynamics between the cases of a normal-to-superradiant and superradiant-to-normal quench. The second case of parameter sweeps that we investigate is the problem of a Landau–Zener sweep in the qubit bias term for a qubit coupled to a harmonic oscillator. We analyze a theoretical formula based on the assumption that the dynamics can be decomposed into a sequence of independent Landau–Zener transitions. In addition to establishing the conditions of validity for the theoretical formula, we find that under suitable conditions, deterministic and robust multi-photon state preparation is possible in this system.