We design, by invariant-based inverse engineering, driving fields that invert the population of a two-level atom in a given time, robustly with respect to dephasing noise and/or systematic frequency shifts. Without imposing constraints, optimal protocols are insensitive to the perturbations but need an infinite energy. For a constrained value of the Rabi frequency, a flat pi pulse is the least sensitive protocol to phase noise but not to systematic frequency shifts, for which we describe and optimize a family of protocols

We theoretically investigate the motional excitation of a single ion caused by spring-constant and position fluctuations of a harmonic trap during trap shuttling processes. A detailed study of the sensitivity on noise for several transport protocols and noise spectra is provided. The effect of slow spring-constant drifts is also analyzed. Trap trajectories that minimize the excitation are designed combining invariant-based inverse engineering, perturbation theory, and optimal control.

We propose a theoretical scheme for implementing nonleaky and accelerated population transfer with a transmon qutrit. For a transmon-regime artificial atom with weak level anharmonicity, the leakage effects on the target population transfer are considerable. Allowed by the level-transition rule, a two-photon resonant interaction can be obtained between the qutrit and microwave drivings. In the regime of large detuning, by adopting the technique of invariant-based inverse engineering, the population transfer with no leakage errors can be sped up drastically when compared with the adiabatic operation. Moreover, the accelerated operation is highly robust against decoherence effects. Thanks to these distinctive advantages, the proposed protocol could offer a promising avenue to optimal quantum operations on transmon artificial atoms.

We investigate the excitation of a quantum particle shuttled in a harmonic trap with weak spring-constant colored noise. The Ornstein-Uhlenbeck model for the noise correlation function describes a wide range of possible noises, in particular for short correlation times the white-noise limit examined by Lu et al. [ Phys. Rev. A 89, 063414 (2014)] and, by averaging over correlation times, “$1/f$ flicker noise.” We find expressions for the excitation energy in terms of static (independent of trap motion) and dynamical sensitivities, with opposite behavior with respect to shuttling time, and demonstrate that the excitation can be reduced by proper process timing and design of the trap trajectory.

The quantum Goos-H\"anchen shift for ballistic electrons is investigated in a parabolic potential well under a uniform vertical magnetic field. It is found that the Goos-H\"anchen shift can be negative as well as positive, and becomes zero at transmission resonances. The beam shift depends not only on the incident energy and incidence angle, but also on the magnetic field and Landau quantum number. Based on these phenomena, we propose an alternative way to realize the spin beam splitter in the proposed spintronic device, which can completely separate spin-up and spin-down electron beams by negative and positive Goos-H\"anchen shifts.