Time-dependent transport processes in the adiabatic approximation

D. M. Tong, X. X. Yi, X.J. Fan +2 more

Charlie Oncebay Segura

We present a study of adiabaticity in Nuclear Magnetic Resonance.First, we present a review on the concept of adiabaticity in closed and open quantum systems.Many commonly used adiabatic processes in Magnetic Resonance perform well even though the adiabatic approximation does not appear to hold throughout the process, then through the use Berry's superadiabatic formalism make corrections to the pulse satisfies the adiabatic condition.This approach, a but time-dependent Hamiltonian slowly evolving is iteratively transformed into time-dependent diagonal frames until the most accurate adiabatic approximation is obtained.Examine the capabilities of superadiabatics iterations to produce a shortcut sequence to adiabaticity system and extend the concept of dynamic superadiabatic for open systems, whose evolution is governed by a master equation of Lindblad form, providing the necessary framework to determine the strategy control needed to achieve superadibaticity.

G. F. Drukarev

Sergio Boixo, Rolando D. Somma

A gapped quantum system that is adiabatically perturbed remains approximately in its eigenstate after the evolution. We prove that, for constant gap, general quantum processes that approximately prepare the final eigenstate require a minimum time proportional to the ratio of the length of the eigenstate path to the gap. Thus, no rigorous adiabatic condition can yield a smaller cost. We also give a necessary condition for the adiabatic approximation that depends on local properties of the path, which is appropriate when the gap varies.

J. Hajdu

T. T. Nguyen‐Dang, Evgueni Sinelnikov, Arne Keller +1 more

A perturbative series is derived for the systematic construction of a dynamical invariant (Lewis invariant) for a time-dependent Hamiltonian which is characterized by a time-scale parameter $\ensuremath{\tau}$, as appears in the usual formulation of the adiabatic theorem. The derivations make efficient use of the quantum averaging method, and the perturbative series obtained permits the construction of the invariant in successive orders in $ϵ\ensuremath{\sim}1/\ensuremath{\tau}$, corresponding to high-order adiabatic approximations. The series can be considered and resummed analytically to all orders, yielding an exact invariant for an harmonic oscillator linearly driven by an external field. For a nondegenerate two-level system, approximate invariants have been obtained up to the fifth order and illustrate how the adiabatic approximations of increasing orders successively approach the exact dynamics. The construct is applicable also to Floquet Hamiltonians and, in this context, it furnishes high-order adiabatic representations for the time evolution of Floquet states associated with a material system in an aperiodic laser pulse. We illustrate in particular how an exact Floquet dynamical invariant, defining exact adiabatic transports of Floquet states, is obtained for a laser-driven harmonic vibrational mode.