High-fidelity quantum driving

TL;DR

This paper demonstrates the experimental implementation of optimal and superadiabatic control protocols in a two-level quantum system, achieving high fidelity, speed, and robustness against parameter fluctuations, advancing quantum control techniques.

Contribution

It introduces experimentally realized short-cut and superadiabatic protocols that optimize speed and robustness in quantum state manipulation.

Findings

Nearly perfect fidelity achieved with optimal control schemes.

Superadiabatic protocols are highly robust against parameter variations.

Protocols operate at the maximum speed allowed by quantum mechanics.

Abstract

The ability to accurately control a quantum system is a fundamental requirement in many areas of modern science such as quantum information processing and the coherent manipulation of molecular systems. It is usually necessary to realize these quantum manipulations in the shortest possible time in order to minimize decoherence, and with a large stability against fluctuations of the control parameters. While optimizing a protocol for speed leads to a natural lower bound in the form of the quantum speed limit rooted in the Heisenberg uncertainty principle, stability against parameter variations typically requires adiabatic following of the system. The ultimate goal in quantum control is to prepare a desired state with 100% fidelity. Here we experimentally implement optimal control schemes that achieve nearly perfect fidelity for a two-level quantum system realized with Bose-Einstein condensates in optical lattices. By suitably tailoring the time-dependence of the system's parameters, we transform an initial quantum state into a desired final state through a short-cut protocol reaching the maximum speed compatible with the laws of quantum mechanics. In the opposite limit we implement the recently proposed transitionless superadiabatic protocols, in which the system perfectly follows the instantaneous adiabatic ground state. We demonstrate that superadiabatic protocols are extremely robust against parameter variations, making them useful for practical applications.