Fast and robust creation of an arbitrary single qubit state by nonadiabatic shortcut pulses in a three-level system

TL;DR

This paper introduces a fast, robust method for preparing arbitrary single-qubit states using nonadiabatic shortcut pulses in a three-level system, improving speed and fidelity for quantum computing applications.

Contribution

It proposes a novel inverse engineering approach to design shortcut pulses that enhance speed and robustness in qubit state initialization, especially in frequency-dense quantum systems.

Findings

Reduces ion excitation time by a factor of 6.

Enhances robustness against systematic errors.

Applicable to various qubit systems like superconducting qubits.

Abstract

High-fidelity qubit initialization is of significance for efficient error correction in fault tolerant quantum algorithms. Combining two best worlds, speed and robustness, to achieve high-fidelity state preparation and manipulation is challenging in quantum systems, where qubits are closely spaced in frequency. Motivated by the concept of shortcut to adiabaticity, we theoretically propose the shortcut pulses via inverse engineering and further optimize the pulses with respect to systematic errors in frequency detuning and Rabi frequency. Such protocol, relevant to frequency selectivity, is applied to rare-earth ions qubit system, where the excitation of frequency-neighboring qubits should be prevented as well. Furthermore, comparison with adiabatic complex hyperbolic secant pulses shows that these dedicated initialization pulses can reduce the time that ions spend in the excited state by a factor of 6, which is important in coherence time limited systems to approach an error rate manageable by quantum error correction. The approach may also be applicable to superconducting qubits, and any other systems where qubits are addressed in frequency.