# Speeding up adiabatic passage with an optimal modified Roland-Cerf protocol

## TL;DR

This paper introduces an optimal modified Roland-Cerf protocol that accelerates adiabatic passage in two-level quantum systems using simple on-off modulation of local adiabaticity, achieving perfect fidelity efficiently.

## Contribution

It presents a novel, optimal control-based modification to the Roland-Cerf protocol that enables faster, monotonic detuning control for adiabatic passage with high fidelity.

## Key findings

- Achieves perfect adiabatic passage for durations above π/Ω
- Uses optimal control to determine minimal-time pulse sequences
- Provides continuous, monotonic detuning control

## Abstract

In this article we propose a novel method to accelerate adiabatic passage in a two-level system with only longitudinal field (detuning) control, while the transverse field is kept constant. The suggested method is a modification of the Roland-Cerf protocol, during which the parameter quantifying local adiabaticity is held constant. Here, we show that with a simple ``on-off" modulation of this local adiabaticity parameter, a perfect adiabatic passage can be obtained for every duration larger than the lower bound $\pi/\Omega$, where $\Omega$ is the constant transverse field. For a fixed maximum amplitude of the local adiabaticity parameter, the timings of the ``on-off" pulse-sequence which achieves perfect fidelity in minimum time are obtained using optimal control theory. The corresponding detuning control is continuous and monotonic, a significant advantage compared to the detuning variation at the quantum speed limit which includes non-monotonic jumps. The proposed methodology can be applied in several important core tasks in quantum computing, for example to the design of a high fidelity controlled-phase gate, which can be mapped to the adiabatic quantum control of such a qubit. Additionally, it is expected to find applications across all Physics disciplines which exploit the adiabatic control of such a two-level system.