The Quantum Speed Limit of Optimal Controlled Phasegates for Trapped Neutral Atoms

TL;DR

This paper investigates the fundamental speed limits of controlled phasegates for ultracold atoms in optical traps, using optimal control theory to determine the shortest possible high-fidelity gate times considering interaction and motional constraints.

Contribution

It introduces a comprehensive analysis of the quantum speed limit for controlled phasegates in neutral atoms, accounting for long-range interactions and motional dynamics.

Findings

Gate time limited by interaction strength or vibrational motion

Optimal pulse shaping restores motional state after gate

Identifies fundamental speed constraints for neutral atom gates

Abstract

We study controlled phasegates for ultracold atoms in an optical potential. A shaped laser pulse drives transitions between the ground and electronically excited states where the atoms are subject to a long-range 1/R^3 interaction. We fully account for this interaction and use optimal control theory to calculate the pulse shapes. This allows us to determine the minimum pulse duration, respectively, gate time T that is required to obtain high fidelity. We accurately analyze the speed limiting factors, and we find the gate time to be limited either by the interaction strength in the excited state or by the ground state vibrational motion in the trap. The latter needs to be resolved by the pulses in order to fully restore the motional state of the atoms at the end of the gate.