Laser-free trapped ion entangling gates with AESE: Adiabatic Elimination of Spin-motion Entanglement

TL;DR

This paper introduces a laser-free entangling gate for trapped ions using adiabatic elimination of spin-motion entanglement, enabling high-fidelity operations without precise mode tuning and reducing decoherence effects.

Contribution

It presents a novel AESE-based gate scheme that suppresses spin-motion entanglement across multiple modes without tuning control fields, applicable with electronic or magnetic field gradients.

Findings

AESE enables simultaneous multi-mode spin-motion decoupling.

The scheme reduces sensitivity to motional decoherence.

High-fidelity gates are achievable at Doppler temperatures.

Abstract

We discuss a laser-free, two-qubit geometric phase gate technique for generating high-fidelity entanglement between two trapped ions. The scheme works by ramping the spin-dependent force on and off slowly relative to the gate detunings, which adiabatically eliminates the spin-motion entanglement (AESE). We show how gates performed with AESE can eliminate spin-motion entanglement with multiple modes simultaneously, without having to specifically tune the control field detunings. This is because the spin-motion entanglement is suppressed by operating the control fields in a certain parametric limit, rather than by engineering an optimized control sequence. We also discuss physical implementations that use either electronic or ferromagnetic magnetic field gradients. In the latter, we show how to ``AESE" the system by smoothly turning on the \textit{effective} spin-dependent force by shelving from a magnetic field insensitive state to a magnetic field sensitive state slowly relative to the gate mode frequencies. We show how to do this with a Rabi or adiabatic rapid passage transition. Finally, we show how gating with AESE significantly decreases the gate's sensitivity to common sources of motional decoherence, making it easier to perform high-fidelity gates at Doppler temperatures.