High fidelity entanglement of neutral atoms via a Rydberg-mediated single-modulated-pulse controlled-PHASE gate

TL;DR

This paper demonstrates a high-fidelity two-qubit controlled-PHASE gate using a single modulated pulse in neutral Rb atoms, achieving over 98% entanglement fidelity, advancing quantum information processing.

Contribution

It introduces a novel single-pulse, Rydberg-mediated controlled-PHASE gate with waveform modulation, improving fidelity and operational simplicity in neutral atom quantum computing.

Findings

Raw entanglement fidelity of 0.945(6)

Operation fidelity of 0.980(7) after error correction

Complete gate operation within a single pulse

Abstract

Neutral atom platform has become an attractive choice to study the science of quantum information and quantum simulation, where intense efforts have been devoted to the entangling processes between individual atoms. For the development of this area, two-qubit controlled-PHASE gate via Rydberg blockade is one of the most essential elements. Recent theoretical studies have suggested the advantages of introducing non-trivial waveform modulation into the gate protocol, which is anticipated to improve its performance towards the next stage. We report our recent experimental results in realizing a two-qubit controlled-PHASE($C_Z$) gate via off-resonant modulated driving(ORMD) embedded in two-photon transition for Rb atoms. It relies upon a single modulated driving pulse with a carefully calculated smooth waveform to gain the appropriate phase accumulations required by the two-qubit gate. Combining this $C_Z$ gate with global microwave pulses, two-atom entanglement is generated with the raw fidelity of 0.945(6). Accounting for state preparation and measurement (SPAM) errors, we extract the entanglement operation fidelity to be 0.980(7). Our work features completing the $C_Z$ gate operation within a single pulse to avoid shelved Rydberg population, thus demonstrate another promising route for realizing high-fidelity two-qubit gate for neutral atom platform.