Single temporal-pulse-modulated parameterized controlled-phase gate for Rydberg atoms

TL;DR

This paper presents a robust, high-fidelity controlled-phase gate for neutral Rydberg atoms using a single temporal pulse modulation, enabling flexible phase control and suitability for NISQ quantum computing.

Contribution

It introduces a novel adiabatic protocol with single-temporal-modulation for implementing a continuous-phase controlled gate with high fidelity in neutral Rydberg atoms.

Findings

Achieves over 99.7% fidelity for various phase angles within 1 microsecond.

Maintains about 98.4% fidelity for a π-phase gate under realistic experimental imperfections.

Provides a robust and flexible method for phase adjustment in neutral-atom quantum gates.

Abstract

We propose an adiabatic protocol for implementing a controlled-phase gate CZ$_{\theta}$ with continuous $\theta$ of neutral atoms through a symmetrical two-photon excitation process via the second resonance line, $6P$ in $^{87}$Rb, with a single-temporal-modulation-coupling of the ground state and intermediate state. Relying on different adiabatic paths, the phase factor $\theta$ of CZ$_{\theta}$ gate can be accumulated on the logic qubit state $|11\rangle$ alone by calibrating the shape of the temporal pulse where strict zero amplitudes at the start and end of the pulse are not needed. For a wide range of $\theta$, we can obtain the fidelity of CZ$_{\theta}$ gate over $99.7\%$ in less than $1~\mu$s, in the presence of spontaneous emission from intermediate and Rydberg states. And in particular for $\theta=\pi$, we benchmark the performance of the CZ gate by taking into account various experimental imperfections, such as Doppler shifts, fluctuation of Rydberg-Rydberg interaction strength, inhomogeneous Rabi frequency, and noise of driving fields, etc, and show that the predicted fidelity is able to maintain at about $98.4\%$ after correcting the measurement error. This gate protocol provides a robustness against the fluctuation of pulse amplitude and a flexible way for adjusting the entangling phase, which may contribute to the experimental implementation of near-term noisy intermediate-scale quantum (NISQ) computation and algorithm with neutral-atom systems.