Spatial dependence of fidelity for a two-qubit Rydberg-blockade quantum gate

TL;DR

This paper investigates how the fidelity of a two-qubit Rydberg-blockade quantum gate varies with spatial parameters, focusing on the effects of atomic states and geometry on gate performance.

Contribution

It provides a detailed analysis of the spatial dependence of the Rydberg blockade gate, including the impact of atomic states and excitation schemes on fidelity.

Findings

Rydberg d-states exhibit stronger angular dependence of blockade shift.

Blockade shift depends on inter-atomic distance and orientation.

Using specific excitation schemes can optimize gate fidelity.

Abstract

We study the spatial performance of the entangling gate proposed by H. Levine et al. (Phys. Rev. Lett. 123, 170503 (2019)). This gate is based on a Rydberg blockade technique and consists of just two global laser pulses which drive nearby atoms. We analyze the multilevel Zeeman structure of interacting $^{87}$Rb Rydberg atoms and model two experimentally available excitation schemes using specific driving beams geometry and polarization. In particular, we estimate the blockade shift dependence on inter-atomic distance and angle with respect to the quantization axis. In addition, we show that using Rydberg $d$-states, in contrast to $s$-states, leads to a pronounced angular dependence of the blockade shift and gate fidelity.