Influence of the interaction geometry on the fidelity of the two-qubit Rydberg blockade gate

Abstract

We present a comparative analysis of physical constraints limiting the quality of spin entanglement created using the Rydberg blockade technique in an ensemble of trapped neutral 87Rb atoms. Based on the approach developed earlier in Phys. Rev. A 106, 042410 (2022)PLRAAN1050-294710.1103/PhysRevA.106.042410, we consider the complete multilevel Zeeman structure of the interacting atoms and apply our simulations to two excitation geometries featured by different transition types, both feasible for experimental verification. We demonstrate that the blockade shift strongly depends not only on the interatomic separation but also on the angular position of the atom pair with respect to the quantization axis determined by polarization of the driving fields. As an example, we have estimated fidelity for a promising design of a CZ gate, recently proposed by Levine et al. [Phys. Rev. Lett. 123, 230501 (2019)PRLTAO0031-900710.1103/PhysRevLett.123.230501] for various possible experimental geometries. Anisotropic effects in entangling gates considered here are important for the optimal choice of proper geometry for quantum computing in two- and three-dimensional arrays of atomic qubits and are of considerable interest for quantum simulators, especially those that are designed for anisotropic physical models.