Interspecies Förster resonances of Rb-Cs Rydberg d-states for enhanced multi-qubit gate fidelities

Neutral atoms arrays have become a prominent platform for quantum computation due to the scalability of optical tweezers allowing for up to 1000 identical qubits, in which multi-qubit gates are mediated by interactions between highly excited Rydberg states. To realise fault tolerance on a neutral atom platform it is necessary to be able to perform independent and cross-talk free mid-circuit readout of ancilla qubits. One approach to overcome this limitation is to use dual-species arrays, which naturally provides a separation in read- out wavelengths to suppress cross-talk, whilst allowing engineering of different inter and intra-species couplings.

We present an analysis of interspecies interactions between Rydberg d-states of rubidium and cesium. We identify the Förster resonance channels offering the strongest interspecies couplings, demonstrating the viability for performing high-fidelity two- and multi-qubit CkZ gates up to k=4, including accounting for blockade errors evaluated via numerical diagonalization of the pair-potentials. Our results show d-state orbitals offer enhanced suppression of intraspecies couplings compared to s-states, making them well suited for use in large-scale neutral atom quantum processors.