A Rb-Cs Quantum Computing Testbed

Infleqtion has implemented a dual-species neutral-atom quantum computer using rubidium and cesium.  This two species approach allows the data and ancilla qubits to interact with independent laser and microwave frequencies.  Unwanted crosstalk between these sets is thereby eliminated, enabling fast global mid-circuit measurement without atom motion or state-based hiding, a key capability for error corrected operation.  In a checkerboard configuration, crosstalk on nearest neighbors during addressed single qubit operations is also not present.  Two qubit inter-species gates are implemented using Rydberg blockade gates.  In our implementation, rubidium and cesium are loaded into a 2D array with 5.5 μm spacing.  We will present Rydberg blockade calculations at various quantum numbers for the Rb-Cs pair, the demonstration and benchmarking of an inter-species CZ gate with 97.5% fidelity, and demonstration of error syndrome readout on a dual-species plaquette.