Entangling quantum logic gates in neutral atoms via the microwave-driven spin-flip blockade

Abstract

The Rydberg dipole-blockade has emerged as the standard mechanism to induce entanglement between neutral atom qubits. In these protocols, laser fields that couple qubit states to Rydberg states are modulated to implement entangling gates. Here we present an alternative protocol to implement entangling gates via Rydberg dressing and a microwave-field-driven spin-flip blockade [Y.-Y. Jau et al, Nat. Phys. 12, 71 (2016)]. We consider the specific example of qubits encoded in the clock states states of cesium. An auxiliary hyperfine state is optically dressed so that it acquires partial Rydberg character. It thus acts as a proxy Rydberg state, with a nonlinear light-shift that plays the role of blockade strength. A microwave-frequency field coupling a qubit state to this dressed auxiliary state can be modulated to implement entangling gates. Logic gate protocols designed for the optical regime can be imported to this microwave regime, for which experimental control methods are more robust. We show that unlike the strong dipole-blockade regime usually employed in Rydberg experiments, going to a moderate-spin-flip-blockade regime results in faster gates and smaller Rydberg decay. We study various regimes of operations that can yield high-fidelity two-qubit entangling gates and characterize their analytical behavior. In addition to the inherent robustness of microwave control, we can design these gates to be more robust to thermal fluctuations in atomic motion as well to laser amplitude, and other noise sources such as stray background fields.

References in corpus (7)

• Many-Body Physics with Individually-Controlled Rydberg Atoms
• An atom-by-atom assembler of defect-free arbitrary 2d atomic arrays
• Demonstration of multi-qubit entanglement and algorithms on a programmable neutral atom quantum computer
• Quantum computing with neutral atoms
• High-fidelity Rydberg quantum gate via a two-atom dark state
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• Quantum control of the hyperfine-coupled electron and nuclear spins in alkali atoms

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• A Mathematical Structure for Amplitude-Mixing Error-Transparent Gates for Binomial Codes
• Symmetric $C_Z$ gate for ultracold neutral atoms based on counterdiabatic driving at Rydberg excitation