Quantum gates with weak van der Waals interactions of neutral Rydberg atoms

TL;DR

This paper proposes a new quantum gate scheme using weak van der Waals interactions between neutral Rydberg atoms, enabling high-fidelity entanglement over large distances with minimal error.

Contribution

It introduces a controlled-phase and CNOT gate method that operates with weak interactions and no rotation error, expanding the feasible range of neutral-atom quantum computing.

Findings

Achieves over 98% fidelity with realistic position fluctuations.

Operates with very weak Rydberg interactions over 20 μm separation.

Requires only three steps for coupling one Rydberg state.

Abstract

Neutral atoms are promising for large-scale quantum computing, but accurate neutral-atom entanglement depends on large Rydberg interactions which strongly limit the interatomic distances. Via a phase accumulation in detuned Rabi cycles enabled by a Rydberg interaction of similar magnitude to the Rydberg Rabi frequency, we study a controlled-phase gate with an arbitrary phase and extend it to the controlled-NOT gate. The gates need only three steps for coupling one Rydberg state, depend on easily accessible van der Waals interaction that naturally arises between distant atoms, and have no rotation error in the weak interaction regime. Importantly, they can work with very weak interactions so that well-separated qubits can be entangled. The gates are sensitive to the irremovable fluctuation of Rydberg interactions, but can still have a fidelity over 98\% with realistic position fluctuation of qubits separated over 20~$\mu$m.