Multi-qubit Rydberg gates between distant atoms

TL;DR

This paper introduces a protocol for implementing multi-qubit gates in neutral atom arrays using Rydberg states and geometric phases, enabling scalable quantum operations with distant atoms.

Contribution

The authors propose a novel method for multi-qubit gates leveraging Rydberg blockade and geometric phases, extending to distant atom interactions via a quantum bus.

Findings

Efficient multi-qubit gates achieved with Rydberg blockade.

Implementation of C$_k$Z and C$_k$NOT gates for multiple atoms.

Extension to gates between distant atoms via a quantum bus.

Abstract

We propose an efficient protocol to realize multi-qubit gates in arrays of neutral atoms. The atoms encode qubits in the long-lived hyperfine sublevels of the ground electronic state. To realize the gate, we apply a global laser pulse to transfer the atoms to a Rydberg state with strong blockade interaction that suppresses simultaneous excitation of neighboring atoms arranged in a star-graph configuration. The number of Rydberg excitations, and thereby the parity of the resulting state, depends on the multiqubit input state. Upon changing the sign of the interaction and de-exciting the atoms with an identical laser pulse, the system acquires a geometric phase that depends only on the parity of the excited state, while the dynamical phase is completely canceled. Using single qubit rotations, this transformation can be converted to the C$_k$Z or C$_k$NOT quantum gate for $k+1$ atoms. We also present extensions of the scheme to implement quantum gates between distant atomic qubits connected by a quantum bus consisting of a chain of atoms.