Coherence and Rydberg blockade of atomic ensemble qubits

TL;DR

This paper demonstrates encoding of multi-atom ensemble qubits using $|W angle$ states, explores their coherence properties, and achieves high-fidelity Rydberg blockade, advancing atomic ensemble entanglement.

Contribution

It introduces a method for $|W angle$ state encoding in atomic ensembles and demonstrates strong Rydberg blockade with high fidelity.

Findings

$T_2$ coherence time of 2.6 ms for 7.6 atoms

Rydberg blockade fidelity of 0.89

Postselected fidelity close to 1.0

Abstract

We demonstrate $|W\rangle$ state encoding of multi-atom ensemble qubits. Using optically trapped Rb atoms the $T_2$ coherence time is 2.6(3) ms for $\bar N=7.6$ atoms and scales approximately inversely with the number of atoms. Strong Rydberg blockade between two ensemble qubits is demonstrated with a fidelity of $0.89(1)$ and a fidelity of $\sim \hspace{-.05cm}1.0$ when postselected on control ensemble excitation. These results are a significant step towards deterministic entanglement of atomic ensembles.