Rydberg assisted light shift imbalance induced blockade in an atomic ensemble

TL;DR

This paper refines the light shift imbalance induced blockade technique by incorporating Rydberg interactions, enabling scalable quantum computing with neutral atoms through collective state qubits that are robust to atom number variations.

Contribution

It demonstrates that Rydberg interactions are essential to achieve light shift imbalance induced blockade, expanding the technique's applicability for quantum computing.

Findings

Rydberg interactions enable blockade for a wide parameter range.

Fidelity of quantum gates is insensitive to atom number.

Analytic results are confirmed by numerical simulations.

Abstract

Previously, we had proposed the technique of light shift imbalance induced blockade which leads to a condition where a collection of non-interacting atoms under laser excitation remains combined to a superposition of the ground and the first excited states, thus realizing a collective state quantum bit which in turn can be used to realize a quantum computer. In this paper, we show first that the light shift imbalance by itself is actually not enough to produce such a blockade, and explain the reason why the limitation of our previous analysis had reached this constraint. We then show that by introducing Rydberg interaction, it is possible to achieve such a blockade for a wide range of parameters. Analytic arguments used to establish these results are confirmed by numerical simulations. The fidelity of coupled quantum gates based on such collective state qubits is highly insensitive to the exact number of atoms in the ensemble. As such, this approach may prove to be viable for scalable quantum computing based on neutral atoms.