Precisely controlling the reflection phase of a photon via a strongly-coupled ancilla dressed qubit

TL;DR

This paper introduces a method using Rydberg dressing of a single qubit to precisely control the phase of reflected photons in optical and microwave systems, enabling low-error quantum gates.

Contribution

It presents a novel scheme for photon phase control via a dressed qubit, reducing errors and applicable to both optical and microwave quantum systems.

Findings

Achieves low error rates (~10^{-3}) suitable for fault-tolerant quantum computing.

Demonstrates feasibility in optical cavity and microwave circuit-QED systems.

Provides a practical approach for high-fidelity photon-qubit interactions.

Abstract

We propose that Rydberg dressing of a single qubit atom can be used to control a surrounding ensemble of three-level atoms and hereby the phase of light reflected by an optical cavity. Our scheme employs an ensemble dark resonance that is perturbed by the qubit state of a single atom to yield a single-atom single-photon gate. We show here that off-resonant Rydberg dressing of the qubit offers experimentally-viable regimes of operation that drastically reduce error compared to schemes using shelved Rydberg population. Such low errors (in the $10^{-3}$ range) are a necessary condition for fault-tolerant optical-photon, gate-based quantum computation. We also demonstrate the technique for microwave circuit-QED, where a strongly-coupled ancilla superconducting qubit can be used in the place of the atomic ensemble to provide high-fidelity coupling to microwave photons.