# Microwave-to-optical frequency conversion using a cesium atom coupled to a superconducting resonator

## TL;DR

This paper proposes a method for microwave-to-optical quantum frequency conversion using a cesium atom coupled to a superconducting resonator, optimizing laser pulses to maximize transfer rates while minimizing spontaneous emission noise.

## Contribution

It introduces a concrete cesium atom-based scheme for quantum frequency conversion, with optimized laser pulse shaping to enhance transfer rates and reduce errors.

## Key findings

- Achieves estimated transfer rates of a few Mega-qubits per second.
- Demonstrates the feasibility of using Rydberg states for strong coupling in quantum conversion.
- Provides a numerical optimization framework for pulse shaping in quantum systems.

## Abstract

A candidate for converting quantum information from microwave to optical frequencies is the use of a single atom that interacts with a superconducting microwave resonator on one hand and an optical cavity on the other. The large electric dipole moments and microwave transition frequencies possessed by Rydberg states allow them to couple strongly to superconducting devices. Lasers can then be used to connect a Rydberg transition to an optical transition to realize the conversion. Since the fundamental source of noise in this process is spontaneous emission from the atomic levels, the resulting control problem involves choosing the pulse shapes of the driving lasers so as to maximize the transfer rate while minimizing this loss. Here we consider the concrete example of a cesium atom, along with two specific choices for the levels to be used in the conversion cycle. Under the assumption that spontaneous emission is the only significant source of errors, we use numerical optimization to determine the likely rates for reliable quantum communication that could be achieved with this device. These rates are on the order of a few Mega-qubits per second.