Precise and extensive characterization of an optical resonator for cavity-based quantum networks

TL;DR

This paper provides a highly precise characterization of a high-finesse optical resonator, crucial for quantum networks, by measuring cavity parameters with minimal environmental influence, enabling improved atom-cavity coupling estimates.

Contribution

It introduces a novel measurement scheme using a wavelength meter to accurately determine cavity parameters, reducing uncertainties and enhancing quantum network component benchmarking.

Findings

Achieved four significant figures in atom-cavity coupling constant estimation.

Measured birefringent splitting below 4.9% of the cavity linewidth.

Demonstrated a method to eliminate environmental fluctuations in cavity parameter measurements.

Abstract

Cavity-based quantum node is a competitive platform for distributed quantum networks. Here, we characterize a high-finesse Fabry-Perot optical resonator for coupling single or few atomic quantum registers. Our cavity consists of two mirrors with different reflectivities: One has minimal optical loss, and the other high transmission loss where more than 90% of the intracavity photons would be emitted. Cavity finesse, birefringent effects, and mechanical resonances are measured using the lasers at 780, 782, and 795 nm. In order to obtain cavity geometric parameters, we drive the adjacent longitudinal or transverse modes with two lasers simultaneously, and measure those frequencies using a precision wavelength meter (WLM). A major novelty of this method is that the parameters' uncertainties are solely determined by the resolution of the WLM, eliminating all of the temporal environment fluctuations. Our scheme makes it possible to quantify the atom-cavity coupling constant up to four significant figures, the most precise and accurate estimation so far, which would become a key ingredient for benchmarking a cavity-based quantum node. Furthermore, the distortion of polarized photonic qubits would be minimized owing to the small birefringent splitting, below 4.9% of the cavity linewidth. Our system should operate in the intermediate atom-cavity coupling regime that would allow us to implement various quantum network protocols.