Ground-state Pulsed Cavity Electro-optics for Microwave-to-optical Conversion

TL;DR

This paper demonstrates efficient microwave-to-optical conversion in a cavity electro-optic system operating near the quantum ground state, highlighting noise sources and suppression strategies crucial for quantum transduction.

Contribution

It presents the first detailed study of noise behavior in a pulsed electro-optic transducer at milli-Kelvin temperatures, advancing quantum microwave-to-optical conversion technology.

Findings

Achieved near-ground state microwave thermal excitation ($ar{n}_ ext{e}=0.09 extpm0.06$).

Identified superconductor absorption of stray light as a dominant noise source.

Demonstrated efficient bi-directional microwave-optical conversion under intense pulsed optical drive.

Abstract

In the development of quantum microwave-to-optical (MO) converters, excessive noise induced by the parametric optical drive remains a major challenge at milli-Kelvin temperatures. Here we study the extraneous noise added to an electro-optic transducer in its quantum ground state under an intense pulsed optical excitation. The integrated electro-optical transducer leverages the inherent Pockels effect of aluminum nitride microrings, flip-chip bonded to a superconducting resonator. Applying a pulsed optical drive with peak power exceeding the cooling power of the dilution refrigerator at its base temperature, we observe efficient bi-directional MO conversion, with near-ground state microwave thermal excitation ($\bar{n}_\mathrm{e}=0.09\pm0.06$). Time evolution study reveals that the residual thermal excitation is dominated by the superconductor absorption of stray light scattered off the chip-fiber interface. Our results shed light on suppressing microwave noise in a cavity electro-optic system under intense optical drive, which is an essential step towards quantum state transduction between microwave and optical frequencies.