A two-dimensional optomechanical crystal for quantum transduction

TL;DR

This work introduces a 2D optomechanical crystal design that improves thermal management, enabling ground-state cooling and strong coupling at cryogenic temperatures, advancing quantum transduction capabilities.

Contribution

The paper presents a novel 2D optomechanical crystal geometry that enhances thermal anchoring and achieves ground-state cooling and strong coupling at millikelvin temperatures.

Findings

Achieved mechanical mode at 7.4 GHz compatible with cryogenic hardware.

Realized ground-state cooling with phononic occupancy as low as 0.35.

Demonstrated pulsed sideband asymmetry and ground-state operation below 10 mK.

Abstract

Integrated optomechanical systems are one of the leading platforms for manipulating, sensing, and distributing quantum information. The temperature increase due to residual optical absorption sets the ultimate limit on performance for these applications. In this work, we demonstrate a two-dimensional optomechanical crystal geometry, named \textbf{b-dagger}, that alleviates this problem through increased thermal anchoring to the surrounding material. Our mechanical mode operates at 7.4 GHz, well within the operation range of standard cryogenic microwave hardware and piezoelectric transducers. The enhanced thermalization combined with the large optomechanical coupling rates, $g_0/2\pi \approx 880~\mathrm{kHz}$, and high optical quality factors, $Q_\text{opt} = 2.4 \times 10^5$, enables the ground-state cooling of the acoustic mode to phononic occupancies as low as $n_\text{m} = 0.35$ from an initial temperature of 3 kelvin, as well as entering the optomechanical strong-coupling regime. Finally, we perform pulsed sideband asymmetry of our devices at a temperature below 10 millikelvin and demonstrate ground-state operation ($n_\text{m} < 0.45$) for repetition rates as high as 3 MHz. Our results extend the boundaries of optomechanical system capabilities and establish a robust foundation for the next generation of microwave-to-optical transducers with entanglement rates overcoming the decoherence rates of state-of-the-art superconducting qubits.