Two-dimensional optomechanical crystal cavity with high quantum cooperativity

Abstract

Optomechanical systems offer new opportunities in quantum information processing and quantum sensing. Many solid-state quantum devices operate at millikelvin temperatureshowever, it has proven challenging to operate nanoscale optomechanical devices at these ultralow temperatures due to their limited thermal conductance and parasitic optical absorption. Here, we present a two-dimensional optomechanical crystal resonator capable of achieving large cooperativity C and small effective bath occupancy n b , resulting in a quantum cooperativity C eff ≡ C/n b > 1 under continuous-wave optical driving. This is realized using a two-dimensional phononic bandgap structure to host the optomechanical cavity, simultaneously isolating the acoustic mode of interest in the bandgap while allowing heat to be removed by phonon modes outside of the bandgap. This achievement paves the way for a variety of applications requiring quantum-coherent optomechanical interactions, such as transducers capable of bi-directional conversion of quantum states between microwave frequency superconducting quantum circuits and optical photons in a fiber optic network.

Superconducting qubit to optical photon transduction

“…Further, using a material such as lithium niobate with a larger piezoelectric coupling rate would allow for devices with a larger energy participation in the optomechanical cavity, translating to a larger intrinsic readout efficiency. Finally, a lower added noise is achievable by reducing optical absorption using surface passivation 34 and by realizing better thermal contact between the localized acoustic mode and the cold environment 35,36 . Adoption of these techniques is expected to improve transduction efficiency (to η t ≈ 0.1) while maintaining a low added noise value (n add ≲ 0.1).…”

Topological phonon transport in an optomechanical system

“…This includes, in particular, mechanical vibrations [13, 19-23, 25, 26, 30, 31], with their potential for far-reaching applications in signal processing and other domains when implemented in compact chip-scale acoustic devices. A very promising approach to lower the footprint for excitation and read-out, and to boost the sensitivity to high-frequency vibrations, is to use radiation pressure forces in so-called optomechanical crystals (OMCs) [32][33][34][35]. OMCs are patterned structures that can be engineered to yield large radiation-pressure coupling between cavity photons and phonons.…”

“…1b and inset). The snowflake pattern is adopted from a well-known single-scale OMC design [34,35] and has also been proposed theoretically as a platform for topological phononics [14,15]. In this work we have increased the snowflake lattice spacing by a factor of ∼ 30, enabling every triangular membrane to harbor an optical nanocavity consisting of a localized defect in the triangular photonic crystal hole pattern.…”

Phonons Manipulation in Silicon Chips Using Cavity Optomechanics

“…To couple a single OM cavity we use a fiber loop taper to selectively measure the cavity under study, as it has been broadened use for OMC characterization [11,31,51]. Other measurement approaches can also be found in the literature as coupling via free space [141], tapered coupling waveguides [44,142,163] or grating couplers [68,111]. However, all these coupling systems only enable the simultaneous excitation of a reduced number of cavities.…”

“…The last point can even avoid the co-integration of multiple photonic, mechanical and electronic elements. However, some limitations can also be found in their functionality since the membrane release limits the device capability for dissipating heat [163], but also reduces the mechanical robustness and hinders the realization of large-area OM devices on a single chip.…”