Proposal for a quantum traveling Brillouin resonator

Abstract

Brillouin systems operating in the quantum regime have recently been identified as a valuable tool for quantum information technologies and fundamental science. However, reaching the quantum regime is extraordinarily challenging, owing to the stringent requirements of combining low thermal occupation with low optical and mechanical dissipation, and large coherent phonon-photon interactions. Here, we propose an on-chip liquid based Brillouin system that is predicted to exhibit ultra-high coherent phonon-photon coupling with exceptionally low acoustic dissipation. The system is comprised of a silicon-based "slot" waveguide filled with superfluid helium. This type of waveguide supports optical and acoustical traveling waves, strongly confining both fields into a subwavelength-scale mode volume. It serves as the foundation of an on-chip traveling wave Brillouin resonator with a single photon optomechanical coupling rate exceeding 240 kHz. Such devices may enable applications ranging from ultra-sensitive superfluid-based gyroscopes, to non-reciprocal optical circuits. Furthermore, this platform opens up new possibilities to explore quantum fluid dynamics in a strongly interacting condensate.

Cryogenic and hermetically sealed packaging of photonic chips for optomechanics

“…For superfluid optomechanics applications, good control over the achieved superfluid film thickness is required to control the speed of sound [33] and access different regimes, as depending on the thickness, the optomechanical interaction may be dominated by third sound waves, capillary waves (ripplons) or first sound [8,[20][21][22]34].…”

“…With the pinch-off tube facing upwards, the distance between the photonic device and the lowest point of the vessel can be reduced to the millimeter scale, resulting in a film thickness of up to 60 nm. Capillary action can be used to create regions with thicker volumes [22], as discussed below.…”

“…In contrast, the use of 3 He buffer gas has recently enabled the strong continuous laser drives required for backaction-evading measurements [7] and laser cooling such nanomechanical resonators to their zero-point energy [18]. Condensed as a superfluid, helium-4 may interact with the photonic chip for a range of applications, including cavity optomechanics and Brillouin scattering [8,[19][20][21][22][23], quantum information [24], the study of quantum hydrodynamics and turbulence [10], as well as applications in gravitational wave [25] or dark matter detection [26]. In our experiments we observe the condensation of superfluid helium-4 films a few nanometers thick on the ring resonator via the optical frequency shift this generates-confirming that the quantity of enclosed gas within our package can be precisely controlled-and observe superfluid acoustic waves confined to the device.…”

Superfluid Optomechanics With Phononic Nanostructures

“…Furthermore, at much smaller scale (i.e. picogram and femtogram), superfluid 4 He resonators have shown great potential for quantum optomechanics experiments [19,20], the study of quantized vorticity in thin films [21,22] and levitating droplets [23], the enhancement of Brillouin interaction [24,25], and the realisation of qubits mechanical systems [26].…”

Superfluid Optomechanics with Phononic Nanostructures

“…Furthermore, at much smaller scale (i.e. picogram and femtogram), superfluid 4 He resonators have shown great potential for quantum optomechanics experiments [19,20], the study of quantized vorticity in thin films [21,22] and levitating droplets [23], the enhancement of Brillouin interaction [24,25], and the realisation of qubits mechanical systems [26].…”