Two-dimensional gallium phosphide optomechanical crystal in the resolved-sideband regime

Area of Science:

• Quantum optics
• Optomechanics
• Materials science

Background:

• Efficient quantum state transfer between photons and mechanical systems requires high conversion rates and low thermal noise.
• Two-dimensional (2D) optomechanical crystals (OMCs) offer high mechanical frequencies and thermal conductance, crucial for quantum protocols.
• Gallium phosphide (GaP) is a suitable material due to its large bandgap and high refractive index, enhancing optomechanical coupling.

Purpose of the Study:

• To fabricate and characterize a 2D OMC made of GaP for quantum state transfer.
• To achieve high optical quality factor and mechanical frequencies exceeding the optical linewidth.
• To demonstrate a substantial vacuum optomechanical coupling rate for quantum memory applications.

Main Methods:

• Fabrication of a 2D OMC using GaP.
• Characterization of optical and mechanical properties, including Q-factor, linewidth, and mechanical frequencies.
• Measurement of the vacuum optomechanical coupling rate.

Main Results:

• Achieved a high optical Q-factor of 7.9 × 10^4 at telecom frequency (195.6 THz) with a linewidth of 2.5 GHz.
• Observed mechanical modes with frequencies exceeding the optical linewidth, with the strongest coupling at 7.7 GHz.
• Demonstrated a substantial vacuum optomechanical coupling rate of 450 kHz.

Conclusions:

• The fabricated GaP 2D OMC platform is a promising candidate for long-lived, deterministic quantum memory.
• The device meets the requirements for fast conversion rates and low thermal noise for quantum state transfer.
• The high mechanical frequency and strong coupling pave the way for advanced quantum information processing.