This paper is a contribution to the Physical Review Applied collection titled Phononics and Metamaterials.

Nanomechanical waveguides offer a multitude of applications in quantum and classical technologies. Here, we design, fabricate, and characterize a compact silicon single-mode phononic waveguide actuated by a thin-film lithium niobate piezoelectric element. Our device directly transduces between microwave-frequency photons and phonons propagating in the silicon waveguide, providing a route for coupling to superconducting circuits. We probe the device at millikelvin temperatures through a superconducting microwave resonant-matching cavity to reveal harmonics of the silicon waveguide and extract a piezoelectric coupling rate $g/2\pi =1.1\mathrm{MHz}$ and a mechanical coupling rate $f/2\pi =5\mathrm{MHz}$. Through time-domain measurements of the silicon mechanical modes, we observe energy relaxation timescales of $T_{1,\mathrm{in}}\approx 500\text{μ}\mathrm{s}$, pure dephasing timescales of $T_{\varphi }\approx 60\text{μ}\mathrm{s}$, and dephasing dynamics that indicate the presence of an underlying frequency-noise process with a nonuniform spectral distribution. We measure phase-noise cross-correlations between silicon mechanical modes and observe detuning-dependent, positively correlated frequency fluctuations. Our measurements provide valuable insights into the dynamics and decoherence characteristics of hybrid piezoelectric silicon acoustic devices, and suggest approaches for mitigating and circumventing noise processes in emerging quantum acoustic systems.

Close

PrevNext

View figure in article

• Quantum information with hybrid systems
• Quantum interconnects
• Acoustic metamaterials
• Phononic crystals
• Transducers
• Waveguides
• Acoustic techniques
• Microwave techniques