Cavity Quantum Acoustic Device in the Multimode Strong Coupling Regime

Area of Science:

• Quantum Acoustics
• Solid-State Quantum Systems
• Circuit Quantum Electrodynamics (cQED) Analogs

Background:

• Circuit Quantum Electrodynamics (cQED) systems are crucial for quantum information processing.
• Achieving strong coupling in multimode systems while managing spontaneous emission is a key challenge.
• Acoustic systems offer a promising platform for exploring quantum phenomena.

Purpose of the Study:

• To demonstrate an acoustical analog of a cQED system.
• To achieve strong multimode coupling in the dispersive regime.
• To suppress spontaneous emission into unconfined acoustic modes.

Main Methods:

• Fabrication of a device comprising a flux-tunable transmon coupled to a surface acoustic wave resonator.
• Characterization of the qubit-resonator coupling strength and cavity properties.
• Analysis of qubit linewidth dependence on frequency to identify spontaneous emission suppression.

Main Results:

• Demonstrated strong qubit-cavity coupling (up to 6.5 MHz), exceeding cavity loss rates and qubit linewidth.
• Achieved operation in both the strong coupling and strong multimode regimes.
• Observed frequency-dependent qubit linewidth, indicating tunable spontaneous emission of phonons.
• Identified operating frequencies for suppressed phonon emission.

Conclusions:

• The demonstrated acoustic system effectively mimics cQED principles.
• Strong multimode coupling and suppressed spontaneous emission are achievable in this acoustic analog.
• This work provides a new platform for exploring quantum acoustics and developing novel quantum devices.