Quantum communication with itinerant surface acoustic wave phonons

Abstract

Surface acoustic waves are commonly used in classical electronics applications, and their use in quantum systems is beginning to be explored, as evidenced by recent experiments using acoustic Fabry–Pérot resonators. Here we explore their use for quantum communication, where we demonstrate a single-phonon surface acoustic wave transmission line, which links two physically separated qubit nodes. Each node comprises a microwave phonon transducer, an externally controlled superconducting variable coupler, and a superconducting qubit. Using this system, precisely shaped individual itinerant phonons are used to coherently transfer quantum information between the two physically distinct quantum nodes, enabling the high-fidelity node-to-node transfer of quantum states as well as the generation of a two-node Bell state. We further explore the dispersive interactions between an itinerant phonon emitted from one node and interacting with the superconducting qubit in the remote node. The observed interactions between the phonon and the remote qubit promise future quantum-optics-style experiments with itinerant phonons.

Deterministic Generation of Multidimensional Photonic Cluster States with a Single Quantum Emitter

“…Furthermore, potentially increasing the anharmonicity η of the qubit through different qubit design [49][50][51] would enable even larger Γ 1D , allowing for a higher fidelity CZ gate with high-bandwidth photons and even more rapid emission of shaped photon pulses. The round-trip delay, τ d , could also be increased by either further reducing the footprint of our unit cell resonators, for example by leveraging compact high kinetic inductance superconducting resonators [52,53], or by incorporation of acoustic delay lines [54][55][56], increasing the photon(phonon)-pulse storage capacity of the delay line and the corresponding size of realizable cluster states.…”

“…Furthermore, the unit cell size could be reduced by leveraging compact high kinetic inductance superconducting resonators [52,53], allowing for more delay per area. And looking forward even further, incorporation of an acoustic delay line into our system could allow for longer round-trip delays without additional dispersion or susceptibility to microwave packaging box modes [54][55][56], increasing the possible size of generated cluster states even further.…”

On-chip distribution of quantum information using traveling phonons

“…Quantum optomechanics has proven to be a versatile toolbox for controlling stationary, strongly confined phonons ( 25 , 26 ). Previously, bulk and surface acoustic waves (BAWs and SAWs, respectively) have been shown to be able to operate in the quantum regime ( 17 , 19 ), for example, by coupling to superconducting qubits for transducer and quantum information applications ( 27 , 28 ), as well as entangling acoustic phonons ( 29 ). These systems benefit from deterministic quantum operations with high fidelities, enabled by the nonlinearity of the superconducting qubit and strong coupling between the qubit and the phononic channel.…”

Tightly Confined Surface Acoustic Waves as Microwave-to-Optical Transduction Platforms in the Quantum Regime

“…Recently, surface acoustic waves (SAWs) -propagating acoustic waves naturally confined to a medium's surface -have emerged as exciting and versatile mechanical modes for quantum systems [22][23][24][25][26]. As electromechanical elements, SAWs efficiently interact piezoelectrically with external microwave circuits -typically through periodic metallic structures called interdigital transducers (IDTs) -and strongly couple with superconducting qubits at GHz frequencies [12,25,27,28]. When confined within cavities [29,30], discreet standing-wave eigenmodes can be selectively and coherently populated [12].…”