Acoustic Phonon Fock States and Phonon-mediated Quantum Entanglement

September 6th, 2019 ANDREW CLELAND John A. MacLean Sr. Professor for Molecular Engineering Innovation and Enterprise; Director, Pritzker Nanofabrication Facility, University of Chicago

Andrew Cleland specializes in experimental quantum information, in particular on the development of superconducting quantum circuits for applications to quantum computing, quantum communication and hybrid quantum systems. He currently focuses on methods to convert quantum information between stationary qubits and itinerant, traveling qubits, including microwave phonons and microwave and infrared photons. Of interest are both practical applications as well as the development of fundamental quantum science. Cleland led the team that built the first quantum machine, which earned recognition as the “Breakthrough of the Year 2010” honors from Science (AAAS). The same work was named a top-ten discovery of 2010 by Physics World, which also listed a related project of Cleland’s as a top-ten discovery of 2011. He is a Fellow of the American Physical Society as well as a Fellow of the American Association of Arts and Sciences, and a Distinguished Sigma Xi Lecturer. He received a BS degree in Engineering Physics and a PhD in Physics from the University of California – Berkeley. He was on the faculty of the physics department of the University of California – Santa Barbara from 1997-2014, before joining the Institute for Molecular Engineering at the University of Chicago. Abstract Superconducting qubits are an excellent system for building quantum computing systems, due to their good individual qubit performance metrics, the availability of a high fidelity two-qubit entangling gate, and their easy lithographic scaling to large qubit numbers. In addition, these qubits provide unique opportunities as testbed systems for quantum communication as well as developing hybrid quantum systems. One compelling opportunity is provided by the ability to use superconducting qubits to control and measure acoustically-active structures, structures that can potentially serve to link these qubits to other two-level systems or to e.g. optical signals. I will describe our recent progress in coupling superconducting qubits to surface acoustic waves, where we have recently demonstrated the quantum control of a single microwave-frequency mechanical mode in a surface acoustic wave (SAW) resonator. We can controllably store and recover single phonons and measure the Wigner function of stored quantum states in the resonator [1]. I will also show more recent results where a long SAW resonator with a 500 ns phonon bounce time was used to release and recapture individual itinerant phonons, and transfer quantum states between two superconducting qubits. By sharing half a phonon between the two qubits, we are able to acoustically generate a high-fidelity Bell state between the two qubits.

[1] K. J. Satzinger et al., “Quantum control of surface acoustic wave phonons”, Nature 563, 661–665 (2018).
[2] A. Bienfait et al., “Phonon-mediated quantum state transfer and remote qubit entanglement”, Science 364, 368-371 (2019).

Friday September 6, 12:00, ICFO Auditorium