Semester Calendar Date

Sensing with optical and acoustic waves

In this seminar, I will discuss several recent and ongoing experimental efforts in the Purdy Lab (which specializes in quantum sensors and transducers with optical, mechanical, and microwave systems), with a focus on some often overlooked or least under-appreciated aspects of relatively simple measurements.  We have recently completed the first detailed study of acoustic blackbody radiation interacting with a nanomechanical system.  While the acoustic equivalent of the well-known electromagnetic blackbody radiation should be equally ubiquitous, there have been almost no experiment

The Most Coherent Superconducting Qubit?

To realize a digital quantum processor based on superconducting qubits, gate error rates must be further reduced by raising coherence times and increasing anharmonicity. I report our group's progress in improving coherence and control of fluxonium superconducting qubits by optimizing the circuit's spectrum and enhancing fabrication methods.

The fine structure of quantum spin ice

Abstract: Quantum spin liquids are low temperature phases of magnetic materials in which quantum fluctuations prevent the establishment of long-range magnetic order. These phases support fractionalized spin excitations (spinons) coupled to emergent photons. In this talk, I will review the basic picture of how quantum electrodynamics emerges in 3D spin ice and then turn to several results regarding its `fine structure'.

All-optical coherent control of solid-state spin qubits toward quantum photonic applications

Abstract: Optically-active spins in the solid-state are useful resources for quantum technologies. The coupling of such systems to photonic structures can generate deterministic spin-photon entanglement, which could contribute to quantum simulations and networking. Ideal spin systems for such applications must combine high quality spin and photonic properties, as well as efficient methods for the coherent manipulation of the spin state.

"Distinguishing between quantum and classical Markovian dephasing dissipation"

Abstract: Understanding whether dissipation in an open quantum system is truly quantum is a question of both fundamental and practical interest. We consider a general model of n qubits subject to correlated Markovian dephasing, and present a sufficient condition for when bath-induced dissipation can generate system entanglement and hence must be considered quantum. Surprisingly, we find that the presence or absence of time-reversal symmetry (TRS) plays a crucial role: broken TRS is required for dissipative entanglement generation.