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• Who: Professor Peter Rakich
• Title: Quantum Optomechanical Control of Bulk Acoustic Phonons
• Abstract: Cavity optomechanical techniques allow efficient control of phonons using light, transforming them into a versatile quantum resource. Efficient photon-phonon coupling permits the use of quantum optics methods to control solid-state phononic excitations, allowing for the manipulation and storage of nonclassical states using light. In this context, long-lived phonons are advantageous as they may permit numerous quantum operations within the phonon’s coherence time, enabling a new class of high-performance quantum sensors, transducers, and memories. However, a key barrier to realizing such new capabilities is protecting these phonons from problematic noise of noise and decoherence.
   
  We present a new quantum optomechanical systems based on bulk acoustic wave resonators that have the potential to overcome these challenges and bring many unique features. Our new optomechanical system utilizes macroscopic high-overtone bulk acoustic-wave resonators (HBARs) are intriguing for their ability to support high frequencies (>10GHz) phonon modes with long coherence times while also minimizing unwanted surface interactions that can contribute to decoherence. In this work, we combine new non-invasive laser spectroscopy techniques with materials analysis to enable the realization of microfabricated HBAR resonators with Q-factors exceeding 140-million at 12.6 GHz frequencies, corresponding to phonon lifetimes of >1.8 milliseconds and a record-level fQ products of 1.8e18 Hz. Using new cavity optomechanical techniques to greatly enhance coupling rates to such ultra-massive (>10 microgram) phonon modes, we demonstrate mode-selective ground-state cooling, a critical advancement necessary to utilize such high coherence phonons as a quantum resource. Since this system demonstrate enhanced robustness to parasitic heating, they open an array of new possibilities for quantum control of phonons.
   

• Who: Dr. Lawrence Cheuk
• Title: Programmable Molecular Tweezer Arrays for Quantum Science
• Abstract: Polar molecules trapped in programmable optical tweezer arrays are an emerging platform for quantum science. In this talk, I will report our group’s work on advancing quantum control of molecular tweezer arrays and our first experiments on using these arrays for quantum information processing and simulation of quantum many-body Hamiltonians.I will first briefly present our work that establishes the essential building blocks for quantum science in this platform. These include preparation and detection of single molecules, control of their interactions, and the deterministic entanglement of pairs of molecules. Next, I will report on our subsequent efforts to further advance molecular control to a level necessary for quantum applications. In particular, I will focus on our recent work that uses mid-circuit measurement to both improve quantum state preparation and to implement erasure error detection and conversion in molecular qubits. Lastly, I will present recent work on simulating interacting quantum spin chains using 1D molecular arrays. Specifically, I will report on several phenomena that we have observed in the quantum dynamics of 1/r3 XX/XXZ/XYZ spin chains. These include coherent quantum walks of single spin excitations, appearance of repulsive bound states, and coherent pair creation and annihilation.

 Live only; no recording