• Session Info

Rydberg and molecule level landscapes: From synthetic dimensions to exotic particle statistics

Abstract: Both Rydberg atoms and molecules in tweezer arrays have provided revolutionary capabilities in quantum science, enabled by their long-range dipolar interactions. I will describe our research that has begun to explore the vast possibilities opened by using the plentiful internal states of these systems (Rydberg levels or rotational states) coupled via microwave fields. These have allowed experiments to create large-spin models and systems with extra "synthetic dimensions," where the internal degrees of freedom mimic motion in a fully-controlled extra spatial dimension. I will describe some of the novel many-body physics that can occur. One particularly interesting direction is that these systems can host excitations that are described by particle exchange statistics neither bosonic nor fermionic, nor confined to two-dimensions (as for anyons), in contrast to the long-held wisdom that fermionic and bosonic statistics are the only possible statistics in our three-dimensional universe.   

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Spin squeezing in an ensemble of nitrogen-vacancy centers in diamond

Spin squeezed states provide a seminal example of how the structure of quantum mechanical correlations can be controlled to produce metrologically useful entanglement. Such squeezed states have been demonstrated in a wide variety of artificial quantum systems ranging from atoms in optical cavities to trapped ion crystals. By contrast, despite their numerous advantages as practical sensors, spin ensembles in solid-state materials have yet to be controlled with sufficient precision to generate targeted entanglement such as spin squeezing. In this work, we present the first experimental demonstration of spin squeezing in a solid-state spin system. Our experiments are performed on a strongly-interacting ensemble of nitrogen-vacancy (NV) color centers in diamond at room temperature and squeezing (-0.5 pm 0.1 dB) is generated by the native magnetic dipole-dipole interaction between NVs. In order to generate and detect squeezing in a solid-state spin system, we overcome a number of key challenges of broad experimental and theoretical interest. First, we develop a novel approach, using interaction-enabled noise spectroscopy, to characterize the quantum projection noise in our system without directly resolving the spin probability distribution. Second, noting that the random positioning of spin defects severely limits the generation of spin squeezing, we implement a pair of strategies aimed at isolating the dynamics of a relatively ordered sub-ensemble of NV centers. Our results open the door to entanglement-enhanced metrology using macroscopic ensembles of optically-active spins in solids.

Bio: Emily J. Davis earned her PhD in the lab of Monika Schleier-Smith at Stanford University. There, she built a cavity QED experiment to study nonlocal spin models. She subsequently completed postdoctoral work as a Miller Research Fellow hosted by Norman Yao at UC Berkeley, where she explored many-body dynamics and metrology using ensembles of solid-state spins. She is currently an assistant professor in the Center for Quantum Phenomena at New York University. 

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Scattering in a Bose-Einstein condensate with multiple momentum components

Atomic Bose-Einstein condensates (BECs) are typically dilute and characterized by a condensate fraction close to 100%. The correlated, beyond mean-field quantum regime, where the condensate fraction can be significantly reduced, has been realized in a number of ways such as by tuning the s-wave scattering length to a large, in magnitude, value; by loading a dilute Bose gas into an optical lattice; by working with spinor BECs; and by periodically modulating the lattice or the s-wave scattering length of an inhomogeneous BEC. This talk reports on the appearance of quantum scattering spheres due to atom-atom scattering processes that are facilitated by preparing the Bose gas in an initial superposition state of two macroscopically occupied momentum states. Lattice coupling and Raman coupling schemes are considered and compared.

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Cold atom experiments in atomtronics and quantum computing

Abstract TBD

• Session Info

Controlling and probing quantum correlations in superconducting circuits

Abstract:
Superconducting circuits provide a versatile platform for exploring many-body physics in synthetic quantum matter. To advance scalable quantum simulation using circuit devices, I will present our recent progress in developing efficient techniques for controlling and measuring quantum correlations and dynamics. We engineer tunable driven-dissipative baths and apply them in coupled superconducting qubit arrays to autonomously stabilize entangled states. Additionally, we investigate how collective qubit decay can be harnessed and combined with coherent control to generate quantum correlations in qubit lattices. To characterize the resulting many-body states, we demonstrate the measurement of in-situ particle current and current statistics, as well as site-resolved tunneling spectroscopy using the tunable baths as tunneling probes. We apply these tools to probe quantum transport and phase transitions in a circuit Bose-Hubbard lattice.

Bio: Alex Ruichao Ma received his Ph.D. in Physics from Harvard University in 2014, where he studied many-body physics using ultracold atoms in optical lattices. From 2015 to 2019, he worked on superconducting qubits for quantum simulation as a Kadanoff-Rice Postdoctoral Fellow at the James Franck Institute, University of Chicago. In 2019, Alex joined Purdue University as an Assistant Professor in the Department of Physics and Astronomy. His experimental group focuses on quantum many-body physics and quantum information science using superconducting circuits. He is a recipient of the NSF CAREER Award in 2022.