Ultracold atomic physics in optical lattices
Charles D. Brown II is an Assistant Professor of Physics at Yale University. He received his undergraduate degree from the University of Minnesota and his Ph.D. from Yale. As a graduate student in Jack Harris’ group, Charles performed experiments with superfluid-helium-filled optical cavities and constructed and characterized a new experiment for studying magnetically levitated drops of superfluid helium in vacuum. Charles was a postdoctoral fellow at the University of California, Berkeley, where he worked with Dan Stamper-Kurn on experiments with ultracold atomic gasses trapped in optical lattices. Charles joined the Yale Department of Physics in 2023.
Professor Brown aims to study single-, few-, and many-body quantum physics by conducting quantum simulation experiments. Quantum simulations are realizations of complex quantum systems for the purpose of understanding their ordered phases and dynamics. His group traps ultracold atoms in optical lattice potentials (an ultracold atom quantum simulator), which is the spatially periodic potential the atoms experience in the intensity standing wave of several intersecting lasers. In doing so, the Brown group aims to learn about exotic order phases of ultracold bosons and fermions in optical lattices, how transport works in lattices with unusual geometry (e.g., a “lattice” that lacks translational symmetry), and what role topology plays in the quantum behavior of bosons and fermions in such unusual lattices
- Quantum Creators Prize, 2021
- National Academies Ford Foundation Postdoctoral Fellowship, 2019
- National Academies Ford Foundation Dissertation Fellowship, 2018
- C. D. Brown, S. W. Chang, M. N. Schwarz, V. Kozii, A. Avdoshkin, T. H. Leung, J. E. Moore, D. M. Stamper-Kurn, “A Direct Geometric Probe of Singularities in Band Structure” arXiv:2109.03354 arXiv:2109.03354 (2021)
- C. D. Brown, Y. Wang, M. Namazi, G. I. Harris, M. Uysal, J. G. E. Harris, “Characterization of Levitated Superfluid Helium Drops in High Vacuum” arXiv:2109.05618 (2021)
- T. H. Leung, M. N. Schwarz, S. W. Chang, C. D. Brown, G. Unnikrishnan, D. Stamper-Kurn, “Interaction-Enhanced Group Velocity of Bosons in the Flat Band of an Optical Kagome Lattice”, Phys. Rev. Lett. 125, 133001 (2020)
- A. B. Shkarin, A. D. Kashkanova, C. D. Brown, S. Garcia, K. Ott, J. Reichel, J. G. E. Harris, “Quantum optomechanics in a liquid” Phys. Rev. Lett 122 153601 (2019)
- A. D. Kashkanova, A. B. Shkarin, C. D. Brown, N. E. Flowers-Jacobs, L. Childress, S. W. Hoch, L. Hohmann, K. Ott, J. Reichel, J. G. E. Harris. “Superfluid Brillouin Optomechanics” Nature Physics 13, 74-79 (2017)
The field of optomechanics studies the interactions between light and the motion of an object. One of the goals in this field is to generate and control highly non-classical motion of a massive mechanical oscillator. There has been progress in generating such non-classical motion via coupling the oscillator to a qubit, or by utilizing the non-linearity of single photon detection. However, interest still remains in generating non-classical motion directly via the optomechanical interaction itself. Doing so requires strong coupling between the light and the mechanical oscillator, as well as low optical and mechanical loss and temperature. The unique properties of superfluid helium (zero viscosity, high structural and chemical purity and extremely low optical loss) addresses some of these requirements.
To exploit the unique properties of superfluid helium we have constructed an optomechanical system consisting entirely of a magnetically levitated drop of superfluid helium in vacuum. Magnetic levitation removes a source of mechanical loss associated with physically clamped oscillators. Levitation also allows the drop to cool itself efficiently via evaporation. The drop’s optical whispering gallery modes (WGMs) and its surface vibrations should couple to each other via the usual optomechanical interactions.
In this dissertation we demonstrate the stable magnetic levitation of superfluid helium drops in vacuum, and present measurements of the drops’ evaporation rates, temperatures, optical modes and surface vibrations. We found optical modes with finesse $\sim 40$ (limited by the drop’s size). We found surface vibrations with decay rates $\sim 1$ Hz (in rough agreement with theory). Lastly, we found that the drops reach a temperature $T\approx 330$ mK, and that a single drop can be trapped indefinitely.