A recent popular science article summarizing our research was published in OU's Sooner Magazine, titled No Small Undertaking.
Additional information can be found on my home page.
My main research interest is coherent quantum dynamics of ultracold atomic gases. Specifically, I focus on ultracold spin-changing collisions in sodium spinor Bose-Einstein condensates (BEC). This research has applications in creating massive entanglement useful for quantum computing and in demonstrating new types of matter-wave quantum optics devices such as a phase-sensitive amplifier for atom number measurements. I am also interested in long-range interactions between ultracold sodium Rydberg atoms, with applications in precision measurements, quantum-assisted sensing, quantum computing and quantum simulation.
For a sodium atom in the ground state, the magnetic quantum number, m, related to the direction of the atomic spin, can be 0,+1 or -1. In a spin-exchange collision, two atoms with m=0 collide and transform into a pair with m=+1 and -1. In an ultracold gas, this causes the macroscopic spin populations to oscillate. This oscillation is a quantum implementation of the non-rigid pendulum. When prepared in a state of dynamical instability, the system is driven solely by small vacuum fluctuations. Over several tens of milliseconds, the collisions cause an amplification of initial vacuum fluctuations to the point were they become measurable by absorption imaging. The same dynamics also creates spin-squeezed quantum states, states with reduced uncertainty in one measurement variable which are useful for precision measurements.
Collisional dynamics in the antiferromagnetic spinor BEC are quite rich. Apart from the quantum pendulum analogy, they can also be understood in terms of the Josephson effect known from superconducting devices, as well as in terms of optical four-wave mixing processes known from nonlinear optics. While there are intriguing similarities and analogies, there are also important differences between the atomic, the solid state and the photonic systems that can be exploited in novel ways.
Recently, we learned that we can exert precise control over the collisional dynamics in a spinor BEC. Using microwaves, RF fields, and applied magnetic fields, we can tune the system to behave, for example, like an interferometer in spin space with reduced noise, or like a phase-sensitive amplifier for sensitive atom number measurements, and explore the field of spin-based matter-wave quantum optics.
"Mean-field spin-oscillation dynamics beyond the single-mode approximation for a harmonically trapped spin-1 Bose-Einstein condensate," J. Jie, Q. Guan, S. Zhong, A. Schwettmann, and D. Blume, Phys. Rev. A, 102, 023324 , (2020) arXiv: arXiv:2008.05118 DOI: 10.1103/PhysRevA.102.023324
"A Versatile Microwave Source for Cold Atom Experiments Controlled by a Field Programmable Gate Array," I. Morgenstern, S. Zhong, Q. Zhang, L. Baker, J. Norris, B. Tran, and A. Schwettmann, Rev. Sci. Instrum., 91, 023202, (2020) arXiv: arXiv:1909.08728 DOI: 10.1063/1.5127880
"Quantum interferometry with microwave-dressed F = 1 spinor Bose-Einstein condensates: Role of initial states and long-time evolution," Q. Zhang and A. Schwettmann, Physical Review A, 100, 063637, (2019) arXiv: arXiv:1909.03361 DOI: https://doi.org/10.1103/PhysRevA.100.063637
"Spinor Bose-Einstein-condensate phase-sensitive amplifier for SU(1,1) interferometry," J. P. Wrubel, A. Schwettmann, D. P. Fahey, Z. Glassman, H. K. Pechkis, P. F. Griffin, R. Barnett, E. Tiesinga, and P. D. Lett, Physical Review A, 98, 023620, (2018) ADS: 2018PhRvA..98b3620W arXiv: arXiv:1807.06676 DOI: 10.1103/PhysRevA.98.023620
"Atom based vector microwave electrometry using rubidium Rydberg atoms in a vapor cell," J. Sedlacek, A. Schwettmann, H. Kübler, and J. P. Shaffer, Physical Review Letters, 111, 063001, (2013) arXiv: http://arxiv.org/abs/1304.4299 DOI: 10.1103/PhysRevLett.111.063001
"Spinor dynamics in an antiferromagnetic spin-1 thermal Bose gas ," H. K. Pechkis, J. P. Wrubel, A. Schwettmann, P. F. Griffin, R. Barnett, E. Tiesinga, and P. D. Lett, Physical Review Letters, 111, 025301, (2013) ADS: 2013PhRvL.111b5301P arXiv: http://arxiv.org/abs/1306.4255 DOI: 10.1103/PhysRevLett.111.025301
"Microwave electrometry with Rydberg atoms in a vapour cell using bright atomic resonances," J. A. Sedlacek, A. Schwettmann, H. Kübler, R. Löw, T. Pfau, and J. P. Shaffer, Nature Physics, 8, 819-824, (2012) DOI: doi:10.1038/nphys2423