B.S. eq. 2001 Universität Hannover Germany
M.S. 2003 University of North Texas
Ph.D. 2012 University of Oklahoma
Ph: (405) 325-6090
Office: 131 Nielsen Hall
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.
"Atom based vector microwave electrometry using rubidium Rydberg atoms in a vapor cell," J. Sedlacek, A. Schwettmann, H. Kübler, and J. P. Shaffer, Phys. Rev. Lett., 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, Phys. Rev. Lett., 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) arXiv: http://arxiv.org/abs/1205.4461 DOI: doi:10.1038/nphys2423
"Effects of electric fields on ultracold Rydberg atom interactions," J. S. Cabral, J. M. Kondo, L. F. Goncalves, V. A. Nascimento, L. G. Marcassa, D. Booth, J. Tallant, A. Schwettmann, K. R. Overstreet, J. Sedlacek and J. P. Shaffer, J. Phys. B: At. Mol. Opt. Phys., 44, 184007, (2011) DOI: doi:10.1088/0953-4075/44/18/184007
"Field-programmable gate array based locking circuit for external cavity diode laser frequency stabilization," A. Schwettmann, J. Sedlacek, and J. P. Shaffer, Rev. Sci. Instrum., 82, 103103, (2011) DOI: doi:10.1063/1.3646477
"Observation of electric-field-induced Cs Rydberg atom macrodimers," K. R. Overstreet, A. Schwettmann, J. Tallant, D. Booth and J. P. Shaffer, Nature Physics, 5, 581 - 585, (2009) arXiv: http://arxiv.org/abs/0901.1825 DOI: doi:10.1038/nphys1307 M3
"Cold Cs Rydberg-gas interactions," A. Schwettmann, J. Crawford, K. R. Overstreet, and J. P. Shaffer, , Phys. Rev. A, 74, 020701(R), (2006) arXiv: http://arxiv.org/abs/0901.1825 DOI: doi:10.1103/PhysRevA.74.020701