Lunchbox Seminars 2009-2010
Every colloquium speaker meets with physics undergraduates in PAB B135 on Mondays at 12:30pm. Pizza will be served for $1 per slab. This is a great way to network with faculty from other universities in case you decide to apply there.
2009 October 12
Mark G. Raizen (University of Texas at Austin)
Title: Comprehenzive Control of Atomic Motion
Abstract: The method of laser cooling has opened the door to low temperature physics of dilute gases. Despite the great success of this method, it has been limited to a very small set of atoms in the periodic table and no molecules. I will describe in this talk new approaches to trapping and cooling that have been developed in my group. The first step uses pulsed magnetic fields to stop atoms and molecules where they can be magnetically trapped. The next step is an experimental realization of informational cooling as first proposed by Leo Szilard in 1929 in an effort to resolve the paradox of Maxwell's demon. Together, these provide a two-step comprehensive solution to trapping and cooling. I will describe our progress in applying these new methods to trapping and cooling of hydrogen isotopes. In the short term, we are working to trap hydrogen and deuterium, which will serve as a step towards trapping of atomic tritium. This system will be used for precision measurement of beta decay towards determination of the neutrino rest mass. Our methods are also very applicable to trapping and cooling of anti-hydrogen, and a collaboration at an accelerator laboratory is being pursued.
Title: Comprehenzive Control of Atomic Motion
Abstract: The method of laser cooling has opened the door to low temperature physics of dilute gases. Despite the great success of this method, it has been limited to a very small set of atoms in the periodic table and no molecules. I will describe in this talk new approaches to trapping and cooling that have been developed in my group. The first step uses pulsed magnetic fields to stop atoms and molecules where they can be magnetically trapped. The next step is an experimental realization of informational cooling as first proposed by Leo Szilard in 1929 in an effort to resolve the paradox of Maxwell's demon. Together, these provide a two-step comprehensive solution to trapping and cooling. I will describe our progress in applying these new methods to trapping and cooling of hydrogen isotopes. In the short term, we are working to trap hydrogen and deuterium, which will serve as a step towards trapping of atomic tritium. This system will be used for precision measurement of beta decay towards determination of the neutrino rest mass. Our methods are also very applicable to trapping and cooling of anti-hydrogen, and a collaboration at an accelerator laboratory is being pursued.
2009 October 5
Ivan Deutsch (University of New Mexico)
Title: Quantum Control and Measurement: Two Keys to Quantum Information Processing
Abstract: When we first learn about quantum mechanics it appears to be a paler version of classical physics. Quantities are fundamentally uncertain, random, and one cannot measure one thing without disturbing another. This notion cannot be further from the truth. Quantum physics is now understood to be fundamentally MORE powerful for performing certain information processing tasks, from factoring large numbers to sharing secrets. Bringing this promise into laboratory and ultimately real devices has been a grand challenge. In this colloquium I will discuss two key components -- quantum control and measurement. These are flip sides of the same coin. In quantum control, one applies an external force to affect a dynamical map on the system of interest. In quantum measurement, information about the system is mapped to the probe, which can then be detected as a macroscopic signal. These paradigms are explored in a near ideal platform -- ultracold atomic spins controlled and measured through magneto-optical interactions. I will discuss the theoretical development of new protocols and their implementation in the laboratory in collaboration with Prof. P. S. Jessen.
Title: Quantum Control and Measurement: Two Keys to Quantum Information Processing
Abstract: When we first learn about quantum mechanics it appears to be a paler version of classical physics. Quantities are fundamentally uncertain, random, and one cannot measure one thing without disturbing another. This notion cannot be further from the truth. Quantum physics is now understood to be fundamentally MORE powerful for performing certain information processing tasks, from factoring large numbers to sharing secrets. Bringing this promise into laboratory and ultimately real devices has been a grand challenge. In this colloquium I will discuss two key components -- quantum control and measurement. These are flip sides of the same coin. In quantum control, one applies an external force to affect a dynamical map on the system of interest. In quantum measurement, information about the system is mapped to the probe, which can then be detected as a macroscopic signal. These paradigms are explored in a near ideal platform -- ultracold atomic spins controlled and measured through magneto-optical interactions. I will discuss the theoretical development of new protocols and their implementation in the laboratory in collaboration with Prof. P. S. Jessen.
June 1, 2009
Thomas Loftus (UW Physics)
Title: An Improved Limit on Permanent Electric Dipole Moment (EDM) of 199Hg
Abstract: A finite permanent electric dipole moment (EDM) of a particle or atom would violate time reversal symmetry (T), and would also imply violation of the combined charge conjugation and parity symmetry (CP) through the CPT theorem. EDMs are suppressed in the standard model of particle physics (SM), lying many orders of magnitude below current experimental sensitivity. It is generally accepted, however, that extra sources of CP violation are needed to account for baryogenesis and many theories beyond the SM, such as supersymmetry, naturally predict EDMs within experimental reach. To date, EDM searches have yielded null results. The most precise and significant limits have been set on the EDM of the neutron[1], the electron[2], and the 199Hg atom[3], leading to tight constraints on supersymmetric extensions of the SM. I will describe the results from a new experimental search for the EDM of 199Hg. We find d (199Hg) = (0.49 กพ 1.29stat กพ 0.76syst) x 10-29 e cm, and interpret this as a new upper bound, d (199Hg) < 3.1 x 10-29 e cm (95% C.L.)[4]. This result improves our previous 199Hg limit by a factor of 7 and offers a yet more exacting probe of possible new sources of CP violation. The experiment utilizes a stack of four spin-polarized Hg vapor cells in a common B-field. The middle two cells have oppositely directed E-fields, resulting in EDM-sensitive Larmor shifts of the opposite sign; the outer two cells, enclosed by the high voltage (HV) electrodes and thus placed at E = 0, are free of EDM effects and instead allow cancelation of B-field gradient noise and checks for spurious HV-correlated B-field shifts. The dataset consists of 166 runs, with each run lasting roughly 24 hours and compromising several hundred E-field reversals. Measurements were performed for nine different vapor cells, four electrodes, two cell-containing vessels, and multiple vapor cell and electrode orientations. An unknown, HV-correlated, EDM-mimicking offset was added to the fitted values of the middle cell precession frequencies. This fixed blind offset masked the measured EDM and was revealed only after the data collection, data cuts, and error analysis were complete. In addition to experimental results, I will briefly outline the resulting new upper bounds on fundamental CP violating parameters.
[1]C.A. Baker, et al., Phys. Rev. Lett. 97, 131801 (2006).
[2]B.C. Regan, et al., Phys. Rev. Lett. 88, 071805 (2002).
[3]M.V. Romalis, et al., Phys. Rev. Lett. 86, 2505 (2001).
[4]W.C. Griffith, et al., Phys. Rev. Lett. 102, 101601 (2009)
Title: An Improved Limit on Permanent Electric Dipole Moment (EDM) of 199Hg
Abstract: A finite permanent electric dipole moment (EDM) of a particle or atom would violate time reversal symmetry (T), and would also imply violation of the combined charge conjugation and parity symmetry (CP) through the CPT theorem. EDMs are suppressed in the standard model of particle physics (SM), lying many orders of magnitude below current experimental sensitivity. It is generally accepted, however, that extra sources of CP violation are needed to account for baryogenesis and many theories beyond the SM, such as supersymmetry, naturally predict EDMs within experimental reach. To date, EDM searches have yielded null results. The most precise and significant limits have been set on the EDM of the neutron[1], the electron[2], and the 199Hg atom[3], leading to tight constraints on supersymmetric extensions of the SM. I will describe the results from a new experimental search for the EDM of 199Hg. We find d (199Hg) = (0.49 กพ 1.29stat กพ 0.76syst) x 10-29 e cm, and interpret this as a new upper bound, d (199Hg) < 3.1 x 10-29 e cm (95% C.L.)[4]. This result improves our previous 199Hg limit by a factor of 7 and offers a yet more exacting probe of possible new sources of CP violation. The experiment utilizes a stack of four spin-polarized Hg vapor cells in a common B-field. The middle two cells have oppositely directed E-fields, resulting in EDM-sensitive Larmor shifts of the opposite sign; the outer two cells, enclosed by the high voltage (HV) electrodes and thus placed at E = 0, are free of EDM effects and instead allow cancelation of B-field gradient noise and checks for spurious HV-correlated B-field shifts. The dataset consists of 166 runs, with each run lasting roughly 24 hours and compromising several hundred E-field reversals. Measurements were performed for nine different vapor cells, four electrodes, two cell-containing vessels, and multiple vapor cell and electrode orientations. An unknown, HV-correlated, EDM-mimicking offset was added to the fitted values of the middle cell precession frequencies. This fixed blind offset masked the measured EDM and was revealed only after the data collection, data cuts, and error analysis were complete. In addition to experimental results, I will briefly outline the resulting new upper bounds on fundamental CP violating parameters.
[1]C.A. Baker, et al., Phys. Rev. Lett. 97, 131801 (2006).
[2]B.C. Regan, et al., Phys. Rev. Lett. 88, 071805 (2002).
[3]M.V. Romalis, et al., Phys. Rev. Lett. 86, 2505 (2001).
[4]W.C. Griffith, et al., Phys. Rev. Lett. 102, 101601 (2009)