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I am the Chief Research Scientist at Aspen Quantum Consulting, a leading firm that…
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Hysteresis in a quantized superfluid ‘atomtronic’ circuit
Nature
Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits—it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as…
Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits—it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose–Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose–Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices).
Other authorsSee publication -
High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride
J. Chem. Phys.
BF3 is transparent in the ultraviolet, making it a viable gaseous scintillator for detecting neutrons.
Other authorsSee publication -
Atom-molecule equilibration in a degenerate Fermi gas with resonant interactions
J. Phys. B: At. Mol. Opt. Phys. 37, L351
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Phase diagrams for an ideal gas mixture of fermionic atoms and bosonic molecules
New J. Phys. 6, 123
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Longitudinal spin waves in a dilute Bose gas
Phys. Rev. Lett. 88, 230405
Patents
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Controller for and controlling neutron orbital angular momentum
Issued US US Patent Application 20160360605
An orbital angular momentum (OAM) controller controls OAM of a plurality of neutrons and includes: a substrate; a first surface of the substrate; and a second surface of the substrate disposed opposingly across the substrate from the first surface and including a contoured shape. A process for controlling OAM of neutrons includes: subjecting an OAM controller to a plurality of neutrons; receiving the neutrons at a first surface of the OAM controller; transmitting the neutrons through the OAM…
An orbital angular momentum (OAM) controller controls OAM of a plurality of neutrons and includes: a substrate; a first surface of the substrate; and a second surface of the substrate disposed opposingly across the substrate from the first surface and including a contoured shape. A process for controlling OAM of neutrons includes: subjecting an OAM controller to a plurality of neutrons; receiving the neutrons at a first surface of the OAM controller; transmitting the neutrons through the OAM controller; and providing a phase shift .theta. to a wavefunction of neutrons transmitted through the OAM controller according to .theta..varies.T.sub.1+T.sub.2(.phi./2.pi.), wherein T.sub.1 is a first thickness of a substrate of the OAM controller, T2 is a second thickness of the substrate, and .phi. is an azimuthal angle of the substrate.
Other inventorsSee patent -
Noble-gas-excimer detectors of slow neutrons
Issued US 8,816,296
The present invention relates to apparatus and methods for use in highly sensitive and efficient neutron detection, that includes using trigger reactions to initiate far-ultraviolet (FUV) optical emissions. In some embodiments of the present invention, a method for the detection of slow neutrons includes absorption of a slow neutron with a high neutron capture-cross-section nucleus, decay of the compound nucleus into energetic particles, creation of excimers from the energetic particles…
The present invention relates to apparatus and methods for use in highly sensitive and efficient neutron detection, that includes using trigger reactions to initiate far-ultraviolet (FUV) optical emissions. In some embodiments of the present invention, a method for the detection of slow neutrons includes absorption of a slow neutron with a high neutron capture-cross-section nucleus, decay of the compound nucleus into energetic particles, creation of excimers from the energetic particles reacting with a background gas to form excimers, radiative decay of excimers resulting in emission of FUV radiation, and detection of the FUV radiation using an optical detector.
Other inventorsSee patent -
Apparatus and method for detecting slow neutrons by Lyman alpha radiation
Issued US 7,791,045
A method and apparatus for detecting slow neutrons by monitoring Lyman alpha radiation produced by the .sup.3He(n,tp) nuclear reaction induced by neutrons incident on a gas cell containing .sup.3He or a mixture of .sup.3He and other atoms and/or molecules. Such a method and/or apparatus includes the use of, for example, liquid .sup.3He and .sup.4He mixtures as a scintillation counter for the sensitive detection of neutrons using Lyman alpha radiation produced by the .sup.3He(n,tp) reaction. The…
A method and apparatus for detecting slow neutrons by monitoring Lyman alpha radiation produced by the .sup.3He(n,tp) nuclear reaction induced by neutrons incident on a gas cell containing .sup.3He or a mixture of .sup.3He and other atoms and/or molecules. Such a method and/or apparatus includes the use of, for example, liquid .sup.3He and .sup.4He mixtures as a scintillation counter for the sensitive detection of neutrons using Lyman alpha radiation produced by the .sup.3He(n,tp) reaction. The radiation can be detected with high efficiency with an appropriate photo-detector, or alternatively, it can be converted to radiation at longer wavelength by absorption in scintillation materials, with the radiation channeled to a photodetector. Because of the simplicity of the system and the fact that the radiation production mechanisms can be measured and/or calculated independently, the method and/or apparatus also has the potential for service as a calculable absolute detector.
Other inventorsSee patent
Projects
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Small-angle scattering interferometry with neutron orbital angular momentum states
Methods to prepare and characterize neutron helical waves carrying orbital angular momentum (OAM) have been demonstrated at small-angle neutron scattering (SANS) facilities. These methods enable access to the neutron orbital degree of freedom which provides new avenues of exploration in fundamental science experiments as well as in material characterization applications. However, it remains a challenge to recover phase profiles from SANS measurements. We introduce and demonstrate a novel…
Methods to prepare and characterize neutron helical waves carrying orbital angular momentum (OAM) have been demonstrated at small-angle neutron scattering (SANS) facilities. These methods enable access to the neutron orbital degree of freedom which provides new avenues of exploration in fundamental science experiments as well as in material characterization applications. However, it remains a challenge to recover phase profiles from SANS measurements. We introduce and demonstrate a novel neutron interferometry technique for extracting phase information that is typically lost in SANS measurements. An array of reference beams, with complementary structured phase profiles, are put into a coherent superposition with the array of object beams, thereby manifesting the phase information in the far-field intensity profile. We demonstrate this by resolving petal-structure signatures of helical wave interference for the first time: an implementation of the long-sought recovery of phase information from small-angle scattering measurements.
Other creators -
Cone beam neutron interferometry: from modeling to applications
https://arxiv.org/abs/2309.01787
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Experimental realization of neutron helical waves
Methods of preparation and analysis of structured waves of light, electrons, and atoms have been advancing rapidly. Despite the proven power of neutrons for material characterization and studies of fundamental physics, neutron science has not been able to fully integrate these techniques because of small transverse coherence lengths, the relatively poor resolution of spatial detectors, and low fluence rates. Here, we demonstrate methods that are practical with the existing technologies and show…
Methods of preparation and analysis of structured waves of light, electrons, and atoms have been advancing rapidly. Despite the proven power of neutrons for material characterization and studies of fundamental physics, neutron science has not been able to fully integrate these techniques because of small transverse coherence lengths, the relatively poor resolution of spatial detectors, and low fluence rates. Here, we demonstrate methods that are practical with the existing technologies and show the experimental achievement of neutron helical wavefronts that carry well-defined orbital angular momentum values. We discuss possible applications and extensions to spin-orbit correlations and material characterization techniques.
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NIST Digital Library of Mathematical Functions
- Present
Digital library of the special functions of mathematics. Free world-wide access online at http://dlmf.nist.gov Book version published by Cambridge University Press, ISBN-13: 978-0521192255 (paperback), 978-0521192255 (hardcover)
Other creatorsSee project -
Atomic Reference Data for Electronic Structure Calculations
- Present
Recommended values of atomic orbital and total energies for several variants of density functional theory.
Other creatorsSee project
Languages
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German
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Organizations
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Cosmos Club
Member
- Present -
Bangladesh Physical Society
Honorary Fellow and Life Member
- Present -
American Association for the Advancement of Science
Fellow
- PresentFellow of the American Association for the Advancement of Science; Member at Large, Section P (Industrial Science and Technology), 2024; Secretary, Section P, 2023; Chair, Section B (Physics), 2011; Member, Annual Meeting Program Committee (2000-2005)
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Optica Worldwide, formerly Optical Society of America
Life Member and Fellow
- PresentLife Member and Fellow of Optica; Associate Editor, Optics Express; Chair, Technical Group on Optical Cooling and Trapping, 2018-2020; Chair, Fellows and Honorary Members Committee, 2006; Topical Editor for Atomic Spectroscopy, Journal of the Optical Society of America B, 1986-1992.
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American Physical Society
Chair, Division of Atomic, Molecular and Optical Physics
-Life Member and Fellow of the American Physical Society; Interim Past Chair, Mid-Atlantic Section (2013); Member, Selection Committee, LeRoy Apker Award (2013-2015); Member, Physics Policy Committee (2005-2007); Member, Davisson-Germer Prize Committee (2004-2006); Member, Fellowship Committee (2003-2005)
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Insitute of Physics
Member, Editorial Board, Journal of Physics B: Atomic, Molecular and Optical Physics
-Fellow of the Institute of Physics
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