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About September 2013

This page contains all entries posted to Physics Announcements in September 2013. They are listed from oldest to newest.

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September 2013 Archives

September 4, 2013

Seminar: Wednesday, Sept. 4, 2013 at 3:30 pm

Quantum interference of expanding BEC in microgravity
Vincenzo Tamma
Institut fur Quantenphysik, Universitat Ulm

Interferometry with expanding Bose-Einstein condensate in microgravity can be exploited to probe fundamental physics at the border between quantum mechanics and general relativity.

In particular millions of atoms in a BEC can be described by a single macroscopic wave function which o ers itself for quantum interference experiments aimed to test the weak equivalence principle.

In this talk I will describe the physics behind the BEC expansion and interference in microgravity in the time-dependent Thomas-Fermi (TF) regime in generic interferometric con gurations and taking into account rst order corrections in perturbation theory.

In particular, by using an asymmetric Mach-Zehender con guration interference fringes for expanding BEC in microgravity have been recently observed in pioneering experiments within our QUANTUS collaboration

[1]. Such experiments not only represent a perfect test for future experiments in orbit but also gives us an important motivation in pursuing further exciting research based on quantum gravimeters for ground based applications.

[1] 1. H. Muentinga, et al., Phys. Rev. Lett. 110, 093602 (2013) (Viewpoint: M. Arndt, Physics 6, 23 (2013)).

Location: Physics Bldg., Room 401

September 10, 2013

PhD Proposal - Dan Jones

Date: Monday, September 23, 2013
Time: 1:00 pm
Location: PHYS 401

Title
"Nonlinear Phase Shifts at Single-Photon Power Levels Using Tapered Optical Fibers in Rubidium Vapor"

Title
Our group has recently proposed a new form of macroscopic “phase-entangled” coherent state pulses with the potential to radically improve Quantum Communications (QC) systems. In contrast to conventional entangled pairs of single-photons which are highly susceptible to loss, these entangled pulses contain large numbers of photons and are predicted to propagate over long distances through lossy fiber channels. The key experimental requirement for generating these new entangled states is the realization of ultra-low power nonlinear phase shifts. Roughly speaking, what is needed is a robust Kerr-type nonlinearity in which the presence of a single-photon imparts a sizable phase shift on a macroscopic coherent state pulse.

Here I propose to experimentally demonstrate this nonlinear single-photon phase shift using a system comprised of a sub-wavelength diameter Tapered Optical Fiber (TOF) suspended in atomic rubidium (Rb) vapor. The proposed work leverages our group’s recent experience and experimental infrastructure in using the “TOF in Rb” system to demonstrate ultra-low power two-photon absorption. A successful demonstration of the proposed single-photon phase shifts would represent a significant advance in quantum optics, with a number of follow-on applications in QC.


September 11, 2013

Seminar: Wednesday, Sept.11, 2013 at 3:30 pm

Exploring topological orders with photons
Mohammad Hafezi
UMCP

Topological properties of physical systems can lead to natural protection against perturbations. Traditionally, this robustness is exemplified by quantized conductance in the electronic systems. In this talk, I demonstrate how similar physics can be observed for photons; specifically, how various quantum spin Hall Hamiltonians can be simulated with linear optical elements using a two dimensional array of coupled optical resonators. I report on the experimental progress towards the implementation of such ideas in silicon-on-insulator technology. Such systems allow the presence of photonic edge states which are insensitive to certain fabrication disorder and paves the way to develop robust integrated optical devices.

Furthermore, the addition of optical non-linearity to the system leads to the possibility of implementing fractional quantum Hall states of photons and anyonic states that have not yet been observed. In particular, I discuss a scheme to engineer three-body interaction, which is absent in nature, to implement some of fractional quantum Hall models in the context of circuit-QED.

Location: Physics Bldg., Room 401

September 16, 2013

Faculty Position in Atmospheric Physics

The Department of Physics invites applications for a tenure-track assistant professor position in atmospheric physics to begin in August 2014. Preference will be given to candidates with specialization in any of the following areas: lidar instrumentation and remote sensing; experience with ground, airborne or laboratory measurements and modeling supporting field campaigns, satellite validation and mission development; basic atmospheric physics research in radiative transfer, light scattering or remote sensing. We seek candidates who have a demonstrated capacity to establish a vigorous, externally funded research program. A Ph.D. in Physics, Atmospheric Science or in a closely related field and the ability to teach effectively in both the graduate atmospheric physics and undergraduate physics curriculum are required. Postdoctoral experience is required and start-up funds are available. The appointment is expected to broaden and complement existing research programs in active and passive remote sensing and atmospheric modeling. Additional collaborative research opportunities exist with affiliated faculty from the UMBC/NASA GSFC Joint Center for Earth Systems Technology (http://www.jcet.umbc.edu). In exceptional cases, the appointment may be made at a higher rank. The department currently consists of 17 tenure-track and 10 research faculty, over 45 graduate students and 150 majors. The department offers a BS in Physics, and both MS and Ph.D. degrees in Atmospheric Physics and in Applied Physics. Research expenditures currently exceed $5M per year. (For more information see: http://physics.umbc.edu).

Please submit an application letter, a resume, research and teaching plans and the names and addresses of at least three references to Chair of the Search Committee, Department of Physics, UMBC, 1000 Hilltop Circle, Baltimore MD 21250, Email: physics@umbc.edu. The selection process will begin November 15, 2013 and will continue until the position is filled. The department is especially interested in candidates who can contribute to the diversity and excellence of the academic community through research, teaching and service. UMBC is an Affirmative Action/Equal Opportunity Employer.

September 18, 2013

Seminar: Wednesday, Nov 13, 2013 at 3:30 pm

Understanding and controlling electron-nuclear spin dynamics in a quantum dot
Ed Barnes
UMCP

The realization of a quantum computer would enable us to solve problems that cannot be solved with even the most powerful supercomputers based on classical technology. Building a quantum computer requires precise control over the state of a system possessing only a few quantum degrees of freedom. In this talk I will focus on a quantum bit represented by a single electron spin trapped in a semiconductor quantum dot. The electron interacts with up to a million nuclear spins in the surrounding material through the hyperfine interaction, leading to a rapid randomization of the electron spin state and a loss of the information it encodes. Understanding how an electron spin evolves in a bath of nuclear spins is an old, challenging problem in theoretical physics known as the Central Spin problem. I will present our recent nonperturbative solution to this problem, which reveals unusual many-body quantum dynamics and offers important lessons on how to reduce the rate of information loss in spin qubits. I will also discuss our new theoretical approach on the dynamic creation of nuclear spin polarization through manipulation of the electron spin, shedding light on recent experimental puzzles.

Location: Physics Bldg., Room 401

September 25, 2013

Seminar: Wednesday, Sept. 25, 2013 at 3:30 pm

Formation and properties of plasmonic nanomaterials
Sharka Prokes
NRL

There is significant interest in the growth of semiconductor nanowires, due to interesting and useful optical, electrical and mechanical properties. They are attractive for a variety of applications, including optical sensing. One of the interesting aspects of these nanostructures is an enhanced plasmonic response, which has been investigated using Surface Enhanced Raman Spectroscopy (SERS). The growth and formation of several nanowire/metal composite structures, the formation of random and ordered arrays of these structures, and their surface enhanced Raman (SERS) properties will be discussed. The effect of geometry will also be examined, and we will show, both experimentally and in electric field simulations, that the intersections of these nanowires are critical in generating the high electric fields necessary for this enhancement.

In addition, we recently developed another novel plasmonic material, based on Plasma Enhanced Atomic Layer Deposition (PEALD) of Ag, which results in strong plasmonic properties of flat Ag films. It will be shown as-deposited flat PEALD Ag films exhibit unexpected plasmonic properties and the plasmonic enhancement can differ significantly, depending on the microstructure of the Ag film. Electric field simulations suggest that the plasmonic behavior is due to air gaps that are an inherent property of the PEALD growth of Ag and account for the trends observed in SERS. This unusual plasmonic behavior is very similar to what would be expected in hybrid spoof plasmonics and suggests that PEALD Ag is a metamaterial.


Location: Physics Bldg., Room 401

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