Groups | Seminars || Courses | Outreach


Seminars will be held held at room S-141 in the Physics and Astronomy Department building on Mondays at 4:00 PM, unless noted otherwise.


Fall 2018

October 1, 2018

Prof. Joseph H. Eberly
University of Rochester

Can there be a Role for Entanglement in Entirely Classical Physics? 

(Host: Hal Metcalf)

The impression obtained from most textbooks, and from discussions with most physicists, is that the presence of entanglement provides a clear indication of a quantum mechanical state or process. Schrödinger is responsible for importing the word entanglement into physics. This was connected to the state of his famous Cat, when he responded to the Einstein-Podolsky-Rosen analysis of the joint behavior of remote quantum parties [1]. The EPR paper was Schrödinger's first citation and his second citation was to a mathematical result containing the essential point of entanglement. It was first reported by Erhard Schmidt in 1907, two decades before quantum mechanics had even been invented. Now relieved of the need to understand quantum mechanics, in order to employ entanglement, we have been using classical optics to exhibit features arising specifically from entanglement [2]. One example will be the definition and experimental observation of previously unknown optical coherences [3,4].  
[1] E. Schr
ödinger, Math. Proc. Cambridge Phil. Soc., v31, pp 555- 563 (1935).
[2] Xiao-Feng Qian and J.H. Eberly, Optics Letters, v36, 4110 (2011).
[3] X.-F. Qian, T. Malhotra, A. Nick Vamivakas, and Joseph H. Eberly, Phys. Rev. Letters v117, 153901 (2016).
[4] J.H. Eberly, X.-F. Qian, and A.N. Vamivakas, Optica v4, 1113 (2017).

October 25, 2018 (Thurs, 1pm)

Dr. Thomas Wolf

Investigating ultrafast processes in photoexcited molecules with x-rays and electrons

(Host: Tom Allison)

Ultrafast dynamics in photoexcited molecules are based on the interplay of electronic and nuclear degrees of freedom under violation of the Born-Oppenheimer approximation. Comprehensive understanding of the underlying processes can only be achieved with detailed knowledge of both electronic and nuclear dynamics. I want to show at two examples, what we can learn from experimental methods with selective sensitivity to ultrafast changes in either the electronic or the nuclear structure of molecules. In the first part of the talk, I will focus on our investigation of the ultrafast photoprotection mechanism in the nucleobase thymine with time-resolved near-edge soft x-ray absorption spectroscopy at LCLS. The site specificity of soft x-ray spectroscopy can here be transformed into selective sensitivity to changes in the electronic structure of thymine. The experimental data unambiguously show that the molecule undergoes internal conversion through a conical intersection between two excited states within 60 fs after photoexcitation.
In the second part of my talk, I want to present results from an investigation of the photoinduced ring opening of 1,3-cyclohexadiene at SLAC's ultrafast electron diffraction (UED) facility. The large accessible momentum transfer range in the diffraction data permits us to directly and selectively follow transient changes of the nuclear structure in time. In the case of cyclohexadiene, we observe the bond dissociation and ring opening on the level of individual atomic distances. The photochemical reaction product 1,3,5-hexatriene exhibits several isomers with low barriers. We can follow coherent oscillations of the hexatriene population between different isomer minima following the ring-opening on a sub-picosecond timescale. Our experimental results are in good agreement with ab initio excited state wavepacket simulations.

October 29, 2018

Prof. Swati Singh
Williams College

Using macroscopic quantum systems as detectors

(Host: Hal Metcalf)

When properly engineered, simple quantum systems such as harmonic oscillators or spins can be excellent detectors of feeble forces and fields. Following a general introduction to this fast growing area of research I will focus on two simple and experimentally realizable examples: a nitrogen vacancy (NV) center in diamond interacting with its many-body environment, and acoustic modes of superfluid helium interacting with gravitational waves.

In the first case, I will demonstrate within a semi-classical description that it is possible to understand (and even control) the quantum many-body environment of the of the NV center, thereby enabling several magnetometry applications. In the second example I will show that for reasonable experimental parameters, a hybrid quantum system consisting of superfluid helium coupled to superconducting cavity could enable the detection of gravitational waves from nearby pulsars.

November 19, 2018

Judith Mizrachi
Stony Brook University

Super Resolution Oblique Light Sheet Microscopy

(Host: Hal Metcalf)

The ability to examine the brain at the mesoscale whole-brain and nanometer scale local level is instrumental to understanding how brain structure gives rise to sensory, motor, and cognitive functions. Visualization of nanometer-scale structures, such as synapse density and distribution, provides deeper understanding of normal brain function and has the potential to reveal structural underpinnings of neuropsychiatric disorders. Large scale and nanometer scale structures can be studied separately, be we lack methodologies that could provide whole brain volumetric imaging, neural tracing, and 3D super-resolution imaging of a mammalian brain simultaneously.
Our project aims to develop such a method by combining oblique lightsheet tomography (OLST), which can image an entire mouse brain at light-resolution level, and 3D superresolution light sheet microscopy for the examination of synapses with nanometer scale resolution in selected brain areas. The method comprises an automated combination of light sheet fluorescence microscopy (LSFM), vibratome sectioning, pixel-wise 3D deconvolution, custom image reconstruction software, super-resolution optical fluctuation imaging (SOFI) processing, and axial super-resolution imaging with a cylindrical lens. The proposed device and technique will be the first instrument capable of generating volumetric whole brain images and 3D super-resolution images for the same mouse brain simultaneously.

December 10, 2018

Dr. Jeremy Reeves
Boston University

MEMS. Nanomanufacturing, and Tunable Metamaterials

(Host: Dominik Schnebke)

I present a set of techniques developed for the nanoscale patterning of three-dimensional elastic mechanical metamaterials. Leveraging a variety of fabrication technologies, metallic patterns are fabricated on 3D-printed polymer scaffolds. Generally, high resolution metallic patterning of substrates such as these would be impossible using conventional photolithographic techniques. However, utilizing microelectromechanical systems (MEMS) devices to manipulate a micro-scale stencil, precise patterning of traditionally challenging substrates can be achieved. Here, I discuss a metamaterial with resonant response in the mid-infrared fabricated using these techniques. Methods for tuning the frequency response of this metamaterial are presented alongside techniques to create truly 3D structures spanning many length scales. I will also discuss potential applications of the fabricated metamaterials.