Eric Sembrat's Test Bonanza

Abstract:

Interference is a characteristic wave phenomenon that played important roles in physics.  For example, two-pathway interferometry is a simple and powerful technique used to establish the wave nature of light in electromagnetism, and that of particles in quantum physics. Such interferometers are typically constructed in the real space, involving two waves traveling along spatially separated paths before being recombined to interfere.  On the other hand, quantum physics allows “waves” (of probability, i.e., wavefunctions) or “paths” to be defined in more general or abstract “spaces”. This opens many possibilities to use interferometry as a powerful “phase sensitive” tool to manipulate, measure or even create novel quantum matter.  In this talk, I will describe our experimental demonstration of quantum matter interferometers where the interfering pathways are not in the real space, but in some “synthetic” spaces involving different (and spin-dependent) trajectories for the evolution of the quantum system. Our experiments are performed with a Bose-Einstein condensate (BEC) of ultracold (⁸⁷Rb) atoms, a highly-tunable synthetic quantum matter. By coupling atoms’ spin (and momentum) quantum states with appropriate electromagnetic (optical and microwave/RF) fields, various “synthetic” spin-orbit coupling (SOC) as well as quantum superposition states can be engineered. We study and control the quantum transport and quantum chemistry in such a BEC with synthetic SOC, and demonstrate two-pathway interferometry in energy-momentum space (synthetic band structure) as well as in chemical reactions (photoassociation), respectively. Time permitting, I may also discuss our experimental realization of a BEC on a synthetic cylinder (where self-interference gives a topological bandstructure mimicking transport on a Mobius strip), and studies of the roles of many-body interactions in two colliding and interfering spin-orbit-coupled BEC.  Our experimental system can be a rich playground to study physics of interests to AMO physics, quantum chemistry, condensed matter physics, and even high energy physics.

Refs:

[1] A. Olson et al., “Tunable Landau-Zener transitions in a spin-orbit coupled Bose-Einstein condensate”, Phys. Rev. A. 90, 013616 (2014); “Stueckelberg interferometry using periodically driven spin-orbit-coupled Bose-Einstein condensates”, Phys. Rev. A. 95, 043623 (2017)

[2] D. Blasing et al., “Observation of Quantum Interference and Coherent Control in a Photo-Chemical Reaction”, Phys. Rev. Lett. 121, 073202 (2018)

[3] C. Li et al., “A Bose-Einstein Condensate on a Synthetic Hall Cylinder”, arXiv: 1809.02122

Ever since the first astronomical telescope observations made by Galileo (1610), optical astronomy has developed increasingly sophisticated methods for exploring the universe using only the  classical (wave-description) properties of light. The quantum mechanical properties of light, including photon bunching and orbital angular momentum, carry substantially more information about the nature of the astronomical sources, yet these properties are currently not exploited.

This talk will describe the development of a new astronomical  capability which exploits the quantum properties of light. The technique has the potential to achieve < 100 micro-arc second angular resolution in the optical wavelengths; such high angular resolution would be sufficient to directly imaging the moons of Jupiter passing across the disk of a main sequence star ~8 light years away. We describe a conclusive demonstration of quantum photon bunching (Hanbury Brown-Twiss Interferometry) in the laboratory using  simulated stars and binary systems. We describe the design of a future ultra-high resolution optical astronomical imaging observatory using existing and future arrays of Imaging Air Cherenkov Telescopes (IACTs). The talk describes the potential optical imaging resolution of the VERITAS IACT observatory array (Amado, Arizona) and the future CTA IACT Observatory (Canary Islands, Spain and Paranal, Chile).

Are we alone in the universe? The scientific hunt for extraterrestrial intelligence is now well into its fifth decade, and we still haven’t discovered any cosmic company. Could all this mean that finding biology beyond Earth, even if it exists, is a project for the ages – one that might take centuries or longer?

New approaches and new technology for detecting sentient beings elsewhere suggest that there is good reason to expect that we could uncover evidence of sophisticated civilizations – the type of aliens we see in the movies and on TV – within a few decades. But why now, and what sort of evidence can we expect?

And how will that affect humanity? Also, if we do find E.T., what would be the societal impact of learning that something, or someone, is out there?

Note: the speaker will give a public talk at 6:00pm in CULC 152 with the same title and abstract.

ABSTRACT:

More than 40 years after its theoretical description, the process of coherent elastic neutrino-nucleus scattering (CEvNS) has been observed for the first time by the COHERENT Collaboration, using the world’s smallest functional neutrino detector: a 14.6-kg CsI[Na] crystal at the Spallation Neutron Source of Oak Ridge National Lab. COHERENT and other groups continue to work towards additional CEvNS measurements because of the breadth of physics sensitivity shown by the process, including connections to nuclear structure, astrophysics, dark sector physics, and other physics beyond the Standard Model.

This talk will discuss the initial observation of the CEvNS process along with the myriad physics connections, and even potential applications, of the process. The complementarity of additional CEvNS measurements will also be explored, emphasizing the importance of the additional, diverse experimental efforts within the large community of researchers seeking to utilize this exciting new tool in neutrino physics.

Abstract:

Light storage and quantum memory are the basis for quantum cryptography and long distance quantum communication. Four-wave mixing is a useful nonlinear optical tool to generate single photons, squeezed light and entangled photons. High optical depth is an important parameter to improve the efficiency of the light storage and four-wave mixing. In this talk, I will present our recent results on cold atoms in a one-dimensional optical trap with high optical depth. We will apply this high optical depth system for realizing light storage and four-wave mixing in the future.

Bio:

Zhanchun ZUO is now an associate professor in Institute of Physics, Chinese Academy of Sciences, China. Before she was a Post-doc in Alain Aspect group, Institut d'Optique (Paris, France) and Nakagawa group, University of Electro-Communication (Tokyo, Japan). Her research interest is the interaction between lasers and atoms, cold atoms, light storage, four-wave mixing, electromagnetically induced transparency.

Abstract

Dynamical systems producing time series data have been examined in a number of ways, including with "black box" systems described by recurrent neural networks and structured approaches such as delay embeddings.  While these approaches can work well in practice and do have theoretical justification for the approach, these techniques have lacked guarantees characterizing the quality of the information representation they produce. Meanwhile, recent results in randomized dimensionality reduction (including the field of compressed sensing and related results) have shown the value of geometry preservation in characterizing the stability of an embedding in a variety of interesting problems in signal and image acquisition.

In this talk, I will give an overview of our recent results establishing stable embedding guarantees as a quality measure for several existing approaches to understanding dynamical systems.  In recurrent networks, we will show new guarantees on the short-term memory capacity of dynamic networks that are exponential improvements over the previous state of the art, showing rigorously for the first time that networks can have memory capacity that scales superlinearly with the size of the network.  In delay embeddings, we extend the classic Takens' embedding theorem to establish conditions under which the image reconstructed from the time-series data is a stable embedding of a system's attractor. Beyond only preserving the attractor topology, a stable embedding preserves the attractor geometry by ensuring that distances between points in the state space are approximately preserved. These results also provide some guidance to choosing system parameters (e.g., number of delays, sampling rate), echoing the tradeoff between irrelevancy and redundancy that has been heuristically investigated in the literature.

 

Abstract

We study possible many body phenomena in the Quantum Anomalous Hall system of weakly interacting spinor bosons in a square lattice. There are various novel spin-bond correlated superfluids and quantum or topological phase transitions among these phases. Most notably, we find an anti-unitary Reflection $ R $ symmetry protected bosonic topological phase transition (BTPT) separating two different ground states which break identical symmetries of the Hamiltonian. The two phases can only be distinguished by the different topology of the BEC condensation momenta (or bosonic zero modes) instead of any differences in the symmetry breaking patterns.

Breaking the $ R $ symmetry explicitly by a Zeeman field will transfer the BTPT to a bosonic Lifshitz transition with accompanying symmetry breakings. This could be the first bosonic analog of the fermionic topological phase transition with the associated change in the topology of the Fermi surfaces, Dirac points or Weyl points or nodal lines. However, the BTPT is interaction driven, so may be more profound than its fermionic counterpart. Finite temperature effects will also be briefly discussed. All these new many body bosonic topological phenomena can be probed in the recently experimentally realized weakly interacting Quantum Anomalous Hall (QAH) model of $ ^{87} Rb $.

Abstract

Universal Darwinism is the observation that any system that undergoes variation, selection and heredity—whether it is living or not—is the subject of Darwinian evolution. The purpose of this talk is to explore the quantitative implications of this bare-bone idea. Taking my cues from seminal contributions of R. Fisher in genetics and statistics, I will show  that fitness distributions are subject to statistical universality: in the space of all possible distributions, fitness distributions are attracted to a low-dimensional manifold of limiting (and generally non-Gaussian) shapes.

This result, I will argue, is the central mathematical prediction of Universal Darwinism, and as such is directly testable from evolutionary data of any kind. I will present an illustration from molecular evolution and contrast my findings with other quantitative approaches such as "fitness wave theory".

Stephen Wolfram is a computer scientist, physicist, and businessman. He is known for his work in computer science, mathematics, and in theoretical physics. In 2012 he was named an inaugural fellow of the American Mathematical Society.

As a businessman, he is the founder and CEO of the software company Wolfram Research where he worked as chief designer of Mathematicaand the Wolfram Alpha answer engine. His recent work has been on knowledge-based programming, expanding and refining the programming language of Mathematica into what is now called the Wolfram Language.