Applied Physics / Physics Colloquium

AP483 Optics & Electronics Seminar presents "Extreme optics with zero-index and flat-band metamaterials"

Topic: 
Extreme optics with zero-index and flat-band metamaterials
Abstract / Description: 

Nanotechnology has enabled the development of nanostructured composite materials (metamaterials) with exotic optical properties not found in nature. In the most extreme case, we can create materials which support light waves that propagate with infinite phase velocity, corresponding to a refractive index of zero. We have developed a variety of in-plane metamaterial designs that permit obtaining a refractive index of zero in the optical regime. We will report on some of the exotic physics of zero-index metamaterials, including strong enhancement of nonlinear optical phenomena, and on flat-bands generated by twisted bilayer photonic crystals.

Date and Time: 
Monday, February 1, 2021 - 4:15pm

AP 483 Seminar presents "Laser Lightsails"

Topic: 
Laser Lightsails
Abstract / Description: 

We are exploring the nanophotonic design principles to enable self-stabilizing optical manipulation, levitation and propulsion of ultralight macroscopic-sized (i.e., mm, cm, or even meter-scale) 'lightsails' via radiation pressure. Reaching this goal requires the conception and design of new ultralight photonic structures composed of materials with extreme optical, mechanical and thermal properties. The design approach for such structures balances the need for sufficiently high reflectivity, required for efficient photon momentum transfer, very low absorption and very low areal mass density. We show that nanophotonic structures including planar dielectric slabs, two-dimensional photonic crystals and metasurfaces can yield designs that minimize mass while maximizing photon momentum transfer.

Nanoscale control of light scattering across a lightsail creates mechanical stability by tailoring the scattered phase, without the need to shape or focus the incident light beam or excessively constrain the shape, size or material composition of the object. We have developed a general, scale-independent theory for the light-induced manipulation of macroscopic objects with patterned nanoscale components that impart optical anisotropy. We investigated specific designs that features semiconductor resonators on dielectric substrates, identifying nanophotonic structures that self-stabilize when rotated and/or translated relative to the optical axis. We also discuss a proof-of-concept experimental prototype, that integrates optomechanical elements into a single structure, yielding restoring behavior along the different rotational (roll-pitch-yaw) and translational degrees of freedom. Our approach is expected to lead to new platforms for optical manipulation of macroscopic objects, with applications ranging from contactless wafer-scale fabrication and assembly, to trajectory control for next-generation ultralight ultrahigh altitude aircraft and spacecraft, and even laser-propelled lightsails for outer planet and interstellar space exploration, such as the effort underway by the Breakthrough Starshot program.

Date and Time: 
Monday, January 25, 2021 - 4:15pm

Applied Physics/Physics Colloquium presents "Perspectives on the LHC and new Frontiers in the search for Dark Matter"

Topic: 
Perspectives on the LHC and new Frontiers in the search for Dark Matter
Abstract / Description: 

By many metrics the Large Hadron Collider has been an astonishing success. It has discovered the mechanism for the origin of mass of fundamental particles and has tested the Standard Model of particle physics over a huge range of scales. However, many of the questions which were open at the start of LHC collisions remain unanswered. In this talk will give a personal perspective on where the LHC has been and where it is going. Looking to the future, I will discuss accelerator-based attempts to solve one of the biggest open questions in particle physics: what is the nature of dark matter?

Date and Time: 
Tuesday, December 1, 2020 - 4:30pm
Venue: 
Zoom ID: 98318706291; +password

Applied Physics/Physics colloquium presents "Frontiers in Optical and CMB Survey Cosmology"

Topic: 
Frontiers in Optical and CMB Survey Cosmology
Abstract / Description: 

Observations of the cosmic microwave background (CMB) and the galaxy-filled sky provide images of the universe at its various stages that are sensitive to its physics from the earliest moments to recent times. These observations are key to expanding our understanding to the physics of inflation, neutrinos, dark matter, and dark energy—some of the most mysterious terrains in physics today. We will present results from current CMB and optical surveys—the South Pole Telescope & BICEP/Keck Array and the optical Dark Energy Survey, respectively—whose unprecedented sensitivities enable us to stringently test the standard cosmological model and constrain new physics. We will discuss their current limitations due to calibration uncertainty and confounding astrophysical effects. To conclude, we will look forward to the bright future of optical, CMB, and joint cosmological experiments that will be performed by the Vera C. Rubin Observatory's Legacy Survey of Space and Time and the CMB-S4 experiment.

Date and Time: 
Tuesday, November 17, 2020 - 4:30pm

Applied Physics/Physics colloquium present "Harnessing Data Revolution in Quantum Matter"

Topic: 
Harnessing Data Revolution in Quantum Matter
Abstract / Description: 

Our desire to better understand quantum emergence drove the community's efforts in improving computing power and experimental instrumentation dramatically. However, the resulting increase in volume and complexity of data present new challenges. I will discuss how these challenges can be embraced and turned into opportunities by employing principled machine learning approaches. The rigorous framework for scientific understanding physicists enjoy through our celebrated tradition requires any machine learning essential to interpret any machine learning. I will discuss our recent results using machine learning approaches designed to be interpretable from the outset. Specifically, I will present discovering order parameters and its fluctuations in voluminous X-ray diffraction data and discovering signature correlations in quantum gas microscopy data as concrete examples.

Date and Time: 
Tuesday, November 10, 2020 - 4:30pm

Applied Physics/Physics Colloquium presents "Advances in our understanding of the airborne transmission of SARS-CoV-2"

Topic: 
Advances in our understanding of the airborne transmission of SARS-CoV-2
Abstract / Description: 

This talk will focus on the latest research on the transmission of SARS-CoV-2.

 

Date and Time: 
Tuesday, October 27, 2020 - 4:30pm
Venue: 
Zoom ID: 93508828137; +Password

Applied Physics/Physics Colloquium presents "Discovering the Highest Energy Neutrinos"

Topic: 
Discovering the Highest Energy Neutrinos
Abstract / Description: 

The detection of high energy astrophysical neutrinos is an important step toward understanding the most energetic cosmic accelerators. IceCube, a large optical detector at the South Pole, has observed the first astrophysical neutrinos and identified at least one potential source. However, the best sensitivity at the highest energies comes from detectors that look for coherent radio Cherenkov emission from neutrino interactions. I will give an overview of the state of current experimental efforts, including recent results, and then discuss a suite of new experiments designed to discover neutrinos at the highest energies and push the energy threshold for radio detection down to overlap with the energy range probed by IceCube, thus covering the full astrophysical energy range out to the highest energies, and opening up new phase space for discovery. These include ground-based experiments such as RNO-G and IceCube-Gen2, as well as the balloon-borne experiment PUEO.

Date and Time: 
Tuesday, October 20, 2020 - 4:30pm
Venue: 
Zoom ID: 946 67 170 862; +passcode

AP/Physics colloquium presents "Frontiers in Cosmic Magnetism and in Many-Body Physics"

Topic: 
Frontiers in Cosmic Magnetism and in Many-Body Physics
Abstract / Description: 

Galaxies like our Milky Way host large-scale, weak magnetic fields. The interstellar magnetic field affects a wide range of physics, from cosmic ray propagation to star formation. The magnetic interstellar medium is also a formidable foreground for experimental cosmology, particularly for the quest to find signatures of inflation in the polarized cosmic microwave background. Despite its importance, the Galactic magnetic field and its role in interstellar processes remain poorly understood. Susan Clark will discuss a few of the big questions that drive her research on cosmic magnetism.

Many-body physics is concerned with the emergent properties - those that characterize the collectivity but not the individual constituents - of macroscopic systems with large numbers of strongly interacting particles. Ensembles of many interacting particles can support qualitatively new phenomena, with the same system able to exist in different universal phases of matter with sharply distinct properties. Due to a variety of conceptual and experimentally motivated reasons, the modern theory of quantum many body systems is largely built around the study of low-temperature and near-equilibrium properties of time independent Hamiltonians. However, such systems represent a small subset of the possible quantum mechanical descriptions of a physical system - which allow for more general unitary evolutions interrupted by non-unitary measurements. Vedika Khemani will describe some highlights of an active research program to advance many-body theory beyond the regime of near-equilibrium time-independent Hamiltonians, with a view towards uncovering complex emergent phenomena in new non-equilibrium regimes. These theoretical efforts are synergistic with recent advances in building controllable quantum devices that naturally implement more general time evolutions generated by circuits of unitary gates, starting from initial states that are not "low energy" in any useful sense.

Date and Time: 
Tuesday, October 6, 2020 - 4:30pm
Venue: 
Zoom ID: 96054036699; +password

AP 483 Seminar presents "Resolving starlight: a quantum perspective"

Topic: 
Resolving starlight: a quantum perspective
Abstract / Description: 

The wave-particle duality of light introduces two fundamental problems to imaging, namely, the diffraction limit and the photon shot noise. Quantum information theory can tackle them both in one holistic formalism: model the light as a quantum object, consider any quantum measurement, and pick the one that gives the best statistics. While Helstrom pioneered the theory half a century ago and first applied it to incoherent imaging, it was not until recently that the approach offered a genuine surprise on the age-old topic by predicting a new class of superior imaging methods. For the resolution of two sub-Rayleigh sources, the new methods have been shown theoretically and experimentally to outperform direct imaging and approach the true quantum limits. Recent efforts to generalize the theory for an arbitrary number of sources suggest that, despite the existence of harsh quantum limits, the quantum-inspired methods can still offer significant improvements over direct imaging for subdiffraction objects, potentially benefiting many applications in astronomy as well as fluorescence microscopy.


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, November 16, 2020 - 4:15pm

AP 483 Seminar presents "Correlated photon physics in mesoscopic atomic chains"

Topic: 
Correlated photon physics in mesoscopic atomic chains
Abstract / Description: 

Tightly packed ordered arrays of atoms (or, more generally, quantum emitters) exhibit remarkable collective optical properties, as dissipation in the form of photon emission is correlated. In this talk, I will discuss the single-, few- and many-body out-of-equilibrium physics of 1D arrays, and their potential to realize versatile light-matter interfaces. For small enough inter-atomic distances, atomic chains feature dark states that allow for dissipationless transport of photons, behaving as waveguides for single-photon states. Atomic waveguides can be used to mediate interactions between impurity qubits coupled to the array, and allow for the realization of multiple paradigms in waveguide QED, from bandgap physics to chiral quantum optics [1]. Due to the two-level nature of the atoms, atomic waveguides are a perfect playground to realize strong photon-photon interactions. At the many-body level, I will address the open question of how the geometry of the array impacts the process of "Dicke superradiance", where fully inverted atoms synchronize as they de-excite, emitting light in a burst (in contrast to the exponential decay expected from independent emitters). While most literature attributes the quenching of superradiance to Hamiltonian dipole-dipole interactions, the actual culprits are dissipative processes in the form of photon emission into different optical modes. I will provide an understanding of the physics in terms of collective jump operators and demonstrate that superradiance survives at small inter-atomic distances [2]. I will finish my talk by discussing the implications of correlated photon emission for quantum information processing and metrology.

[1] S. J. Masson, A. Asenjo-Garcia, Atomic-waveguide Quantum Electrodynamics, arXiv: 1912.06234 (2019)

[2] S. J. Masson, I. Ferrier-Barbut, L. A. Orozco, A. Browaeys, A. Asenjo-Garcia, Many-body signatures of collective decay in atomic chains, arXiv: 2008.08139 (2020)


This seminar is sponsored by the department of Applied Physics and the Ginzton Laboratory.

Date and Time: 
Monday, November 9, 2020 - 4:15pm

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