Department Calendar

December 2017

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"QCD in extremis: the heavy ion physics program at the LHC"
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12/01/2017 - 11:00am
 
 
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"Bit threads and holographic entanglement"

"Bit threads and holographic entanglement"

Date: 
Mon, 12/04/2017 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

Matt Headrick

Brandeis University

"Bit threads and holographic entanglement"

The by-now classic Ryu-Takayanagi formula associates the entanglement entropy of a spatial region in a holographic field theory with the area of a certain minimal surface in the bulk. As I will explain, despite its simplicity and beauty, this formula raises a number of stubborn conceptual problems. I will present a reformulation that does not involve the areas of surfaces, and that leads to a picture of entanglement in the field theory being carried by Planck-thickness "bit threads" in the bulk. I will argue that this picture helps to resolve a number of the conceptual difficulties surrounding the RT formula, and that it illuminates the special entanglement structure of holographic systems.

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12/04/2017 - 2:10pm
 
"Neutrinos, Quintessence and Structure Formation in the Universe"

"Neutrinos, Quintessence and Structure Formation in the Universe"

Date: 
Mon, 12/04/2017 - 4:15pm
Location: 
428 Pupin Hall

Marilena Loverde

Stony Brook University

"Neutrinos, Quintessence and Structure Formation in the Universe"

The large-scale structure of our universe (the distribution of galaxies on very large-scales for instance) contains a wealth of information about the origin, evolution, and matter content of the universe. Extracting this information relies crucially on understanding how galaxies and other biased objects trace the large-scale matter distribution. In a universe such as our own, with both cold dark matter and massive neutrinos, or in alternative cosmologies with clustered quintessence, this problem is much more complicated. I will discuss new tools that my group has developed to study gravitational evolution in cosmologies with multiple fluids, the novel signatures we have identified including a new probe of neutrino mass, and the broader implications for models of large-scale structure. 

About the speaker

Marilena Loverde is an Assistant Professor in the C. N. Yang Institute for Theoretical Physics and the Department of Physics and Astronomy at Stony Brook University.  She did her undergraduate studies at the University of California, Berkeley and earned her PhD at Columbia University.  Following her PhD Marilena spent time as a post doc at the Kavli Institute for Cosmological Physics at the University of Chicago and at the Institute for Advanced Study in Princeton. 

Marilena's research is in theoretical cosmology, broadly interested in developing tools to use observations of galaxies and the cosmic microwave background to learn about the origin and evolution of the universe. She has spent a lot of time thinking about: weak gravitational lensing, primordial non-Gaussianity as a test of inflation, and the cosmic neutrino backround. Currently, Marilena's research focuses on the massive cosmic neutrino background and structure formation.

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12/04/2017 - 4:15pm
 
 
 
 
 
 
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"Searching for Ultralight Particles with Black Holes and Gravitational Waves"

"Searching for Ultralight Particles with Black Holes and Gravitational Waves"

Date: 
Mon, 12/11/2017 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

Masha Baryakhtar

Perimeter Institute

"Searching for Ultralight Particles with Black Holes and Gravitational Waves"

The LIGO detection of gravitational waves has opened a new window on the universe. I will discuss how the process of superradiance, combined with gravitational wave measurements, makes black holes into nature's laboratories to search for new light bosons, from axions to dark photons. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance of these bosons into `hydrogenic' bound states extracts energy and angular momentum from the black hole. The occupation number of the levels grows exponentially and the black hole spins down. One candidate for such an ultralight boson is the QCD axion with decay constant above the GUT scale. Current black hole spin measurements disfavor a factor of 30 (400) in axion (vector) mass; future measurements can provide evidence of a new boson. Particles transitioning between levels and annihilating to gravitons may produce thousands of monochromatic gravitational wave signals, and turn LIGO into a particle detector.

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12/11/2017 - 2:10pm
 
"Coherent Coupling of Spin and Light"

"Coherent Coupling of Spin and Light"

Date: 
Mon, 12/11/2017 - 4:15pm
Location: 
428 Pupin Hall

Jason Petta

Princeton University, Department of Physics

"Coherent Coupling of Spin and Light"

Tremendous progress has been achieved in the coherent control of single quantum states (single charges, phonons, photons, and spins). At the frontier of quantum information science are efforts to hybridize different quantum degrees of freedom. For example, by coupling a single photon to a single electron fundamental light-matter interactions may be examined at the single particle level to reveal exotic quantum effects, such as single atom lasing. Coherent coupling of spin and light, which has been the subject of many theoretical proposals over the past 20 years, could enable a quantum internet where highly coherent electron spins are used for quantum computing and single photons enable long-range spin-spin interactions. In this colloquium I will describe experiments where we couple a single spin in silicon to a single microwave frequency photon. The coupling mechanism is based on spin-charge hybridization in the presence of a large magnetic field gradient. Spin-photon coupling rates gs/2p > 10 MHz are achieved and vacuum Rabi splitting is observed in the cavity transmission, indicating single spin-photon strong coupling. These results open a direct path toward entangling single spins at a distance using microwave frequency photons.

About the speaker

Jason Petta's research group focuses on quantum control of nanometer scale systems. Semiconductor quantum dots are used to isolate single electron spins, which exhibit long quantum coherence times. These systems allow quantum mechanics to be harnessed in a solid state environment for the implementation of quantum gates. They use nanofabrication to create artificially structured systems with experimentally tunable Hamiltonians that can be controlled on sub-nanosecond timescales. Recent research examines strong light-matter interactions in the circuit quantum electrodynamics architecture, with a goal of generating long-range many body entanglement. Silicon and diamond are ideal host materials for spin coherence, leading to spin coherence times that now approach 10 seconds. A major effort in the group consists of developing a scalable quantum computing architecture in isotopically purified silicon. Research advances are enabled by a tight feedback loop that links nanoscale materials synthesis and advanced transport measurements.

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12/11/2017 - 4:15pm
 
 
 
"Duality symmetry and the superconductor-insulator transition"

"Duality symmetry and the superconductor-insulator transition"

Date: 
Thu, 12/14/2017 - 12:00pm
Location: 
705 Pupin Hall

Dan Shahar

Weizmann Institute of Science

"Duality symmetry and the superconductor-insulator transition"

The superconductor-insulator transition exhibits a remarkable duality symmetry directly relating the resistance measured in the superconducting regime to the conductance measured in the insulator. This symmetry points to a deep relation between these two seemingly-opposing phases. At very low temperatures (below 200 mK for our amorphous indium-oxide films) this beautiful symmetry is severely violated. We demonstrate that this violation is associated with the emergence of a new insulating ground-state in which the electrons are effectively decoupled from the host phonons[1]. We further show that duality symmetry can be effectively restored by driving the system out of equilibrium.
 
[1] D.M. Basko, I.L. Aleiner, B.L. Altshuler, Annals of Physics 321, 1126 (2006);  D.M. Basko, I.L. Aleiner, B.L. Altshuler, Phys. Rev. B 76, 052203 (2007)
 

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12/14/2017 - 12:00pm
 
“Teaching to the Diverse Classroom: How to Gauge Student Understanding and Respond Effectively”
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12/15/2017 - 11:00am
 
 
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