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Nanophotonic Quantum Phase Switch with a Single Atom

Quantum optical switches are important elements of quantum circuits and quantum networks, analogous to transistors in classical electronic circuits. Operated at the fundamental limit where a single quantum of light or matter controls another field or material system...

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Subnanometre Resolution in Three-Dimensional Magnetic Resonance Imaging of Individual Dark Spins

New MRI technique provides subnanometre spatial resolution in three dimensions, with single electron-spin sensitivity...

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The Morris Loeb Lecture in Physics: Marc Mézard

Colloquium (Apr 28): "The spin glass cornucopia"
Lecture I (Apr 29): "Phase transitions in hard computer science problems"
Lecture II (Apr 30): "Occam’s razor in massive data acquisition: a statistical physics approach"

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EPB Annual Symposium

On Saturday, April 26, the annual Engineering and Physical Biology (EPB) Symposium will be held in Room B103 of the Northwest Building, 52 Oxford St. Speakers from constituent fields - Physics, Engineering, Chemistry and Molecular Biology - will present significant recent findings ranging from the physics of protein conformation to DNA knotting.

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Gamma-Ray Emissions from Dark Matter?

Past studies have identifed a spatially extended excess of 1-3 GeV gamma rays from the region surrounding the Galactic Center, consistent with the emission expected from annihilating dark matter. Harvard Physics grad student Tansu Daylan, Prof. Douglas Finkbeiner, and researchers from Fermilab, University of Chicago, MIT, and Princeton revisited and scrutinized this signal with the intention of further constraining its characteristics and origin...

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UPCOMING EVENTS

Today

Special CMP Seminar: Saad Zaheer, University of Pennsylvania
- Title: Three dimensional Dirac semimetals
  
  Abstract: Dirac points on the Fermi surface of two dimensional graphene are responsible for its unique electronic behavior. One can ask whether any three dimensional materials support similar pseudorelativistic physics in their bulk electronic spectra. This possibility has been investigated theoretically and is now supported by two successful experimental demonstrations reported during the last year. In this talk, I will summarize the various ways in which Dirac semimetals can be realized in three dimensions with primary focus on a specific theory developed on the basis of representations of crystal spacegroups. A three dimensional Dirac (Weyl) semimetal can appear in the presence (absence) of inversion symmetry by tuning parameters to the phase boundary separating a bulk insulating and a topological insulating phase. More generally, we find that specific rules governing crystal symmetry representations of electrons with spin lead to robust Dirac points at high symmetry points in the Brillouin zone. Combining these rules with microscopic considerations identifies six candidate Dirac semimetals. Another method towards engineering Dirac semimetals involves combining crystal symmetry and band inversion. Several candidate materials have been proposed utilizing this mechanism and one of the candidates has been successfully demonstrated as a Dirac semimetal in two independent experiments.
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HQOC/ITAMP JQS Seminar - Igor Lesanovsky, University of Nottingham
- Igor Lesanovsky, University of Nottingham
  Talk Title: Out-of-equilibrium dynamics of strongly interacting Rydberg gases in a
  dissipative environment
  
  The most recent generation of cold atom experiments uses
  atoms in Rydberg states to explore many-body phenomena. In this talk I
  will focus on the non-equilibrium dynamics of such systems where
  non-trivial behaviour is generated by the competition between coherent
  laser excitation, dissipation and the strong interaction between Rydberg
  atoms. I will discuss the relaxation of Rydberg lattice gases, showing
  that it is hierarchical and strongly correlated. This establishes a
  connection to kinetically constrained systems that are used in soft
  condensed matter physics as models for the description of glassy phenomena.
- View in Google Calendar
LPPC Seminar: The nuPRISM detector: An experimental solution to the neutrino energy measurement problem - Mike Wilking (TRIUMF)
- The frequency with which a neutrino oscillates is dictated by its energy. Therefore, in order to determine neutrino oscillation parameters, experiments must accurately measure the energy of each neutrino. Unfortunately, neutrino energy is not directly observable, and, instead, experiments can only measure the outgoing charged lepton from a charged current neutrino interaction, and perhaps some constraint on the energy of the final state hadrons. To translate these measurements to neutrino energy, it is necessary to rely on theoretical models of neutrino interactions with atomic nuclei.
  
  In recent years, neutrino interaction models have undergone drastic modifications. Many models now predict that neutrinos interact with correlated sets of nucleons within the nucleus, which causes large biases in reconstructed neutrino energy for 20-30% of interactions at neutrino energies near 1 GeV. These effects were not included in the state of the art neutrino models just 5 years ago. These nucleon correlation effects are difficult to calculate, and large discrepancies exist between currently available models. This results in large systematic uncertainties in neutrino oscillation experiments, the size of which cannot be determined from a comparison data.
  
  The nuPRISM concept places a detector ~1 km from the neutrino production source that spans a range of off-axis angles relative to the neutrino beam direction. As the off-axis angle changes, the beam energy changes, which can provide a direct, data-driven constraint on the relationship between neutrino energy and experimental observables. This technique is currently being pursued as a near detector upgrade for the T2K experiment, but it is generally applicable to all long-baseline neutrino experiments.
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Ken Kamrin; MIT
- Modeling the strange flow behaviors of granular media
  
  Despite the ubiquity of granular matter in the world around us, the challenge of predicting the motion of a collection of flowing grains has proven to be a difficult one, from both computational and theoretical perspectives. In this talk, we begin by presenting a number of the "unusual" behaviors exhibited by dry granular media, which have posed hurdles from the perspective of developing a continuum model. These behaviors include: steady-flow fields that do not obey any local flow rheology, flow onset and stoppage phenomena that do not abide by a standard yield stress, and the motion-induced "quicksand" effect whereby far-away motion changes the flow resistance everywhere. We then proceed to develop a non-local constitutive retaion for granular matter, and demonstrate how the model is capable of reconciling these various phenomena in a general manner. This is achieved by comparing its predictions to hundreds of existing experimental data sets, which elucidate the aforementioned behaviors.
- View in Google Calendar

Tomorrow

CMP Seminar: Koenraad Schalm, Leiden and Harvard
- Title: Far from equilibrium energy flow in quantum critical systems
  
  Abstract: We investigate far from equilibrium energy transport in strongly coupled quantum critical systems. Combining results from gauge-gravity duality, relativistic hydrodynamics, and quantum field theory, we argue that long-time energy transport after a local thermal quench occurs via a universal steady-state for any spatial dimensionality. This is described by a Lorentz boosted thermal state. We determine the transport properties of this emergent steady state, including the average energy flow and its long-time fluctuations.
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Joint Harvard / MIT Seminar: Hirosi Ooguri (Caltech) " Anomalies and Hydrodynamics in AdS/CFT"
- View in Google Calendar

Saturday, April 26th

Engineering and Physical Biology Annual Symposium
- On Saturday, April 26, the annual Engineering and Physical Biology (EPB) Symposium will be held in Room B103 of the Northwest Building, 52 Oxford St. Speakers from constituent fields -Physics, Engineering, Chemistry and Molecular Biology - will present significant recent findings ranging from the physics of protein conformation to DNA knotting.
  
  As in the past, the EPB Symposium day has been organized to bring together students and faculty from three Harvard areas (MCB, Physics and SEAS) with outstanding visiting scholars. (For a review of last year’s Symposium, see https://www.mcb.harvard.edu/mcb/news/news-detail/3684/symposium-features-physical-biology-research/) EPB is now in its eighth year as a PhD track for students wishing to “probe living systems through the lens of physics and engineering.”
  
  The day will be divided into two parts. The morning (until 12:30 pm) will be a public symposium featuring four visiting faculty. (See poster to your right) The public is welcome to attend, and the talks should be of wide interest to the Harvard science community.
  
  The afternoon will feature graduate student presentations and discussions in a more intimate setting that should promote the cross-fertilization of disciplines that EPB encapsulates. (These sessions will not be open to the general public.)
  
  Work at physics and engineering interface is rapidly becoming an established part of the life sciences. EPB particularly welcomes members of the MCB community to engage with these speakers working on the frontiers of physical biology.
  
  Morning Schedule - Public Event:
  
  9:00 - 9:45:
  Marco Foiani Prof. of Molecular Biology, Dept. of Biosci., University
  of Milan and IFOM-IEO “Mechanosensing at the nuclear envelope: an ATR-mediated
  response to control cell plasticity”
  
  9:45 – 10:30
  Kerry Bloom Dept. of Biology, Univ. of North Carolina, Chapel Hill
  "The landscape of forces in mitosis"
  
  10:30 – 11:00 Coffee Break
  
  11:00 – 11:45
  Jonathon Howard Eugene Higgins Prof. of Molecular Physics & Biochem., Yale University
  and Max Planck Inst., Dresden "Ciliary and flagellar motility: From single molecules to
  collective motion"
  
  11:45 – 12:30
  Olaf Sparre Andersen Prof. of Physiol. & Biophys., Weill Cornell Medical College
  "Interactions of drugs and other amphiphiles with membranes: Implications for membrane
  protein function and drug development"
- View in Google Calendar

Monday, April 28th

Physics Colloquium Tea
- View in Google Calendar
"The Spin Glass Cornucopia," Marc Mézard, Ecole Normale Supérieure, Paris
- For more than 30 years, the spin glass puzzle has stimulated a large activity in statistical physics, and led to several breakthroughs. While the puzzle of spin glass materials is still not fully solved, their theoretical analysis has created a very rich conceptual framework, as well as powerful techniques, to study emergent properties of strongly disordered and interacting systems. These have been successfully applied to a broad spectrum of
  other disciplines, from finance to computer science and information theory, where slow -glassy- dynamics and phase transitions play a key role. The talk will survey this spin glass saga, focusing on its developments outside of physics.
- View in Google Calendar

Tuesday, April 29th

“Phase transitions in hard computer science problems,” Marc Mézard, Ecole Normale Supérieure, Paris
- A new field of research is rapidly expanding at the crossroad between statistical physics, information theory and combinatorial optimization. It deals with problems which are very important in each of these fields, like spin glasses, error correction, or satisfiability. In recent years, it has been realized that physical phenomena, familiar from glass phenomenology, occur in large classes of algorithms that have been developed to study some of the hardest computer science problems. Realizing that extreme slowdown and glassy phase transitions occur in computer programs is interesting both theoretically, as it opens new perspectives to the study of algorithmic complexity, as well as practically : it allows to develop new kind of efficient algorithms, inspired from insights obtained through the “replica method” and the “cavity method’’. This talk will survey these recent developments, focusing on the conceptual leap induced by the use of spin glass theory in hard constraint satisfaction problems.
- View in Google Calendar
Anže Slosar (Brookhaven) "BICEP2 and the future of cosmological observations"
- I will give an overview of the recent BICEP2 detection of the primordial gravitational waves from an experimentalist's perspective, discussing reasons to believe the result and reasons to worry about. I will next discuss how this result, if confirmed, affects our priors about the inflation and planning of the future experiments. I will discuss which observables we should try to measure, how to do these measurements and what are the leading systematics.
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