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Events on Friday, March 11th, 2016

R. G. Herb Condensed Matter Seminar
Microwave response and photon emission of a voltage baised Josephson junction
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Salha Jebari, CEA Grenoble
Abstract: The readout of superconducting qubits and other quantum devices operating at microwave frequencies requires amplifiers combining noise close to the quantum limit[1 ], high gain, large bandwidth, and sufficient dynamic range[2 ]. Josephson parametric amplifiers using Josephson junctions in the 0-voltage state, driven by a large microwave signals, begin to perform sufficiently well in all 4 of these aspects to be of practical use, but remain difficult to optimize and use. Recent experiments with superconducting circuits consisting of a DC voltage-biased Josephson junction in series with a resonator, showed that a tunneling Cooper pair can emit one or several photons with a total energy of 2e times the applied voltage[3 ]. We present microwave reflection measurements on this device in [3], indicating that amplification is possible with a simple DC voltage-biased Josephson junction.<br>
We compare these measurements with the noise power emitted by the junction and show that, for low Josephson energy, transmission and noise emission can be explained within the framework of P(E) theory of inelastic Cooper pair tunneling. Combined with a theoretical model, our results indicate that voltage-biased Josephson junctions might be useful for amplification near the quantum limit, offering simpler design and a different trade-off between gain, bandwidth and dynamic range, which could be advantageous in some situations.
Host: Robert McDermott
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Theory Seminar (High Energy/Cosmology)
Compactifying M-theory on a G2 manifold to describe our world
Time: 1:30 pm
Place: 5280 Chamberlin Hall
Speaker: Gordon Kane, University of Michigan
Abstract: Compactified M-theory generically describes many features of our world, including gravity; Yang-Mills forces like S(U3)xSU(2)xU(1); chiral fermions (so parity violation); softly broken supersymmetry; a solution to the hierarchy problem; electroweak symmetry breaking and Higgs physics (including the ratio of the Higgs boson mass to the Z mass, and Higgs decay branching ratios); grand unification; small EDMs; no flavor changing problems and more. It predicts a non-thermal cosmological history and addresses the form(s) of dark matter and the ratio of matter to dark matter. And it predicts the superpartner spectrum: heavy (tens of TeV) squarks and sleptons, light (~ TeV) gluino and LSP. Superpartners should not have been found in Run I at LHC, and can be found in Run II (gluinos about 1..5 TeV, winos about 640 GeV). Five general assumptions are made, and there are no parameters to vary. There has been good progress in calculating and elucidating the predictions, but there is still much to do. I will explain the Higgs and superpartner predictions in some detail.
Host: lisa Everett
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Physics Department Colloquium
Status and Future of Tau physics at the LHC
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Isobel Ojalvo, University of Wisconsin - Madison
Abstract: The observation of a Higgs boson by the LHC experiments through its decays
to vector bosons was an extremely significant milestone in particle physics
research; one which redefined the research priorities in the field. After
this discovery the first step was to test the compatibility of the new
particle with the SM Higgs by searching for the different possible Higgs
couplings. The decay to fermions is of fundamental importance since it
proves the presence of Yukawa couplings in the theory. Since Higgs couples
to mass, it breaks lepton universality, therefore decays to tau leptons are
enhanced. The next step is to use the Higgs as a tool for new physics
searches through its decays (i.e. lepton flavor violation) or through its
associated production with other particles (A->Zh, H->hh, etc.)

The experimental challenges of triggering and identifying tau leptons will
be described. Then the recent Higgs results will be presented for the SM
Higgs and the SUSY extensions. Finally, the future prospects of Higgs and
tau physics will be summarized.
Host: Lisa Everett
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