Fall 2018

Mechanism of metal-like transport in bacterial protein nanowires

Speaker(s): 
Dr. Nikhil Malvankar & Sibel Yalcin
Dates: 
Thursday, September 20, 2018 - 4:00pm

A cornerstone of quantum physics is the interference of electron waves arising from the superposition principle. Metallic conductivity is an effect of interference of partial electron waves multiply scattered at the ion cores of the crystal lattice. But proteins are generally insulators. Electron transfer in proteins occurs through either tunneling or hopping a few nanometers via inorganic cofactors. However, the common soil bacteriaGeobacter sulfurreducens transfer electrons over hundreds of micrometers, to insoluble electron acceptors1 or syntrophic partner species2 for...

Building a quantum computer using silicon quantum dots

Speaker(s): 
Dr. Sue Coppersmith
Dates: 
Thursday, October 11, 2018 - 4:00pm

In principle, quantum computers that exploit the nature of quantum physics can solve some problems much more efficiently than classical computers can.  Motivated by the tremendous scalability of classical silicon electronics, we are working to build a large-scale quantum computer using silicon technology similar to that used to build current classical computers.  This talk will discuss the fundamental physics and materials science challenges that arise, and how close coupling between theory and experiment has enabled substantial progress towards the goal of high fidelity qubits.  Prospects...

Orbital selective pairing in Fe-based superconductors

Speaker(s): 
Dr. Peter Hirschfeld
Dates: 
Thursday, October 18, 2018 - 4:00pm

Iron-based superconductors are unconventional superconductors with relatively high Tc that derive from metallic parent compounds with several Fe d-states dominant at the Fermi level. This gives rise to a number of novel effects based on differentiated degree of correlation of the different orbital states. I discuss the influence on spin-fluctuation pairing theory of orbital selective strong correlation effects in Fe-based superconductors, particularly Fe chalcogenide systems. This paradigm yields remarkably good agreement with the experimentally observed anisotropic gap structures in both...

Coupling a Superconducting Qubit to a Metamaterial Resonator

Speaker(s): 
Dr. Britton Plourde
Dates: 
Tuesday, November 27, 2018 - 4:00pm

Superconducting metamaterials formed from arrays of thin-film lumped circuit elements provide a route for implementing novel dispersion relations and band structure in a circuit QED environment. We have implemented metamaterial resonators from left-handed transmission lines and characterized their dense spectrum of modes through a combination of microwave transmission measurements and laser scanning microscopy imaging of the standing-wave structure on the various resonances. By appending a segment of a conventional transmission line on one end of our metamaterial, we have coupled a flux-...

Are we quantum computers, or merely clever robots?

Speaker(s): 
Matthew Fisher
Dates: 
Monday, October 15, 2018 - 4:00pm

Of course quantum information processing is not possible in the warm wet brain. There is, however, one \loophole" - oered by nuclear spins - that must be closed before acknowledging that we are merely clever robots. Putative neural quantum processing with nuclear spins seemingly requires fulllment of many unrealizable conditions: for example, a common biological element with a very isolated nuclear spin to serve as a qubit, a mechanism for quantum entangling qubits, a mechanism for quantum memory storage and processing, a quantum to biochemical transduction that modulates neuron ring rates...

Variations on a theme of Aharonov and Bohm

Speaker(s): 
Sir Michael Victor Berry
Dates: 
Tuesday, September 25, 2018 - 4:30pm to 5:30pm

The Aharonov-Bohm effect (AB) concerns the role in quantum physics of the vector potential of an impenetrable line of magnetic flux. Its partial anticipation by Ehrenberg and Siday, in terms of interference, was an approximation whose wavefunction was not singlevalued, and whose connection with the singlevalued AB wave involves topology: waves winding round the flux (‘many-whirls representation’). AB is a fine illustration of idealization in physics. There are four AB effects, depending on whether the waves and the flux are classical or quantum. In the classical-classical case, many...

2018 Conference on Materials for Quantum Computing (Day 1/4)

Speaker(s): 
Multiple Speakers
Dates: 
Tuesday, October 30, 2018 - 8:00am to 5:00pm

Schedule:

Morning Session Chair: Roger Mong, University of Pittsburgh

9:05 Jay Sau, University of Maryland. Transport and Josephson response signatures of Andreev versus Majorana states

9:45 Vlad Pribiag, University of Minnesota. Magneto-transport in ballistic InSb nanowires with ferromagnetic contacts 

10:55 David Cobden, University of Washington. Topological, superconducting, ferroelectric and magnetic phenomena in thin WTe2

11:35 Felix von Oppen, FU Berlin. Quantum Computation with Majorana fermion codes

12:15 Lunch Break...

Optica fantastica: images to illuminate the physics of light

Speaker(s): 
Sir Michael Victor Berry
Dates: 
Wednesday, September 26, 2018 - 4:00pm to 5:00pm

A talk based entirely on pictures. Seas sparkle, sunshine generates rainbows, ships make waves. The explanations of these familiar phenomena are as abstract as elsewhere in physics, but pictures are helpful because in light and waves on water we can often see what we are thinking about. There are other optical phenomena that are not immediately perceived (associated with polarization or fine-scale interference, for example), but even with these we can generate pictures to help our understanding. Poets and novelists, as well as painters, have sometimes represented optical phenomena in ways...

Faster than fourier (pre)revisited: vorticulture, fractals, escape…

Speaker(s): 
Sir Michael Victor Berry
Dates: 
Monday, September 24, 2018 - 4:30pm to 5:30pm

Band-limited functions can oscillate arbitrarily faster than their fastest Fourier component over arbitrarily long intervals: they can ‘superoscillate’. In physics, this counterintuitive mathematical phenomenon is associated with almost-destructive interference, and occurs near phase singularities in optics and on the world’s ocean tides; and it is associated with quantum weak measurements. Where superoscillations occur, functions are exponentially weak and vulnerable to noise. They are an unexpectedly compact way of representing fractals. Superoscillations in red light can escape as gamma...

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