Theory Seminars

Optimal control of quantum evolution: quantum state transformation, cooling, and nonadiabatic braiding

Speaker: 
Armin Rahmani (UBC)
Event Date and Time: 
Mon, 2014-11-10 12:00 - 13:00
Location: 
Henning 318
Intended Audience: 
Graduate
Nonadiabatic unitary evolution with tailored time-dependent Hamiltonians can prepare many-body quantum states with various desired properties. We explore novel application of optimal control to problems ranging from cooling cold atoms beyond the current state of the art to beating the barrier of adiabaticity in the braiding of non-Abelian anyons. We show that highly nonadiabatic "bang-bang" protocols provide powerful shortcuts to the adiabatic evolution.

"Nematic order in fractional quantum Hall liquids"

Speaker: 
Joseph Maciejko (U Alberta)
Event Date and Time: 
Mon, 2014-09-29 12:00 - 13:00
Location: 
Room 318
Local Contact: 
Marcel Franz
The fractional quantum Hall (FQH) nematic is a conjectured state of matter in which a fractional quantized Hall conductivity coexists with the spontaneous breaking of rotational symmetry characteristic of a nematic liquid crystal. Although effective field theories and model wave functions for this state have been constructed, no direct evidence for its occurrence in a microscopic model of interacting electrons has been found so far.

Superradiance of Degenerate Fermi Gases in a Cavity

Speaker: 
Zhenhua Yu (Tsinghua University)
Event Date and Time: 
Mon, 2014-04-28 12:00 - 13:00
Location: 
Hennings 318
The interaction between matter and electromagnetic field is the most fundmental and of widest applications at the energy scales relevant to human beings. Electromagnetic field in cavities has its own characteristics. We consider spinless Fermi gases placed inside a cavity. Due to the interaction between the Fermi gases and the cavity field, a superradiance transition occurs in the system when the pumping laser field applied on the fermions reaches a critical strength.

The Life and Times of a Superfluid Vortex Ring

Speaker: 
Michael McNeil Forbes (Washington State University)
Event Date and Time: 
Mon, 2014-03-31 12:00 - 13:00
Location: 
Hennings 318
In this talk I will tell the tale of a superfluid soliton. Starting its life as a phase imprinted domain wall in cold cloud of 6Li at MIT [1], it behaved mysteriously, moving an order of magnitude more slowly than expected.

Fractional Solitons on the edge of the Fractional Quantum Hall states: Revealing topology through a non-linear dynamics

Speaker: 
Prof. Paul Wiegmann (Simon's Center/U of Chicago)
Event Date and Time: 
Mon, 2014-03-17 12:00 - 13:00
Location: 
Hennings 318
Intended Audience: 
Graduate
In the talk I argue that dynamics of Fractional Quantum Hall Edge states is essentially non-linear and that it features fractionally quantized solitons propagating along the edge. Observation of solitons would be a direct evidence of fractional charges. We show that the non-linear dynamics of the Laughlin's FQH state is governed by the quantum Benjamin-Ono equation.

Contacts and Unitary Atoms

Speaker: 
Eric Braaten (Ohio State University)
Event Date and Time: 
Wed, 2014-01-22 12:00 - 13:00
Location: 
Room 318 Hennings (TBF)
Local Contact: 
Fei Zhou

Effective field theory of p-wave interacting fermions in two dimensions

Speaker: 
Sergej Moroz(INT, UW, Seattle)
Event Date and Time: 
Mon, 2014-01-13 12:00 - 13:00
Location: 
Hennings 318
Due to the current search of Majorana fermions, the physics of two-dimensional identical fermions with short-range p-wave interactions is of considerable interest. The seminar will be about the effective theory of a chiral p+ip fermionic superfluid at zero temperature. This theory naturally incorporates the parity and time reversal violating effects such as the Hall viscosity and the edge current. It also allows to study an isolated vortex in a chiral superfluid and identify the leading chirality effect in the density depletion profile.

Giant magnetoresistance in the variable range hopping regime

Speaker: 
Boris Spivak (University of Washington)
Event Date and Time: 
Mon, 2014-01-27 12:00 - 13:00
Location: 
Hennings 318
We predict the universal power law dependence of localization length on magnetic field in the strongly localized regime. This effect is due to the orbital quantum interference. Physically, this dependence shows up in an anomalously large negative magnetoresistance in the hopping regime. The reason for the universality is that the problem of the electron tunneling in a random media belongs to the same universality class as directed polymer problem even in the case of wave functions of random sign.

Symmetry protected topological orders in interacting bosonic and fermionic systems

Speaker: 
Zhengcheng Gu (Perimeter)
Event Date and Time: 
Mon, 2014-02-03 12:00 - 13:00
Location: 
Hennings 318
Intended Audience: 
Graduate
Symmetry protected topological (SPT) states are bulk gapped states with gapless edge excitations protected by certain symmetries. The SPT phases in free fermion systems, like topological insulators, can be classified by the K-theory. However, it is not known what SPT phases exist in general interacting systems.

Cancelled and rescheduled to Wednesday

Speaker: 
TBA
Event Date and Time: 
Mon, 2014-01-20 12:00 - 13:00
Location: 
Hennings 318
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