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BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20190924T191034Z
DTSTART:20190926T181500Z
DTEND:20190926T191500Z
UID:event2173@bu.edu
URL:http://physics.bu.edu/events/show/2173
SUMMARY:Quantum simulation with the DW-2000Q
DESCRIPTION:Featuring Dr. Denny Dahl\, D-Wave Systems\nHosted by: Anders Sa
ndvik\n\nPart of the Condensed Matter Theory Seminar Series.\n\nThe first t
hree D-Wave product generations allowed users to specify a Hamiltonian and
use it in forward annealing. The fourth generation\, the DW-2000Q\, provid
es more control over the annealing trajectory. It is now possible to shape
the trajectory to include pausing\, quenching or even reverse annealing.
Interesting models can be investigated using these features. Recent exampl
es include a 3D spin glass\, topological order in a 2D transverse field Isi
ng model and a Z(2) lattice gauge theory.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20191001T143752Z
DTSTART:20191002T193000Z
DTEND:20191002T203000Z
UID:event2199@bu.edu
URL:http://physics.bu.edu/events/show/2199
SUMMARY:Path to building quantum spin liquids and topological qubits within
existing quantum hardware
DESCRIPTION:Featuring Zhicheng Yang\, Boston University Physics Department\
n\nPart of the Condensed Matter Theory Seminar Series.\n\nWe address a cent
ral problem in the creation and manipulation of quantum states: how to buil
d topological quantum spin liquids with physically accessible interactions.
Theorists have been studying models of quantum spin liquids that rely on `
`multi-spin" interactions since the 1970s\, and\, more recently\, have real
ized that these models can be used for quantum computing. However\, nature
does not provide such interactions in real materials. We construct a lattic
e gauge model where the required\, fully quantum\, multi-spin interactions
can in fact be emulated exactly in any system with only two-body Ising inte
ractions plus a uniform transverse field. The latter systems do exist\, and
we provide an explicit embedding of our model into one such system\, the c
ommercially available D-Wave machine. Therefore\, our solution is an altern
ative path to building a workable topological quantum computer within exist
ing hardware. Our bottom-up construction is generalizable to other gauge-li
ke theories\, including those with fractonic topological order such as the
X-cube model. Taken as a whole\, our approach is a blueprint to emulate top
ologically ordered quantum spin liquids in programmable quantum machines.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20191010T133655Z
DTSTART:20191009T193000Z
DTEND:20191009T203000Z
UID:event2209@bu.edu
URL:http://physics.bu.edu/events/show/2209
SUMMARY:Topological classes of quantum dynamics in quasi-periodically drive
n systems
DESCRIPTION:Featuring Phil Crowley\, Boston University\n\nPart of the Conde
nsed Matter Theory Seminar Series.\n\nAdvances in the control and manipulat
ion of experimental quantum systems has allowed us to realise new driven ph
ases of quantum matter in the laboratory. In periodically driven systems ne
w phases occur when the steady states\, determined by Bloch-Floquet theorem
\, have novel spatio-temporal or topological order.\n\nIn this talk I show
how the Bloch-Floquet theorem is generalised to cases when the drives are n
ot periodic\, but rather quasi-periodic. \n\nI apply this framework to the
simplest case of a few level system\, and show that steady state dynamics
admit a topological classification. When the classification is non-trivial
the system exhibits a quantised pumping of energy\, and a sensitivity to in
itial conditions\, neither of which is present in the trivial case.\n\nI fu
rther discuss the stability of this classification\, the behaviour near the
critical point where the topological class changes\, and ongoing work to o
bserve this in experiments.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20191010T145656Z
DTSTART:20191016T193000Z
DTEND:20191016T203000Z
UID:event2196@bu.edu
URL:http://physics.bu.edu/events/show/2196
SUMMARY:High temperature superconductivity in semiconductor artificial grap
hene
DESCRIPTION:Featuring Julian Ingham\, Boston University\, Physics Departmen
t\n\nPart of the Condensed Matter Theory Seminar Series.\n\nSemiconductor a
rtificial graphene (AG) seeks to replicate the properties of graphene\, by
subjecting a two-dimensional electron gas to a periodic potential with the
same symmetries as the atomic lattice in graphene. In this talk I will expl
ain how this material can realise a new mechanism for high temperature supe
rconductivity ā due to the antiscreened fluctuations of the emergent pseu
dospin degree of freedom. The mechanism originates solely from the repulsiv
e Coulomb interaction\, and relies on the Dirac dispersion and a strong per
iodic potential ā and could therefore in principle be realised in other D
irac materials. The ability to artificially tune the lattice spacing\, pote
ntial strength and density in AG allows this regime to be engineered\, and
the calculations I present show that Tc can be order 25 K for realistic exp
erimental parameters.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20191017T195325Z
DTSTART:20191023T193000Z
DTEND:20191023T203000Z
UID:event2210@bu.edu
URL:http://physics.bu.edu/events/show/2210
SUMMARY:Bosonization and the Shear Sound of Metals and The Non-linear Hall
Effect in Time-Reversal-Invariant Materials
DESCRIPTION:Featuring Inti Sodemann\, Max Planck Institute for the Physics
of Complex Systems\nHosted by: Claudio Chamon\n\nPart of the Condensed Matt
er Theory Seminar Series.\n\nIn the first part of the talk\, we will review
the bosonization approach to Fermi liquids in above one dimension and use
it to study a sharp change in the excitation spectrum of fermi liquids that
occurs beyond a critical interaction strength whereby an unconventional co
llective mode exits the particle-hole continuum. This mode is a collective
shear wave that features purely transverse current oscillations\, in analog
y to the transverse sound of crystals. We will argue that the shear sound m
ight be "hiding`' in several metals and describe experimental strategies to
probe it\, including the appearance of sharp conductivity dips in ultra-cl
ean narrow channels and its coupling to charge-fluctuations under weak magn
etic fields.\n\nIn the second part\, we will describe a correction to Newto
nās second law when electrons move in Bloch bands without inversion symme
try\, whereby\, their acceleration acquires a term proportional to the squa
re of the electric field and orthogonal to it. This "non-linear Hall accele
ration"\ngives rise to a "non-linear Hall effect" in time reversal invarian
t materials that is controlled by a quantum geometric tensor called the "Be
rry curvature dipole". We will also discuss a remarkable "quantum rectifica
tion sum rule" according to which the frequency integrated rectification co
nductivity is entirely controlled by the Berry geometry and is independent
of the band energies.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20191018T205832Z
LAST-MODIFIED:20191017T195519Z
DTSTART:20191030T193000Z
DTEND:20191030T203000Z
UID:event2217@bu.edu
URL:http://physics.bu.edu/events/show/2217
SUMMARY:Extending the Gutzwiller approximation to intersite interactions
DESCRIPTION:Featuring Garry Goldstein\, Rutgers University\nHosted by: Clau
dio Chamon\n\nPart of the Condensed Matter Theory Seminar Series.\n\nWe dev
elop an extension of the Gutzwiller Approximation (GA) formalism which incl
udes the effects of Coulomb interactions of arbitrary range (including dens
ity density\, exchange\, pair hopping and Coulomb assisted hopping terms).
This formalism reduces to the ordinary GA formalism for the multi-band Hubb
ard models in the presence of only local interactions.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
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