BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180122T153358Z
DTSTART:20180129T160000Z
DTEND:20180129T170000Z
UID:event1886@bu.edu
URL:http://physics.bu.edu/events/show/1886
SUMMARY:"Buckling transition and antiferromagnetic liquids in two dimension
s"
DESCRIPTION:Featuring Danny Podolsky\, Technion\nHosted by: Anushya Chandra
n\n\nPart of the Condensed Matter Theory Seminar Series.\n\nCrystals of tra
pped ions are an example of ordered states of matter that emerge from the c
ompetition between kinetic energy and repulsive forces in confined volumes.
These systems can give us unique access to interesting questions in class
ical and quantum magnetism. For instance\, I will show that ions confined
to 2D undergo a buckling transition\, which is described by a six-state qua
ntum clock model. Motivated by this system\, I will discuss the melting of
2D antiferromagnets\, and will show that under certain conditions it is pos
sible to stabilize an antiferromagnetic liquid in two dimensions.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180130T152533Z
DTSTART:20180202T173000Z
DTEND:20180202T183000Z
UID:event1921@bu.edu
URL:http://physics.bu.edu/events/show/1921
SUMMARY:"Quantum Annealing to Solve 3-Regular 3-XORSAT on a Lattice"
DESCRIPTION:Featuring Pranay Patil \, Boston University\, Physics Departmen
t\n\nPart of the Condensed Matter Theory Seminar Series.\n\nHere we show ho
w we can embed the 3-regular 3-XORSAT on a square lattice made out of gates
which couple the bits in a manner that recreates the constraints. This sys
tem can be annealed to the solution by tuning a transverse field to zero. W
e explore ways to avoid two potential obstacles that limit how fast one can
anneal this system: 1) the nature of the phase transition as we tune the t
ransverse field and 2) the avoided level crossings for small transverse fie
ld strength. We discuss how the second pitfall can possibly be avoided in t
he lattice embedding. We also present Quantum Monte Carlo results on the na
ture of the phase transition for the embedding of XORSAT on the square latt
ice. We compare the results to the embedding on a random regular graph\, wh
ere the phase transition is known to be first order.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180208T195424Z
DTSTART:20180212T160000Z
DTEND:20180212T170000Z
UID:event1887@bu.edu
URL:http://physics.bu.edu/events/show/1887
SUMMARY:"Operator Spreading and the Quantum Butterfly Effect in Random Unit
ary Circuits"
DESCRIPTION:Featuring Sagar Vijay\, Massachusetts Institute of Technology\n
Hosted by: Philip Crowley\n\nPart of the Condensed Matter Theory Seminar Se
ries.\n\nWe provide universal\, long-distance descriptions for the ‘quant
um butterfly effect’\, which describes the spreading of a local disturban
ce in a quantum medium\, and is quantified by the ‘out-of-time-order corr
elator’ (OTOC). We obtain these results by studying quantum circuits mad
e of random unitaries\, which yield minimally structured models for chaotic
quantum dynamics\, and are able to capture universal properties of quantum
entanglement growth. In this setting\, we demonstrate a mapping between t
he OTOC and classical growth processes\, which leads to exact results and e
xplicit universal scaling forms for the OTOC. \nIn 1+1D\, we demonstrate th
at the OTOC satisfies a biased diffusion equation\, which gives exact resul
ts for its spatial profile\, and for the butterfly speed. In higher dimensi
ons\, we show that the averaged OTOC can be understood exactly via a corres
pondence with a classical droplet growth problem. We support our analytic a
rgument with simulations in 2+1D and demonstrate that in a lattice model\,
the late time shape of the spreading operator is in general not spherical.
However when full spatial rotational symmetry is present in 2+1D\, our mapp
ing implies an exact asymptotic form for the OTOC in terms of the Tracy-Wid
om distribution. For an alternative perspective on the OTOC in 1+1D\, we ma
p it to the partition function of an Ising-like model. As a result of speci
al structure arising from unitarity\, this partition function reduces to a
random walk calculation which can be performed exactly. We argue that the
coarse-grained pictures carry over to operator spreading in generic many-bo
dy systems.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180214T162949Z
DTSTART:20180216T170000Z
DTEND:20180216T180000Z
UID:event1924@bu.edu
URL:http://physics.bu.edu/events/show/1924
SUMMARY:Entanglement Spectrum in Quantum Many-Body Dynamics and Braiding of
Non-Abelian Anyons
DESCRIPTION:Featuring Zhicheng Yang \, Boston University\, Physics Departme
nt\n\nPart of the Condensed Matter Theory Seminar Series.\n\nWe study the e
ntanglement spectrum of highly entangled states in two different contexts:
(1) time evolved states after a quantum quench with Hamiltonians exhibiting
different dynamical phases; (2) braiding of non-abelian anyons capable or
not of universal quantum computation. In the first case\, we show that the
three distinct dynamical phases known as thermalization\, Anderson localiza
tion\, and many-body localization are marked by different patterns in the e
ntanglement spectrum after a quantum quench. While the entanglement spectru
m displays Poisson statistics for the case of Anderson localization\, it di
splays universal Wigner-Dyson statistics for both the cases of many-body lo
calization and thermalization\, albeit within very different time scales. W
e further show that the complexity of entanglement\, revealed by the possib
ility of disentangling the state through a Metropolis-like algorithm\, is s
ignaled by whether the entanglement spectrum is Poisson or Wigner-Dyson. In
the second part\, we study the entanglement spectrum of states generated o
ut of braiding two types of non-abelian anyons: the Majorana fermions and t
he Fibonacci anyons. We show that the information on whether certain repres
entations of the braid group associated with non-abelian anyons are capable
of universal quantum computation can also be extracted from the entangleme
nt spectrum.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180222T144758Z
DTSTART:20180223T170000Z
DTEND:20180223T180000Z
UID:event1930@bu.edu
URL:http://physics.bu.edu/events/show/1930
SUMMARY:"Draining a superfluid hose"
DESCRIPTION:Featuring Dries Sels\, Boston University\, Physics Department\n
\nPart of the Condensed Matter Theory Seminar Series.\n\nIn this talk I wil
l discuss ongoing work on the dynamics of quantum systems subject to contin
uous local measurement. Specifically\, I will discuss some preliminary resu
lts on 1D condensates in which particles are continuously being lost. In th
e thermodynamic limit\, a non-trivial non-equilibrium steady state will dev
elop. I will provide evidence for the fact that Hawking radiation is emitte
d from the drain.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180220T181233Z
DTSTART:20180226T160000Z
DTEND:20180226T170000Z
UID:event1897@bu.edu
URL:http://physics.bu.edu/events/show/1897
SUMMARY:"Physics of spin-orbit coupled wires in magnetic field: Majorana mo
des and Lifshitz transitions"
DESCRIPTION:Featuring Jay Sau\, University of Maryland\nHosted by: Anushya
Chandran\n\nPart of the Condensed Matter Theory Seminar Series.\n\nThe comb
ination of spin-orbit coupling and magnetic field produces an interesting b
andstructure with a co-existing Dirac point and Fermi points. In the first
part of my talk I will review how proximity-induced superconductivity is e
xpected to realize Majorana zero modes. I will discuss theoretical understa
nding of the results from the experimental search for Majorana zero modes i
n spin-orbit coupled semiconductor-based topological superconducting system
s. I will conclude this part discussing the possibility of interferometric
detection of topological superconducivity. \nIn the second part we discuss
strongly interacting Bosons subject to the same Hamiltonian\, which would b
e the Tonks gas version of the spin-orbit coupled gases realized in experim
ents. We use the effective Lagrangian formalism for classifying non-relativ
istic Nambu-Goldstone modes due to derive the existance of an Ising transit
ion between two gapless phases that can be thought of as a superfluid minim
ally coupled to an Ising gauge field. This coupling between the Ising model
and the superfluid turns out to modify the dynamical critical exponent fro
m Lorentz-like (z~1) to Lifshitz-like (z~2). We find these predictions to b
e consistent with DMRG simulations.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180301T140604Z
DTSTART:20180302T170000Z
DTEND:20180302T180000Z
UID:event1931@bu.edu
URL:http://physics.bu.edu/events/show/1931
SUMMARY:"Unbiased Markov chain Monte Carlo with couplings joint work with J
ohn O'Leary\, Yves F. Atchadé"
DESCRIPTION:Featuring Pierre E. Jacob\, Harvard University\n\nPart of the C
ondensed Matter Theory Seminar Series.\n\nMarkov chain Monte Carlo (MCMC) m
ethods provide consistent approximations of integrals as the number of iter
ations goes to infinity. MCMC estimators are generally biased after any fix
ed number of iterations\, which complicates both parallel computation and t
he construction of confidence intervals. We propose to remove this bias by
using couplings of Markov chains together with a telescopic sum argument of
Glynn & Rhee (2014). The resulting unbiased estimators can be computed in
parallel\, with confidence intervals following directly from the Central Li
mit Theorem for i.i.d. variables. We discuss practical couplings for popula
r algorithms such as Metropolis-Hastings\, Gibbs samplers\, and Hamiltonian
Monte Carlo. We establish the theoretical validity of the proposed estimat
ors and study their efficiency relative to the underlying MCMC algorithms.
Finally\, we illustrate the performance and limitations of the method on va
rious examples\, involving discrete and continuous high dimensional state s
paces.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180312T141548Z
DTSTART:20180319T150000Z
DTEND:20180319T170000Z
UID:event1933@bu.edu
URL:http://physics.bu.edu/events/show/1933
SUMMARY:"Quantum dimer models for high temperature superconductors"
DESCRIPTION:Featuring Garry Goldstein\, University of Cambridge\n\nPart of
the Condensed Matter Theory Seminar Series.\n\nIn this talk we review the s
lave boson meanﬁeld formulation of the fermion+boson quantum dimer model
for the pseudogap phase of the high temperature superconductors. We show th
at in the presence of weak slowly varying external magnetic and electric
elds the fermionic dimers undergo semiclassical motion in the external ﬁ
eld. As a result in the presence of magnetic ﬁelds strong enough to destr
oy superconductivity the dimers undergo quantum oscillations. Indeed they s
atisfy Onsager quantization for their orbits and Lifshtiz-Kosevich formula
for the amplitude of oscillations. We also compute the eﬀective charges o
f the dimers in the presence of external magnetic ﬁelds as a function of
temperature. We show that the eﬀective magnetic charge changes sign from
negative −e at low temperature to positive +e at high temperature. This l
eads to a change of the sign of the Hall coeﬃcient as a function of tempe
rature. We also compute the magnetoresistance as a function of the external
ﬁeld and temperature within a linearized Boltzmann equation approximatio
n for the fermionic dimers. Furthermore we further show that the dimers und
ergo a Lifshitz transition as a function of doping with a van Hove singular
ity appearing at the Fermi surface near optimal doping ∼ 20%. Indeed the
van Hove singularity leads to a divergence of the density of states and as
such an optimum Tc. We study the interplay of nematic ﬂuctuations and the
van Hove singularity both of which occur near optimal doping. We show that
the van Hove singularity modiﬁes the critical properties of the QCP (qua
ntum critical point) for nematic ﬂuctuations and that the QCP may be desc
ribed by Hertz Millis like theory with z = 4. This allows us to calculate t
he critical exponents of the nematic ﬂuctuations and to show that the fer
mionic dimers have non-Fermi liquid behavior near the QCP with the self ene
rgy diverging∼ ω3/4 near the QCP.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180117T165725Z
DTSTART:20180326T150000Z
DTEND:20180326T160000Z
UID:event1898@bu.edu
URL:http://physics.bu.edu/events/show/1898
SUMMARY:CM Monday Seminar TBA
DESCRIPTION:Featuring Antonello Scardicchio\, International Centre for Theo
retical Physics\nHosted by: Christopher Laumann\n\nPart of the Condensed Ma
tter Theory Seminar Series.\n\n
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180322T171935Z
DTSTART:20180328T170000Z
DTEND:20180328T180000Z
UID:event1938@bu.edu
URL:http://physics.bu.edu/events/show/1938
SUMMARY:"Aspects of ETH in various systems"
DESCRIPTION:Featuring Mark Srednicki\, UCSB\n\nPart of the Condensed Matter
Theory Seminar Series.\n\nI will discuss the status of ETH in systems with
spontaneous symmetry breaking\,\nin large subsystems\, and in systems near
integrability.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180117T165737Z
DTSTART:20180402T150000Z
DTEND:20180402T160000Z
UID:event1899@bu.edu
URL:http://physics.bu.edu/events/show/1899
SUMMARY:CM Monday Seminar TBA
DESCRIPTION:Featuring Eduardo Fradkin\, University of Illinois at Urbana-Ch
ampaign \nHosted by: Christopher Laumann\n\nPart of the Condensed Matter Th
eory Seminar Series.\n\n
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180214T163022Z
DTSTART:20180420T160000Z
DTEND:20180420T170000Z
UID:event1884@bu.edu
URL:http://physics.bu.edu/events/show/1884
SUMMARY:CM Friday Seminar TBA
DESCRIPTION:Featuring Mark Mineev-Weinstein\, Natal\nHosted by: Anatoli Pol
kovnikov\n\nPart of the Condensed Matter Theory Seminar Series.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20180324T042745Z
LAST-MODIFIED:20180117T165922Z
DTSTART:20180427T163000Z
DTEND:20180427T173000Z
UID:event1885@bu.edu
URL:http://physics.bu.edu/events/show/1885
SUMMARY:CM Friday Seminar TBA
DESCRIPTION:Featuring Ivan Schuller\, University of California\, Santa Barb
ara\nHosted by: Kevin Smith\n\nPart of the Condensed Matter Theory Seminar
Series.\n\n
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR