2010 seminars
Schedule of winter semester (start from 13:00 @ #933)
Oct. 7
Takahiro Sagawa (Ueda absent)
Oct. 14
Shuta Nakajima (Kawaguchi absent)
Oct. 21 (skip, Ueda and Kawaguchi absent)
Oct. 28
Shun Uchino (Otsuka group in Univ. of Tokyo)
Nov. 2
Masatoshi Sato (ISSP)
Nov. 4 (skip, move to Nov. 2)
Nov. 11
Naoyuki Sakumichi (Kawaguchi absent)
Nov. 18
Yu Watanabe
Nov. 25
Simone De Liberato
Dec. 2 (skip, Student chapter)
Dec. 9
Yuki Kawaguchi (Ueda absent)
Dec. 16
Pascal Naidon(Ueda absent)
Dec. 23 (skip, National holiday)
Dec. 30 (skip, winter vacation)
Jan. 6 (skip, move to Jan.13)
Jan. 12
Shimpei Endo
Jan. 20
Nguyen Thanh Phuc
Jan. 27
Hideki Yamaguchi
Feb. 1
Susumu Okazawa (KEK)
Feb. 3
Masahiro Takahashi
Feb. 10
Shingo Kobayashi
Feb. 17
Tatsuhiko Ikeda
Feb. 24
Yui Kuramochi
Mar. 3
Takehiro Deguchi and Yuya Tanizaki
Mar. 10 Guest
Mar. 17 Guest
Mar. 24 (skip, Mar. 2528 JPS meeting)
Abstract
2010/10/7(Thu) 13:00
speaker 
Takahiro Sagawa

title 
Information Thermodynamics in Small Systems

abstract 
Due to the recent technologies of manipulating nonequilibrium
systems at nano and micro scales such as biological molecular motors,
stochastic aspects of thermodynamics have been more and more important
in terms of experiments as well as theories of nonequilibrium
statistical mechanics. In this seminar, I would like to talk about
thermodynamics of nonequilibrium information processing, which leads
us to the foundations of thermodynamics and statistical mechanics with
the assistance of the celebrated "Maxwell's daemon." Starting with a
short introduction of basic concepts of information theory, I will
talk about general theory of "information thermodynamics," in
particular its second law and the generalized Jarzynski equality. I
will also talk about a recent experiment that realized Szilardtype
informationheat engine for the first time, and also verified the
generalized Jarzynski equality.

2010/10/14(Thu) 13:00
speaker 
Shuta Nakajima

title 
Measurement of an Efimov trimer binding energy in a threecomponent mixture of ^{6}Li

abstract 
Recently, T. Lompe et.al. demonstrated a radiofrequency (RF)
association of an Efimov trimer state in a threecomponent mixture of
^{6}Li atoms. This method provides a way to determine the binding energy
of the Efimov trimers not only at particular points, but also in a
continuous range of magnetic field.
In this talk, I will talk about our recent measurement of the binding
energy of the Efimov states in the threecomponent mixture of ^{6}Li
atoms via "Atomdimer loss measurement" and "RF association". In the
latter experiment, We precisely measured the binding energy of an
Efimov state by RF association over a range of magnetic field of 50 G.
We performed the spectroscopy at various temperatures and confirmed
that the lowest temperature condition in our experiment does not
suffer from any finitetemperature shift in the spectroscopy. The
obtained trimer binding energy was found to significantly deviate from
our nonuniversal theory prediction based on a threebody parameter
with a monotonic energy dependence, and suggests a more complicated
variation of the threebody parameter.

2010/10/28(Thu) 13:00
speaker 
Shun Uchino

title 
Phase Structure and Lowenergy Excitation in Spinor BoseEinstein Condensates

abstract 
Based on the theory of weakly interacting Bose gases, I will dicuss phase structure and lowenergy excitations in spinor BoseEinstein condensates. My focus will be on the LeeHuangYang corrections that are the first quantum corrections of physical quantities, and on the Nambu Goldstone (NG) modes that are the dominant degrees of freedom to determine the lowenergy behavior of the system. In connection with the latter focus, it is shown that quasiNG modes (QNG), which play prominent roles in highenergy physics, emerge in the spin2 nematic phase. I will delineate the physical significance of the QNG modes.
References:
[1]S. Uchino, M. Kobayashi, M. Ueda, Phys. Rev. A81, 063032(2010)
[2]S. Uchino, M. KObayashi, M. Nitta, M. Ueda, arXiv:10102864

2010/11/2(Tus) 13:00
speaker 
Masatoshi Sato

title 
Topological superconductors

abstract 
Starting from the basic properties of topological phases such as the
bulkedge correspondence, I would like to explain recent topics on
topological properties of superconductors. In particular, nonAbelian
topological order in noncentrosymmetric superconductors/superfluids and topological phases in spintriplet(or oddparity) superconductors are explained.
[1]MS, Bussei Kenkyu 94 (2010) 311.
[2]MS, Phys. Rev. B79, 214526 (2009); Phys. Rev. B81, 220504(R) (2010)
[3]MS, Satoshi Fujimoto, Phys. Rev. B79, 094504 (2009); arXiv.1007.4369, MS, Yoshiro Takahashi, Satoshi Fujimoto, Phys. Rev. Lett. 103, 020401 (2009); arXiv:1006.4487

2010/11/11(Thu) 13:00
speaker 
Naoyuki Sakumichi

title 
Quantum cluster expansion study of the BCSBEC crossover

abstract 
We address the BCSBEC crossover in a twocomponent cold Fermi gas
with shortrange interaction. To this end, we use the LeeYang quantum
cluster expansion method, which enables us to expand the logarithm of
the grand partition function in a power series of fugacity [1]. We can
formally sum up an infinite series of the clusters which are expressed
in terms of ladder graphs. The critical fugacity can be defined as the
divergent point of the grand partition function for any value of a
scattering length. The obtained critical fugacity agrees with the BEC
transition fugacity in the BEC limit. And we discuss the critical
fugacity at the unitarity limit.
[1] T. D. Lee and C. N. Yang, Phys. Rev. 113, 1165 (1958)

2010/11/18(Thu) 13:00
speaker 
Yu Watanabe

title 
Uncertainty Relation Revisited from Quantum Estimation Theory

abstract 
The uncertainty relation is among the most salient properties of quantum theory,
imposing fundamental constraints on precise measurement of noncommutable observables.
Thus, there must exist some tradeoff relations concerning the information that is obtained by quantum measurements.
By invoking quantum estimation theory we formulate the uncertainty relation for arbitrary quantum states and measurements in a finitedimensional Hilbert space.
In general, an estimation process from the measurement outcomes is essential to clarify the tradeoff relation of our knowledge obtained by measurement.
We introduce a measurement error that involves such estimation processes.
We derive the tradeoff relation of the measurement errors of two observables such that the bound is achievable for all quantum states and observables.
In particular, we find the tightest ever bound that is achievable for all quantum states and observables.
Yu Watanabe, Takahiro Sagawa, and Masahito Ueda, arXiv:1010.3571 (2010).

2010/11/25(Thu) 13:00
speaker 
Simone De Liberato

title 
Carnot's Theorem for nonequilibrium reservoirs

abstract 
Carnot's theorem poses a fundamental limit on the maximum efficiency
achievable from an engine that works between two reservoirs at thermal
equilibrium.
In this talk I will show how it is possible to extend this result to
the case of arbitrary nonequilibrium and even quantum coherent
reservoirs by proving that a single nonequilibrium reservoir is
formally equivalent to multiple equilibrium ones.
In order to show an application of such theorem I will discuss the
possibility of realizing an engine powered by quantum coherence that
works at unit efficiency.
S. De Liberato and M. Ueda arXiv:1007.0335

2010/12/9(Thu) 13:00
speaker 
Yuki Kawaguchi

title 
Spontaneous Magnetic Ordering in a Ferromagnetic Spinor Dipolar BoseEinstein Condensate

abstract 
We study the spin dynamics of a spin1 ferromagnetic BoseEinstein condensate with magnetic dipoledipole interaction (MDDI) based on the GrossPitaevskii and Bogoliubov theories. We find that various magnetic structures such as checkerboards and stripes emerge in the course of the dynamics due to the combined effects of spinexchange interaction, MDDI, quadratic Zeeman and finitesize effects, and nonstationary initial conditions. However, the shortrange magnetic order observed by the Berkeley group [Phys. Rev. Lett. 100, 170403 (2008)] is not fully reproduced in our calculations; the periodicity of the order differs by a factor of 3 and the checkerboard pattern eventually dissolves in the course of time. Possible reasons for the discrepancy are discussed.
YK, Saito, Kudo, and Ueda, PRA 82, 043627 (2010).

2010/12/16(Thu) 13:00
speaker 
Pascal Naidon

title 
The physics of 3component gas of lithium 6

abstract 
This seminar will review our current understanding of the physics
of ultracold gases of lithium 6 atoms that are prepared in 3 different
internal spin states. When an external magnetic field is applied to these
systems, the scattering lengths between the atoms become very large, and the
physics acquires some universal character. In particular, 3 atoms in
different spin states can bind together according to a universal mechanism
called the Efimov effect. Various indirect signatures and firsttime direct
spectroscopy of these 3body bound states have been demonstrated in recent
experiments. These results are essentially consistent with the universal
Efimov effect, but nonuniversal deviations remain to be understood.

2010/1/12(Wed) 13:00 @445
speaker 
Shimpei Endo

title 
Manybody effects of BECBCS crossover in an ultracold Fermi gas.

abstract 
The study of the BECBCS crossover has a long history, and various kinds of manybody techniques have been applied. However, there still remains some controversies on the topic. One reasons is that it is important but technically difficult to incorporate threebody and fourbody correlations into thermodynamic calculations. Thus, it is nice if we have some ways to incorporate the effect of threebody correlations in a simple manner. In this seminar, I propose an approximate way to solve threebody problem in the vacuum for a two component Fermi system, which may be able to be naturally incorporated in a thermodynamic calculations to include the effect of the atomdimer collision. It turns out that it predicts the atomdimer scattering length 1.08, which is close to the exact value 1.18. I will discuss some properties of this approximation and some possible future prospects.

2010/1/20(Thu) 13:00
speaker 
Nguyen Thanh Phuc

title 
Phase Diagram of a ThreeDimensional Spin1 Ferromagnetic Condensate under a Quadratic Zeeman Effect

abstract 
In this seminar, the thermal equilibrium properties of a uniform F=1 Rb87 spinor condensate under a quadratic Zeeman effect are presented. From the finitetemperature phase diagram, obtained by using the Popov approximation, it can be seen that a twostep phase transition occurs, in which the system changes from normal phase to nonmagnetized polar phase, and then to BA phase with a finite transverse magnetization. It also turns out that due to the coupling with the condensate, there exists a coherence within the thermal part, and thus it exhibits a finite magnetization. Finally the effects of noncondensed atoms at temperatures near absolute zero in a spinor BEC are investigated by using the expansion of the order parameter with respect to the small noncondensate fraction. The result shows that the Popov approximation breaks down at temperatures near absolute zero, and the groundstate phase diagram is the same as that obtained by neglecting the whole effects of noncondensed atoms, which is a nontrivial result.

2010/1/27(Thu) 13:00
speaker 
Hideki Yamaguchi

title 
A nonequilibrium study on molecular motors

abstract 
Molecular motors have been intensively investigated for around 20 years. They are special proteins that can move unidirectionally using energy gained by consuming "fuel" molecules (ATPs). This property make them actual motors, which are targets of nonequilibriumstatistical studies. In this seminar, nonequilibrium properties of molecular motors revealed by experiments are reviewed, with theoretical analyses.
This seminar is divided into two parts: in the former part, I review two experiments. One is on the ratio of realization probability of forward/backward movements, and the other is on dwell time (interval between two successive movements). These two data are considerd theoretically in the latter part.

2010/2/1(Tue) 13:00 @1320
speaker 
Susumu Okazawa

title 
Black Holes and the Fluctuation Theorem

abstract 
We investigate nonequilibrium nature of fluctuations of black hole horizons by applying the fluctuation theorem. The theorem reveals a violation of the generalized second law of black hole thermodynamics. In this talk, we explain the derivation of effective equation of motion of matter field and show the fluctuation theorem for black holes and matters in a certain approximation. After that, we introduce a model which imitate an evaporating black hole.

2010/2/3(Thu) 13:00
speaker 
Masahiro Takahashi

title 
Vortex State in BoseEinstein Condensates with FiniteRange Interactions

abstract 
We investigate the vortex nature of BoseEinstein condensates (BECs) with finiterange interactions. The interparticle interaction is described by contact interaction in ordinary BECs. However, by introducing Ramancoupled Rydberg atoms with the large detuned lasers, BECs with finiterange interaction can be realized[1]. In such systems, the groundstate density profile will be significantly changed to periodically oscillating one. We introduce how such system is realized by lasers, and how vortex states will be affected by spatially modulated density. This presentation is based on the results of numerical calculation of the GrossPitaevskii and Bogoliubovde Gennes equations derived by mean field approximation.
[1] N. Henkel, R. Nath, and T. Pohl, Phys. Rev. Lett. 104, 195302 (2010).

2010/2/10(Thu) 17:00
speaker 
Shingo Kobayashi

title 
Selection rule of Topological Excitations in Spin1 BECs

abstract 
We have already known that spinar BoseEinstein Condensates accommodate many kind of topological excitations due to a lot of internal degree of freedoms. These topological excitations are defined for each order phases independently. In this talk, we try to realize the connection between topological exctations for different phases in spin1 BECs.Our calculation is based on a homotopy exact sequence and a mathematical model.

2010/2/17(Thu) 13:00
speaker 
Tatsuhiko Ikeda

title 
An approach to establish the foundation of statistical mechanics

abstract 
The foundation of statistical mechanics has long been unclear.
Recently, the problem is being studied on socalled eigenstate thermalization hypothesis(ERH).
I will talk about our approach based on a new hypothesis we call eigenstate randomization hypothesis(ERH).
Reference: T. N. Ikeda, Y. Watanabe, and M. Ueda, arXiv:1012.3237

2010/2/24(Thu) 13:00
speaker 
Yui Kuramochi

title 
Continuous Measurement on a Particle in 1Dimensional Optical Lattices

abstract 
In this seminar, my study on the continuous position measurement process
on a paricle in 1dimensional lattices is reported.
According to previous works on a continuous position measurement on a particle in free 1dimensional space,
with any initial condition, the distribution of the quantum states goes to stational one in which
all the wave functions are Gaussian with fixed second order momments.
We consider a similar measurement process on a particle in 1dimensional lattice
where the position operator takes discrete values.
Numerical analysis shows that stational distribution of the position dispersion is not simply peaked,
while in continuous case it is accumulated in a single value.
The physical origins of such behaviors are not fully understood.

2010/3/3(Thu) 13:00
speaker 
Takehiro Deguchi

title 
New approach to classical statistical mechanics

abstract 
The ordinal way to explain classical statistical mechanics is based on the idea of number of states and Boltzmann entropy. But if we take that way, the relationship to thermodynamics or information theory becomes unclear. In this seminar, I offer the one based on heat, work and conditions about temperature, which can solve these issues.

speaker 
Yuya Tanizaki

title 
The scattering between the 3particle bound state and the atom

abstract 
As is well known, two heavy fermions and one another kind of fermion can form a Efimov trimer
if the mass ratio is larger than about 13.6. Recently, Kartavtev and Malykh have shown that for the smaller
mass ratio > 8.17 the threebody bound state exists. I will talk about the scattering problem between the
trimer and the atom using the AGS equation, which describes the scattering amplitude for the fourprticle
collision process.

Schedule of summer semester (start from 13:00 @ #933)
Apr. 15(Thu) Takahiro Sagawa
"On the generators of quantum dynamical semigroups"
G. Lindblad, Commun. Math. Phys.
48, 119130 (1976).
Apr. 19(Mon) #933 13:00
speaker 
Prof. P. Blair Blakie (Otago University)

title 
Dynamics and statistical mechanics of ultracold Bose gases using cfield techniques

abstract 
I will discuss phase space techniques based on the Wigner
representation that provide an approximate description of dilute
ultracold Bose gases. In this approach the quantum field evolution can be
represented using equations of motion of a similar form to the
GrossPitaevskii equation but with stochastic modifications that include
quantum effects in a controlled degree of approximation. These techniques
provide a practical quantitative description of both equilibrium and
dynamical properties of Bose gas systems. We develop versions of the
formalism appropriate to zero temperature, where quantum fluctuations can
be important, and at finite temperature where thermal fluctuations
dominate. Applications to a wide range of phenomena will be discussed.

Apr. 22(Thu) Yu Watanabe
"Monotone metrics on matrix spaces"
Dénes Petz, Linear Algebra and its Applications.
244,(1996), Page 8196.
reference
1,
2,
3,
4,
5,
6,
7,
8,
9.
May. 6(Thu) Shingo Kobayashi
"Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells"
B. Andrei Berneving, Taylor L. Hughes, ShouCheng Zhang, Science
314, (2006), 1757
May. 13(Thu) 15:00 Tatsuhiko Ikeda
"Nonequilibrium Equality for Free Energy Differences"
C. Jarzynski, Phys. Rev. Lett.
78 , (1997) 2690
"Equilibrium freeenergy differences from nonequilibrium measurements: A masterequation approach"
C. Jarzynski, Phys. Rev. E
56, (1997) 5018
May. 17(
Mon) #445 Yui Kuramochi
"Time in the Quantum Theory and the Uncertainty Relation for Time and Energy"
Y. Aharanov and D. Bohm, Phys. Rev.
122, (1961) 1649
May. 24(
Mon) 15:00 #445 Naoyuki Sakumichi
"Confinement of quarks"
Kenneth G. Wilson , Phys. Rev. D,
10 (1974) 2445
Jun. 4(
Fri) Yusuke Endo
"OffDiagonal LongRange Order in Solids"
Hirotsugu Matsuda and Toshihiko Tsuneto, Prog. Theor. Phys.
Suppl.
46, (1970) 411436
Jun. 17(Thu) Naoki Hiratani
"Proof of the Ergodic Theorem and the HTheorem in Quantum Mechanics"
John von Neumann, arXiv:1003.2133v1
Jun. 24(Thu) Ken Huno
"Particle creation by black holes "
S. W. Hawking, Communication in Mathematical Physics,
43 , (1975) 199
Jul. 1(Thu) Shimpei Endo
"A quantum gas microscope for detecting single atoms in a Hubbardregime optical lattice"
Waseem S. Bakr, Jonathon I.Gillen, Amy Peng, Simon Fölling and Markus Greiner, Nature,
462 (2009) 74
"In situ observation of incompressible Mottinsulating domains in ultracold atomic gases"
Nathan Gemelke, Xibo Zhang, ChenLung Hung and Cheng Chin, Nature,
460 (2009) 995
"Probing the SuperfluidMottInsulator Transition at the SingleAtom Level"
W. S. Bakr, A. Peng, M. E. Tai, R. Ma, J. Simon, J. I. Gillen, S. Fölling, L. Pollet, and M. Greiner, 10.1126/science.1192368, Science Express Reports (2010)
Jul. 8(Thu) Nguyen Thanh Phuc
"Ordering, metastability and phase transitions in twodimensional systems"
J. M. Kosterlitz and D. J. Thouless, J. Phys. C,
6, (1973) 1181
"Universal Jump in the Superfluid Density of TwoDimensional Superfluids"
David R. Nelson and J. M. Kosterlitz, Phys. Rev. Lett,
39, (1977) 1201
Jul. 15(Thu)
12:00 Hideki Yamaguchi
"SteadyState Thermodynamics of Langevin Systems"
Takahiro Hatano and Shinichi Sasa, Phys. Rev. Lett
86, (2001 )3463
"Integral fluctuation theorem for the housekeeping heat
"
T. Speck and U. Seifert , J. Phys. A
38, (2005)L581