## [more] Seminars & Workshops

The following seminars and workshops are planned:

Seminars

Prof. Matthias Troyer, Institute for Theoretical Physics, ETH Zurich, Switzerland

Quantum Annealing and the D-Wave Devices

Wednesday, March 19, 2014, 16 : 00 ～ 17 : 00

Main Research Building Seminar room 435-437 (located in the Fourth Floor)

Seminars

Prof. Matthias Troyer, Institute for Theoretical Physics, ETH Zurich, Switzerland

Validation of quantum devices

Wednesday, March 19, 2014, 14 : 00 ～ 15 : 00

Main Research Building Seminar room 435-437 (located in the Fourth Floor)

About a century after the development of quantum mechanics we have now reached an exciting time where non-trivial devices that make use of quantum effects can be built. While a universal quantum computer of non-trivial size is still out of reach there are a number commercial and experimental devices: quantum random number generators, quantum encryption systems, and analog quantum simulators. In this colloquium I will present some of these devices and validation tests we performed on them. Quantum random number generators use the inherent randomness in quantum measurements to produce true random numbers, unlike classical pseudorandom number generators which are inherently deterministic. Optical lattice emulators use ultracold atomic gases in optical lattices to mimic typical models of condensed matter physics. Finally, I will discuss the devices built by Canadian company D-Wave systems, which are special purpose quantum simulators for solving hard classical optimization problems.

Seminars

Dr. Hui Jing, Department of Physics, Henan Normal University, China

Ultralow-threshold phonon laser in PT-symmetric resonators

Friday, March 14, 2014, 14 : 00 ～

Main Research Building Seminar room 535-537 (located in the Fifth Floor)

The parity-time-symmetric structure was experimentally accessible very recently in coupled optical resonators (COR); also for normal or non-PT-symmetric COR, a phonon laser had been created in Caltech. Here we study cavity optomechanics of this system with now a tunable gain-loss ratio. We find that nonlinear behaviors emerge for cavity photons around the balanced point, resulting giant enhancement of optical pressure and then enabling an ultralow-threshold phonon laser. I will try to give a summary of this project and also other related works on optomechanics, aiming to get your comments/suggestions/interests on it.

Workshops

International Molecule-type Workshop on New correlations in exotic nuclei and advances of theoretical models

March 10 - 23, 2014

Yukawa Institute, Kyoto University

URL: http://www.yukawa.kyoto-u.ac.jp/contents/seminar/detail.php?SNUM=51665

Seminars

Igor Shovkovy (Arizona State University)

Magnetic Dance in a Quantum World

15:00-, March 5, 2014 (planned)

room 433 (planned)

Studies of relativistic matter in strong magnetic fields attracted a lot of attention in recent years. Some of these studies are motivated by the relativistic physics in compact stars, the Early Universe, and relativistic heavy ion collisions. Many aspects of the same underlying physics are also relevant for a growing class of novel quasi-relativistic condensed matter materials. The examples include graphene and Dirac/Weyl semimetals. Such materials attracted a lot of attention in recent years because of their unusual electronic properties and a great potential for wide-ranging applications. I will review some conceptual ideas about the underlying physics of relativistic matter in strong magnetic fields from a standpoint of a high-energy physicist with cross-disciplinary interests.

Workshops

Interdisciplinary workshop "Quarks, nuclei, and neutron stars"

March 5, 2014, 10:00 am- (time is tentative)

Faculty of Science, Kyushu University

program : TBA

link : TBA

Seminars

Prof. Cheng Lu (Department of Physics, Nanyang Normal University, Nanyang 473061, P. R. China)

Structural evolution of carbon dioxide under high pressure

March 3 (Mon), 13:00-14:00

Main Research Building, Room 109

It has been a long-standing and challenging objective to stabilize Carbon (C) in hypervalent state and bonded with nonmetallic elements. Most of the works so far focused on synthesizing organic molecules with high coordination number of C. Equipped with an efficient structure search method, we take carbon dioxide (CO2) solid as a prototype system and study the evolution of its structure under high pressure. Our results show that although undertaking many structural transitions under pressure, CO2 is quite resistive to structures with C beyond 4-fold coordination. For the first time, we are able to identify two 6-fold structures of CO2 solid with Pbcn and Pa-3 symmetries that become stable at pressures close to 1TPa. Both structures consist of network of C?O octahedron, showing hypervalence of the central C atoms. The C?O bond length varies from 1.30 to 1.34 A at the 4-fold to 6-fold transition, close to the C?O distance in the transition state of a corresponding SN2 reaction. Our results provide a good measure of the resistivity of C toward forming hypervalent compounds with nonmetallic elements and of the barrier of reaction involving C-O bonds.

[1] Cheng Lu et al., J. Am. Chem. Soc., 2013, 135 (38), pp 14167-14171

Seminars

Stefano Gandolfi (Los Alamos National Laboratory)

Microscopic Calculations of Homogeneous and Inhomogeneous Neutron Matter

15:00-, Feb. 26, 2014

RIBF Hall (rm.201), RIBF bldg.２F

http://indico2.riken.jp/indico/conferenceDisplay.py?confId=1425

Workshops

RIKEN-OIST Mathphys Workshop

Room B503, Lab 1, Main Campus,

Okinawa Institute of Science and Technology Graduate University (OIST)

https://sites.google.com/site/oistrikenjointworkshop2014/

Seminars

Lembit Sihver (Chalmers Univ. of Technology, Sweden)

Charged Particle Transport Simulations for Radiotherapy and Space Dosimetry

Feb. 6, 2014, 13:30

RIBF Hall (rm.201), RIBF bldg. 2F

Seminars

Dr. Daoyi Dong, School of Engineering and Information Technology, UNSW Canberra at the Australian Defence Force Academy, Australia

Quantum State Tomography via Linear Regression Estimation

Wednesday, January 15, 2014, 16:00-

Main Research Building Seminar room 433 (located in the Fourth Floor)

Seminars

Dr. Sangchul Oh, University at Buffalo, The State University of New York, USA

Cycloid on a Bloch Sphere

Monday, January 13, 2014, 16:00-

Main Research Building Seminar room 435-437 (located in the Fourth Floor)

Workshops

非平衡物理、異分野の集い。--- Interdisciplinary mini-workshop on nonequilibrium physics ---

December 7 - 8, 2013

Kyoto university (Room 525, Bldg. No. 5, Faculty of Science)

http://ribf.riken.jp/~hidaka/workshop/iwnp.html

Seminars

Mr. George Knee, Department of Materials, University of Oxford, U.K.

Weak values and quantum estimation

Dec. 2nd, Monday, 2013, 14:00

5F seminar room (535-537), Main Research Bldg.

I will discuss some of the recent laboratory applications of Aharonov et al's 'Time-Symmetric Quantum Mechanics' . In particular I will argue that weak-value amplification, a prominent effect arising through postselection, is of no fundamental advantage over standard techniques for a number of information processing tasks, even in the presence of noise.

Seminars

Dr. Wei Ku (Brookhaven National Laboratory, USA)

Can high-Tc superconductivity be an entirely different beast under strong correlation?

Nov. 26 (Tuesday) 16:00~17:30

Main Research Building, room #124,126

After decades of intensive research, the fundamentals of high-Tc superconductivity remain elusive. In this talk, I will discuss issues related to the strongly correlated behavior in modern high-Tc superconductors, including the Fe-based superconductors and the cuprates. For Fe-based superconductors, the rich spin/orbital correlation will be addressed, and the effects of the disordered chemical impurities be examined.

For the cuprates, a strong-binding picture will be presented to explain the recently found doping independence of the superconducting gap, and to demonstrate the formation of the superconducting dome with d-wavy superfluid, the glassy electronic structure and the suppression of the Nerst signal at low doping.

Seminars

Prof. Andrew Cleland, Department of Physics, University of California Santa Barbara, U.S.

Coupling microwaves and light

Nov. 25, Monday, 2013 13 : 30 - 15 : 00

5F seminar room (535-537), Main Research Bldg.

Seminars

Prof. Jing Lu, Hunan Normal University

Single-photon router: Coherent Control of multi-channel scattering for single-photons with quantum interferences

Nov. 22, Friday, 2013 14:00-15:00

5F seminar room (535-537), Main Research Bldg.

We propose a single-photon router using a single atom with an inversion center coupled to quantum multichannels made of coupled-resonator waveguides. It is found that the spontaneous emission of the atom is used to redirect single photons from one quantum channel into another. The on-demand classical field perfectly switches-off the single-photon routing due to the quantum interference in the atomic amplitudes of optical transitions. Total reflections in the incident channel are due to the photonic bound state in the continuum. Two virtual channels, named as scatter-free and controllable channels, are found, which are coherent superpositions of quantum channels. Any incident photon in the scatter-free channel is totally transmitted. The propagating states of the controllable channel are orthogonal to those of the scatter-free channel. Single photons in the controllable channel can be perfectly reflected or transmitted by the atom.

References:

e-print arXiv: 1310.7286

http://arxiv.org/abs/1310.7286

Seminars

Dr. Neill Lambert, RIKEN

Photon mediated transport in Hybrid QED

Nov. 22, Friday, 2013 11:00-12:00

3F Room (315), Main Research Bldg.

I explore photon-mediated transport processes in a hybrid circuit-QED structure consisting of two double quantum dots coupled to a common microwave cavity. Under suitable resonance conditions, electron transport in one double quantum dot is facilitated by the transport in the other dot via photon-mediated processes through the cavity. We calculate the average current in the quantum dots, the mean cavity photon occupation, and the current cross-correlations using a recursive perturbation scheme that allows us to include the influence of the cavity order-by-order in the couplings between the cavity and the quantum dot systems. Within this framework we can clearly identify the photon-mediated processes in the transport.

Seminars

Dr. Sergey Shevchenko, B. Verkin Institute for Low Temperature Physics (ILTPE)

Dynamical behavior of the driven qubit-resonator system

Nov. 21, Thursday, 2013 13 : 30 - 15 : 00

5F seminar room (535-537), Main Research Bldg.

In my talk I would like to report about recent activity related to the system with superconducting qubits coupled to classical nanomechanical resonator [1] or quantum transmission-line resonator [2]. In Ref. [1] we have studied how the strongly driven superconducting qubit can be probed by a nanomechanical resonator (direct Landau-Zener-Stuckelberg interferometry) and, vice versa, how position of the nanomechanical resonator can be defined by the qubit's state (inverse interferometry). There, in relation to the experimental realization, we considered the situation when the resonator is slow in comparison to qubit's dynamics. When the frequency of the resonator is compared to the qubit's characteristic frequency, the convenient tool for the description of the coalesced atom and field is the notion of dressed states. In our recent work [2] we considered particular case when the transmission-line resonator was driven at two harmonics, where we were interested how one of the signals can be changed by another signal via qubit.

References:

[1] S. N. Shevchenko, S. Ashhab, and F. Nori, Inverse Landau-Zener-Stuckelberg problem for qubit-resonator systems, Phys. Rev. B 85, 094502 (2012).

[2] S. N. Shevchenko, G. Oelsner, Ya. S. Greenberg, P. Macha, D. S. Karpov, M. Grajcar, A. N. Omelyanchouk, and E. Il’ichev, Amplification and attenuation of the transmitted signal by doubly-dressed states, arXiv:1309.2619, submitted to Phys. Rev. B.

[1] http://prb.aps.org/pdf/PRB/v85/i9/e094502

[2] http://arxiv.org/pdf/1309.2619v1.pdf

Seminars

Mr. Martin Leib, Technische Universitat at Muenchen

Strongly Interacting Many Body Physics with Circuit Quantum Electrodynamics Networks

Nov. 21, Thursday, 2013 11:00-12:00

3F Room (315), Main Research Bldg.

In its infancy circuit quantum electrodynamics (cQED) has quickly started reproducing fundamental quantum optical experiments, e.g. observation of vacuum rabi oscillations in frequency and time domain, with unprecedented cooperativity. This was possible because of the large coupling strength of the quasi one-dimensional microwave field of the superconducting transmission line resonators to the macroscopic dipole moment of superconducting qubits.

Since then cQED has matured to a discipline of experimental physics capable of performing fundamental quantum information tasks and is currently on the verge of crossing the border between few- to many body physics [1]. This opens up a exciting realm of completely new physical phenomena. Because of the ubiquitous influence of the electromagnetic environment however the number of microwave photons is not conserved which separates cQED systems from other quantum simulators involving atoms, e.g. cold atoms in optical latices. Instead cQED is ideally suited for exploring quantum many-body physics in the driven dissipative regime where the interplay of constant injection of microwave photons and the unpreventable loss of microwave photons into the electromagnetic environment generates a whole new class of steady- but not equilibrium states.

I am presenting our ideas for the simulation of many body physics in the circuit QED framework after a short introduction into the world of circuit QED and many body physics.

New J. Phys. 12 093031

New J. Phys. 14 075024

Phys. Scr. 2013 014042

PRL 110 163605

Seminars

Prof. Su Yi, Institute of Theoretical Physics, Chinese Academy of Sciences

Ultracold Fermi gases with resonant dipole-dipole interaction

Nov. 20, Wednesday, 2013 14:00-15:00

5F seminar room (535-537), Main Research Bldg.

In this talk, I will report the studies on the superfluid phases of an ultracold Fermi gases with resonant dipole-dipole by the standard mean-field theory. I will show that, in contrast to the crossover from BEC to BCS superfluid in Fermi gases with isotropic interactions, resonant dipolar interaction leads to two completely different BEC phases of the tight-binding Fermi molecules on both sides of the resonance, which are characterized by two order parameters with distinct internal symmetries. Near the resonances, these two competitive phases can coexist, and an emergent relative phase between the two order parameters spontaneously breaks time-reversal symmetry. I will also discuss the experimental observation of these phases via momentum resolved rf spectroscopy.

Reference: T. Shi, S.-H. Zou, H. Hu, C.-P. Sun, and S. Yi, Phys. Rev. Lett. 110, 045301 (2013).

http://prl.aps.org/abstract/PRL/v110/i4/e045301

Seminars

Prof. Fabio Marchesoni, University of Camerino and INFN

Diffusion of two-sided Janus particles inside narrow channels

Nov. 18, Monday, 2013 16:00-17:00

4F seminar room (424-426), Main Research Bldg.

Directed Brownian transport in asymmetric narrow channels of various geometries [1] is discussed in the presence of different external biases, including periodic drives and other time correlated energy sources.

High-efficiency autonomous ratcheting is obtained [2] by employing active (or self-propelling) Brownian particles (e.g., Janus particles) both in a dilute solution and in binary mixtures. In the latter case a small fraction of active Brownian particles suffices to force collective transport of the entire mixture along the channel.

In the case of elongated (rod-like) Janus particles driven in channel transport properties selectively depend on the particle shape; under certain conditions giant negative mobility is observed [3].

References

[1] P. Hanggi and F. Marchesoni, Rev. Mod. Phys. 81, 387 (2009)

[2] P.K. Pulak, V.R. Misko, F. Marchesoni, F. Nori, Phys. Rev. Lett. 110, 268301 (2013)

[3] work in preparation

Seminars

Prof. Han Pu, Rice University

Cavity-Assisted Spin-Orbit Coupling in Cold Atoms

Nov. 18, Monday, 2013 14:00-15:00

4F seminar room (424-426), Main Research Bldg.

Synthetic spin-orbit coupling (SOC) in cold atoms has been one of the most active fields over the past few years. In experiment, SOC is realized by Raman coupling two atomic hyperfine states. In this work, we consider the effect of SOC in ultracold atoms induced by a quantized light field inside an optical cavity, where the back-action from the atom to the cavity light field plays an essential role. We show that the atom-photon feedback induces intriguing properties in this system.

References: arXiv:1309.4369

http://arxiv.org/abs/1309.4369

Seminars

By Prof. Hui Jing, HeNan Normal University

Optomechanics with a multi-component quantum gas

Nov. 18, Monday, 2013 11:00-12:00

4F seminar room (424-426), Main Research Bldg.

I will talk about cavity optomechanical control of a multiple atomic Bose condensate. Firstly, for a three-component (spin-1) gas I will show how to get coherent optical control of a quantum rotor (opto-rotational control of the spin gas) especially quantum squeezing of the rotor gas; secondly, for a two-species mixture, I will show how to get linearly coupled quantum oscillators by tuning atomic scattering lengths. By applying a time-varying Feshbach magnetic field, it is also possible to observe the optomechanical geometric (Berry's) phase or even phase transition in a cavity quantum gas.

References:

H. Jing, D. S. Goldbaum, L. Buchmann, and P. Meystre, Phys. Rev. Lett. 106, 223601 (2011).

H. Jing, X. Zhao, and L. Buchmann, Phys. Rev. A 86, 065801 (2012).

S. Singh, H. Jing, E. M. Wright, and P. Meystre, Phys. Rev. A 86, 021801 (2012).

L. F. Buchmann, H. Jing, C. Raman, and P. Meystre, Phys. Rev. A Rapid Communication 87, 031601 (2013).

http://publish.aps.org/search?c%5B%5D%5Bfield%5D=author&c%5B%5D%5Bvalue%5D=H.+Jing&c%5B%5D%5Boperator%5D=AND&c%5B%5D%5Bfield%5D=abstitle&c%5B%5D%5Boperator%5D=AND&c%5B%5D%5Bfield%5D=fulltext&c%5B%5D%5Boperator%5D=AND

Workshops

iTHES-HPCI Joint WS on "Nuclear equation of state with strangeness"

November 11 - 15, 2013

Main research building room 213

http://www.jicfus.jp/jp/131111-15hpci/#program

http://www.jicfus.jp/jp/131111-15hpci/

Seminars

Prof. Bo Thide, Swedish Institute of Space Physics, Sweden

Photon Angular Momentum at Radio Frequencies

Oct. 31st, Thursday, 2013, 14:00

3F (315), Main Research Bldg.

Photons carry not only energy and spin angular mometum (SAM) but also orbital angular momentum (OAM). I will present some results from our OAM research at low frequencies in Uppsala, Sweden, and Padua, Italy. Low-frequency OAM is a new radio technique that can provide more detail than can be obtained with methods in optics using diffractive optics element. It can be used in radio astronomy as well as in radio communication applications.

Some of the fundamental physical properties of angular momentum, the related physical observables and their measurement in radio experiments will be described. New results, including experimental verification of multi-channel wireless information transfer within a given frequency bandwidth, using the topological properties of photons carrying OAM will be presented.

Seminars

Prof. Tobias Brandes, Institute for Theoretical Physics, Technical University of Berlin, Germany

Hardwiring a Maxwell demon

Oct. 24th, Thursday, 2013, 16:00 - 17:00

4F seminar room (435-437), Main Research Bldg.

We present a physical implementation of a Maxwell demon which consists of a conventional single electron transistor (SET) capacitively coupled to another quantum dot detecting its state. Altogether, the system is described by stochastic thermodynamics. We identify the regime where the energetics of the SET is not affected by the detection, but where its coarse-grained entropy production is shown to contain a new contribution compared to the isolated SET. This additional contribution can be identified as the information flow generated by the ‘‘Maxwell demon’’ feedback in an idealized limit.

Seminars

Dr. Haitao Quan, School of Physics, Peking University, China

Nanoscale Carnot engines

Oct. 24th, Thursday, 2013, 14:00 - 16:00

4F seminar room (435-437), Main Research Bldg.

*abstract (if any):

We study the maximum efficiency of a Carnot engine based on a small system. It is revealed that due to the finite size of the working substance, irreversibility may arise in the thermodynamic cycle. As a result, a correction to the usual Carnot efficiency is required. This result defies the long-standing belief that the maximum efficiency of a heat engine does not depend on the details of the working substance. Furthermore, we find a general and simple expression for the maximum efficiency of heat engines. This maximum efficiency approaches the usual Carnot efficiency when the size of the working substance increases to macroscopic size. Hence our result reconcile with the traditional theories of thermodynamics in the thermodynamic limit and include it as a special case. Our study demonstrates the subtleties of thermodynamics of small systems.

Workshops

Todai/Riken joint workshop on Super Yang-Mills, solvable systems and related subjects

October 23 - 24 2013

Rm. 1320, Science Bldg.4, Hongo Campus, Univ. of Tokyo

Recent years has seen a lot of interesting research and attempts regarding super Yang-Mills theories, solvable statistical systems, and of course, conformal field theories and their interrelations. There are many novel discoveries revealed by these efforts. It would be a good time for us to get together and share those insights with each other. This small workshop is motivated for that purpose. We hope that those who are interested in the subjects can participate and engage in active discussions at our workshop.

Organizers: Yutaka Matsuo (Tokyo), Tsukasa Tada (Riken)

Speakers: K. Ito (T.I.T.), H. Itoyama (Osaka C.U.), V. Kazakov (E.N.S.), I. Kostov (Saclay), Y. Matsuo (Tokyo), K. Ohmori (Tokyo), T. Okuda (Tokyo), D. Serban (Saclay), H. Shimada (OIQP), E. Sobko (ENS), F. Sugino (OIQP), T. Tada (Riken), M. Taki (Riken), S. Terashima (YITP)

http://susy.theoreticalscience.info

Seminars

Dr. Sahin Kaya Ozdemir, Washington University in St. Louis, USA

Parity-time symmetric whispering gallery optical microcavities

Oct. 22nd, Tuesday, 2013, 14:00 - 16:00

5F seminar room (535-537), Main Research Bldg.

Parity (space-)-time- (PT-) symmetry- an abstract notion and a mathematical tool in quantum field theory has emerged as a new and powerful tool to design and fabricate artificial materials (meta-materials) with unique properties that cannot be found or attained in natural materials having only gain or loss. PT-symmetric Hamiltonian systems have attracted great interest following the work of Bender and Boettcher [1] who showed that the eigenvalue spectra of non-Hermitian Hamiltonians ?†≠ ? can still be entirely real if they respect PT-symmetry, PT? = ?PT. The interest was further fueled by the first demonstration of PT-symmetry in optics [2]. Systems respecting the PT-symmetry are interpreted as non-isolated physical systems with carefully balanced loss and gain. When the PT symmetry is broken, such systems undergo phase transitions which are reflected as the emergence of complex eigenvalues. In the broken-symmetry phase, such systems are expected to exhibit several striking properties [3] such as field localization, unidirectional invisibility, enhanced or reduced reflections, nonreciprocal light transmission, loss induced transparency and co-existing coherent-perfect-absorber and laser. Some of these features have been experimentally demonstrated in optical domain using coupled waveguides with gain and loss. Up to date, all optical experiments have been performed using waveguide structures with dimensions ranging from a few centimeters to hundreds of meters. In this talk, after giving a brief introduction to whispering gallery mode (WGM) optical microcavities and PT-symmetric concepts, I will discuss the PT-symmetric concepts in optics and report the first demonstration of PT-symmetry in on-chip WGM microcavities [4]. I will also show the first observation of nonreciprocal light transmission (an optical diode) in the broken PT-symmetry phase using these microcavities. We envisage PT-symmetric microcavities to play significant role for building unconventional optical devices to manipulate light and control energy flow as well as to become a platform for realizing co-existing coherent perfect absorber (CPA) and lasers.

[1] S. Boettcher, C. M. Bender, Real spectra in non-Hermitian Hamiltonians having PT symmetry. Phys. Rev. Lett. 80, 5243 (1998).

[2] C. E. Ruter, K. G. Makris, R. El-Ganainy, D. N. Christodoulides, M. Segev & D. Kip, Observation of parity-time symmetry in optics. Nature Phys. 6, 192 (2010).

[3] A. Regensburger, C. Bersch, M.-A. Miri, G. Onishchukov, D. N. Christodoulides & U. Peschel, Parity?time synthetic photonic lattices. Nature 488, 167 (2012).

[4] B. Peng, S. K. Ozdemir, F. Lei, F. Monifi, M. Gianfreda, G. L. Long, S. Fan, F. Nori, C. M. Bender & L. Yang. Nonreciprocal light transmission in parity-time-symmetric whispering-gallery microcavities. arXiv:1308.4564

Seminars

N. Iizuka (ithes-phys team), P. Ghosh (ithes-cond team)

October 15 (Tuesday)

room 433 (main building)

15:00-16:00 N. Iizuka (ithes-phys team)

"Applications of the gauge/gravity duality to condensed matter physics"

16:00-17:00 P. Ghosh (ithes-cond team)

"Study of photosynthesis and other biological phenomena using methods of statistical mechanics and condensed matter physics”

Seminars

Professor Yoshitaka Tanimura (Department of Chemistry, Kyoto University)

October 10 Thursday: Theory of Reduced Hierarchy equations of motion

1st lecture: 1:30 to 3 pm

Break: 3 to 4 pm

2nd lecture: 4 pm to 5:30

Location: 435 and 437 (newer seminar room in the 4^th floor of the Main Research building)

October 11 Friday: Theory of Multidimensional Spectroscopies

1st lecture: 1:30 to 3 pm

Break: 3 to 4 pm

2nd lecture: 4 pm to 5:30

Location: the large seminar room located right on top of the large cafeteria.

The Friday lectures are about nonlinear response of systems, and related to the first lectures.

The Power Point lecture notes for the above subjects are in his homepage:

http://theochem.kuchem.kyoto-u.ac.jp/members/tanimura.htm

Seminars

Prof. Kenneth M. Merz Jr.

Director, Institute for Cyber Enabled Research (iCER), Joseph Zichis Chair in Chemistry Department of Chemistry, Department of Biochemistry and Molecular Biology, Michigan State University, USA

Free Energies from a Molecular Printing Press

September 26 (Thursday), 2013 16:00-18:00

RIKEN Wako Campus, Main research building 4F 435/437

Docking (posing) calculations coupled with binding free energy estimates (scoring) are a mainstay of structure-based drug design. Docking and scoring methods have steadily improved over the years, but remain challenging because of the extensive sampling that is required, the need for accurate scoring functions and challenges encountered in accurately estimating entropy effects. This talk addresses the use of ensemble principles to directly address these issues and, thereby, accurately estimate protein-ligand binding free energies. In particular, we analytically demonstrate that sampling reduces computed binding free energy uncertainties and then highlight several methods that incorporate these concepts. For example, the moveable type method, employs an elegant approach to generate the necessary ensembles by using a “binned” pairwise knowledge-based potential combined with atom pair probabilities extracted from known protein-ligand complexes. This allows us to rapidly compute the ligand, protein and protein-ligand (inclusive of solvation effects) ensembles which then can be used to directly estimate protein-ligand binding free energies using basic statistical mechanical principles. This approach improves the quality of the potential (scoring) function by reducing computational uncertainty, sampling phase space in one shot and accurately incorporating entropy effects. This allows us to compute binding free energies rapidly, accurately and yields molecular poses at a minimal computational cost relative to currently available methods based on statistical mechanics.

Seminars

Mr. Pavel Maksimov, Institute for Theoretical and Applied Electrodynamics, Russia, Moscow Institute for Physics and Technology, Russia

Localized electron states near the graphene armchair edge

Sep. 13th, Friday, 2013, 14:00 - 15:00

4F seminar room (435-437), Main Research Bldg.

For a finite graphene sheet there are two distinct types of edge: zigzag and armchair. Zigzag edge is known for more than fifteen years [1] to be able to support localized electron states and bind electrons: there is a non-dispersive single-electron band localized near the edge.

But it is generally believed that the armchair edge does not support such localized states [2]. This result is a consequence of two assumptions: that (i) the hopping integrals between nearest-neighbor carbon atoms both are the same in the bulk of the sample and near the edge, and that (ii) no non-carbon atoms or functional groups are attached to the carbon atoms on the edge. In principle, either of these two conditions may be violated (for instance, Fig.1 shows the situation where non-carbon radicals R passivate the unpaired carbon chemical bonds at the edge). Effectively, deviations from (i) or (ii) lead to new boundary conditions for the electron wave function. As a result, in a certain parameter range localized states emerge on the armchair edge.

We demonstrate that, depending on which condition is violated, properties of the localized band differ. Namely, if the hopping integral at the edge is modified [that is, when (i) is invalid], the eigenenergy of the localized states has pronounced dependence on the electron momentum along the edge, and the edge-state branches appear in electron-hole symmetric pairs. At the same time, when graphene π-orbitals hybridize with the non-carbon orbitals near the edge [condition (ii) is no longer true, see Fig.1], the resultant pair of localized edge bands is nearly flat, with no electron-hole symmetry.

These states may be detected experimentally with the help of STM.

References:

[1] K. Nakada, M. Fujita, G. Dresselhaus, and M.S. Dresselhaus, Phys. Rev. B 54 (1996) 24.

[2] Y. Zhao, W. Li, and R. Tao, Physica B: Condensed Matter 407 (2012) 4.

Seminars

Dr. Jacob Biamonte, ISI Foundation, Italy

Universal adiabatic quantum computation

Aug. 27th, Tuesday, 2013, 14:00

4F seminar room (435-437), Main Research Bldg.

The complexity of finding the ground state energy of interacting spins unites computer science and physics in a profound way. On the one hand, it ties computational complexity directly to solving a problem of practical importance regularly faced in several areas of modern physics. On the other hand, measuring the ground state energy gap of such a physical spin system would enable one to solve such problems directly. How then might we extend current adiabatic computing architectures being developed for practical calculations in a way to also enable them to perform universal quantum computation?

Seminars

Dr. Pulak Kumar Ghosh, Quantum Condensed Matter Research Group, CEMS, RIKEN

Quantum effects in energy and charge transfer in a wheel-shaped artificial photosynthetic complex

Aug. 26th, Monday, 2013, 19:00

4F seminar room (435-437), Main Research Bldg.

We investigate the quantum dynamics of energy and charge transfer in a wheel-shaped artificial photosynthetic antenna-reaction center complex. This complex consists of six light-harvesting pigments and an electron-acceptor fullerene. To describe quantum effects on a femtosecond time scale, we derive a set of modified Redfield equations taking into account the time evolution of the off-diagonal elements of the density matrix. We show that the energy of the initially-excited antenna chromophores is efficiently funneled to the porphyrin-fullerene reaction center, where a charge-separated state is set up in a few picoseconds, with a quantum yield of the order of 95 %. In the single-exciton regime, with one antenna chromophore being initially excited, we observe quantum beatings of energy between two resonant antenna pigments with a decoherence time of ~ 100 fs. We also analyze the double-exciton regime, when two porphyrin molecules involved in the reaction center are initially-excited. In this regime we obtain pronounced quantum oscillations of the charge on the fullerene molecule with a decoherence time of about 20 fs (at liquid nitrogen temperatures). These results show a way to directly detect quantum effects in artificial photosynthetic systems.

Seminars

Dr. Robert Johansson, Quantum Condensed Matter Research Group, CEMS, RIKEN

Engineered quantum mechanics with nano-electronics

Aug. 26th, Monday, 2013, 17:00

4F seminar room (435-437), Main Research Bldg.

Nanoelectrical and nanomechanical devices can be engineered to behave quantum mechanically at cryogenic temperatures. With different device designs, a rich variety of quantum systems can be implemented, including artificial atoms, resonators, controllable and tunable coupling and high-fidelity measurements. The intrinsic nonlinearities and dissipation-free nature of Josephson junctions makes superconducting electrical circuits an ideal test-bed for experiments on analogues and simulations of quantum mechanical phenomena from different fields of physics. In particular, many problems from quantum optics, atomic physics, quantum field theory, and solid-state physics can be explored in nanoelectrical circuits, and often with significant advantages. Here I will first give a brief overview of recent progress in quantum electronics and how these devices can be used as quantum simulators. I will continue with a summary of a few selected projects that I have worked on, including nanoelectrical implementations of the Dynamical Casimir effect, single-atom lasing and Landau-Zener-Stuckelberg interferometry. I will also briefly describe a computational project where we have developed a highly versatile framework for quantum dynamics simulations that is suitable for computational analysis of the evermore complex nanoelectrical devices.

Seminars

Dr. Mark Everitt, Loughborough University, UK

Enhanced engineering of Schrodinger cat states.

Aug. 8th, Thursday, 2013, 13:30

4F seminar room (435-437), Main Research Bldg.

We look at engineering macroscopically distinct superpositions of states (Schrodinger cat) in fields, ensembles of spins and SQUIDs and, for selected examples, the effects of decoherence may be mitigated or used to advantage (note we will also make use of a new spin Wigner function).

Seminars

Dr. Justin Dressel, Quantum Condensed Matter Research Group, CEMS, RIKEN

Weakly Measuring Observables with Generalized Eigenvalues

Jul. 30th, Thursday, 2013, 14:00

4F seminar room (435-437), Main Research Bldg.

The common wisdom in quantum mechanics is that observables are intrinsically defined by projective measurements and eigenvalues. We challenge this wisdom by demonstrating a general algebraic formalism for completely measuring observables using indirect detectors. We find that the eigenvalues are inappropriate when considering noisy detectors that do not make projective measurements; instead one must assign generalized eigenvalues to the accessible detector outcomes. We illustrate this procedure with a simple example: a polarization measurement using only two correlated spatial modes produced by a glass microscope coverslip. We then use this simple system to violate nonlocal Leggett-Garg inequalities by post-selecting the weakened measurements. We also revisit the "weak measurement" protocol of Aharonov et al. and solve it exactly in terms of the general formalism, showing the universality of weak values in the process.

Workshops

PHENIX Workshop on Physics Prospects with Detector and Accelerator Upgrades

July 29 - Aug.2, 2013

Nishina Hall, RIKEN

http://indico2.riken.jp/indico/conferenceDisplay.py?confId=1221

The PHENIX experiment has been successfully contributing to understand of our long standing questions in nuclear/ hadron physics, since the experiment was launched in 2001. Given the abundant physics we have addressed so far, we have been proposing to build a electron-ion collider at RHIC as a further step on addressing still unexplored issues in the field. This work fest is an opportunity to introduce this attractive project widely to east Asian nuclear physicists who are not necessarily be involved in current PHENIX/RHIC program and may prompt the interest on this topic. This work fest is sponsored by Radiation Labororatory and iTHES.

iTHES mini-workshop on

Exploration of hidden symmetries in atomic nuclei

July 27th, 2013

RIKEN

Symmetry is a key element of discovery of fundamental principles in a variety of physical systems. The ubiquitous quasi-degeneracy between single-particle orbitals (n-1, l+2, j=l+3/2) and (n, l, j=l+1/2) indicates a kind of hidden symmetry in atomic nuclei which was found in 1960s by two groups (Arima, Harvey, and Shimizu; Hecht and Adler). This is the so-called pseudospin symmetry (PSS). Both the splitting of spin doublets and pseudospin doublets play critical roles in the evolution of magic numbers in exotic nuclei discovered by modern spectroscopic studies with RIB facilities.

Since the PSS was recognized as a relativistic symmetry in 1990s, it has been suggested that this symmetry is relevant to the QCD sum rule and shares the same kind of origin of the spin symmetry (SS) in hadrons spectra. During the past decade, many special features were investigated and many new concepts were introduced. In addition, the semi-classical theory for shell structure has been extensively developed. In this mini-workshop, we will exchange ideas on these recent progresses and deepen our understanding of the conservation and breaking of SS and PSS in a quantitative and interdisciplinary way. Possible topics include PSS in deformed nuclei, exact PSS in resonant states, SS in anti-nucleon spectra, PSS within supersymmetric quantum mechanics, shell structures in finite quantum systems in terms of periodic orbits, and so on.

Organizers:

Haozhao Liang (RIKEN)

Jie Meng (Peking U., China)

Takashi Nakatsukasa (RIKEN)

Speakers:

Kenichiro Arita (Nagoya Institute of Technology) Joseph N. Ginocchio* (Los Alamos National Lab, US) Ikuko Hamamoto (RIKEN) Stefan Typel* (GSI, Germany) Shan-Gui Zhou (Institute of Theoretical Physics, CAS, China)

https://indico2.riken.jp/indico/conferenceDisplay.py?confId=1237

Seminars

Dr. T. Kanazawa (Univ. Tokyo)

Symmetries and effective field theories in QCD

July 26 (Fri.) 10:00am-11:00am

room 435-437, main building (4th floor)

The first part of this talk is planned to be a rudimentary introduction to gauge theories and strong interactions. In the second part I will review my own contributions to understanding dense QCD-like theories through effective field theories and matrix models.

Workshops

Current challenges in the Physics of Neutron Star

July 5 (Fri.) 2013, 13:30-

room 433, Main building

13:30-14:15 Mark Alford (Washington U.)

"Hybrid stars and the quark matter equation of state"

14:15-14:45 Kota Masuda (Tokyo/RIKEN)

"Hadron-Quark Crossover and Massive Hybrid Stars"

14:45-15:00 Break

15:00-15:45 Thomas Hell (Munich)

"How neutron stars constrain the nuclear equation of state"

15:45-16:15 Nobutoshi Yasutake (Chiba-tech.) "TBA"

16:15- Free discussions

Seminars

Dr. Konstantin Bliokh, A. Usikov Institute for Radiophysics & Electronics, National Academy of Sciences of Ukraine

Electron vortex beams in a magnetic field: A new twist on Landau levels and Aharonov-Bohm states

Jul. 4th, Thursday, 2013, 13:30

4F seminar room (435-437), Main Research Bldg.

We examine the propagation of the recently-discovered electron vortex beams in a longitudinal magnetic field. We consider both the Aharonov-Bohm configuration with a single flux line and the Landau case of a uniform magnetic field. While stationary Aharonov-Bohm modes represent Bessel beams with flux- and vortex-dependent probability distributions, stationary Landau states manifest themselves as non-diffracting Laguerre-Gaussian beams. Furthermore, the Landau-state beams possess field- and vortex-dependent phases: (i) the Zeeman phase from coupling the quantized angular momentum to the magnetic field and (ii) the Gouy phase, known from optical Laguerre-Gaussian beams. Remarkably, together these phases determine the structure of Landau energy levels. This unified Zeeman-Landau-Gouy phase manifests itself in a nontrivial evolution of images formed by various superpositions of modes. We demonstrate that, depending on the chosen superposition, the image can rotate in a magnetic field with either Larmor, cyclotron, or zero frequency. At the same time, its centroid always follows the classical trajectory, in agreement with the Ehrenfest theorem. Our results open up an avenue for the direct electron-microscopy observation of fundamental properties of free quantum electron states in magnetic fields.

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