aspuru-list February 2015

aspuru-list@lists.fas.harvard.edu

19 participants
48 discussions

[Aspuru-Guzik group list] One more spot for Theochem speaker Benoit Roux

by Martin Blood-Forsythe

Dear colleagues, I have one more meeting available 2-2:30pm, on Tuesday for discussion with Benoit Roux. His group does lots of research involving polarizable forcefields, implicit solvation models, and free energy calculations, so if studying biomolecules is of interest to you I highly recommend meeting with him! We also have a group slot at 5-5:30pm. Best wishes, -Martin

9 years, 1 month

[Aspuru-Guzik group list] March MBTA Pass

by Marlon Cummings

Hi Guys: My wife has an MBTA pass for the month of March. She is selling it for $37 -- face value. If you're interested, please let me know and you can get it Monday morning. Thanks, Marlon. ----------------- Marlon G. Cummings Lab Manager, Aspuru-Guzik Group Mallinckrodt M112 Department of Chemistry and Chemical Biology Harvard University 12 Oxford Street Cambridge, MA 02138 617-496-9964 617-496-9411 (fax) http://aspuru.chem.harvard.edu/

9 years, 1 month

[Aspuru-Guzik group list] 03/04/2015 - Vladimir Shalaev - HQOC/ITAMP Joint Quantum Sciences Seminar, 4PM

by Coleman, Karl

HQOC/ITAMP Joint Quantum Sciences Seminar Wednesday, March 4, 2015 4:00 PM, Jefferson 250 Prof. Vladimir Shalaev, Purdue University Merging Metamaterials with Quantum Photonics Over the past decade, one of the major focuses for the area of nanophotonics has been on developing a new class of “plasmonic” structures and “metamaterials” as potential building blocks for advanced optical technologies, including data processing, exchange and storage; a new generation of cheap, enhanced-sensitivity sensors; nanoscale-resolution imaging techniques; new concepts for energy conversion including improved solar cells, as well as novel types of light sources. Designing plasmonic metamaterials with versatile properties that can be tailored to fit almost any practical need promises a range of potential breakthroughs. However, to enable these new technologies based on plasmonics, grand limitations associated with the use of metals as constituent materials must be overcome. In the structures demonstrated so far, too much light is absorbed in the metals (such as silver and gold) commonly used in plasmonic metamaterials. The fabrication and integration of metal nanostructures with existing semiconductor technology is challenging, and the materials need to be more precisely tuned so that they possess the proper optical properties to enable the required functionality. Our recent research aims at developing new designs and plasmonic materials (other than the metals used so far) that will form the basis for future low-loss, durable, CMOS-compatible devices that could enable full-scale development of the plasmonic and metamaterial technologies. Can these recently developed plasmonic structures and metamaterials based on new material platforms help in unfolding the potential of quantum photonics? We report on our first efforts in that direction. Alex High, Park Lab Visible Frequency Hyperbolic Metasurfaces Postdoc Presentation begins at 4:00 PM Refreshments are served from 4:10-4:30 PM Guest Presentation begins at 4:30 PM Karl Coleman HQOC Laboratory Administrator Faculty Assistant to Profs. Greiner and Lukin Harvard University Department of Physics 17 Oxford Street Cambridge, MA 02138 P: (617) 496-2544 F: (617) 496-2545

9 years, 1 month

[Aspuru-Guzik group list] [qip] Friday the 27th

by Edward Farhi

Hi Quanta Tomorrow, Friday the 27th, we will meet in 6-310 at 11:00. We will have a presentation by our own postdoc Nima Lashkari who will speak on an "Information theorist's guide to quantum fields and gravity”. At 1:30 we will have a talk by Ramis Movassagh. See you there! Eddie Edward Farhi farhi(a)mit.edu _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

9 years, 1 month

[Aspuru-Guzik group list] ITAMP lunch seminar: Michael Knap (2/27)

by Singh, Swati

*ITAMP Topical Lunch Discussion* Date: Friday, Feb. 27th Time: 12:00-1:30 pm Pizza will be served. Location: B-106 @ Center for Astrophysics (60 Garden Street) Directions: after entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, and B-106 is there. *Speaker: *Dr. Michael Knap (Harvard) *Title:* Dynamics of disordered many-body systems: from thermal transport to many-body localization *Abstract:* This talk provides an introduction to disordered interacting many-body systems. We analyze the generic phase diagram of such systems, which consists of a thermal phase at weak disorder and a many-body localized (MBL) phase at strong disorder. Near the phase transition, Griffiths effects become important which result in new rare-region dominated phases. Furthermore, we discuss the response of the different phases to transport probes (e.g. conductivity) as well as non-transport probes (e.g. spin-echo interferometry) and demonstrate how the peculiar properties of the MBL phase can be unveiled. -- Dr. Swati Singh Institute for Theoretical Atomic, Molecular, and Optical Physics (ITAMP), Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-14, Cambridge, MA 02138 https://www.cfa.harvard.edu/~ssingh/

9 years, 1 month

[Aspuru-Guzik group list] Old Group Computers/Monitors (VERY OLD Ones)

by Marlon Cummings

Dear friends: Kai has agreed to lead the computer recycling effort. If you have an old (cleaned) computer and non-working monitor in your work space, please let him know. He will coordinate to have them recycled over in the science center. Please feel free to assist. For for folks in M104, please be kind by placing those computers in one area by the door for Kai with a sign (For Recycling). For the MCB squatters, please contact Kai directly. Thanks, Marlon. ------------- Marlon G. Cummings Lab Manager, Aspuru-Guzik Group Mallinckrodt M112 Department of Chemistry and Chemical Biology Harvard University 12 Oxford Street Cambridge, MA 02138 617-496-9964 617-496-9411 (fax) http://aspuru.chem.harvard.edu/

9 years, 1 month

[Aspuru-Guzik group list] [Aspuru-meetings-list] Group Meeting, 2/26, 2:30pm Div Room -- mini APS meeting

by Jennifer Wei

Hi everyone, We will have a special group meeting tomorrow. This will feature Salvatore, Ryan, and Gian presenting the APS talks they will be giving next week. The schedule is as follows. 2.30pm - 2.50pm Salvatore 2.50pm - 3.10pm Ryan 3.10pm - 3.30pm Gian Giacomo Please see below for titles and abstracts of their talks. Cheers, Jennifer --------------------------------------- Annealing of Embedded Spin Glasses Salvatore Mandra We discuss recent results on thermal and quantum annealing of random spin glasses on fully-connected graphs and on fully-connected bipartite graphs. After the description of the embedding of their classical Hamiltonian onto Chimera graphs, we discuss what are the optimal embedding parameters, in relation with the signatures of the quantum phase transitions occurring during the annealing. Finally, we compare numerical simulations and analytical expectations for both the embedded spin glass models with results on the non-embedded models and with runs on D-Wave Machine installed at NASA Ames. -------------------------------------------- The Chemical Basis of Trotter Errors in Quantum Simulations of Chemistry Ryan Babbush Although the simulation of quantum chemistry is one of the most anticipated applications of quantum computing, the scaling of known upper bounds on the complexity of these algorithms is daunting. Prior work has bounded errors due to Trotterization in terms of the norm of the error operator and analyzed scaling with respect to the number of spin-orbitals. However, we find that these error bounds can be loose by up to sixteen orders of magnitude for some molecules. Furthermore, numerical results for small systems fail to reveal any clear correlation between ground state error and number of spin-orbitals. We instead argue that chemical properties, such as the maximum nuclear charge in a molecule and the filling fraction of orbitals, can be decisive for determining the cost of a quantum simulation. Our analysis motivates several strategies to use classical processing to further reduce the required Trotter step size and to estimate the necessary number of steps, without requiring additional quantum resources. ------------------------------------------------ Dimensionality reduction for adiabatic quantum optimizer in presence of local disorder Gian Guerreschi Adiabatic quantum optimization (AQO) is a procedure to solve a vast class of optimization problems by slowly changing the Hamiltonian of a quantum system. The evolution time necessary for the algorithm to be successful scales inversely with the minimum energy gap encountered during the dynamics. Unfortunately, the direct calculation of such gap is strongly limited by the exponential growth in dimensionality of quantum systems. Although many special-purpose methods have been devised to reduce the effective dimensionality of the Hilbert space, they are strongly limited to particular classes of problems with evident symmetries. Here, we propose and implement a reduction method that does not rely on any explicit symmetry and which requires, under certain but quite general conditions, only a polynomial amount of classical resources. A natural and important application is the analysis of AQO in presence of local disorder. In this respect, we show that AQO, even when affected by random noise, can still be faster than any classical algorithm. _______________________________________________ Aspuru-meetings-list mailing list Aspuru-meetings-list(a)lists.fas.harvard.edu https://lists.fas.harvard.edu/mailman/listinfo/aspuru-meetings-list

9 years, 1 month

[Aspuru-Guzik group list] Cloud Forest and MCB 1st Floor (AAG Group Members)

by Marlon Cummings

Let's starting purging/cleaning and start preparing to move. Move on the move by Thursday. ----------------- Marlon G. Cummings Lab Manager, Aspuru-Guzik Group Mallinckrodt M112 Department of Chemistry and Chemical Biology Harvard University 12 Oxford Street Cambridge, MA 02138 617-496-9964 617-496-9411 (fax) http://aspuru.chem.harvard.edu/

9 years, 1 month

[Aspuru-Guzik group list] [qip] Seminar - Ramis Movassagh (this Friday)

by Cyril Stark

Dear All, The qip seminar series will be starting agin this Friday. The first speaker of this semester is Ramis. Title: A counterexample to the area law for quantum matter Abstract: Entanglement is a quantum correlation which does not appear classically, and it serves as a resource for quantum technologies such as quantum computing. The area law says that the amount of entanglement between a subsystem and the rest of the system is proportional to the area of the boundary of the subsystem and not its volume. A system that obeys an area law can be simulated more efficiently than an arbitrary quantum system, and an area law provides useful information about the low-energy physics of the system. It was widely believed that the area law could not be violated by more than a logarithmic factor (e.g. based on critical systems and ideas from conformal field theory) in the system’s size. We introduce a class of exactly solvable one-dimensional models which we can prove have exponentially more entanglement than previously expected, and violate the area law by a square root factor. We also prove that the gap closes as n^{-c}, where c >= 2, which rules out conformal field theories as the continuum limit of these models. In addition to using recent advances in quantum information theory, we have drawn upon various branches of mathematics and computer science in our work and hope that the tools we have developed may be useful for other problems as well. (Joint work with Peter Shor) The talk is at 1:30pm on Friday (Feb 27) in the Cosman Seminar Room (6C-442). Hope to see you there, Cyril — Cyril Stark Center for Theoretical Physics Massachusetts Institute of Technology 77 Massachusetts Ave, 6-304 Cambridge, MA 02139, USA _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip

9 years, 1 month

[Aspuru-Guzik group list] Theochem next week: Benoit Roux

by Martin Blood-Forsythe

Hi all, Professor Benoit Roux from the University of Chicago will be visiting Harvard next Tuesday afternoon (03/03) for the Theochem lecture series Please let me know if you're interesting in a half hour or an hour meeting with him. We have spots available for dinner as well. He will be giving the Theochem lecture on Wednesday (03/04) at MIT room 4-163. The talk title and abstract are below. Thanks, -Martin --------------------------------------------------- Martin Blood-Forsythe Graduate Student in Physics Harvard University Aspuru-Guzik Lab *"Membrane Potential And Small Charge Movement In Membrane Protein Systems"* 03/04/15 4:00PM MIT Building 4, Room 163 Benoit Roux University of Chicago Abstract: A theoretical framework is elaborated to account for the effect of a transmembrane potential in explicit solvent computer simulations of membrane proteins [1]. The framework relies on a modified Poisson-Boltzmann equation previously developed from statistical mechanical considerations [2]. It is shown that a simulation with a constant external electric field applied in the direction normal to the membrane is equivalent to the influence of surrounding infinite baths maintained to a voltage difference via ion-exchanging electrodes connected to an electromotive force. It is also shown that the linearly-weighted displacement charge within the simulation system tracks the net flow of charge through the external circuit comprising the electromotive force and the electrodes. Using a statistical mechanical reduction of the degrees of freedom of the external system, three distinct theoretical routes are formulated and examined for the purpose of characterizing the free energy of a protein embedded in a membrane that is submitted to a voltage difference: the W-route constructed from the variations in the voltage-dependent potential of mean force along a reaction path connecting two conformations of the protein, the Q-route based on the average displacement charge as a function of the conformation of the protein, and the G-route based on the relative charging free energy of specific residues, with and without applied membrane potentials. The theory is applied to examine atomic models of the Kv1.2 potassium channel in the active and resting state [2]. Methodologies to treat asymmetric membrane conditions have also been developed [3]. Calculations of the fractional transmembrane potential, acting upon key charged residues of the voltage sensing domain of the Kv1.2 potassium channel, reveals that the applied field varies rapidly over a narrow region of 10 to 15 Angstroms, corresponding to the outer leaflet of the bilayer [4]. The focused field allows the transfer of a large gating charge without translocation of S4 across the membrane. The theory is also applied to examine the binding of sodium and potassium ions to the Na,K ATPase membrane pump. 1. B. Roux. Influence of the membrane potential on the free energy of an intrinsic protein. Biophysical Journal. 1997;73(6):2980-9. 2. B. Roux. The membrane potential and its representation by a constant electric field in computer simulations. Biophys J. 2008;95(9):4205-16. 3. F. Khalili-Araghi, B. Ziervogel, J.C. Gumbart, B. Roux. Molecular dynamics simulations of membrane proteins under asymmetric ionic concentrations. J Gen Physiol. 2013;142(4):465-75. 4. F. Khalili-Araghi, V. Jogini, V. Yarov-Yarovoy, E. Tajkhorshid, B. Roux, K. Schulten. Calculation of the gating charge for the Kv1.2 voltage-activated potassium channel. Biophys J. 2010;98(10):2189-98.

9 years, 1 month

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aspuru-list February 2015