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enIQI Weekly Seminar: Lower bounds on the non-Clifford resources for quantum computationsbjleung@caltech.edu (Bonnie Leung)IQI Weekly Seminar<strong>Speaker(s):</strong> Michael Beverland (Microsoft)<br><strong>Location:</strong> Annenberg 213<br><p><b>Abstract</b>: Treating stabilizer operations as free, we establish lower-bounds on the number of resource states, also known as magic states, needed to perform various quantum computing tasks. Our bounds apply to adaptive computations using measurements with an arbitrary number of stabilizer ancillas. We consider (1) resource state conversion, (2) single-qubit unitary synthesis, and (3) computational subroutines including the modular adder and the multiply-controlled-Z gate. To prove our resource conversion bounds we introduce two new monotones, the stabilizer nullity and the dyadic monotone, and make use of the already-known stabilizer extent. We consider conversions that borrow resource states, known as catalyst states, and return them at the end of the algorithm. We show that catalysis is necessary for many conversions and introduce new catalytic conversions, some of which are close to optimal. By finding a canonical form for post-selected stabilizer computations, we show that approximating a single-qubit unitary to within diamond-norm precision epsilon requires at least 1/7 log_2(1/epsilon) - 4/3 T states on average. This is the first ever lower bound that applies to fully general synthesis protocols; those using fall-back, mixing techniques, and where the number of ancillas used can depend on epsilon. Up to multiplicative factors, we optimally lower bound the number of T or CCZ states needed to implement the ubiquitous modular adder and multiply-controlled-Z gate. When the probability of Pauli measurement outcomes is 1/2, some of our bounds become tight to within a small additive constant.</p><p><a href="https://arxiv.org/abs/1904.01124">https://arxiv.org/abs/1904.01124</a></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p>Tue, 24 Sep 2019 15:00:00 -0700http://cms.caltech.edu/events/86683TCS+ Talk: Chasing Convex Bodiesbjleung@caltech.edu (Bonnie Leung)TCS+ Talk<strong>Speaker(s):</strong> Mark Sellke (Stanford)<br><strong>Location:</strong> Annenberg 322<br><p><b>Abstract:</b> I will explain our recent understanding of the chasing convex bodies problem posed by Friedman and Linial in 1991. In this problem, an online player receives a request sequence K_1,...,K_T of convex sets in d dimensional space and moves his position online into each requested set. The player's movement cost is the length of the resulting path. Chasing convex bodies asks if there an online algorithm with cost competitive against the offline optimal path. This is both an challenging metrical task system and (equivalent to) a competitive analysis view on online convex optimization.</p><p>This problem was open for d>2 until last year but has recently been solved twice. The first solution gives a 2^{O(d)} competitive algorithm while the second gives a nearly optimal min(d,sqrt(d*log(T))) competitive algorithm for T requests. The latter result is based on the Steiner point, which is the exact optimal solution to a related geometric problem called Lipschitz selection and dates from 1840. In the talk, I will briefly outline the first solution and fully explain the second.</p><p>Partially based on joint works with Sébastien Bubeck, Bo'az Klartag, Yin Tat Lee, and Yuanzhi Li.</p><p></p>Wed, 25 Sep 2019 10:00:00 -0700http://cms.caltech.edu/events/86728CMX Lunch Seminar: Primal dual methods for Wasserstein gradient flowsjbrink@caltech.edu (Jolene Brink)CMX Lunch Seminar<strong>Speaker(s):</strong> Jose A. Carrillo (Imperial College London)<br><strong>Location:</strong> Annenberg 213<br><p></p><p>Combining the classical theory of optimal transport with modern operator splitting techniques, I will present a new numerical method for nonlinear, nonlocal partial differential equations, arising in models of porous media,materials science, and biological swarming. Using the JKO scheme, along with the Benamou-Brenier dynamical characterization of the Wasserstein distance, we reduce computing the solution of these evolutionary PDEs to solving a sequence of fully discrete minimization problems, with strictly convex objective function and linear constraint. We compute the minimizer of these fully discrete problems by applying a recent, provably convergent primal dual splitting scheme for three operators. By leveraging the PDE’s underlying variational structure, ourmethod overcomes traditional stability issues arising from the strong nonlinearity and degeneracy, and it is also naturally positivity preserving and entropy decreasing. Furthermore, by transforming the traditional linear equality constraint, as has appeared in previous work, into a linear inequality constraint, our method converges in fewer iterations without sacrificing any accuracy. Remarkably, our method is also massively parallelizable and thus very efficient in resolving high dimensional problems. We prove that minimizers of the fully discrete problem converge to minimizers of the continuum JKO problem as the discretization is refined, and in the process, we recover convergence results for existing numerical methods for computing Wasserstein geodesics. Finally, we conclude with simulations of nonlinear PDEs and Wasserstein geodesics in one and two dimensions that illustrate the key properties of our numerical method.</p>Wed, 25 Sep 2019 12:00:00 -0700http://cms.caltech.edu/events/86393Autoregressive Simulation of Many-body Quantum Systems: Autoregressive Simulation of Many-body Quantum Systemszeldaw@caltech.edu (Zelda Wong)Autoregressive Simulation of Many-body Quantum Systems<strong>Speaker(s):</strong> Or Sharir ()<br><strong>Location:</strong> Annenberg 213<br><p></p><p>Understanding phenomena in systems of many interacting quantum particles, known as quantum many-body systems, is one of the most sought-after objectives in contemporary physics research. The challenge of simulating such systems lies in the extensive resources required for exactly modeling quantum wave-functions, which grows exponentially with the number of particles. Recently, neural networks were demonstrated to be a promising approximation method of quantum wave functions. However, thus far, this approach was mostly focused on more traditional architectures such as Restricted Boltzmann Machines and small fully-connected networks. In this talk, we propose a method for scaling this approach to support large modern architecture. Though significantly more expressive, such architectures do not lend themselves to the conventional methods for employing neural networks for simulating quantum systems. A key part of the simulation is to sample according to the underlying distribution of particle configurations. Current methods rely on Markov-Chain Monte-Carlo sampling, which is too expensive for use with modern architectures, effectively limiting their usable size and capacity. Inspired by recent generative models, we propose a specialized deep convolutional architecture that supports efficient and exact sampling, completely circumventing the need for Markov Chain sampling. We demonstrate our approach can obtain accurate results on larger system sizes than those currently accessible to other neural-network representation of quantum states.</p><p></p>Fri, 27 Sep 2019 11:00:00 -0700http://cms.caltech.edu/events/86608IST Lunch Bunch: How deep learning is transforming earthquake seismologydiane@cms.caltech.edu (Diane Goodfellow)IST Lunch Bunch<strong>Speaker(s):</strong> Zach Ross (Caltech)<br><strong>Location:</strong> Annenberg 105<br><p> </p><p>The volume of seismic data recorded around the world is exploding. At the same time, standard techniques for earthquake detection still routinely miss the smallest earthquakes, which represent the vast majority of seismic activity that occurs naturally. These hidden events, however, are essential to advancing our understanding of earthquakes and faults because they fill in the gaps between larger events and provide a more complete picture of how earthquake sequences evolve in space and time. Reliable measurements of time and amplitude properties of seismic waves also enable tomographic images of Earth’s interior, and delineate the earthquake rupture process below the surface. Earthquake early warning requires rapid identification that a large earthquake has occurred with only a tiny fraction of the total data available at that moment.</p><p>Seismology is a field that is rich in labeled data and has many difficult data-driven problems with some unique challenges. These aspects have led to a surge in recent applications of deep learning to seismology, resulting in state-of-the-art performance on numerous tasks. In this talk, I will discuss several important problems in seismology related to earthquake detection, localization, and earthquake early warning, and the development of deep learning algorithms to address them. Machine learning will play a prominent role in the future of seismology by improving real-time earthquake monitoring, as well as advancing earthquake science to the next level from analysis of large high-dimensional datasets.</p>Tue, 08 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86468TCS+ Talk: TBAbjleung@caltech.edu (Bonnie Leung)TCS+ Talk<strong>Speaker(s):</strong> Shachar Lovett (UCSD)<br><strong>Location:</strong> Annenberg 322<br><p><b>Abstract:</b> TBA</p>Wed, 09 Oct 2019 10:00:00 -0700http://cms.caltech.edu/events/86729Finance Seminar: Policy Announcement Designsabrina@hss.caltech.edu (Sabrina Hameister)Finance Seminar<strong>Speaker(s):</strong> Semyon Malamud (Ecole Polytechnique Fédérale de Lausanne)<br><strong>Location:</strong> Baxter B125<br><p>Please check later for additional details</p><p><i>Finance Seminars at Caltech are funded through the generous support of The Ronald and Maxine Linde Institute of Economic and Management Sciences (lindeinstitute.caltech.edu).</i></p>Thu, 10 Oct 2019 16:00:00 -0700http://cms.caltech.edu/events/86207IST Lunch Bunch: TBAdiane@cms.caltech.edu (Diane Goodfellow)IST Lunch Bunch<strong>Speaker(s):</strong> Stefano Ermon (Stanford)<br><strong>Location:</strong> Annenberg 105<br><p>TBA</p>Tue, 15 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86470CMX Lunch Seminar: TBAjbrink@caltech.edu (Jolene Brink)CMX Lunch Seminar<strong>Speaker(s):</strong> Rupert Frank (Caltech)<br><strong>Location:</strong> Annenberg 213<br><p>TBA</p>Wed, 16 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86674IQIM Postdoctoral and Graduate Student Seminar: Defect-Level Switching: A New Mechanism for Electronic Devicesmarciab@caltech.edu (Marcia Brown)IQIM Postdoctoral and Graduate Student Seminar<strong>Speaker(s):</strong> Rafael Jaramillo (MIT)<br><strong>Location:</strong> East Bridge 114<br><p><b>Abstract:</b> Many semiconductors exhibit large and persistent photoconductivity due to lattice relaxations that follow light absorption; examples are ZnO, CuInS2, and AlGaAs [1-3]. We recently demonstrated that a similar phenomenon is responsible large and persistent photoconductivity in CdS [4]. Sulfur vacancies are deep donors in the dark, but under photoexcitation they convert to shallow donors. This donor-level switching mechanism suggests a new way to control conductivity in electronic devices.</p><p>In this talk we will first discuss the mechanism of large and persistent photoconductivity. We will then introduce the concept of defect-level switching, and demonstrate electrical devices that operate by this mechanism. The devices exhibit bipolar resistive switching due to triggering the same lattice relaxations that cause photoconductivity – akin to photoconductivity, but without the photons. We also present complementary studies that support the defect-level switching hypothesis, including Raman spectromicroscopy, capacitance profiling, numerical simulation, and systematic material substitutions. We summarize with an outlook for defect-level switching as a new and generalizable mechanism for designing electronic devices, including selectors and memristors for analog computing, and employing a selection of different switching materials.</p><p>If time allows we will briefly discuss ongoing work in other fields including layered chalcogenides for integrated photonics, and chalcogenide perovskite semiconductors.</p><p>[1] S. B. Zhang, S.-H. Wei & A. Zunger, Phys. Rev. B <b>63</b>, 075205 (2001).</p><p>[2] S. Lany & A. Zuner, Phys. Rev. B <b>72</b>, 035215 (2005).</p><p>[3] P. M. Mooney, <i>Journal of Applied Physics</i> <b>67,</b> R1–R26 (1990).</p><p>[4] H. Yin, A. Akey & R. Jaramillo, Phys. Rev. Mater. <b>2</b>, 084602 (2018).</p><p></p>Fri, 18 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86667H.B. Keller Colloquium: Machine Learning and Dynamical Systems meet in Reproducing Kernel Hilbert Spaces.dbohler@caltech.edu (Diana Bohler)H.B. Keller Colloquium<strong>Speaker(s):</strong> Boumediene Hamzi (Imperial College London), ()<br><strong>Location:</strong> Annenberg 105<br><p></p>Mon, 21 Oct 2019 16:00:00 -0700http://cms.caltech.edu/events/86474TCS+ Talk: TBAbjleung@caltech.edu (Bonnie Leung)TCS+ Talk<strong>Speaker(s):</strong> Hao Huang (Emory University)<br><strong>Location:</strong> Annenberg 322<br><p><b>Abstract:</b> TBA</p>Tue, 22 Oct 2019 10:00:00 -0700http://cms.caltech.edu/events/86730CMX Lunch Seminar: TBAjbrink@caltech.edu (Jolene Brink)CMX Lunch Seminar<strong>Speaker(s):</strong> Steven Low (Caltech)<br><strong>Location:</strong> Annenberg 213<br><p>TBA</p>Wed, 23 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86675Finance Seminar: Topic to be announcedsabrina@hss.caltech.edu (Sabrina Hameister)Finance Seminar<strong>Speaker(s):</strong> Stavros Panageas (UCLA)<br><strong>Location:</strong> Baxter B125<br><p>Please check later for additional details</p><p><i>Finance Seminars at Caltech are funded through the generous support of The Ronald and Maxine Linde Institute of Economic and Management Sciences (lindeinstitute.caltech.edu).</i></p>Thu, 24 Oct 2019 16:00:00 -0700http://cms.caltech.edu/events/86166Social and Information Sciences Laboratory (SISL) Seminar: Topic to be announcedmmartin@caltech.edu (Mary Martin)Social and Information Sciences Laboratory (SISL) Seminar<strong>Speaker(s):</strong> Kathleen Ngangoue (New York University)<br><strong>Location:</strong> Baxter 125<br><p>Please check later for additional details</p>Fri, 25 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86639CMX Lunch Seminar: TBAjbrink@caltech.edu (Jolene Brink)CMX Lunch Seminar<strong>Speaker(s):</strong> Gianluca Favre (University of Vienna)<br><strong>Location:</strong> Annenberg 213<br><p>TBA</p>Wed, 30 Oct 2019 12:00:00 -0700http://cms.caltech.edu/events/86676Watson Lecture - Opportunities in Atomic-Scale Legoland: From Novel Electronic Phases to Quantum Devices: TBDevents@caltech.edu (the Caltech Ticket Office)Watson Lecture - Opportunities in Atomic-Scale Legoland: From Novel Electronic Phases to Quantum Devices<strong>Speaker(s):</strong> Stevan Nadj-Perge (Caltech)<br><strong>Location:</strong> Beckman Auditorium<br><p>Are there limits to how small electronic devices can be? In this lecture, Nadj-Perge will discuss materials that are only a few atoms thick and how, just like Lego bricks, they can be stacked together in limitless different configurations to explore new phenomena at atomic scales.</p><p>This event is free; no tickets or reservations are required. A minimum of 700 seats will be available on a first-come, first-served basis, beginning at 7:30 p.m. Reserved section tickets are available to members of <a href="/content/fob">The Friends of Beckman Auditorium</a> and the <a href="http://associates.caltech.edu/">Caltech Associates</a>, and to <a href="https://www.alumni.caltech.edu/">Caltech alumni</a>.</p><p><b>About the Speaker</b></p><a href="http://www.eas.caltech.edu/people/stevannp">Stevan Nadj-Perge</a> is Assistant Professor of Applied Physics and Materials Science and a KNI-Wheatley Scholar in the Division of Engineering and Applied Science.<p><b>About the Series</b></p>Since 1922, The Earnest C. Watson Lecture Series has has brought Caltech's most innovative scientific research to the public. The series is named for Earnest C. Watson, a professor of physics at Caltech from 1919 until 1959. Spotlighting a small selection of the pioneering research Caltech's faculty is currently conducting, the Watson Lectures are geared toward a general audience, as part of the Institute's ongoing commitment to benefiting the local community through education and outreach. Through a gift from the estate of Richard C. Biedebach, the lecture series is able to highlight an assistant professor's research each season.<p>Find CaltechLive! on <a href="https://facebook.com/caltechlive">Facebook</a>, <a href="https://instagram.com/caltechlive">Instagram</a>, and <a href="https://twitter.com/caltechlive">Twitter</a>.</p>Wed, 06 Nov 2019 20:00:00 -0800http://cms.caltech.edu/events/86273Finance Seminar: Topic to be announcedsabrina@hss.caltech.edu (Sabrina Hameister)Finance Seminar<strong>Speaker(s):</strong> Giorgia Piacentino (Columbia University)<br><strong>Location:</strong> Baxter B125<br><p>Please check later for additional details</p><p><i>Finance Seminars at Caltech are funded through the generous support of The Ronald and Maxine Linde Institute of Economic and Management Sciences (lindeinstitute.caltech.edu).</i></p>Thu, 14 Nov 2019 16:00:00 -0800http://cms.caltech.edu/events/86161Special CMX Seminar: TBAjbrink@caltech.edu (Jolene Brink)Special CMX Seminar<strong>Speaker(s):</strong> Matthew Thorpe (Carnegie Mellon University)<br><strong>Location:</strong> Annenberg 213<br><p>TBA</p>Tue, 19 Nov 2019 16:30:00 -0800http://cms.caltech.edu/events/86677TCS+ Talk: TBAbjleung@caltech.edu (Bonnie Leung)TCS+ Talk<strong>Speaker(s):</strong> Jason Li (Carnegie Mellon University)<br><strong>Location:</strong> Annenberg 322<br><p><b>Abstract:</b> TBA</p>Wed, 20 Nov 2019 10:00:00 -0800http://cms.caltech.edu/events/86731