Quantum Brachistochrone Curves as Geodesics: Obtaining Accurate Minimum-Time Protocols for the Control of Quantum Systems

Most methods of optimal control cannot obtain accurate time-optimal protocols. The quantum brachistochrone equation is an exception, and has the potential to provide accurate time-optimal protocols for a wide range of quantum control problems. So far, this potential has not been realized, however, due to the inadequacy of conventional numerical methods to solve it. Here we show that the quantum brachistochrone problem can be recast as that of finding geodesic paths in the space of unitary operators. We expect this brachistochrone-geodesic connection to have broad applications, as it opens up minimal-time control to the tools of geometry. As one such application, we use it to obtain a fast numerical method to solve the brachistochrone problem, and apply this method to two examples demonstrating its power.National Science Foundation (U.S.) (Project PHY-1005571)United States. Army Research Office. Multidisciplinary University Research Initiative (Grant W911NF-11-1-0268)National Science Foundation (U.S.) (Project CCF-1350397

A low temperature expansion for matrix quantum mechanics

We analyze solutions to loop-truncated Schwinger-Dyson equations in massless N = 2 and N = 4 Wess-Zumino matrix quantum mechanics at finite temperature, where conventional perturbation theory breaks down due to IR divergences. We find a rather intricate low temperature expansion that involves fractional power scaling in the temperature, based on a consistent “soft collinear” approximation. We conjecture that at least in the N = 4 matrix quantum mechanics, such scaling behavior holds to all perturbative orders in the 1/N expansion. We discuss some preliminary results in analyzing the gauged supersymmetric quantum mechanics using Schwinger-Dyson equations, and comment on the connection to metastable microstates of black holes in the holographic dual of BFSS matrix quantum mechanics.Harvard University (Fundamental Laws Initiative Fund)National Science Foundation (U.S.) (Award PHY-0847457

High-fidelity quantum state evolution in imperfect photonic integrated circuits

We propose and analyze the design of a programmable photonic integrated circuit for high-fidelity quantum computation and simulation. We demonstrate that the reconfigurability of our design allows us to overcome two major impediments to quantum optics on a chip: it removes the need for a full fabrication cycle for each experiment and allows for compensation of fabrication errors using numerical optimization techniques. Under a pessimistic fabrication model for the silicon-on-insulator process, we demonstrate a dramatic fidelity improvement for the linear optics controlled-not and controlled-phase gates and, showing the scalability of this approach, the iterative phase estimation algorithm built from individually optimized gates. We also propose and simulate an experiment that the programmability of our system would enable: a statistically robust study of the evolution of entangled photons in disordered quantum walks. Overall, our results suggest that existing fabrication processes are sufficient to build a quantum photonic processor capable of high-fidelity operation.United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Grant FA9550-14-1-0052)iQuISE FellowshipNational Science Foundation (U.S.). Graduate Research Fellowship (Grant 1122374)American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipAlfred P. Sloan Foundation (Sloan Research Fellowship

Nuclear Theory and Science of the Facility for Rare Isotope Beams

The Facility for Rare Isotope Beams (FRIB) will be a world-leading laboratory for the study of nuclear structure, reactions and astrophysics. Experiments with intense beams of rare isotopes produced at FRIB will guide us toward a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, help provide an understanding of matter in neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society. FRIB will be essential for gaining access to key regions of the nuclear chart, where the measured nuclear properties will challenge established concepts, and highlight shortcomings and needed modifications to current theory. Conversely, nuclear theory will play a critical role in providing the intellectual framework for the science at FRIB, and will provide invaluable guidance to FRIB's experimental programs. This article overviews the broad scope of the FRIB theory effort, which reaches beyond the traditional fields of nuclear structure and reactions, and nuclear astrophysics, to explore exciting interdisciplinary boundaries with other areas. \keywords{Nuclear Structure and Reactions. Nuclear Astrophysics. Fundamental Interactions. High Performance Computing. Rare Isotopes. Radioactive Beams.Comment: 20 pages, 7 figure

Engineering at San Jose State University, Spring 2006

https://scholarworks.sjsu.edu/engr_news/1003/thumbnail.jp

Entropic Inflation

One of the major pillars of modern cosmology theory is a period of accelerating expansion in the early universe. This accelerating expansion, or inflation, must be sustained for at least 30 e--foldings. One mechanism used to drive the acceleration is the addition of a new energy field, called the Inflaton; often this is a scalar field. We propose an alternative mechanism which, like our approach to explain the late-time accelerating universe, uses the entropy and temperature intrinsic to information holographically stored on a surface enclosing the observed space. The acceleration is due in both cases to an emergent entropic force, naturally arising from the information storage on the horizon.Comment: 12 pages; version to appear in IJMP

Nanotechnology and the Developing World

How nanotechnology can be harnessed to address some of the world's most critical development problem

R&D and the arms race : an analytical look

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Guides for the Journey: Supporting High-Risk Youth with Paid Mentors and Counselors

Strategies to concentrate resources on high-risk youth have long been a goal in the youth field, but the practical means of doing so frequently have eluded practitioners. High-risk youth often are highly transient, and they may need sustained, costly services to address their needs effectively. Guides for the Journey explores a concrete, flexible approach to the problem: the use of paid counselors who stay with young people for extended periods of time. The report profiles three programs now using this strategy and discusses how public funding to support wider use of paid mentors and counselors may be mobilized