Speaker: Tommaso Calarco, University of Ulm
Title: Steering Many-Body Quantum Dynamics
Quantum technologies are based on the manipulation of individual degrees of freedom of quantum systems with exquisite precision. Achieving this in a real environment requires pushing to the limits the ability to control the dynamics of quantum systems of increasing complexity. Optimal control techniques are known to enable steering the dynamics of few-body systems in order to prepare a desired state or perform a desired unitary transformation. I will present a recently developed optimal control method that allows doing so for a many-body quantum system undergoing e.g. a quantum phase transition in the non-adiabatic regime. This opens the way to a range of applications, from the suppression of defects in a superfluid-Mott-insulator transition with ultra-cold atoms in an optical lattice to the achievement of various quantum gates at the quantum speed limit. I will present detailed calculations we performed for different experimental scenario, together with the corresponding results obtained by experimental groups in different fields, from cold atoms to diamond NV centers. Our control method also allows for exploring more general questions like the complexity of reversing quantum many-body dynamics, steering it back to its initial state even without the ability to revert the sign of the whole Hamiltonian. I will conclude by showing some recent results we obtained in this context, as well as further questions opened by our investigations.
Host: Steven van Enk
Speaker: Sid Nagel, University of Chicago
Title: Speak, Memory! What can a material memorize?
Out-of-equilibrium disordered systems may preserve a memory of external driving that can be read out at a later time. I will present one form of memory that does this in a remarkable fashion: the system remembers multiple values from a series of training inputs yet forgets nearly all of them at long times despite their continual repetition. However, all the memories can be preserved indefinitely if noise is added. We have found these features in two very different systems: traveling charge-density waves and cyclically sheared non-Brownian suspensions. Thus this type of memory appears to be generic. Moreover, it provides a concrete example of how “plasticity” in memory can arise.
Host: Eric Corwin
Speaker: Heidi Schellman, Oregon State University
Title: “Neutrino Nus“
Neutrinos are almost massless chargeless particles that only feel the weak interaction. They are hard to make (unless you have a nuclear reactor lying around) and even harder to detect. Despite these obstacles, a whole new field of neutrino studies has opened up since the definite observation of neutrino oscillations in the late 90’s. I will review a small fraction of the exciting recent results in neutrino physics and outline some of our plans for the future.
Host: Dave Soper
Speaker: Hailin Wang, University of Oregon
Title: Communicating Between Disparate Quantum Systems via Radiation Pressure Force
It is well known that radiation pressure force of light can be used for the manipulation of mechanical motion in microscopic systems. Notable examples include laser cooling and laser tweezers. In this talk, I will discuss recent experimental advances on the use of radiation pressure force to control mechanical motion in macroscopic systems, with a focus on potential applications in quantum networks. Experimental studies on storing light as a mechanical excitation and on converting coherent optical fields between vastly different optical wavelengths via radiation pressure forces will be highlighted. Special physical processes that can exploit mechanical interactions while avoiding effects of thermal mechanical noise will also be discussed.
Host: Eric Corwin, Dietrich Belitz
Speaker: Tommaso Baldacchini, Newport Corporation
Title: Making and Characterizing Small Things
Two-photon polymerization (TPP) is an enabling technology that allows fast prototyping of parts with feature sizes smaller than 100 nm. Due to its ability to fabricate microstructures with arbitrary three-dimensional geometries, TPP has been employed in diverse fields such as photonics, microelectronics, microelectromechanical systems, microfluidics, and bioengineering. However, no information is available to date that microscopically correlates the experimental conditions used in TPP with the properties of the ultimate microstructure. A study is presented where the distribution of polymer cross-linking in three-dimensional microstructures fabricated by TPP is visualized by means of nonlinear microscopy. In particular, coherent anti-Stokes Raman scattering (CARS) microscopy is employed to image polymer microstructures with chemical specificity. The characterization of the microstructures based on the acquired images permits rational optimization of the TPP process.
Biosketch: After studying Chemistry at the University of Rome “La Sapienza”, Tommaso Baldacchini pursued doctoral research at Boston College. Under the guidance of Professor John T. Fourkas, he worked on unconventional methods to fabricate three-dimensional microstructures and received a Ph.D. in Physical Chemistry in 2004. He then joined the research group of Professor Eric Mazur at Harvard University as a postdoctoral fellow, where his work focused on the wettability properties of micro- and nano-structured surfaces prepared by femtosecond laser ablation. In 2006 he joined the Technology and Applications Center at Newport Corporation as a Staff Scientist. His research interests lie in the applications of nonlinear optics in microscopy and nanofabrication.
Host: Bryan Boggs
Steven van Enk : University of Oregon
Detecting Errors in Quantum Computers
In the best quantum computing devices we have nowadays errors occur very rarely.
We do have to know what type of errors occur as only certain types can be corrected.
Unfortunately, the best quantum computing experiments employ so many qubits that we cannot possibly simulate the experiment anymore on a classical computer. So, how do we figure out whether only the right types of errors occur? After a brief introduction to quantum computing I’ll discuss a solution to this problem based on model selection and the Akaike Information Criterion.
Grzegorz Szamel :
Colorado State University
Glassy Dynamics: Fundamental Differences Between Two and Three Dimensions
The two-dimensional freezing transition is very different from its three-dimensional counterpart. In contrast, the glass transition is usually assumed to have similar characteristics in two and three dimensions. Using computer simulations we show that glassy dynamics in supercooled two- and three-dimensional fluids are fundamentally different. Specifically, transient localization of particles upon approaching the glass transition is absent in two dimensions, whereas it is very pronounced in three dimensions. Moreover, the temperature dependence of the relaxation time of orientational correlations is decoupled from that of the translational relaxation time in two dimensions but not in three dimensions. Lastly, the relationships between the characteristic size of dynamically heterogeneous regions and the relaxation time are very different in two and three dimensions. These results strongly suggest that the glass transition in two dimensions is different than in three dimensions.
Host: Eric Corwin
Yasutomo J. Uemura, Columbia University
MuSR Studies of Itinerant-Electron Magnets MnSi and (Mn,Fe)Si: First-Order Quantum Phase Evolution, Effect of Disorder, and Fluctuating Skyrmion Liquids
Abstract: MnSi is an interesting metallic magnet which orders into helical/conical/ferromagnetic spin structure below Tc = 29 K at ambient pressure with a small ordered moment of 0.4 Bohr magneton per Mn. Application of hydrostatic pressure of 16 kbar drives this system to be paramagnetic at T = 0. (Mn,Fe) substitution also suppresses magnetic order, yet with the additional effect of randomness, Several years ago, “Skyrmion” spin correlation was discovered in a small region near Tc in applied external field in bulk MnSi and (Mn,Fe)Si, and a larger region of B-T phase diagram in thin films of these systems.
We have performed Muon Spin Relaxation (MuSR) measurements on these systems at TRIUMF (Vancouver) and PSI (Zurich). MuSR results revealed: (1) in a bulk single crystal of MnSi, first order phase transition, with phase separation between magnetically ordered and paramagnetic regions, appears near the phase boundary to paramagnetic state, associated with suppression of dynamic critical behavior; (2) in a bulk single crystal of (Mn,Fe)Si with applied pressure, features for second order quantum evolution is recovered, revealing hidden quantum critical point for pure MnSi; (3) Skyrmion region has reduced order parameter and enhanced dynamic muon spin relaxation rate in MnSi and (Mn,Fe)Si; (4) dynamic critical behavior is gradually suppressed by the applied field in these systems, and (5) dynamic critical behavior is completely absent between the static Skyrmion lattice and fluctuating Skyrmion liquid regions in a thin film of MnSi with 50 nm thickness. These results will be compared with theories of Belitz and collaborators for itinerant magnets and of Nagaosa for Skyrmion spin systems.
Manoj Kanskar, nLight
High Power Lasers – Industry Perspective
Diode lasers in the near infra-red have improved in power, efficiency, reliability and cost over the past several decades. As a result lasers have transformed from being scientific instruments to tools pervasively used in manufacturing cars, planes, ships, industrial equipment, electronics, hand-held mobile devices and touch-screens and large displays. Part of this revolution is due to the advent of fiber lasers which are impressive brightness converters producing multiple kilowatts of average power and hundreds of kilowatt of peak power. The critical technological advancements that have enabled the rise of high power diode and fiber lasers to their current state will be briefly reviewed. Further power-scaling in fiber lasers is currently limited by nonlinear effects such as stimulated Brillouin scattering (SBS), stimulated Rayleigh scattering (SRS) and the recently-identified roadblock – modal instability. Included in the talk will be discussion of ongoing work to solve these issues using Chirally-coupled Core (CCC) fiber. Chiral architecture results in interaction between CCC fiber modes involving both spin and orbital angular momentum of the waves. This enables a new degree of freedom for controlling fiber modal properties.
Jen Dionne, Stanford University
Mind the Gap: Quantum Effects and Optical-frequency Magnetism in Plasmonic Particle Junctions
Electrons and photons can coexist as a single entity called a surface plasmon—an elementary excitation found at the interface between a conductor and an insulator. Plasmons are evident in the vivid hues of rose windows, which derive their color from small metallic nanoparticles embedded in the glass. They also provide the basis for color-changing biosensors, photo-thermal cancer treatments, improved photovoltaic cell efficiencies, and nano-optical tweezers. While most applications have relied on classical plasmonic effects, quantum phenomena can also strongly influence the plasmonic properties of nanometer-scale systems. In this presentation, I’ll describe my group’s efforts to probe plasmon modes spanning both classical and quantum domains. We first explore the optical resonances of individual metallic nanoparticles as they transition from a classical to a quantum-influenced regime. We then use these results to monitor heterogeneous catalytic reactions on individual nanoparticles. Subsequently, using real-time manipulation of plasmonic particles, we investigate plasmonic coupling between pairs of particles separated by nanometer- and Angstrom-scale gaps. For sufficiently small separations, we observe the effects of classical coupling and quantum tunneling between metallic particles on their plasmon resonances. By utilizing these effects, we demonstrate the colloidal synthesis of an isotropic metafluid or “metamaterial paint” that exhibits a strong magnetic response – and the potential for negative refractive indices – at visible frequencies. Finally, we introduce a new technique, cathodoluminescence tomography, that enables three-dimensional visualization of light-matter interactions with nanoscale spatial and spectral resolution.