Events: Centre: Physics Centre events at Chalmers University of TechnologyFri, 16 Nov 2018 11:05:52 +0100 Advanced TEM/STEM School 19-21 November 2018<p>Kollektorn, lecture room,</p><p>​Learn about recent developments in advanced electron microscopy techniques from leading experts.</p>​The School will concentrate on advanced techniques for high-resolution electron microscopy of interest to scientists currently using transmission electron microscopes for materials science studies. Laboratory sessions will highlight state-of-the-art instrumentation. People attending the school should preferably have some basic understanding of conventional electron microscope operation.<br /><br /> coffee seminar with Benjamin Rousseaux<p>Kollektorn, lecture room,</p><p>Title: ​Strong coupling out of the dark: observing vacuum Rabi splitting by coupling a quantum emitter to non-radiative plasmonic cavity modes​</p> Colloquium: Quantum Cloud Computing<p>Kollektorn, lecture room,</p><p>​Talk by Elham Kashefi, Université Pierre et Marie Curie, France and The University of Edinburgh, UK</p>​Abstract:<div>The recent interest in quantum technologies has brought forward a vision of quantum Internet that could implement a collection of known protocols for enhanced security or communication complexity. On the other hand the rapid development of quantum hardware has increased the computational capacity of quantum servers that could be linked in such a communicating network. This raised the necessity/importance of privacy preserving functionalities such as the research developed around quantum computing on encrypted data that I briefly review in my talk. However, there exist some challenges in adapting widely the above vision: A reliable long-distance quantum communication network connecting all the interested parties might be very costly. Moreover, currently, some of the most promising quantum computation devices (e.g. superconducting such as the devices developed by IBM, Google, etc) do not yet offer the possibility of ``networked'' architecture, i.e. cannot receive and send quantum states. For this reason, there has been extensive research focusing on the practicality aspect of quantum delegated computation protocols (and related functionalities). A recent direction to address this challenge is to consider fully-classical client protocols, compatible with the no-go results, that can therefore achieve more restricted levels of security. I summarise our work and others towards a realistic quantum cloud platform.  ​<br /></div> by Alessandro Tredicucci<p>Kollektorn, lecture room,</p><p>The Graphene Center at Chalmers (GCC) will organize a monthly GCC seminar on the recent advances in the field of graphene and 2D materials.  Welcome to attend! Lecturer: Alessandro Tredicucci, University of Pisa, Italy​ Title of talk: Between photonics and electronics: is THz the promised land of graphene technologies?</p><h4 class="chalmersElement-H4">Abstract:</h4> <div>Graphene is attracting considerable attention for a variety of photonic applications, including fast photodetectors, transparent electrodes in displays and photovoltaic modules, and saturable absorbers. Owing to its high carrier mobility, gapless spectrum, tunable chemical potential, and frequency-independent absorption coefficient, it has been recognized as a very promising element for the development of detectors and modulators operating in the Terahertz (THz) region of the electromagnetic spectrum, which is still severely lacking in terms of solid-state devices.</div> <div> </div> <div>In the last few years, progress in the realization of graphene-based THz photonic devices has advanced very rapidly. In this talk I will focus in particular on the realization of THz detectors based on antenna-coupled graphene field-effect transistors (FETs), discuss the various mechanisms involved in their operation, and examine extension to other 2D materials and integration into future THz cameras. I will also address the development and applications of electrically switchable metamaterial devices as well as the prospects for the use of graphene in a new generation of THz sources, either directly as active element, or as waveguide optical component (for instance acting as saturable absorber in laser mode-locking). Finally, schemes to implement coherent control of absorption in graphene and the possible entailing device / diagnostic applications will be analysed.</div> ​ Physics Colloquium by the Nobel Prize Laureate Takaaki Kajita​<p>Gustaf Dalén-salen, lecture hall,</p><p>Welcome to attend the Physics Colloquium by Takaaki Kajita, University of Tokyo​​. Title of talk: Neutrino researches at Kamioka ​​</p><div><p class="chalmersElement-P"><strong><img src="/SiteCollectionImages/Institutioner/F/350x305/1_Takaaki_Kajita_350x305.jpg" class="chalmersPosition-FloatRight" alt="" style="margin:5px;width:240px;height:216px" />About Takaaki Kajita​'s research</strong><br />Neutrinos are elusive particles that were created at the birth of the Universe and are created today in nuclear processes, both in the Cosmos and in our laboratories, as well as in nuclear reactors.</p></div> <div>There are three types (flavors) of known neutrinos and they comprise some of the basic building blocks of our current theory of particle physics, the Standard Model. Originally assumed to be massless, they have been shown to have a small but non-zero mass and this discovery has had profound implications on e.g. stellar structure and cosmology. </div> <div> </div> <div><br /></div> <div> </div> <div>Professor Takaaki Kajita has been leading the experiments Kamiokande and its successor, Super-Kamiokande in Japan, aimed at study, amongst other things, neutrino oscillations, that is the transmutations between neutrino flavors that is predicted to occur by virtue of them not being massless. <br /><br /><strong>Awarded the Nobel prize 2015</strong><br />For this groundbreaking work he, together with Professor Arthur McDonald has been awarded the 2015 Nobel Prize <em>&quot;For the discovery of neutrino oscillations, which shows that neutrinos have mass”. </em><br />In his talk he is giving an account of the fascinating journey which led to this groundbreaking discovery.<br /><br /><a href=""><span><img class="ms-asset-icon ms-rtePosition-4" src="/_layouts/images/icgen.gif" alt="" />​</span> Read an article about Takaaki Kajita in conjunction with his visit to Chalmers</a><br /></div> <div><a href="" style="outline:0px"><img class="ms-asset-icon ms-rtePosition-4" src="/_layouts/images/icgen.gif" alt="" /></a> <a href="">M​ore facts about Takaaki Kajita​</a> (Nobel Prize organisation web page)<br /><br />Image credit: Bengt Nyman/Wikimedia commons<br /><br />The lecture by Professor Takaaki Kajita will be open to the public. No registration is needed.<br />Coffee and cake will be served in the entrance hall, (Gustaf Dalén lecture hall) before the lecture from 14.45.​<br /></div> <div> </div> Lecture with Witlef Wieczorek - Microtechnology and Nanoscience<p>Kollektorn, lecture room,</p><p>​ Title: The quantum regime of mechanical resonators - challenges and perspectives for research and applications</p><div><strong>Abstract: <img src="/SiteCollectionImages/Institutioner/MC2/Staff/witlef_wieczore_250px.jpg" class="chalmersPosition-FloatRight" alt="" style="margin:5px" /><br /></strong>Recent experiments have demonstrated the control over micro- and nanomechanical resonators in the quantum regime, such as cooling mechanical motion to the quantum ground state. This regime yields the ultimate limits in measuring and controlling mechanical motion. Furthermore, it offers qualitatively novel features in form of nonclassical mechanical states that can be exploited for novel sensing protocols or for addressing fundamental physics questions.<br /></div> <br />In my talk, I will give a short introduction to the field of quantum &quot;mechanics&quot;. I will present our activities in this field, whereby we focus on two experimental platforms: cavity optomechanics and superconducting magnetic levitation. Cavity optomechanical devices are a leading experimental platform for quantum control of mechanical motion. In my talk, I will present our efforts to advance this control further by developing so-called multi-element mechanical arrays. Further, I will present a completely different approach of controlling mechanical motion that employs superconducting levitation: A magnetically levitated, micrometer-sized object takes the role of a mechanical resonator. This experimental platform promises to reach unrivaled low mechanical dissipation, which offers new prospects for macroscopic quantum experiments and quantum-enhanced sensing.,-Microtechnology-and-Nanoscience.aspx,-Microtechnology-and-Nanoscience.aspxAndreas Nylander, Microtechnology and Nanoscience<p>C511, H-bar</p><p>​Title: Fabrication and Characterisation of Carbon Nanotube Array Thermal Interface Materials</p><div>​<span>Andreas Nylander is PhD student at the department of Microtechnology and Nanoscience</span></div> <div><br /></div> <div><div>Discussion leader: Christofer Markou, M.Sc. from Ericsson AB<br /></div> <div>Examinar: Prof. Johan Liu<span style="display:inline-block"><span style="display:inline-block"></span></span></div> <span><span style="display:inline-block"></span></span></div> view on ultrafast exciton dynamics in atomically thin materials<p>PJ, lecture hall,</p><p>​​ Promotion lecture by Ermin Malic, for the title as Professor, Department of Physics.</p><h4 class="chalmersElement-H4">​Abstract:</h4> <img src="/SiteCollectionImages/Institutioner/F/Blandade%20dimensioner%20inne%20i%20artikel/150px_ermin_malic.jpg" class="chalmersPosition-FloatRight" alt="" style="margin:5px" /><div>​<span style="background-color:initial">The remarkably rich exciton landscape in atomically thin nanomaterials and related heterostructures presents </span><span style="background-color:initial">a challenge for fundamental research, where formation and dynamics of excitons has remained in the dark. The focus of my research is to shed light on elementary many-particle processes behind the optical fingerprint and the ultrafast dynamics of excitons. Using the density matrix formalism with semiconductor Bloch equations in its core, we are able to track - in time and energy - the dynamics of the full spectrum of bright and dark, intra- and interlayer, as well as free and localized excitonic states. The vision is to exploit the fundamental insights to predict novel exciton-based technology concepts for optical sensing, light emission and light harvesting. </span><div> </div> <div> </div> <div> </div> <div>In this talk, I will give a flavor of our research by showing the exciton relaxation cascade, by demonstrating signatures of dark excitons and by suggesting a possible technological application in dark-exciton-based molecule sensors. </div></div>,-Microtechnology-and-Nanoscience.aspx,-Microtechnology-and-Nanoscience.aspxRavikiran Kakarla, Microtechnology and Nanoscience<p>Kollektorn, lecture room,</p><p>​Title: Phase sensitive amplifiers for free space optical communications</p>​<span class="text-normal page-content"><span>Ravikiran Kakarla is PhD student at the department of Microtechnology and Nanoscience</span></span><div>Discussion leader: Dr. Jonas Hansryd, Ericsson research<br /></div> <div>Examinar: Prof. Peter Andrekson</div> Control Calibration and System Characterization for Scalable Quantum Computers<p>Kollektorn, lecture room,</p><p>​Talk by Shai Machnes, Universität des Saarlandes</p><h5 class="chalmersElement-H5">​<span>Abstract: ​</span></h5> <div><span style="background-color:initial">Quantum computing is a revolution in the making, but the field is facing difficulties scaling up from the current 20-30 qubits to larger scale devices. For Josephson junction quantum computers, manufacturing variabilities necessitate individual characterization of each qubit and each coupling, and calibration of each control sequence, totaling many thousands of measurements and calibrations for a 100 qubit chip, and many months of dedicated work by a large team. Further, control pulses are currently designed using highly simplified analytic models, resulting in initially poor fidelities. The controls are then calibrated in-situ, achieving high-fidelities, but without a corresponding model. We are therefore left with a ridiculous situation: a model we know is inaccurate, working controls for which we do not have a matching model, and a calibration process from which we learned nothing about the system. We propose a novel procedure to rectify the above problems, clearing a path to scalable quantum computation. </span></div> <div><span style="background-color:initial"><br /></span></div> <div> </div> <div>We begin with a quick review of the current state of quantum computing hardware. We then detail the new quantum optimal control technique, and how it may be utilized to merge control sequence design, calibration and system characterization into a single, scalable process. Finally, we'll present how a Computer Algebra System may be utilized to derive simplified system models, guiding automatic progressive characterization and calibration of large complex systems, and how generative-adversarial learning may be utilized to allow small quantum computers to boot-up larger ones.</div> <div><br /></div> <div> </div> <div>We believe these new approaches will greatly improve both the accuracy of current quantum computers and our understanding of their dynamics - both critical components on the road to large scale quantum computation.</div> <div><br /></div> <div> </div> <div>Main reference: <span style="text-decoration:underline">Shai Machnes</span>, Elie Assémat, David Tannor, and Frank K. Wilhelm - <a href="">Phys. Rev. Lett. 120, 150401 (2018)</a> - Tunable, Flexible, and Efficient Optimization of Control Pulses for Practical Qubits</div> <div> </div> <div><br /></div> <div> </div> seminar: Daniel Andrén<p>PJ, lecture hall,</p><p>​Title of thesis: Optical manipulation and heating of gold nanoparticles near interfaces.</p><h4 class="chalmersElement-H4">Abstract: </h4> <div><span style="background-color:initial">By focusing laser light to small volumes, its momentum can be used to trap and manipulate objects in the size range from cells down to single atoms. Devices using this effect are called optical tweezers, and have found use in measuring and applying minuscule forces and torques, contributed to deepening our knowledge of molecular motors, unraveling the mechanics of cells and DNA, and better understand statistical mechanics and hydrodynamic interactions at the nanoscale. In short, the optical tweezer is a crucial component in our aspiration to understand and unlock the potential of nano-scaled objects.</span></div> <div> </div> <div><br /></div> <div> </div> <div>One class of nano-elements worth devoting special attention to are nanoparticles supporting plasmonic resonances. These present strongly enhanced light-matter interactions and may find use in as diverse fields as high-density data storage, single molecule detection, and personalized medicine. One potential use of plasmonic nanorods is as rotary nanomotors. These are capable of reaching record rotation frequencies of several tens of kilohertz when optically trapped in water against a glass surface. This thesis focuses on studying vital questions related to such rotary nanomotors, which are interesting to resolve from both a fundamental and from an applied point of view.</div> <div> </div> <div><br /></div> <div> </div> <div>It is well-known that metallic nanoparticles are efficiently heated by light. This will give rise to several photothermal effects affecting the nanoparticle and its surrounding. How these influence the performance of the nanomotor is evaluated. Through spectroscopic measurements, morphological changes induced by atomic migration is observed. Moreover, the elevated thermal environment around the nanoparticle is probed using two separate techniques, and temperatures above $200^\circ$C are routinely reached, but could be kept as low as a few degrees above ambient under the right circumstances.</div> <div> </div> <div><br /></div> <div> </div> <div>The gold nanoparticle is trapped at a small, but hitherto unknown, distance from a glass interface. The vicinity to a surface can affect several of a nanoparticles properties, including its diffusion and thermal environment, and knowing this distance is hence critical for any claims about the nanomotors' performance. Therefore, total internal reflection microscopy is performed on the trapped nanoparticles and it is found that they are confined less than 100 nm from the surface. The distance can be controlled by altering the radiation pressure, or Coulomb repulsion.</div> <div> </div> <div><br /></div> <div> </div> <div>In summary, the work performed in this thesis present important building blocks towards a complete understanding of this highly promising rotary motor system.}</div> <div> </div> <div> </div> <div> <strong>Keywords:</strong> <em>optical tweezers, plasmonics, gold nanorod, nanomotor, photothermal effects, thermal reshaping, LSPR spectroscopy, Brownian dynamics, TIRM, particle-surface separation distance.</em></div> <div><em></em></div> Lindgren: Materials Science<p>PJ, lecture hall,</p><p>T​itle of doctoral thesis: &quot;Effects of Irradiation and Thermal Ageing on the Nanoscale Chemistry of Steel Welds</p>​<strong>Abstract</strong>: to be announced Colloquium: Quantum optics with solid-state artificial atoms<p>Kollektorn, lecture room,</p><p>​Talk by Pascale Sennellart, CNRS/Paris Sud University, France ​</p>,-Microtechnology-and-Nanoscience.aspx,-Microtechnology-and-Nanoscience.aspxNiklas Dittmann, Microtechnology and Nanoscience<p>Kollektorn, lecture room,</p><p>​Title: Dynamics and fluctuations in single-electron tunneling devices</p><div>​<br /></div> <div>Niklas Dittmann is PhD student at the department of Microtechnology and Nanoscience</div> <div><br /></div> <div>Examiner: Prof. Mikael Fogelström<br />Main supervisor: Associate Professor Janine Splettstoesser <br /></div> <br /> seminar: Lajos Nagy<p>Raven and the Fox, multifunctional room, Fysik forskarhus</p><p>​ Title: Campbell formulae for compound Poisson processes with applications in nuclear safeguards.</p><strong>​<br />Abstract</strong>: To be announced.<div></div>,-Microtechnology-and-Nanoscience.aspx,-Microtechnology-and-Nanoscience.aspxFatemeh Hajiloo, Microtechnology and Nanoscience<p>Kollektorn, lecture room,</p><p>​Title: Phase-dependent heat currents in superconducting junctions</p><div>​<span>​Fatemeh Hajiloo is a<span></span><span class="text-normal page-content"> PhD student at the department of Microtechnology and Nanoscience</span><span style="display:inline-block"></span>  <span style="display:inline-block"></span></span></div> <div><br /></div> <br /> turbulence (blobs) in the Wendelstein 7-X stellarator<p>PJ, lecture hall,</p><p>Seminar by Sandor Zoletnik, Wigner Research Center for Physics, Budapest, Hungary</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div>Filaments or blobs are well known phenomena at the edge of tokamak plasmas. They represent a plasma filament detaching from the edge and propagating through the Scrape Off Layer (SOL) due to polarisation caused ExB drift. In the SOL filaments are the major cross-field transport mechanism. On the Wendelstein 7-X stellarator similar features have been seen from the first experiments and they seem to play an important role in the edge-SOL transport. In the standard configuration of this 3D device the edge is defined by a chain of magnetic islands, therefore the situation is much more complex than  in a tokamak. The talk presents multi-diagnostic observation of filaments, their response to changes in magnetic configuration and edge plasma conditions.</div> seminar: Mathias Hoppe<p>PJ, lecture hall,</p><p>​ T​itle of thesis: Simulation and analysis of ofradiation from runaway electrons</p><strong><br />A​bstract: </strong>To be announced