Events: Centre: Physics Centre events at Chalmers University of TechnologyFri, 18 Jan 2019 09:00:32 +0100 lecture: Andreas Ekström<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>Andreas Ekström will give the promotion lecture &quot;Precision nuclear physics&quot; for the title as oavlönad docent.</p><h4 class="chalmersElement-H4"><span><h4 class="chalmersElement-H4"><img src="/SiteCollectionImages/Institutioner/F/340x296px/IMG_9135Andreasinne340x296.jpg" class="chalmersPosition-FloatRight" alt="" style="margin:5px;width:200px;height:174px" />Abstract:</h4></span></h4> <div>Nuclear physics is a cornerstone in our scientific endeavour to understand the universe. Indeed, atomic nuclei bring us closer to study both the stellar explosions in the macrocosmos, where the elements are formed, and the fundamental symmetries of the microcosmos. Having access to a a precise description of the interactions between protons and neutrons would provide a key to new knowledge across 20 orders of magnitude; from neutrinos to neutron stars.<br /></div> <div> </div> <div>In this lecture I will discuss novel methodologies to use experimental information from heavy atomic nuclei in the construction of nuclear interactions from chiral effective field theory. I expect this strategy to create clear scientific advantage and allow me to tackle the following big research questions: To what extent can nuclei be described in effective field theories of quantum chromo dynamics? How do we estimate the uncertainties in theoretical predictions ?</div> Physics Colloquium by Matthias Neubert<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>​Title: Probing beyond the Standard Model with Flavor Physics Matthias Neubert, Johannes Gutenberg University Mainz, Germany</p><h4 class="chalmersElement-H4">Abstract:</h4> <div>The persistent flavour anomalies in semileptonic and rare leptonic decays of B mesons are among the most compelling hints of physics beyond the Standard Model (SM). Particular exciting in this context are the hints for violations of lepton-flavour universality. The status of these anomalies will be reviewed and their implications for physics beyond the SM will be discussed.​</div> concert at Physics: Vivi Felice!<p>Physics Centre Personnel room, Origo building, 4th floor</p><p>​Enjoy your Friday lunch accompanied by some live music.​ Talk about and keyboard music by Domenico Scarlatti with Måns Henningson, Physics Dept. GU.​ Welcome to attend!</p> Centre seminar by Claudia Backes<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</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. The seminars will be on a monthly basis and will take place every last Monday in the month. ​ Welcome to attend! Title: Many candidates new in the zoo: Towards unifying principles in liquid exfoliation of various layered crystals Lecturer: Claudia Backes, Applied Physical Chemistry, Heidelberg University, Germany</p><div><h4 class="chalmersElement-H4">Abstract:</h4> <div><span style="background-color:initial">2D materials are exciting for two reasons: i) layer number dependent properties and ii) the broad palette of accessible layered crystals potentially giving access to any desired function. Ten years ago, it was demonstrated that 2D nanosheets can be obtained from layered crystals via liquid phase exfoliation (LPE) resulting in colloidal dispersions. However, sample polydispersity was a problem until recently. Now, we have arrived at a point where size selection (e.g. liquid cascade centrifugation, LCC) and size measurement protocols are in place, which can be readily applied to the whole nanosheet zoo. By comparing various materials, a model to understand the exfoliation was developed. </span></div></div> <div>With our realisation that both size and thickness result in changes in optical extinction spectra due to edge and confinement effects, it became possible to quantitatively determine the nanosheet dimensions optically. Such metrics have now been developed for ~15 materials. The understanding of the optical spectra is useful to monitor degradation kinetics in various liquids as function of time/temperature. Activation energies can be determined and passivation of defects, e.g. by functionalisation, subsequently studied. Functionalisation in general has the potential to ultimately enable the fabrication of hybrids, vertical and horizontal heterostacks etc. for new functional materials. </div> seminar: Mathias Hoppe<p>PJ, lecture hall,</p><p>​ T​itle of thesis: Simulation and analysis of radiation from runaway electrons</p><h4 class="chalmersElement-H4">Abstract:</h4> <div><span style="background-color:initial">Runaway electrons constitute one of the primary threats to future </span><span style="background-color:initial">toka</span><span style="background-color:initial">mak</span><span style="background-color:initial"> fusion reactors such as ITER. Successful prevention and mitigation </span><span style="background-color:initial">of runaways relies on the development of theoretical models which ac-</span></div> <div> </div> <div></div> <div> </div> <div>curately describe the dynamics of runaway electrons, and these models <span style="background-color:initial">must in turn be validated in experiments. Experimental validation of </span><span style="background-color:initial">models is however often made difficult by the fact that the diagnostic </span><span style="background-color:initial">signals obtained in experiments only depend indirectly on the particle </span><span style="background-color:initial">dynamics. In this thesis we present a synthetic diagnostic model, im</span><span style="background-color:initial">plemented in the Synchrotron-detecting Orbit Following Toolkit (Soft),</span></div> <div> </div> <div></div> <div> </div> <div>that bridges this divide between theory and experiment. The synthetic <span style="background-color:initial">diagnostic calculates the bremsstrahlung and synchrotron radiation di</span><span style="background-color:initial">agnostic signals corresponding to a given runaway electron population, </span><span style="background-color:initial">which can be directly compared to camera images and radiation spec</span><span style="background-color:initial">tra obtained in experiments. Bremsstrahlung and synchrotron radiation </span><span style="background-color:initial">from runaway electrons are particularly sensitive to the runaway dynam</span><span style="background-color:initial">ics, and, as we show in this thesis, they provide insight into the runaway </span><span style="background-color:initial">energy, direction of motion and position.</span></div> <div> </div> <div></div> <div> </div> <div><br /></div> <div> </div> <div></div> <div> </div> <div>This thesis focuses on the so-called geometric effects observed in the <span style="background-color:initial">detected radiation when magnetic field inhomogeneities and detector </span><span style="background-color:initial">p</span><span style="background-color:initial">roperties are taken into account, something which previous studies have</span></div> <div> </div> <div></div> <div> </div> <div>neglected. We characterize the dependence of the observed radiation on <span style="background-color:initial">the magnetic field geometry, detector properties and runaway parame</span><span style="background-color:initial">ters, and explain how geometric effects limit the otherwise monotonous </span><span style="background-color:initial">growth of the diagnostic response function with the runaway pitch angle.</span></div> <div> </div> <div></div> <div> </div> <div><br /></div> <div> </div> <div></div> <div> </div> <div>The synthetic diagnostic model is applied to experiments in the Alca<span style="background-color:initial">tor</span><span style="background-color:initial"> C-Mod and DIII-D tokamaks, and is used to validate kinetic theory </span><span style="background-color:initial">predictions of the electron distribution function. It is found that the</span></div> <div> </div> <div></div> <div> </div> <div>kinetic model agrees well in certain scenarios, and fails in others. In the <span style="background-color:initial">scenarios where it fails, the synthetic diagnostic model suggests that a </span><span style="background-color:initial">mechanism causing a larger spread in pitch angle may be missing from</span></div> <div> </div> <div></div> <div> </div> <div>the kinetic model.​​</div> Physics Colloquium by Sebastian Eggert<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>​Speaker: Sebastian Eggert, Technische Universität​, Kaiserslautern, Germany Title of talk: Time-periodic driving: beyond Floquet engineering</p><br />Abstract: To be announced.​ Centre Seminar with Christophe Voisin<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</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. The seminars will be on a monthly basis and will take place every last Monday in the month. ​ Lecturer: Christophe Voisin, Paris, France Welcome to attend!</p><h5 class="chalmersElement-H5">​Abstrac​t:</h5> <div>TBA</div> concert at Physics<p>Physics Centre Personnel room, Origo building, 4th floor</p><p>​ Enjoy your Friday lunch accompanied by some live music. ​​</p>​​ Seminar Advancing AI<p>Lindholmen Conference Centre, conference hall,</p><p>​Save the dates 4-5 March 2019 for the upcoming initiative seminar on AI. ​Event webpage: Registration will open in January.</p> Physics ​Colloq​uium by Anna Herland<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>​​Title: Organs-on-Chip, new models of human physiology Anna Herland from the Royal Institute of Technology, (KTH), Stockholm, Sweden</p><div>Abstract: To be announced.​</div> <div>​Coffee will be served outside PJ lecture hall before the lecture at 14.45.​ The colloquium starts at 15.15.</div> Colloquium with​ David Pappas<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>Colloquium with​ David Pappas, National Institute of Standards and Technology Boulder, USA​​ Title: Fabrication of superconducting circuits and universal gate set for strongly σ1zσ2z-coupled superconducting qubits.</p><h5 class="chalmersElement-H5">​Abstract:</h5> <div><span></span><p class="chalmersElement-P">Superconducting qubits are very promising candidates for realizing a fault-tolerant quantum computer. In this talk we review the basic design, fabrication, and testing of multi-qubit, superconducting transmon circuits, with an emphasis on scalable methods of fabrication. Research and progress to make small quantum processors is advancing rapidly, however, implementing two-qubit entangling gates with short gate operation time and high fidelity is still a challenge. Using our circuits, we demonstrate a new type of two-qubit entangling gate, the SWIPHT gate [1], on a coupled-transmon device. The two-transmon system, strongly coupled through a bus resonator, is tuned into the secondary resonance regime, where the effective σ<sup>1</sup><sub>z</sub> σ<sup>2</sup><sub>z</sub>-interaction is enhanced due to the coupling to higher levels of the transmons. This allows a SWIPHT CNOT gate with roughly ~100 ns gate time. While the strong interaction is shown to allow for faster 2-qubit operations, the single qubit operations then become more challenging. We have therefore developed a method for implementing unconditional single qubit gates in the two-transmon systems with strong  σ<span><sup>1</sup></span><span><sub>z</sub></span>σ<span><sup>2</sup></span><span><sub>z</sub></span>-interaction. The gate fidelity is extracted by quantum process tomography.</p> <div><br /></div> <div>[1] X. Wu, J. L. Long, H. S. Ku, R. e. Lake, M. Bal, D. P. Pappas, APL 111, 032502 (2017).</div> <div>[2] Sophia E. Economou and Edwin Barnes. Phys. Rev. B 91, 161405 (2015)​</div></div> Centre Seminar med Annick Loiseau<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>Grafencentrum på Chalmers arrangerar varje månad under våren 2019 en seminarieserie om de senaste framstegen inom grafen och 2D-material. ​​Seminarierna hålls månadsvis, sista måndagen i månaden. Dagens föreläsare: Annick Loiseau, France Välkommen!</p><h5 class="chalmersElement-H5">​Abstrak​t:</h5> <div>TBA</div> spectroscopies of superconducting collective modes: new advances and open questions<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>Linnaeus Colloquium with ​Lara Benfatto, ISC-CNR and Department of Physics, Sapienza University of Rome, Italy</p><h5 class="chalmersElement-H5">​Abstrac​t:</h5> <div><div>Spontaneous symmetry breaking across the superconducting critical temperature is characterized by the emergence of a finite order parameter and by collective electronic excitations connected to its fluctuations. The amplitude fluctuations are usually named Higgs mode for their analogy with the massive boson of the standard model, while phase fluctuations identify the Goldstone massless excitation expected when the broken symmetry is a continuous one. Their description requires to go beyond BCS theory, which nonetheless explains with great accuracy the conventional spectroscopies in standard superconductors. The reason is that these collective excitations are spectroscopically inert in ordinary single-band BCS superconductors. Nonetheless, in the last few years, a number of experiments carried out with very intense THz fields, either in transmission or in pump-probe configuration, have been interpreted in terms of excitations of the Higgs mode. Despite the clear interest in the fundamental and applicative aspects of these techniques, a clear theoretical paradigm for the description of these experiments is still lacking. In this talk I will first review the general theoretical problem of the description of superconducting collective modes, and then I will discuss the case of unconventional spectroscopies[1,2,3]. Finally, I will present a direct application of our interpretative scheme to the light-induced excitation of the so-called Leggett mode in the multi band MgB2 superconductor[3].</div> <div><br /></div> <div>[1]T. Cea, C. Castellani, L. Benfatto, Phys. Rev. B 93, 180507(R) (2016)</div> <div>[2] T. Cea, P. Barone, C. Castellani, L. Benfatto, Phys. Rev. B 97, 094516 (2018)  </div> <div>[3] F. Giorgianni, T. Cea, C. Vicario, C. P. Hauri, W. K. Withanage, X. Xi, and L. Benfatto, to appear on Nature Physics (2018).</div> <div>​<br /></div> </div> Physics Colloquium by Stefano Vitale<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>Title of talk: Gravitational wave astronomy within ESA Science Programme​ Colloquium by Stefano Vitale from LISA mission,  University of Trento, Italy ​Coffee will be served outside PJ lecture hall from 14.45.​ The colloquium starts at 15.15.​</p><div><h4 class="chalmersElement-H4">Abstract: </h4> <div>The talk reports on the international effort to develop the space-borne gravitational wave observatory known as LISA. In particular it will review the science case for such an observatory, particularly in the context of ESA's science programme. It will then report on the results from LISA's precursor LISA Pathfinder, which has been successfully flown by the European Space Agency (ESA) in 2015-17. Finally the talk will illustrate the status of LISA development within an international collaboration led by ESA, and including several of ESA member states and NASA.</div></div> chemistry algorithms on a superconducting qubit quantum processor<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>​Linnaeus Colloquium with Stefan Filipp, IBM Research Zurich, Switzerland</p><h5 class="chalmersElement-H5">​Abstrac​t:</h5> <div><div>In recent years we have observed a rapid development of quantum technologies for the realization of quantum computers that promise to outperform conventional computers in certain types of problems. This includes problems in optimization, machine learning, finite element calculations, but also in the computation of complex molecules. We utilize a fixed-frequency superconducting qubit system, an architecture characterized by its stability, relatively long coherence times and scalability. On this platform we use variational algorithms to compute the ground state of small molecules. Such algorithms are well suited for near-term applications on non-error corrected quantum hardware because they only rely on a small number of quantum operations. To compute the energy spectra of molecular hydrogen we employ parametrically-driven flux-tunable couplers to realize exchange-type interactions that preserve the number of qubit excitations corresponding to the fixed number of electrons in the molecule. With this choice of gates we can make best use of the available hardware and realize short algorithms that finish within the coherence time of the system. With gate fidelities around 95% we compute the eigenstates within an accuracy of 50 mHartree on average, a good starting point for near-term applications with scientific and commercial relevance.</div> <div>​<br /></div> </div> certifiable quantum advantages of quantum devices<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>​Linnaeus Colloquium with Jens Eisert, Freie Universität Berlin, Germany</p><h5 class="chalmersElement-H5">​Abstra​ct:</h5> <div>Quantum devices promise computational speedups over classical computers. Fully‐fletched fault tolerant quantum computers, once realised, allow to solve some problems in polynomial time that are believed to be intractable on quantum computers. They do not exist yet, however, despite recent progress in experimental realizations. What does exist are quantum simulators ‐ large scale quantum devices providing new insights into dynamical and static properties of complex quantum systems. There is already some good evidence that quantum simulators have the potential to outperform classical computers. Yet, in order to be prone against arguments claiming a lack of imagination, this superior computational capabilities should be expressed in terms of notions of computational complexity. One of the main milestones in quantum information science is hence to devise quantum devices that exhibit an exponential computational advantage over classical ones without being universal quantum computers in complexity theoretic terms, a state of affairs dubbed exponential quantum advantage. In this talk, we will discuss several surprisingly simple and physically plausible schemes that once realized show such a quantum advantage. Both aspects of physical implementation are discussed as well as mathematical arguments used in proofs relating to notions of computational complexity. We will see that while there is good evidence that these devices computationally outperform classical computers, they can still be efficiently and rigorously certified in their trustworthy functioning, in an error detecting fashion. The discussed schemes are experimentally implementable and if time allows, we will discuss data from a proof‐of‐principle experiment involving trapped ions.​</div> Centre Seminar with Christoph Stampfer<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</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. The seminars will be on a monthly basis and will take place every last Monday in the month. ​ Lecturer: Christoph Stampfer, Aachen, Germany Welcome to attend!</p><h5 class="chalmersElement-H5">​Abstra​ct:</h5> <div>TBA</div> Physics Colloquium by Federico Capasso<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>Speaker: Federico Capasso, Harvard University, USA Title: Flat optics with metasurfaces​ Abstract: To be announced.​ ​Coffee will be served outside PJ lecture hall from 14.45.​ The colloquium starts at 15.15.</p> Effects and Superconductivity in Oxide Heterostructures<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>​​Linnaeus Colloquium with Jean-Marc Triscone, DQMP, University of Geneva, Switzerland</p><div><h5 class="chalmersElement-H5"><span>​​Abstract:</span></h5></div> <p class="chalmersElement-P"> <span></span></p> <p class="chalmersElement-P"><span lang="EN-US">Oxide materials display within the same family of compounds a variety of exciting electronic properties ranging from ferroelectricity to ferromagnetism and superconductivity. These systems are often characterized by strong electronic correlations, complex phase diagrams and competing ground states. This competition makes these materials very sensitive to external parameters such as pressure or magnetic field. An interface, which naturally breaks inversion symmetry, is a major perturbation and one may thus expect that electronic systems with unusual properties can be generated at oxide interfaces [1,2]. A striking example is the interface between LaAlO3 and SrTiO3, two good band insulators, which was found to be conducting [3], and, in some doping range, superconducting with a maximum critical temperature of about 300 mK [4]. </span></p> <p class="chalmersElement-P"> </p> <p class="chalmersElement-P"><span style="background-color:initial">In this presentation, I will motivate the search for novel properties at oxide interfaces before to focus on the LaAlO3/SrTiO3 interface. In this system, the thickness of the conducting layer is found to be a few nanometers at low temperatures. This electron liquid with low electronic density, typically 5 1013 electrons/cm2, and naturally sandwiched between two insulators is ideal for performing electric field effect experiments allowing the carrier density to be tuned and superconductivity to be switched on and off. I will discuss the origin of the electron liquid [5]; superconductivity [4,6]; field effect experiments and the phase diagram of the system [6]; and the comparison between superconductivity at the interface and in bulk doped SrTiO3 before to give perspectives on the future of this research field [7].</span><span style="background-color:initial"> </span></p> <p class="chalmersElement-P"> </p> <p class="chalmersElement-P"><span lang="EN-US">[1] J. Mannhart and D. Schlom, Science 327, 1607 (2010).<br /></span><span lang="EN-US" style="background-color:initial">[2] </span><span lang="EN-US" style="background-color:initial">P. Zubko, S. Gariglio, M. Gabay, P. Ghosez, and J.-M. Triscone, Annual Review : Condensed Matter Physics 2, 141 (2011).<br /></span><span style="background-color:initial">[3] A. Ohtomo, H. Y. Hwang, Nature 427, 423 (2004).<br /></span><span style="background-color:initial">[4] N. Reyren, S. Thiel, A. D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C. W. Schneider, T. Kopp, A.-S. Ruetschi, D. Jaccard, M. Gabay, D. A. Muller, J.-M. Triscone and J. Mannhart, Science 317, 1196 (2007).<br /></span><span lang="EN-US" style="background-color:initial">[5]</span><span lang="EN-US" style="background-color:initial"> M.L. Reinle-Schmitt, C. Cancellieri, D. Li, D. Fontaine, S. Gariglio, M. Medarde, E. Pomjakushina, C.W. Schneider, Ph. Ghosez, J.-M. Triscone, and P.R. Willmott, Nature Communications, 3, 932 (2012).<br /></span><span style="background-color:initial">[6] A. Caviglia, S. Gariglio, N. Reyren, D. Jaccard, T. Schneider, M. Gabay, S. Thiel, G. Hammerl, J. Mannhart, and J.-M. Triscone, Nature 456, 624 (2008).<br /></span><span style="background-color:initial">[7] S. Gariglio, M. Gabay, and J.-M. Triscone, Research Update, APL Materials 4, 060701 (2016).</span></p> <p class="chalmersElement-P"> </p> Physics Colloquium: Experiments on antimatter at CERN<p>PJ, lecture hall, Fysikgården 2B, Fysik Origo</p><p>​ Speaker: Michael Doser, CERNAbstract: To be announced.​ ​Coffee will be served outside PJ lecture hall before the lecture at 14.45.​ The colloquium starts at 15.15.</p> Colloquium with Eleni Diamanti<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</p><p>​Eleni Diamanti, CNRS, Université Pierre et Marie Curie, France</p><h5 class="chalmersElement-H5">​Abstrac​t:</h5> <div>TBA </div> Centre Seminar with Wang Yao<p>Kollektorn, lecture room, Kemivägen 9, MC2-huset</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. The seminars will be on a monthly basis and will take place every last Monday in the month. ​ Lecturer: ​Wang Yao, Hong Kong Welcome to attend!​</p><div><h5 class="chalmersElement-H5"><span>Abstract:</span></h5></div> <div>TBA</div>