Program summer term 2016

Friday, April 08, 2016, 2:00pm, Hörsaal 28 D 001

Prof. Leo DiCarlo (Delft University of Technology)

Protecting quantum data in superconducting circuits

Safeguarding quantum data from decoherence and faulty control hardware is an outstanding challenge for all quantum information platforms. Quantum error correcting codes require a stringent combination of quantum and classical capabilities to reach the break-even point at which one encoded quantum datum (a logical qubit) is as well preserved as an unencoded one (a physical qubit). Steady advances in the coherence and control of superconducting processors based on circuit quantum electrodynamics prompt a worldwide effort to reach this mile post. I will present an overview of experimental progress, with special focus on the quantum engineering and engineering-for-quantum underway in QuTech. 

Barbara Terhal


Monday, April 18, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Ariel Goobar (University of Stockholm)

Supernovae and the Acceleration of the Universe

Our understanding of the cosmic composition has changed drasticallyover the last two decades, primarily due to the realization that theexpansion of the Universe is speeding up, rather than slowing down aswas expected from the attractive effect of gravity. This rather poorlyunderstood phenomenon, attributed to the existence of some  fluid with negative pressure, "dark energy", was first discoveredusing Type Ia supernovae (SNe Ia) as distance estimators. The key question being addressed now, as well as in planned futurecosmological surveys, is if the dark energy density is constant (intime and space) or not. This is the main dividing feature between darkenergy models and their connections with fundamental physics. After a historical account of the discovery of the acceleratedexpansion with SNe Ia, I plan to discuss ongoing efforts to minimizethe astrophysical uncertainties limiting the ultimate accuracy of supernovaeas distance indicators in cosmology. 

Julien Lesgourgues


Monday, May 09, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Michele Heurs (MPI Hannover)

The Gravitational Universe

The recent announcement of the first direct detection of gravitational
waves (the merger of a binary black hole system) has heralded the new
era of gravitational wave astronomy. It opens a new window to the
universe, and will help reveal its “dark” secrets, inaccessible to
astronomy in the electromagnetic spectrum and neutrino astronomy.

After an introduction to gravitational waves and their effect on
space-time I will explain the principle of interferometric
gravitational wave detection. I will present advanced interferometer
noise-reduction techniques and detector sensitivities. Finally, I will
touch upon the current status of the field, including plans for
spaceborne detectors.

Christopher Wiebusch


Monday, May 23, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Livia Ludhova (RWTH Aachen University)

Neutrino Physics with Liquid Scintillator-Based Detectors

The liquid-scintillator based particle detection technique has gained
a fundamental role in neutrino physics. High light yield, and
consequently a possibility of low-energy threshold and good energy
resolution, are fundamental in a wide variety of applications. With
the use of this technique in the detection of reactor antineutrinos,
KamLAND experiment in Japan provided one of the first observations of
neutrino oscillations. When combined with extreme radio-purity of
liquid scintillator, as achieved by Borexino experiment in Italy,
solar-neutrino spectroscopy below 1 MeV became a
reality. Geo-neutrinos, messengers about the radioactive decays inside
the Earth, have been detected as well in liquid scintillator
detectors. The recent discovery of non-zero q13 mixing angle by Daya
Day was based on the same detection technique. Liquid scintillators,
when doped with special isotopes, are entering in the field of
neutrino-less double-beta decay search, as KamLAND using 136Xe. There
are several future projects based on liquid-scintillator detectors in
different stages of their proposal and/or construction. SNO+, opting
for 130Te-loaded scintillator, should come on scene in a near
future. The first detector exceeding the existing 1-kton mass scale,
will be the JUNO 20 kton detector, which will start taking data in
2020. The colloquium will review the status and prospects of the
neutrino physics based on the liquid-scintillator detection

Achim Stahl


Monday, June 06, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Grace Lu (University of Southern California)

Physics of Semiconducting Nanowires

Nanowires exhibit novel physical properties owing to their large
surface-to-volume ratio. They are the potential building blocks for a
wide range of device applications. We have synthesized and studied a
variety of semiconducting nanowires. Some of their basic structural,
electrical, and optical properties will be highlighted. A particular
interesting system is Sb2Te3 which belongs to a new class of material
- topological insulators (TI). It has an insulating bulk, but gapless
Dirac cone surface states with spin-momentum locking
carriers. Magnetoresistance on these wires with different
cross-sectional areas are cross-examined with nanoscale angle-resolved
photoemission spectroscopy, elucidating their remarkable topological
surface states. In outlook, a powerful experimental tool will be to
utilize single electron Coulomb blockade to explore coexisting effects
of coherence, confinement and spin-orbit coupling in these TI

Markus Morgenstern


Monday, June 20, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Alexander Khajetoorians (Radboud University Nijmegen)

Magnetic LEGOs: magnetic design at the single atom level

Some of the most fascinating discoveries in the last century, such as
complex magnetic order and superconductivity, are based on the
collective nature of quantum particles. The field of quantum matter
aims at harnessing these many-body properties in materials toward
energy-efficient technologies based on the interplay of the charge,
spin, and orbital degrees of freedom. Insight into the quantum world
requires access to individual spins and the ability to manipulate
their interactions with their environment. I will review exciting
developments based on scanning tunneling microscopy (STM) which opens
the capabilities of magnetic imaging at the single atom level and
bottom-up fabrication of atomic magnets toward what we coin “magnetic
LEGOs.” I will exemplify how magnetic atoms may be used for bit
storage, as well as Boolean logic based on the magnetic interactions
of single atoms, and address the future outlook.

Markus Morgenstern


Monday, July 04, 2016, 4:15pm, Hörsaal 28 D 001

Prof. Michael Czakon (RWTH Aachen University)

The top-quark and the fuss around its mass 

The year 2015 has marked the 20th anniversary of the discovery of the
top-quark at the Tevatron proton-anti-proton collider at Fermilab near
Chicago. The top-quark not only still is the heaviest known elementary
particle, but it also interacts through every known fundamental force
of nature. It seems surprising that the interpretation of the value of
the measured mass is currently a hotly debated topic with possible
relations and implications to the long term fate of the
Universe. Furthermore, experimental data on the top-quark production
cross sections at the Large Hadron Collider allows amongst others to
gain insight into the structure of the proton and to hunt for hints of
the existence of new particles. In this talk, I will review the
successes of both theoretical and experimental physics together with
the central role of the Large Hadron Collider in this field.