Research focuses on quantum transport experiments investigating quantum coherence, electron spins and nuclear spins and interactions in semiconductor and graphene nanostructures. Ongoing projects include
We are interested in coherent manipulation of individual quantum systems in solid state nanostructures with quantum computation as a long term goal.
Experiments investigate quantum transport through semiconductor nanostructures which are fabricated in house using high mobility 2D electron gas materials obtained from collaborating molecular beam epitaxy labs. Experiments are typically performed in dilution refrigerators at millikelvin temperatures in magnetic fields. Measurements are done using electronic low-noise techniques and may involve nanosecond-pulsing and microsecond readout schemes.
Positions are currently available, please see the positions page.
We are affiliated with
Our group enjoys numerous ongoing collaborations, including the following groups (in arbitrary order)
The growing demands of quantum materials, engineering and technology make access to microkelvin temperatures ever more essential. Experience in Europe suggests that new working methods, encouraged by an imaginative funding atmosphere, can accelerate progress in this frontier field. The EMP comprises ~20 leading European ultralow-temperature academic physics and technology partners in Europe, eight of which provide access to milli- and microkelvin experimental facilities. The node in Basel, Zumbuhl group, is specialized in cooling nanoelectronic circuits using a parallel network of magnetic refrigerators, recently reaching 150 microK with the network of refrigerators, and reporting 2.8 mK in a Coulomb blockade thermometer, the lowest temperature reported to date in a nanoelectronic circuit.
Nature Materials Review by George Pickett, Lancaster, and Christian Enss, Heidelberg.
The Center for Quantum Science and Quantum Computing (QSC) of the Universities of Basel (Switzerland) and Freiburg (Germany), embedded in EUCOR – The European Campus, invites applications for up to ten Georg H. Endress Postdoc Fellowships to start in 2018. The Center seeks to attract outstanding and highly motivated early-career scientists in QSC to engage in cutting-edge projects involving existing research groups at Basel and Freiburg. The ideal Endress Fellow has recently finished a PhD in experimental or theoretical physics (or related areas) and is eager to shape the academic environment in research and teaching at both nodes. Fellows will be appointed typically for up to three years, and will be selected on the basis of scientific excellence as well as quality and innovative potential of proposed research in the QSC target areas of the Center, such as quantum information processing (quantum computation, simulation, and metrology), quantum technologies, complex quantum systems, quantum materials, and other emerging topics in quantum science.
Astronomers have examined the distribution and movement of dwarf galaxies in the constellation Centaurus, but their observations do not fit with the standard model of cosmology that assumes the existence of dark matter. The international team of researchers led by the University of Basel reported their findings in the journal Science.
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The growing demands of quantum materials, engineering and technology make access to microkelvin temperatures ever more essential. Experience in Europe suggests that new working methods, encouraged by an imaginative funding atmosphere, can accelerate progress in this frontier field. Review by George Pickett and Christian Enss in Nature Materials.
Topological qubits based on Majorana fermions have the potential to revolutionize the emerging field of quantum computing by making information processing significantly more robust to decoherence. Nanowires (NWs) are a promising medium for hosting these kinds of qubits, though branched NWs are needed to perform qubit manipulations. Here we report gold-free templated growth of III-V NWs by molecular beam epitaxy using an approach that enables patternable and highly regular branched NW arrays on a far greater scale than what has been reported thus far. Friedl et al. ArXiv:1803.00647
One of the most intriguing and fundamental properties of topological materials is the correspondence between the conducting edge states and the gapped bulk spectrum. So far, it has been impossible to access the full evolution of edge states in a magnetic field with critical system parameters due to poor resolution, remnant bulk conductivity, or disorder. Here, we present a novel type of tunneling spectroscopy which allows us to track the center of mass edge state positions with great precision and which can discriminate even spatially overlapping states due to their differing momenta based on tunneling along an extended GaAs quantum wire with translational symmetry. This results in unprecedented spatial resolution of about 1 nm at Tesla fields, while keeping the driving bias in the low microV regime in linear response. Patlatiuk et al. arXiv:1802.03847.
We are looking for a highly motivated master student who is interested in working on low temperature quantum transport experiments. The goal of those experiments is to utilize a new spectroscopy technique developed in our group with the aim to obtain the velocities of edge states in cleaved edge overgrown samples. For further information please refer to the following pdf document or contact Prof. Dr. Zumbühl and/or Taras Patlatiuk.
After hours of deliberations, changes and small-group work sessions, it's quite energizing to see the progress on the proposal achieved in the past three days in Heidelberg on the European Microkelvin Platform EMP!!
In this work, we show that the physics of the quantum corrections to the conductivity around the persistent spin helix symmetry point can be treated very similar to the case with weak spin-orbit (SO) coupling, where the small parameter is the deviation from the PSH point due to either the mismatch a-b of the Rashba a and Dresselhaus b linear terms or due to the cubic SO term b3. This similarity makes it possible to derive closed-form equation for the weak (anti)localization magnetoconductivity including all these SO terms, which turns out to be identical in form to the well-known Hikami-Larkin-Nagaoka expression, but is now reparametrized im terms of the small parameters a-b and b3. Further, we perform quantum transport experiments in the same PSH regime, and develop a reliable two-step method to extract all parameters from fits to the new expression, obtaining excellent agreement with other recent experiments. This provides experimental confirmation of the new theory, and helps advancing SO coupling towards a powerful resource in emerging quantum technologies. Weigele et al. arXiv:1801.05657.