Furthermore, we aim at uncovering correspondencies and hierarchies in quantum correlations over multiple length (and time) scales, ranging from macroscopic via mesoscopic to the atomic and molecular levels by combining experimental and theoretical studies from condensed-matter physics, nanoscience and chemistry.
Magnetism and superconductivity are quantum phenomena that will be studied in novel materials with strong electronic correlations, mostly transition-metal oxides and pnictides, as well as rare-earth compounds. Quantum phase transitions, i.e., transitions between different ground states, like the ones just mentioned, are governed by coherent quantum fluctuations that extend essentially over the whole specimen, and thus providing yet another level of quantum effects. The unusual behaviour of quantum-critical materials at finite temperatures will be investigated using microscopic (electron and neutron spectroscopies) and macroscopic techniques.
In addition, we will investigate quantum properties of nanostructures experimentally, focussing on superconducting hybrid devices and Josephson chains. On the theory side, we will explore the whole range of properties of quantum dots and one-dimensional correlated electron systems to identify the relations between quantum phase transitions in nanostructures and bulk systems.
Carbon-based materials present a unique case of condensed-matter systems. The different carbon allotropes are characterised by their different dimensionalities, i.e., zero-, one-, two- and three-dimensions, exemplified by C60, carbon nanotubes, graphene and diamond, respectively. To fully unravel and exploit the unique electronic, optoelectronic and magnetic properties towards applications is our primary objective.
Only few commercialisations of molecular electronics, spintronics, photonics or sensorics do exist at the single/few molecule level. This reflects the immense difficulty of reproducibly forming single-molecule junctions with the necessary atomic precision so as to address and read out the quantum states of individual molecules. An interdisciplinary molecular engineering approach comprising iterative cycles of “on-demand” synthesis, property measurements, simulation, device assembly and testing is required. In addition to their nanotechnological potential, molecular junctions are of great fundamental scientific interest because they offer a new way of benchmarking theory on multiple length scales.
The Helmholtz Future Project “Scalable Solid State Quantum Computing” began in March 2017. It is funded by the Helmholtz Initiative and Networking Fund. The focus of the STN contribution is the exploration of multi-qubit superconducting quantum circuits required for scalable quantum processors, on one side, and the development of scalable electronics for qubit readout and control, on the other side. The current expertise in quantum technology covers all of the experimental aspects of two major solid-state qubit types, superconducting (Josephson) and molecular (spin) qubits. Assemblies of relatively small numbers of devices will already be capable of enacting quantum simulations, presaging the large-scale applications that we foresee in this area.