QUROPE Quantum Information Processing and Communication in Europe

Superconducting quantum circuits, metamaterials, detectors

The group studies Bose-Einstein condensates of excitons and exciton-polaritons in various crystal structures. We are particularly interested in application of bosonic condensates for realisation of the exciton-mediated superconductivity. Our research paves way to realisation of quantum simulators based on the gratings of trapped exciton-polariton condensates linked by Josephson and radiative coupling. Some of materials we study allow for the room temperature function (in particular, ZnO, transition metal dichalcogenides).

We demonstrate that arbitrary time evolutions of many-body quantum systems can be reversed even in cases when only part of the Hamiltonian can be controlled. The reversed dynamics obtained via optimal control—contrary to standard time-reversal procedures—is extremely robust to external sources of noise. We provide a lower bound on the control complexity of a many-body quantum dynamics in terms of the dimension of the manifold supporting it, elucidating the role played by integrability in this context.

In a recent publication in Scientific Reports the group led by SOLID partner Jonathan Finley at the Walter Schottky institut of TUM achieve fast, all optical spin control in a single quantum dot without magnetic fields.

In their recent article in Science Magazine the SOLID group at KIT led by Alexey Ustinov demonstrated experimentally that minute deformation of the oxide barrier changes the energies of the atomic tunneling systems, and measured these changes by microwave spectroscopy of the superconducting qubit through coherent interactions between these two quantum systems.

In a recent publication in Physical Review Letters the TU-Delft group led by SOLID partner Leo DiCarlo demonstrated an indirect partial measurement of a transmon qubit in circuit quantum electrodynamics.  This was don by interaction with an ancilla qubit and projective ancilla measurement with a dedicated readout resonator. Accurate control of the interaction and ancilla measurement basis allowed the group to show how it is possible to tailor the measurement strength and operator.

In a recent publication in Nature Communications the TU-Delft team including SOLID partner Leo Kouwenhoven demonstrated a semiconductor nanowire based single photon source with a near unity efficiency.  To do this, the group positioned single quantum dots on the axis of a tailored nanowire waveguide using bottom-up growth.

IThe SOLID group of Lieven Vandersypen recently published a paper in Physical Review Letters in which they investigated phonon-induced spin and charge relaxation mediated by spin-orbit and hyperfine interactions for a single electron confined within a double quantum dot. They extract an electron spin relaxation rate that varies nonmonotonically with the detuning between the dots and confirm this model with experiments performed on a GaAs double dot.

The Quantronics group at SOLID partner CEA have recently published a paper in Physical Review Letters in wihch they measure the quantum fluctuations of a pumped nonlinear resonator using a superconducting artificial atom as an in situ probe. The qubit excitation spectrum provided access to the frequency and amount of excitation of the intracavity field fluctuations, from which we infer its effective temperature.

The Chalmers team led by Chris Wilson recently published a paper in Physical Review Letters in which they investigated the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom that is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross–Kerr coupling.