• Séminaire nano-électronique quantique
• Personne à contacter : Romain Maurand ()
• Lieu :

Résumé : When twisted to angles near 1 degre, graphene multilayers provide a new window on electron correlation physics by hosting gate-tuneable strongly-correlated states, including insulators, superconductors, and unusual magnets. I will report the discovery of a new member of the family(1), a correlated electron-hole state, in double bilayer graphene (2,3). This state can be viewed as a density wave state and is intimately linked to equilibrium exciton condensation and superfluidity. The correlated states in moiré materials can be tuned without introducing chemical dopants, thus opening the door to a new class of devices. I will show the successful realization of an exemplary device, a gate-defined Josephson Junction in magic angle twisted bilayer graphene (4). By using multilayer gate technology we define the superconducting and insulating regions of a Josephson junction (JJ) in a single-crystal and observe tunable DC and AC Josephson. This work is an initial step towards devices where gate-defined correlated states are connected in single-crystal nanostructures with applications in superconducting electronics and quantum information technology. (1) P.Rickhaus, F. K. De Vries, E. Portolés, G. Zheng, T. Taniguchi, K. Wantanabe, A. H. Macdonald, T. Ihn, and K. Ensslin, ArXiv:2005.05373 (2020). (2) F. K. de Vries, J. Zhu, E. Portolés, G. Zheng, M. Masseroni, A. Kurzmann, T. Taniguchi, K. Watanabe, A. H. MacDonald, K. Ensslin, T. Ihn, and P. Rickhaus, PRL 125 (17) (3) P. Rickhaus, G. Zheng, J. L. Lado, Y. Lee, A. Kurzmann, M. Eich, R. Pisoni, C. Tong, R. Garreis, C. Gold, M. Masseroni, T. Taniguchi, K. Wantanabe, T. Ihn, and K. Ensslin, Nano Lett. 19, 8821 (2019). (4) F. K. de Vries, E. Portolés, G. Zheng, T. Taniguchi, K. Wantanabe, T. Ihn, K. Ensslin, and P. Rickhaus, arXiv:2011.00011, accepted in Nat. Nano

Liens :[Peter Rickhaus][ETH Zurich]

• Séminaire nano-électronique quantique
• Personne à contacter : romain maurand ()
• Lieu :

Résumé : Quantum computing's greatest challenge is scaling up. Several decades ago, classical computers faced the same problem and a single solution emerged: very-large-scale integration using silicon. Today's silicon chips consist of billions of field-effect transistors (FinFETs) in which current flow along the fin-shaped channel is controlled by wrap-around gates. The semiconductor industry currently employs fins of sub-10 nm width, small enough for quantum applications: at low temperature, an electron or hole can be trapped under the gate and serve as a spin qubit. An attractive benefit of silicon's advantageous scaling properties is that quantum hardware and its classical control circuitry can be integrated in the same package. This, however, requires qubit operation at temperatures greater than 1 K where the cooling is sufficient to overcome the heat dissipation. Here, we demonstrate that a silicon FinFET is an excellent host for spin qubits that operate even above 4 K. We achieve fast electrical control of hole spins with driving frequencies up to 150 MHz and single-qubit gate fidelities at the fault-tolerance threshold. The number of spin rotations before coherence is lost at these “hot” temperatures already matches or exceeds values on hole spin qubits at mK temperatures. While our devices feature both industry compatibility and quality, they are fabricated in a flexible and agile way to accelerate their development. This work paves the way towards large-scale integration of all-electrical and ultrafast spin qubits.

• Séminaire nano-électronique quantique
• Personne à contacter :
• Conférence Zoom : consulter le lien de connexion dans les emails d'annonce ou contacter l'organisateur

Résumé : Travelling wave parametric amplifiers (TWPAs) recently became crucial tools in superconducting quantum technologies since they allow broadband and near quantum-noise-limited microwave detection. The main obstacle in developing TWPAs is the attainment of the phase matching condition between thepump field, which provides the energy for the amplification, and the signal field, to be amplified. I will present a new experimental approach to solving the phase matching problem by exploiting a Josephson metamaterial with in-situ tunability and sign reversal of the Kerr nonlinearity: reversed Kerr phase matching. Such novel reversed Kerr TWPA (1), composed of a chain of asymmetric Josephson junction-based inductive elements, shows amplification performance superior to the ones of previous state of the art TWPAs. In this talk, I will present the design, fabrication, and amplification characterization focusing on the novel reversed Kerr phase matching method. In addition, I will show recent experimental results on the generation of two-mode squeezed statesand discuss the exciting perspective of using such a device as a source of multimode entangled states in microwave photonics. (1) Ranadive et al.A reversed Kerr traveling wave parametric amplifier(2021)http://arxiv.org/abs/2101.05815