Josephson φ_0-junction in nanowire quantum dots

The Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier. This current is driven by a superconducting phase difference ϕ between the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process2, the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken can the supercurrent for ϕ = 0 be finite. This corresponds to a ground state of the junction being offset by a phase ϕ_0, different from 0 or π. Here, we report such a Josephson ϕ0-junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase offsets and demonstrate that ϕ_0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux- and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems

Josephson φ0-junction in nanowire quantum dots

\u3cp\u3eThe Josephson effect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier. This current is driven by a superconducting phase difference φbetween the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process, the current is strictly zero when φvanishes. Only if these underlying symmetries are broken can the supercurrent for φ= 0 be finite. This corresponds to a ground state of the junction being offset by a phase φ0, different from 0 or π. Here, we report such a Josephson φ0 -junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase offsets and demonstrate that φ0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux- and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems.\u3c/p\u3

Erratum: Josephson φ0-junction in nanowire quantum dots (vol 12, pg 568, 2016)

In the version of this Letter originally published ref. 34 was not updated and should have read: Gingrich, E. C. et al. Controllable 0-π Josephson junctions containing a ferromagnetic spin valve. Nature Phys. 12, 564–567 (2016). This has now been corrected in the online versions of the Letter

Andreev spectrum of a Josephson junction with spin-split superconductors

The Andreev bound states and charge transport in a Josephson junction between two superconductors with intrinsic exchange fields are studied. We find that for a parallel configuration of the exchange fields in the superconductors the discrete spectrum consists of two pairs of spin-split states. The Josephson current in this case is mainly carried by bound states. In contrast, for the antiparallel configuration we find that there is no spin-splitting of the bound states and that for phase differences smaller than a certain critical value there are no bound states at all. Hence the supercurrent is only carried by states in the continuous part of the spectrum. Our predictions can be tested by performing a tunneling spectroscopy of a weak link between two spin-split superconductors

Erratum: Josephson φ0-junction in nanowire quantum dots (vol 12, pg 568, 2016)

In the version of this Letter originally published ref. 34 was not updated and should have read: Gingrich, E. C. et al. Controllable 0-π Josephson junctions containing a ferromagnetic spin valve. Nature Phys. 12, 564–567 (2016). This has now been corrected in the online versions of the Letter

Energetics of a Single Qubit Gate

Qubits are physical, a quantum gate thus not only acts on the information carried by the qubit but also on its energy. What is then the corresponding flow of energy between the qubit and the controller that implements the gate? Here we exploit a superconducting platform to answer this question in the case of a quantum gate realized by a resonant drive field. During the gate, the superconducting qubit becomes entangled with the microwave drive pulse so that there is a quantum superposition between energy flows. We measure the energy change in the drive field conditioned on the outcome of a projective qubit measurement. We demonstrate that the drive's energy change associated with the measurement backaction can exceed by far the energy that can be extracted by the qubit. This can be understood by considering the qubit as a weak measurement apparatus of the driving field

Optimierung des akustischen und schwingungstechnischen Verhaltens wirtschaftlicher Dieselleichttriebwagen fuer den Regionalverkehr Abschlussbericht zum Arbeitspaket 2 und zum lauftechnischen Teil des Arbeitspakets 3. Entwicklungsbericht

Available from TIB Hannover: RR 7581(17-96)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Data and code: Supercurrent interference in few-mode nanowire Josephson junctions

Data and code for the paper: "Supercurrent interference in few-mode nanowire Josephson junctions" by Vincent Mourik, Daniel B. Szombati, Bas Nijholt, David J. van Woerkom, Attila Geresdi, Jun Chen, Viacheslav P. Ostroukh, Anton R. Akhmerov, Sebastian R. Plissard, Diana Car, Erik P. A. M. Bakkers, Dmitry I. Pikulin, Leo P. Kouwenhoven, and Sergey M. Frolov