The Experts below are selected from a list of 44064 Experts worldwide ranked by ideXlab platform
C. Urbina - One of the best experts on this subject based on the ideXlab platform.
-
Asymmetric noise probed with a Josephson Junction
Physical Review Letters, 2009Co-Authors: Q. Le Masne, H. Pothier, Norman O. Birge, C. Urbina, Daniel EsteveAbstract:Fluctuations of the current through a tunnel Junction are measured using a Josephson Junction. The current noise adds to the bias current of the Josephson Junction and affects its switching out of the supercurrent branch. The experiment is carried out in a regime where switching is determined by thermal activation. The variance of the noise results in an elevated effective temperature, whereas the third cumulant, related to its asymmetric character, leads to a difference in the switching rates observed for opposite signs of the current through the tunnel Junction. Measurements are compared quantitatively with recent theoretical predictions.
-
rabi oscillations in a large Josephson Junction qubit
Physical Review Letters, 2002Co-Authors: John M. Martinis, Jose Aumentado, C. UrbinaAbstract:: We have designed and operated a circuit based on a large-area current-biased Josephson Junction whose two lowest energy quantum levels are used to implement a solid-state qubit. The circuit allows measurement of the qubit states with a fidelity of 85% while providing sufficient decoupling from external sources of relaxation and decoherence to allow coherent manipulation of the qubit state, as demonstrated by the observation of Rabi oscillations. This qubit circuit is the basis of a scalable quantum computer.
E Goldobin - One of the best experts on this subject based on the ideXlab platform.
-
Tunable φ Josephson Junction ratchet.
Physical Review E, 2016Co-Authors: R. Menditto, R Kleiner, D Koelle, H. Sickinger, Martin Weides, Hermann Kohlstedt, E GoldobinAbstract:We demonstrate experimentally the operation of a deterministic Josephson ratchet with tunable asymmetry. The ratchet is based on a φ Josephson Junction with a ferromagnetic barrier operating in the underdamped regime. The system is probed also under the action of an additional dc current, which acts as a counterforce trying to stop the ratchet. Under these conditions the ratchet works against the counterforce, thus producing a nonzero output power. Finally, we estimate the efficiency of the φ Josephson Junction ratchet.
-
Effective model for a short Josephson Junction with a phase discontinuity
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2016Co-Authors: E Goldobin, D Koelle, R. G. Mints, S. Mironov, A. Buzdin, R. KleinerAbstract:We consider a short Josephson Junction with a phase discontinuity $\kappa$ created, e.g., by a pair of tiny current injectors, at some point $x_0$ along the length of the Junction. We derive the effective current-phase relation (CPR) for the system as a whole, i.e., reduce it to an effective point-like Junction. From the effective CPR we obtain the ground state of the system and predict the dependence of its critical current on $\kappa$. We show that in a large range of $\kappa$ values the effective Junction behaves as a $\varphi_0$ Josephson Junction, i.e., has a unique ground state phase $\varphi_0$ within each $2\pi$ interval. For $\kappa\approx\pi$ and $x_0$ near the middle of the Junction one obtains a $\varphi_0\pm\varphi$ Junction, i.e., the Josephson Junction with degenerate ground state phase $\varphi_0\pm\varphi$ within each $2\pi$ interval. Further, in view of possible escape experiments especially in the quantum domain, we investigate the scaling of the energy barrier and eigenfrequency close to the critical currents and predict the behavior of the escape histogram width $\sigma(\kappa)$ in the regime of the macroscopic quantum tunneling.
-
phase retrapping in a pointlike φ Josephson Junction the butterfly effect
Physical Review Letters, 2013Co-Authors: E Goldobin, R Kleiner, D Koelle, R. G. MintsAbstract:: We consider a φ Josephson Junction, which has a bistable zero-voltage state with the stationary phases ψ = ±φ. In the nonzero voltage state the phase "moves" viscously along a tilted periodic double-well potential. When the tilting is reduced quasistatically, the phase is retrapped in one of the potential wells. We study the viscous phase dynamics to determine in which well (-φ or +φ) the phase is retrapped for a given damping, when the Junction returns from the finite-voltage state back to the zero-voltage state. In the limit of low damping, the φ Josephson Junction exhibits a butterfly effect-extreme sensitivity of the destination well on damping. This leads to an impossibility to predict the destination well.
John M. Martinis - One of the best experts on this subject based on the ideXlab platform.
-
Quantum Josephson Junction circuits and the dawn of artificial atoms
Nature Physics, 2020Co-Authors: John M. Martinis, Michel H. Devoret, John ClarkeAbstract:In 1985, experiments revealed the quantum behaviour of a macroscopic degree of freedom: the phase difference across a Josephson Junction. The authors recount the history of this milestone for the development of superconducting quantum circuits.
-
rabi oscillations in a large Josephson Junction qubit
Physical Review Letters, 2002Co-Authors: John M. Martinis, Jose Aumentado, C. UrbinaAbstract:: We have designed and operated a circuit based on a large-area current-biased Josephson Junction whose two lowest energy quantum levels are used to implement a solid-state qubit. The circuit allows measurement of the qubit states with a fidelity of 85% while providing sufficient decoupling from external sources of relaxation and decoherence to allow coherent manipulation of the qubit state, as demonstrated by the observation of Rabi oscillations. This qubit circuit is the basis of a scalable quantum computer.
D Koelle - One of the best experts on this subject based on the ideXlab platform.
-
Tunable φ Josephson Junction ratchet.
Physical Review E, 2016Co-Authors: R. Menditto, R Kleiner, D Koelle, H. Sickinger, Martin Weides, Hermann Kohlstedt, E GoldobinAbstract:We demonstrate experimentally the operation of a deterministic Josephson ratchet with tunable asymmetry. The ratchet is based on a φ Josephson Junction with a ferromagnetic barrier operating in the underdamped regime. The system is probed also under the action of an additional dc current, which acts as a counterforce trying to stop the ratchet. Under these conditions the ratchet works against the counterforce, thus producing a nonzero output power. Finally, we estimate the efficiency of the φ Josephson Junction ratchet.
-
Effective model for a short Josephson Junction with a phase discontinuity
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2016Co-Authors: E Goldobin, D Koelle, R. G. Mints, S. Mironov, A. Buzdin, R. KleinerAbstract:We consider a short Josephson Junction with a phase discontinuity $\kappa$ created, e.g., by a pair of tiny current injectors, at some point $x_0$ along the length of the Junction. We derive the effective current-phase relation (CPR) for the system as a whole, i.e., reduce it to an effective point-like Junction. From the effective CPR we obtain the ground state of the system and predict the dependence of its critical current on $\kappa$. We show that in a large range of $\kappa$ values the effective Junction behaves as a $\varphi_0$ Josephson Junction, i.e., has a unique ground state phase $\varphi_0$ within each $2\pi$ interval. For $\kappa\approx\pi$ and $x_0$ near the middle of the Junction one obtains a $\varphi_0\pm\varphi$ Junction, i.e., the Josephson Junction with degenerate ground state phase $\varphi_0\pm\varphi$ within each $2\pi$ interval. Further, in view of possible escape experiments especially in the quantum domain, we investigate the scaling of the energy barrier and eigenfrequency close to the critical currents and predict the behavior of the escape histogram width $\sigma(\kappa)$ in the regime of the macroscopic quantum tunneling.
-
phase retrapping in a pointlike φ Josephson Junction the butterfly effect
Physical Review Letters, 2013Co-Authors: E Goldobin, R Kleiner, D Koelle, R. G. MintsAbstract:: We consider a φ Josephson Junction, which has a bistable zero-voltage state with the stationary phases ψ = ±φ. In the nonzero voltage state the phase "moves" viscously along a tilted periodic double-well potential. When the tilting is reduced quasistatically, the phase is retrapped in one of the potential wells. We study the viscous phase dynamics to determine in which well (-φ or +φ) the phase is retrapped for a given damping, when the Junction returns from the finite-voltage state back to the zero-voltage state. In the limit of low damping, the φ Josephson Junction exhibits a butterfly effect-extreme sensitivity of the destination well on damping. This leads to an impossibility to predict the destination well.
J S Tsai - One of the best experts on this subject based on the ideXlab platform.
-
rabi oscillations in a Josephson Junction charge two level system
Physical Review Letters, 2001Co-Authors: Yasunobu Nakamura, Yu A Pashkin, J S TsaiAbstract:We investigated temporal behavior of an artificial two-level system driven by a strong oscillating field; namely, quantum-state evolution between two charge states in a small Josephson-Junction circuit irradiated with microwaves. Rabi oscillations corresponding to 0-, 1-, and 2-photon resonances were observed. As a function of microwave amplitude, the Rabi frequencies followed a first-kind Bessel function of the corresponding order to the number of photons.
