Coexistence of stable and metastable<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>0</mml:mn></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>states in Josephson junctions

Radović, Z.; Dobrosavljević-Grujić, Ljiljana; Vujičić, Božidar

doi:10.1103/physrevb.63.214512

Cited by 75 publications

(75 citation statements)

References 39 publications

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“…For instance, in ferromagnet/superconductor (FM/SC) junctions, novel phenomena due to the competition between ferromagnetism and superconductivity are expected [15,16]. There have also been extensive theoretical studies of Josephson π junctions consisting of a ferromagnet sandwiched between two superconductors (SC/FM/SC) [17,18,19,20,21,22]. In this respect, several experimental observations of the π state have been reported [23,24,25,26,27,28].…”

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SuperconductingπQubit with a Ferromagnetic Josephson Junction

et al. 2005

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Solid-state qubits have the potential for the large-scale integration and for the flexibility of layout for quantum computing. However, their short decoherence time due to the coupling to the environment remains an important problem to be overcome. We propose a new superconducting qubit which incorporates a spin-electronic device: the qubit consists of a superconducting ring with a ferromagnetic π junction which has a metallic contact and a normal Josephson junction with an insulating barrier. Thus, a quantum coherent two-level state is formed without an external magnetic field. This feature and the simple structure of the qubit make it possible to reduce its size leading to a long decoherence time.PACS numbers: 03.67. Lx, 74.50.+r, 74.45.+c, 85.25.Cp The quantum computer is an innovative device in the sense that it would make it possible to solve problems which require unrealistically long computation times on a classical computer [1]. In the quantum computer, the information is stored in a basic element called the qubit, which is a quantum coherent two-level system. The superposition of the two-level state is utilized in the process of quantum computing. For the physical realization of the qubit, various systems have been proposed, e.g., ion traps, nuclear spins, and photons. Among the proposals, solid-state devices have the advantage of large-scale integration and flexibility of layout. On the other hand, a challenging problem for the solid state qubits is the reduction of the decoherence effect, since the solid states qubits in general have a short decoherence time due to their coupling to the environment. In recent years, several qubits based on the Josephson effect have been proposed [2,3,4,5,6,7,8,9,10,11,12,13]. One of the proposals involves a Cooper-pair box type of qubit [2,3,4,5]. In this case, quantum oscillations between the quantum two-level states (Rabi oscillations) have been detected [2,3], and the operation of coupled two qubits has been demonstrated [4,5]. Another example is a flux qubit which uses the superconducting phase. For this proposal, a circuit with a single and relatively large

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“…This causes the currentphase relation to be shifted by π from that of a normal Josephson junction. This is the so-called π junction [17,18,19,20,21,22,23,24,25,26,27,28].…”

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SuperconductingπQubit with a Ferromagnetic Josephson Junction

et al. 2005

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“…This is of considerable interest with respect to possible applications in quantum computing, which rely on systems with a double degenerate ground state [14,15]. The free energy of the junction, W ' , is given by [16] …”

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Direct Observation of the Transition from the Conventional Superconducting State to theπState in a Controllable Josephson Junction

et al. 2002

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“…The observed substructure is not the predicted frequency doubling effect, expected for a dominant second harmonic contribution to the CPR. 6 As we show below, it can be explained in terms of two coupled loops, even for a sinusoidal CPR of both 0 and junctions.…”

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confidence: 91%

“…1 In some cases, the first order coefficient I c ͑1͒ can even vanish, for instance, in asymmetric 45°grain boundary junctions in d-wave symmetry superconductors, 2,3 in out of equilibrium superconductornormal-metal-superconductor junctions 4 and for ballistic superconductor-ferromagnet-superconductor ͑SFS͒ junctions at the 0-transition. 5,6 The remaining second order coefficient I c ͑2͒ will result in a doubling of the frequency in the interference pattern. Although, a frequency doubling has been observed experimentally, 7 its origin is still under debate, since there are also dynamic effects in inhomogeneous junctions, which can lead to this effect.…”

Section: Introductionmentioning

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Bistability in superconducting rings containing an inhomogeneous Josephson junction

et al. 2008

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We investigate the magnetic response of a superconducting Nb ring containing a ferromagnetic PdNi Josephson junction and a tunnel junction in parallel. Doubling of the switching frequency is observed within certain intervals of the external magnetic field. For sinusoidal current-phase relations in both junctions, our model of a double superconducting quantum interference device ͑a small two-junction loop that interrupts the larger ring͒ explains this feature by a sequence of current reversals in the ferromagnetic section of the junction in these field intervals. The switching anomalies are induced by the coupling between the magnetic fluxes in the two superconducting loops.

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Coexistence of stable and metastable0andπstates in Josephson junctions

Cited by 75 publications

References 39 publications

SuperconductingπQubit with a Ferromagnetic Josephson Junction

SuperconductingπQubit with a Ferromagnetic Josephson Junction

Direct Observation of the Transition from the Conventional Superconducting State to theπState in a Controllable Josephson Junction

Bistability in superconducting rings containing an inhomogeneous Josephson junction

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