Quantum dynamics of a superconducting tunnel junction

Eckern, Ulrich; Schön, Gerd; Ambegaokar, Vinay

doi:10.1103/physrevb.30.6419

Cited by 353 publications

(297 citation statements)

References 44 publications

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“…It was also written phenomenologically in Simanek (1979) assuming however that the variable ϕ varied from −∞ to ∞. The existence of the term S ts was realized later (Eckern et al, 1984) and used for a system of Josephson junctions by Chakravarty et al (1987).…”

Section: Phase Functional For the Granular Superconductorsmentioning

confidence: 99%

Granular electronic systems

et al. 2007

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A granular metal is an array of metallic nano-particles imbedded into an insulating matrix. Tuning the intergranular coupling strength a granular system can be transformed into either a good metal or an insulator and, in case of superconducting particles, experience superconductor-insulator transition. The ease of adjusting electronic properties of granular metals makes them most suitable for fundamental studies of disordered solids and assures them a fundamental role for nanotechnological applications. This Review discusses recent important theoretical advances in the study of granular metals, emphasizing on the interplay of disorder, quantum effects, fluctuations and effects of confinement in formation of electronic transport and thermodynamic properties of granular materials.

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Section: Phase Functional For the Granular Superconductorsmentioning

confidence: 99%

Granular electronic systems

et al. 2007

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“…This expression can be obtained [8] from the Langevin equation (11) with the appropriate high frequency spectrum of ξ(t) [9]. It describes the shot noise of individual Cooper pairs tunneling incoherently through the junction and dissipating each energy 2eV into the microscopic modes of the resistor [10].…”

Section: S(t) B(t)mentioning

confidence: 99%

“…It corresponds to the Josephson energŷ (9) which can be considered as an effective Hamiltonian for the Josephson junction with the spin. The spin suppresses the Josephson energy due to the negative contribution (3/4)T 2 s to I 0 which can lead to the formation of a π-junction when I 0 changes sign [7].…”

Section: S(t) B(t)mentioning

confidence: 99%

Nondemolition Measurements of a Single Quantum Spin using Josephson Oscillations

et al. 2004

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We consider a Josephson junction containing a single localized spin 1/2 between conventional singlet superconducting electrodes. We study the spin dynamics and measurements when a dcmagnetic field B z acts on the spin and the junction is embedded into a dissipative circuit. We show that when tunneling or a voltage are turned on at time t = 0 the Josephson current starts to oscillate with an amplitude depending on the initial (t = 0) value of the spin z-component, Sz = ±1/2. At low temperatures, when effects of quasiparticles may be neglected, this procedure realizes a quantum-non-demolition (QND) measurement of Sz.PACS numbers: 74.50.+r, 03.65.Yz Quantum measurements in mesoscopic systems by use of tunneling attracted recently great interest. One of the motivations is the challenge of the single spin detection [1][2][3]. The other motivation comes from the quantum computing where the final state (after the computation) of a qubit must be measured. The meter couples, usually, to a single observable of the qubit, e.g., σ z . If this observable commutes with the spin Hamiltonian, the QND regime is realized, i.e., the two possible eigenvalues of σ z can be measured with proper probabilities even by a weakly coupled meter. Otherwise the initial state is quickly destroyed and one can only observe the steady state properties of the qubit and the meter performing continuous measurements [4][5][6]. In the spin detecting tunneling schemes all components of the localized spin are coupled to the tunneling electrons via the exchange interaction. Thus QND measurements seem impossible.In this paper we show that in fact QND measurements of the spin projection on the direction of the applied field B z are possible with the use of spin dependent Josephson tunneling at low temperatures, when the effect of quasiparticles is negligible. In this case the amplitude of Josephson oscillations depends on the state of the spin just before the measurement. The amplitude can be measured, e.g., in a circuit containing Josephson junction with the spin, a dc-voltage source V and a resistor R, see Fig. 1. The dissipative spin-dependent current in the circuit appears when the voltage exceeds a threshold and, effectively, it measures the squared amplitude of the Josephson-current oscillations.The measurement can begin either when the voltage exceeding a threshold [12] or the tunneling in the presence of such a voltage is switched on. The first possibility appears more natural for mesoscopic circuits, while the second could be realized with the use of the STM with a superconducting tip and a molecule with spin on the superconducting substrate. As the tip approaches the molecule, tunneling is turned on. The system we consider, i.e. a spin in a Josephson junction with applied voltage, is interesting also from the general viewpoint of quantum measurements. The entanglement of the spin with the measurement apparatus is realized here by use of the non-dissipative macroscopic quantum system as an intermediate step, namely with the superconducting pha...

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“…It is important to note with regard to the inner quasiparticle mechanism of dissipation in superconductors with Josephson contacts at zero temperature, that quantum fluctuations in both the ScS and SIS contacts with characteristic frequencies ω ≪ ∆ 0 were shown 24,25 to correspond to equilibrium fluctuations of a quantum oscillator without damping and with a renormalized contact capacitance. In the opposite limit of high frequencies ω ≫ ∆ 0 the impact of quasiparticle excitations in the contacts gives rise to an effective linear dissipation described by the Caldeira-Leggett model.…”

Section: Model and Numerical Analysismentioning

confidence: 99%

A Tunable Coupler with ScS Quantum Point Contact to Mediate Strong Interaction Between Flux Qubits

Soroka

2013

J Low Temp Phys

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Quantum dynamics of a superconducting tunnel junction

Cited by 353 publications

References 44 publications

Granular electronic systems

Granular electronic systems

Nondemolition Measurements of a Single Quantum Spin using Josephson Oscillations

A Tunable Coupler with ScS Quantum Point Contact to Mediate Strong Interaction Between Flux Qubits

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