| 1. |
- Aad, G, et al.
(author)
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- 2015
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swepub:Mat__t
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| 2. |
- Bezuglyi, Eugene, et al.
(author)
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Multiparticle tunnelling in diffusive superconducting junctions
- 2007
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In: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 20:6, s. 529-541
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Journal article (peer-reviewed)abstract
- We formulate a theoretical framework to describe multiparticle current transport in planar superconducting tunnel junctions with diffusive electrodes. The approach is based on the direct solving of quasiclassical Keldysh-Green function equations for nonequilibrium superconductors, and consists of a combination of circuit theory analysis and improved perturbation expansion. The theory predicts a much greater scaling parameter for the subharmonic gap structure of the tunnel current in diffusive junctions compared to the one in ballistic junctions and mesoscopic constrictions with the same barrier transparency. © IOP Publishing Ltd.
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| 3. |
- Bezuglyi, Eugene, 1947, et al.
(author)
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Resonant subgap current transport in Josephson field effect transistor
- 2017
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 95:1
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Journal article (peer-reviewed)abstract
- We study theoretically the current-voltage characteristics (IVCs) of the Josephson field effect transistor - a ballistic SNINS junction with superconducting (S) electrodes confining a planar normal-metal region (N), which is controlled by the gate-induced potential barrier (I). Using the computation technique developed earlier for long single-channel junctions in the coherent multiple Andreev reflection (MAR) regime, we find a significant difference of the subgap current structure compared to the subharmonic gap structure in tunnel junctions and atomic-size point contacts. For long junctions, whose lengths significantly exceed the coherence length, the IVC exhibits current peaks at multiples (harmonics) of the distance ?m between the static Andreev levels eVn=n?m. Moreover, the averaged IVC follows the powerlike behavior rather than the exponential one and has a universal scaling with the junction transparency. This result is qualitatively understood using an analytical approach based on the concept of resonant MAR trajectories. In shorter junctions having lengths comparable to the coherence length, the IVC has an exponential form common for point contacts, however the current structures appear at the subharmonics of the interlevel distance eVn=?m/n rather than the gap subharmonics 2?/n.
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| 4. |
- Bezuglyi, E. V., et al.
(author)
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Current-voltage characteristics of asymmetric double-barrier Josephson junctions
- 2014
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In: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 499, s. 15-23
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Journal article (peer-reviewed)abstract
- We develop a theory for the current-voltage characteristics of diffusive superconductor-normal metal-superconductor Josephson junctions with resistive interfaces and the distance between the electrodes smaller than the superconducting coherence length. The theory allows for a quantitative analytical and numerical analysis in the whole range of the interface transparencies and asymmetry. We focus on the regime of large interface resistance compared to the resistance of the normal region, when the electron-hole dephasing in the normal region is significant and the finite length of the junction plays a role. In the limit of strong asymmetry we find pronounced current structures at the combination subharmonics of Delta + Delta(g), where Delta(g) is the proximity minigap in the normal region, in addition to the subharmonics of the energy gap 2 Delta in the electrodes. In the limit of rather transparent interfaces, our theory recovers a known formula for the current in a short mesoscopic connector - a convolution of the current through a single-channel point contact with the transparency distribution for an asymmetric double-barrier potential. (C) 2014 Elsevier B. V. All rights reserved.
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| 5. |
- Bezuglyi, E. V., et al.
(author)
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Dissipative charge transport in diffusive superconducting double-barrier junctions
- 2011
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 83:18, s. 184517-
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Journal article (peer-reviewed)abstract
- We solve the coherent multiple Andreev reflection (MAR) problem and calculate current-voltage characteristics (IVCs) for Josephson SINIS junctions, where S are local-equilibrium superconducting reservoirs, I denotes tunnel barriers, and N is a short diffusive normal wire, the length of which is much smaller than the coherence length, and the resistance is much smaller than the resistance of the tunnel barriers. The charge transport regime in such junctions qualitatively depends on a characteristic value gamma = tau(d)Delta of relative phase shifts between the electrons and retroreflected holes accumulated during the dwell time tau(d). In the limit of small electron-hole dephasing gamma
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| 6. |
- Pinto, R. A., et al.
(author)
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Analysis of a tunable coupler for superconducting phase qubits
- 2010
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 82:10, s. 104522-
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Journal article (peer-reviewed)abstract
- This paper presents a theoretical analysis of the recently realized tunable coupler for superconducting phase qubits [R. C. Bialczak et al., arXiv: 1007.2219 (unpublished)]. The coupling can be turned off by compensating a negative mutual inductance with a tunable Josephson inductance. The main coupling in this system is of the XX type and can be zeroed exactly, while there is also a small undesired contribution of the ZZ type. We calculate both couplings as functions of the tuning parameter (bias current) and focus on the residual coupling in the OFF regime. In particular, we show that for typical experimental parameters the coupling OFF/ON ratio is few times 10(-3), and it may be zeroed by proper choice of parameters. The remaining errors due to physical presence of the coupler are on the order of 10(-6).
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| 7. |
- Slutskin, A.A., et al.
(author)
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Non-Markovian decoherence of a two-level system weakly coupled to a bosonic bath
- 2011
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In: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 96:4, s. 4003-
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Journal article (peer-reviewed)abstract
- The Bloch-Redfield equation is a common tool for studying the evolution ofqubit systems weakly coupled to the environment. We investigate the accuracy of the Bornapproximation underlying this equation. We find that the high-order terms in the perturbativeexpansion contain accumulating divergences that make straightforward Born approximationinappropriate. We develop a diagrammatic technique to formulate, and solve the improvedself-consistent Born approximation. This more accurate treatment reveals an exponential timedependentprefactor in the non-Markovian contribution dominating the qubit long-time relaxationfound in Di Vincenzo D. P. and Loss D., Phys. Rev. B, 71 (2005) 035318. At the same time, theassociated dephasing is not affected and is described by the Born-Markov approximation.
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| 8. |
- Staudt, Matthias, 1977, et al.
(author)
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Coupling of an erbium spin ensemble to a superconducting resonator
- 2012
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 1361-6455 .- 0953-4075. ; 45:12, s. Art. no. 124019-
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Journal article (peer-reviewed)abstract
- A quantum coherent interface between optical and microwave photons can be used as a basic building block within a future quantum information network. The interface is envisioned as an ensemble of rare-earth ions coupled to a superconducting resonator, allowing for coherent transfer between optical and microwave photons. Towards this end, we have realized a hybrid device coupling a Er3+-doped Y2SiO5 crystal in a superconducting coplanar waveguide cavity. We observe a collective spin coupling of 4 MHz and a spin linewidth of down to 75 MHz.
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| 9. |
- Zazunov, A., 1968, et al.
(author)
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Dynamics and phonon-induced decoherence of Andreev level qubit
- 2005
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In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 71
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Journal article (peer-reviewed)abstract
- We present a detailed theory for the Andreev level qubit, a system consisting of a highly transmissive quantum point contact embedded in a superconducting loop. The two-level Hamiltonian for Andreev levels interacting with quantum phase fluctuations is derived by using a path integral method. We also derive a kinetic equation describing qubit decoherence due to interaction of the Andreev levels with acoustic phonons. The collision terms are nonlinear due to the fermionic nature of the Andreev states, leading to slow nonexponential relaxation and dephasing of the qubit at temperatures smaller than the qubit level spacing.
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