| 1. |
- Dobsicek, Miroslav, et al.
(författare)
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Arbitrary accuracy iterative quantum phase estimation algorithm using a single ancillary qubit: A two-qubit benchmark
- 2007
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the implementation of an iterative quantum phase estimation algorithm with a single ancillary qubit. We suggest using this algorithm as a benchmark for multiqubit implementations. Furthermore, we describe in detail the smallest possible realization, using only two qubits, and exemplify with a superconducting circuit. We discuss the robustness of the algorithm in the presence of gate errors, and show that seven bits of precision is obtainable, even with very limited gate accuracies.
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| 2. |
- Ingerman, Åke, 1973, et al.
(författare)
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Coherent multiple Andreev reflections and current resonances in SNS quantum point contacts
- 2001
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 64
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Tidskriftsartikel (refereegranskat)abstract
- We study coherent multiple Andreev reflections in ballistic superconductor-normal conductor-superconductor junctions with a quantum point contact in the normal region of the junction (superconductor-normal region-quantum point contact-normal region-superconductor) with arbitrary transparency. The presence of superconducting bound states in these junctions gives rise to great enhancement of the subgap current. The effect is most pronounced in low-transparency junctions, D≪1, and in the interval of applied voltage Δ/2
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| 3. |
- Johansson, Göran, 1971, et al.
(författare)
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Implementation of the three-qubit phase-flip error correction code with superconducting qubits
- 2008
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 77
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the performance of a three qubit error correcting code in the framework of superconducting qubit implementations. Such a code can recover a quantum state perfectly in the case of dephasing errors but only in situations where the dephasing rate is low. Numerical studies in previous work have however shown that the code does increase the fidelity of the encoded state even in the presence of high error probability, during both storage and processing. In this work we give analytical expressions for the fidelity of such a code. We consider two specific schemes for qubit-qubit interaction realizable in superconducting systems; one σz σz -coupling and one cavity mediated coupling. With these realizations in mind, and considering errors during storing as well as processing, we calculate the maximum operation time allowed in order to still benefit from the code. We show that this limit can be reached with current technology.
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| 4. |
- Johansson, Göran, 1971, et al.
(författare)
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Readout methods and devices for Josephson-junction-based solid-state qubits
- 2006
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Ingår i: Journal of Physics Condensed Matter. - 0953-8984 .- 1361-648X. ; 18:21, s. S901-S920
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the current situation concerning measurement and readout of Josephson-junction based qubits. In particular, we focus attention on dispersive low-dissipation techniques involving reflection of radiation from an oscillator circuit coupled to a qubit, allowing single-shot determination of the state of the qubit. In particular, we develop a formalism describing a charge qubit read out by measuring its effective (quantum) capacitance. To exemplify, we also give explicit formulas for the readout time.
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| 5. |
- Samuelsson, Peter, et al.
(författare)
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Coherent current transport in wide ballistic Josephson junctions
- 2004
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 70:21, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental and theoretical investigation of coherent current transport in wide ballistic superconductor-two dimensional electron gas-superconductor junctions. It is found experimentally that upon increasing the junction length, the subharmonic gap structure in the current-voltage characteristics is shifted to lower voltages, and the excess current at voltages much larger than the superconducting gap decreases. Applying a theory of coherent multiple Andreev reflection, we show that these observations can be explained in terms of transport through Andreev resonances.
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| 6. |
- Bátorfi, R., et al.
(författare)
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EuroTraining courses of microsystems technology and Nanotechnology for Electronics
- 2010
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Ingår i: 2010 IEEE 16th International Symposium for Design and Technology of Electronics Packages, SIITME 2010, Pitesti, 23-26 September 2010. - 9781424481248 ; :Article number 5653755,, s. 73-78
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Konferensbidrag (refereegranskat)abstract
- EuroTraining is the part of the EC initiated Europractice service, which aims to stimulate the wider exploitation of state-of-the-art micro/nano electronics and microsystem technologies by the European industry and academia. EuroTraining invites engineers and scientists from companies, SMEs, universities and institutes to upgrade their knowledge by professional and awareness courses entitled "Design Your Own Microsystem" and "Nanotechnology for Electronics". The courses were lectured by highly qualified experts in cooperation with local scientists, whose institutes were also invited to facilitate further scientific connection between the course participants and the national institute. A large emphasis were put on multidisciplinarity, as trends point to integration, therefore, the courses have been developed for engineers coming from a very different background (electrical-, biomedical-, chemical-, mechanical engineers) and for physicists, medical doctors, chemists, etc. The courses were very successful, participants benefited much from that they have learned: refreshed and widened their knowledge, and might open new opportunities in their studies and careers.
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| 7. |
- Beiu, V., et al.
(författare)
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Aspects of computing with locally connected networks
- 2012
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735410916 ; 1479:1, s. 1875-1879
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Konferensbidrag (refereegranskat)abstract
- This paper outlines an ongoing effort to develop and use networks of nanoscalememristivecomponents for unconventional information processing.
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| 8. |
- Bezugly, Eugene, et al.
(författare)
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Subgap current in superconducting tunnel junctions with diffusive electrodes
- 2006
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- We calculate subgap current in planar superconducting tunnel junctions with thin-film diffusive leads. It is found that the subharmonic gap structure of the tunnel current scales with an effective tunneling transparency which may exceed the junction transparency by up to two orders of magnitude depending on the junction geometry, and the ratio between the coherence length and the elastic scattering length. These results provide an alternative explanation of anomalously high values of the subgap current in tunnelling experiments often ascribed to imperfectness of the insulating layer. We also discuss the effect of finite lifetime of quasiparticles as the possible origin of additional enhancement of multiparticle tunnel currents.
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| 9. |
- Bezuglyi, Eugene, et al.
(författare)
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Multiparticle tunnelling in diffusive superconducting junctions
- 2007
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 20:6, s. 529-541
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Bezuglyi, Eugene, et al.
(författare)
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Nonequilibrium effects in tunnel Josephson junctions
- 2005
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- We study nonequilibrium effects in current transport through voltage biased tunnel junction with long diffusive superconducting leads at low applied voltage eV 2Δ, and finite temperatures. Due to a small value of the Josephson frequency, the quasiparticle spectrum adiabatically follows the time evolution of the superconducting phase difference, which results in the formation of oscillating bound states in the vicinity of the tunnel junction (Andreev band). The quasiparticles trapped by the Andreev band generate higher even harmonics of the. Josephson ac current, and also, in the presence of inelastic scattering, a nonequilibrium dc current, which may considerably exceed the dc quasiparticle current given by the tunnel model. The distribution of traveling quasiparticles also deviates from the equilibrium due to the spectrum oscillations, which results in an additional contribution to the dc current, proportional to V.
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