BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Ultrastrong Coupling of matter and radiation: detection of virtua l photons and multiqubit quantum gates DTSTART;VALUE=DATE-TIME:20190622T080000Z DTEND;VALUE=DATE-TIME:20190622T083000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-215@cern.ch DESCRIPTION:Speakers: Giuseppe Falci (University of Catania)\nUltrastrong coupling (USC) between light and matter has been recently achieved in erch itectures of solid state artificial atoms coupled to cavities. They may pr ovide new building blocks for quantum state processing\, where ultrafast q uantum gates can be performed thus meeting the requirements for fault-tole rant quantum computation.\nHowever it has been shown [1] that in the USC r egime the dynamical Casimir effect (DCE)\, may pose limits on the fidelity of quantum operations\, as for protocols based on quantum Rabi oscillatio ns [1]. These latter are used for processing in strongly coupled (SC) circ uit-QED systems where only single excitations are manipulated across the s ystem the cavity working as a quantum bus. In the USC\nmultiphoton generat ion deteriorates the fidelity of such quantum operations [1] even in absen ce of decoherence.\n\nTo overcome this problem we propose a communication channel based on an adiabatic protocol similar to STIRAP [2]. Ideally the cavity is never populated\, operating as a virtual bus\, thus it is expect ed to greatly reduce the impact of DCE. Indeed we show that high fidelity operations can be performed for moderate couplings in the USC regime [3] t hus allowing to operate faster than in SC. Moreover properly crafted contr ol exends the high fidelity region to even larger couplings. The protocol is extremely robust agaist DCE\, in the absence of decoherence yields almo st 100% fidelity for remote population [3] and state trensfer. It is also resilient to decay due to leakage from the cavity\, which is the main deco herence mechanism for present USC architectures [3]. In this more realisti c scenario it is seen that for larger coupling (entering the deep strong c oupling regime) the fidelity decreases due to the interplay between decohe rence and DCE.\n\nThe communication channel we address being a prototype o f family of adiabatic protocols for state transfer and multiqubit gate\, o ur results suggest that adiabatic manipulations\, which has been recently proposed for detecting\ndynamically USC [4]\, may be a promising tool for quantum state processing in the USC regime.\n\n[1] G. Benenti\, A. DArrigo \, S. Siccardi\, and G. Strini\, Phys. Rev. A 90\, 052313 (2014).\n\n[2] N . V. Vitanov\, A. A. Rangelov\, B. W. Shore\, and K. Bergmann\, Rev. Mod. Phys. 89\, 015006 (2017).\n\n[3] M. Stramacchia\, A. Ridolfo\, G. Benenti\ , E. Paladino\, F. M. D. Pellegrino\, G. D. Maccarrone\, G. Falci\, arXiv: 1904.04141\n\n[4] G. Falci\, A. Ridolfo\, P.G. Di Stefano\, and E. Paladin o\, arXiv 1708.00906.\n\nhttps://indico.unina.it/event/18/contributions/21 5/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/215/ END:VEVENT BEGIN:VEVENT SUMMARY:Fast high fidelity quantum non-demolition qubit readout via a non- perturbative cross-Kerr coupling DTSTART;VALUE=DATE-TIME:20190620T140000Z DTEND;VALUE=DATE-TIME:20190620T143000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-247@cern.ch DESCRIPTION:Speakers: Rémy Dassonneville (Institut Néel)\nQubit readout is an indispensable element of any quantum information processor. In this work\,\nwe propose an original coupling scheme between a qubit and a cavi ty mode based on a non-perturbative\ncross-Kerr interaction. This scheme\, using the same experimental techniques as the perturbative cross-Kerr cou pling (dispersive interaction)\, leads to an alternative readout mechanism for superconducting qubits. This\nnew process\, being non-perturbativ e\, maximizes the speed of qubit readout\, its single-shot readout fid elity and\nits quantum non-demolition (QND) behavior at the same time\, wh ile minimizing the effect of unwanted decay channels such as\, for example \, the Purcell effect. We observed 97.4 % single-shot\nreadout fidel ity for short 50 ns pulses. Using long measurement\, we quantifi ed the QND-ness to\n99 %.\n\nhttps://indico.unina.it/event/18/contribut ions/247/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/247/ END:VEVENT BEGIN:VEVENT SUMMARY:Superconducting Quantum-Classical Information Processing Systems DTSTART;VALUE=DATE-TIME:20190620T143000Z DTEND;VALUE=DATE-TIME:20190620T150000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-220@cern.ch DESCRIPTION:Speakers: Oleg Mukhanov (SeeQC)\nTraditionally\, the control a nd measurement of superconducting quantum devices including arrays of qubi ts are done using room-temperature classical electronics connected to cryo genic environment via high fidelity cables. This poses daunting technical challenges to quantum system scaling as the heat load\, latency\, noise as sociated with bringing signals in and out of the cryostat rise dramaticall y with number of quantum devices. By integrating the control and readout e lectronics into the cryostat in proximity to quantum devices\, these probl ems can be drastically reduced to enable large-scale quantum arrays. This can finally lead to quantum processing systems that can outperform the bes t available classical supercomputers. Superconducting Single Flux Quantum (SFQ) digital logic can be a basis for the implementation of a proximal c lassical co-processor for low-overhead qubit control and measurement. SFQ digital circuits also can perform in situ classical processing of the resu lts of quantum measurement to enable fast error tracking and feedback to s tabilize the quantum array. Furthermore\, hybrid quantum-classical systems integrating together the quantum and classical processing hardware units can match to various application algorithm architectures which typically c ombine quantum and classical algorithmic modules. Latest results in the S FQ-based digital control of superconducting qubits will be presented. The implementation of a scalable quantum-classical 3D integrated system extend ing across multiple temperature stages will be discussed.\n\nhttps://indic o.unina.it/event/18/contributions/220/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/220/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Fluctuation Phenomena in Quasi-1D Superconductors DTSTART;VALUE=DATE-TIME:20190622T100000Z DTEND;VALUE=DATE-TIME:20190622T103000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-214@cern.ch DESCRIPTION:Speakers: Konstantin Arutyunov (National Research University H igher School of Economics\, Moscow Institute of Electronics and Mathematic s\, 101000\, Moscow\, Russia\; P.L. Kapitza Institute for Physical Problem s RAS\, 119334\, Moscow\, Russia.)\nSuperconducting properties of metallic nanowires can be entirely different from those of bulk superconductors be cause of the dominating role played by thermal and quantum fluctuations of the order parameter [1]. Fundamental attributes of superconductivity such as zero resistivity\, persistent currents in closed loops\, energy gap in excitation spectra can be drastically violated by fluctuations. Quasi-one -dimensional superconducting channels host sound-like plasma modes propaga ting along the sample which are associated with fluctuations of the phase of the superconducting order parameter [2]. Interaction between these elec tromagnetic excitations and charge carriers affects the electron density o f states (DOS) [3]. Here we report the experimental study of I-V charact eristics of tunnel S1-I-S2 junctions\, where superconducting S2 electrode is a thin nanowire in the regime of quantum fluctuations. The observed bro adening of the I-V dependencies at the gap edge is interpreted as the reno rmalization of DOS. The results are in reasonable agreement with the model [3]\, taking into consideration plasma modes in quasi-one-dimensional sup erconductors.\n\n\n[1] Arutyunov K. Yu.\, Golubev D. S. \, Zaikin A. D. 20 08 Physics Reports 464 1.\n\n[2] Mooij J.E. and G. Schön\, 1985 Phys. R ev. Lett. 55 114.\n\n[3] Radkevich A. A.\, Semenov A. G.\, Zaikin A. D. 2 017 Phys. Rev. B 96 085435.\n\nhttps://indico.unina.it/event/18/contribut ions/214/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/214/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum fluctuations and phase coherence in superconducting nanowi res DTSTART;VALUE=DATE-TIME:20190622T093000Z DTEND;VALUE=DATE-TIME:20190622T094500Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-248@cern.ch DESCRIPTION:Speakers: Alexey Radkevich (Lededev Physical Institute)\nQuant um behavior of superconducting nanowires may essentially depend on the emp loyed experimental setup. Here we investigate a setup that enables passing equilibrium supercurrent across an arbitrary segment of the wire without restricting fluctuations of its superconducting phase. The low temperature physics of the system is determined by a combined effect of collective so und-like plasma excitations and quantum phase slips. At $T=0$ the wire exh ibits two quantum phase transitions\, both being controlled by the dimensi onless wire impedance $g$. While thicker wires with $g>16$ stay supercondu cting\, in thinnest wires with $g<2$ the supercurrent is totally destroyed by quantum fluctuations. The intermediate phase with $2\n\nhttps://indico .unina.it/event/18/contributions/248/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/248/ END:VEVENT BEGIN:VEVENT SUMMARY:Coulomb drag effect in a system of coupled superconducting nanowir es. DTSTART;VALUE=DATE-TIME:20190622T094500Z DTEND;VALUE=DATE-TIME:20190622T100000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-249@cern.ch DESCRIPTION:Speakers: Alexandr Latyshev (Higher school of economics\, Leb edev Physical institute.)\nAl low temperatures superconducting nanowires d emonstrate wide range of intriguing physical phenomena. Of particular inte rest are those that are due to quantum phase slips (QPS)\, as an example t he change in nonlocal transport in superconducting nanowires. This work is devoted to studying the interplay between Coulomb drag effect and QPS in a system of coupled superconducting nanowires. It is important that QPS ge nerate plasmon waves that propagate in separating wires and QPS in one wir e affect on the physical properties of another.\n\nhttps://indico.unina.it /event/18/contributions/249/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/249/ END:VEVENT BEGIN:VEVENT SUMMARY:Superconductor-insulator quantum transition in extra-long\, one-di mensional chains of Josephson junctions DTSTART;VALUE=DATE-TIME:20190622T090000Z DTEND;VALUE=DATE-TIME:20190622T093000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-209@cern.ch DESCRIPTION:Speakers: Alexey Bezryadin (University of Illinois\, Departmen t of Physics\, Urbana\, IL 61801)\nA quantum phase transition (QPT) repres ents a discontinuous change of the ground state of an extended\, ideally i nfinite\, system. Such transitions occur at zero temperature and they are driven by tuning a parameter in the Hamiltonian. If an effective Hamiltoni an is such that it includes some temperature-dependent parameters\, then a temperature-controlled quantum transition (TC-QPT) can be expected. Here we present a TC-QPT between superconducting and insulating regimes in a ch ain of weakly coupled superconducting islands. The transition appears at a temperature where the Josephson energy equals the effective Coulomb charg ing energy\, defined by the electric capacitance between the islands. The insulating state is manifested by a resistance peak\, characterized by an exponential growth of resistance with cooling\, while the superconducting state is represented by an exponential drop of the resistance with cooling . A scaling analysis\, which takes into account the temperature-dependent critical parameter of the observed TC-QPT\, is presented. The temperature dependence of the QPT critical point comes about because the Josephson cou pling energy depends on the BCS energy gap\, which is temperature dependen t.\n\nhttps://indico.unina.it/event/18/contributions/209/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/209/ END:VEVENT BEGIN:VEVENT SUMMARY:Adiabatic quantum computation in a dissipative environment DTSTART;VALUE=DATE-TIME:20190622T073000Z DTEND;VALUE=DATE-TIME:20190622T080000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-223@cern.ch DESCRIPTION:Speakers: Procolo Lucignano (CNR-SPIN Napoli)\nQuantum anneali ng (QA) is getting more and more relevant as powerful solver of optimizati on problems. Thanks to the availability of“commercial​”adiabatic qua ntum computers\, based on QA\, there is plenty of proposals both on the fu ndamental and on the applied side. In QA a target ground state encodes the solution of a computationally hard problem. Such ground state is approach ed exploring the energy landscape\, employing quantum flutcuations that ar e adiabatically decreased towards to zero.\nAnnealing machines are made by arrays of superconducting quantum interferometric devices embedded in cla ssical circuits. They act as a dissipative environment\, that is well know n to modify the dynamics of any quantum two level system\, affecting in a detrimental way the annealing performances.\nI will review some recent res ults regarding the role of dissipation in adiabatic quantum computation\, discussing a simple model i.e. the ferromagnetic p-spin model that\, in th e large p limit\, encodes in its ground state the solution to the Grover ’s algorithm for searching in unsorted databases (that is known to prov ide a quadratic speed-up with respect to its best classical counterpart). Unexpectedly\, under some particular conditions\, the system-bath coupling can improve the annealing performances. I will discuss the role of pausin g as well as the problem of the embedding on real devices.\nTo conclude\, in the presence of a dissipative bath\, the question whether the dynamics has driven the system to the target state through a quantum or a classical path\, up to now\, remained unanswered and only partially addressed in th e literature\, and the question is still controversial.\nHence I will desc ribe a new method that we have proposed to assess the quantumness of the s ystem during its adiabatic dynamics\, based on the Leggett Gargs inequalit ies (LGI)\, evaluated in the framework of weak measurements.\n\nG. Passare lli\, G. De Filippis\, V. Cataudella\, P. Lucignano PRA 97\, 022319 (2018) \nL. M. Cangemi\, G. Passarelli\, V. Cataudella\, P. Lucignano\, G. De Fil ippis PRB 98 184306 (2018)\nG. Passarelli\, V. Cataudella\, P. Lucignano a rXiv:1902.06788 \nV. Vitale\, G. De Filippis\, A. De Candia\, A. Tagliaco zzo\, V. Cataudella\, P. Lucignano arXiv:1902.08257\n\nhttps://indico.uni na.it/event/18/contributions/223/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/223/ END:VEVENT BEGIN:VEVENT SUMMARY:Universal Scaling of Quantum Geometric Tensor in Disordered Metals DTSTART;VALUE=DATE-TIME:20190622T070000Z DTEND;VALUE=DATE-TIME:20190622T073000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-237@cern.ch DESCRIPTION:Speakers: Gergely Zarand (Exotic Quantum Phases “Momentum” Research Group\, Department of Theoretical Physics\, Budapest University of Technology and Economics\, 1111 Budapest\, Budafoki ut 8\, Hungary)\nTh e geometrical structure of the Hilbert space continues to receive a lot of attention. The Fubini-Study metric tensor of the Hilbert space\, also ref erred to as Fisher information metric\, provides a natural measure of dist ance in the Hilbert space\, related to quantum fidelity – a fundamental concept in quantum information science. Interestingly\, the concepts of th e Fubini-Study metric tensor and the Berry phase can be unified through th e so-called quantum geometric tensor (QGT).\n\nIn the work to be presented [1]\, we demonstrate that the quantum geometric tensor offers deep insigh t into a long-standing problem in condensed matter physics\, Anderson’s disorder-driven metal insulator (MI) transition in small external magnetic fields. In particular\, the structure of the QGT reflects the universalit y class of the Anderson transition. Elements of the QGT display universal finite size scaling close to the metal-insulator transition\, and capture the flow between the orthogonal (B = 0) and unitary (B 6=.. 0) universalit y classes. At the transition\, the elements of the QGT have universal dist ributions\, characteristic of the underlying symmetry of the transition\, but\, surprisingly\, independent of the direction of the external field. W e predict that these universal fluctuations show up as universal and isotr opic Hall conductance fluctuations at the metal-insulator transition.\n\n[ 1] Miklós Antal Werner\, Arne Brataas\, Felix von Oppen\, Gergely Zaránd \, Phys. Rev. Lett. 122 (2019) 106601.\n\nhttps://indico.unina.it/event/18 /contributions/237/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/237/ END:VEVENT BEGIN:VEVENT SUMMARY:Superconductivity\, ferromagnetism and Rashba spin-orbit coupling in oxide 2DES DTSTART;VALUE=DATE-TIME:20190621T100000Z DTEND;VALUE=DATE-TIME:20190621T103000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-213@cern.ch DESCRIPTION:Speakers: Daniela Stornaiuolo (Dipartimento di Fisica Ettore P ancini\, Università degli Studi di Napoli Federico II)\nTwo dimensional e lectron systems (2DES) formed at the interface between insulating transiti on metal oxides have demonstrated an extraordinary range of properties. Th e coexistence among these properties can be studied vie electric field eff ect\, making these systems an ideal test bench for the investigation of no vel quantum phenomena.\nA notable example is the coexistence between super conductivity and Rashba spin-orbit coupling in the 2DES at the interface b etween LaAlO3 and SrTiO3 (LAO/STO). We will review the recent remarkable p rogresses in realization of complex LAO/STO superconducting nanodevices an d focus on indications of an unconventional superconducting order paramete r obtained in LAO/STO Josephson junctions [1].\nMoreover\, thanks to the i ntroduction of a delta-doping layer of EuTiO3 sandwiched between STO and L AO\, ferromagnetic correlations were recently added to this picture [2]. W e will present a study of the interplay between ferromagnetism and Rashba spin-orbit coupling in LAO/ETO/STO heterostructures performed by analyzing the magnetotransport data as a function of the carrier density and of the temperature [3]. We will show also that the ferromagnetic correlations in this system can be tuned by light illumination. \n\n[1] G.Cheng et al.\, Nature 521\, 196 (2015)\; L. Kuerten et al.\, Phys. Rev. B 96\, 014513 (20 17)\; G.E.D.K Prawiroatmodjo et al.\, Nat. Comm. 8\, 395 (2017)\, D. Storn aiuolo et al.\, Physical Review B\, 95\, 140502(R) (2017)\n[2] D. Stornaiu olo et al.\, Nature Materials 15\, 278-283 (2016).\n[3] D. Stornaiuolo et al.\, Physical Review B 98 (7)\, 075409 (2018)\n\nhttps://indico.unina.it/ event/18/contributions/213/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/213/ END:VEVENT BEGIN:VEVENT SUMMARY:Unconventional superconductivity induced in the surface states of 3D Topological insulators DTSTART;VALUE=DATE-TIME:20190621T093000Z DTEND;VALUE=DATE-TIME:20190621T100000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-250@cern.ch DESCRIPTION:Speakers: Floriana Lombardi (Department of Microtechnology and Nanoscience\, Chalmers University of Technology\, SE-412 96 Göteborg\, S weden)\nJosephson junctions involving a conventional superconductor and an exotic conductor\, represented by the surface of a 3D topological insulat or (TI)\, a Dirac semimetal or the edge states of two-dimensional quantum wells\, are ideal systems to emulate topological superconductivity charact erized by unconventional order parameter (OP)\, with an orbital component assuming the form of a chiral px + ipy wave. Topological superconductivity is instrumental for the nucleation of Majorana fermion at the basis for topological quantum computation \nHere I will report our results on phase- sensitive measurements\, based on the quantum interference in a Josephson junction\, realized using Al- Bi2Te3-Al devices. The experiment allows to establish that the proximity with a conventional superconductor induces an order parameter in the surface states of the topological insulator Bi2Te3 \, which is consistent with a chiral px + ipy (p-wave) order parameter (OP ). This is achieved by measuring the magnetic field pattern of the juncti ons which shows a dip at zero external magnetic field\, a signature of the simultaneous existence of “0” and “π” coupling within the juncti on\, inherent to an OP with a non trivial phase1. The peculiar nano-textur ed nature of the morphology of the Bi2Te3 flakes\, and the dramatic role p layed by thermal strain are the surprising key factors for the display of an effective induced chiral px + ipy OP. \nTo reduce the number of modes and to reveal the 4π-periodic current-phase relation inherent to Major ana bound states in superconducting hybrids we have also realized Josephso n junctions using 3DTI nanowires 2. In such devices we observe a contribut ion of 4π-periodic Majorana bound states to the supercurrent in Al- Bi2Se 3-Al devices revealed by studying the junction under GHz microwave irradia tion and the Josephson current as a function of the temperature. \n \n\n[ 1] S. Charpentier\, L. Galletti\, G. Kunakova\, R. Arpaia\, Y. Song\, R. B aghdadi\, S. M. Wang\, A. Kalaboukhov\, E. Olsson\, F. Tafuri\, D. Golubev J. Linder\, T. Bauch and F. Lombardi Nature Communications 8\, (2017) \ n\n[2] G. Kunakova\, L. Galletti\, S. Charpentier\, J. Andzane\, D. Ert s\, F. Léonard\, C. D. Spataru\, T. Bauch and F. Lombardi Nanoscale 10\, 19595 (2018)\n\nhttps://indico.unina.it/event/18/contributions/250/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/250/ END:VEVENT BEGIN:VEVENT SUMMARY:In situ tailoring of single superconducting junctions and nano-SQU IDs via current-induced atom migration DTSTART;VALUE=DATE-TIME:20190621T090000Z DTEND;VALUE=DATE-TIME:20190621T093000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-202@cern.ch DESCRIPTION:Speakers: Alejandro Silhanek (Université de Liège\, Belgium) \nWe demonstrate the in situ engineering of superconducting nanowires via modulation of material properties through high applied current densities [ 1]. We show that the sequential repetition of such customized electro-anne aling in a niobium nanoconstriction can broadly tune the superconducting c ritical temperature Tc and the normal-state resistance Rn in the targeted area. Once a sizable Rn is reached\, clear magneto-resistance oscillations are detected along with a Fraunhofer-like field dependence of the critica l current\, indicating the formation of a weak link with adjustable charac teristics [2]. Applying this method to aluminum nanoconstrictions\, it is possible to modify their geometry and consequently their weak links’ pro perties beyond the limit of current lithography techniques [3]. Furthermor e\, conducting parallel electromigration in aluminum SQUIDs allows us to i nvestigate the evolution of the superconducting properties of the SQUID as function of the cross section of the weak links and eventually access a r egime where the SQUID can be operated in the dissipative state. We will al so discuss the possibility to change the local oxygen doping in constricti ons made of High-Tc materials [4]. \n\n[1] V. Zharinov et al. Rev. Sci. In strum. 89\, 043904 (2018)\n[2] J. Lombardo et al. Nanoscale 10\, 1987 (201 8)\n[3] X.D.A. Baumans et al. Nat. Commun. 7\, 10560 (2016)\n[4] X.D.A. Ba umans et al. Small 13\, 1700384 (2017)\n\nhttps://indico.unina.it/event/18 /contributions/202/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/202/ END:VEVENT BEGIN:VEVENT SUMMARY:The Coulomb drag effect induced by the third cumulant of current DTSTART;VALUE=DATE-TIME:20190621T080000Z DTEND;VALUE=DATE-TIME:20190621T083000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-218@cern.ch DESCRIPTION:Speakers: Eugene Sukhorukov (University of Geneva\, Switzerlan d)\nThe Coulomb drag effect arises due to electron-electron interactions\, when two metallic conductors are placed in close vicinity to each other. It manifests itself as a charge current or voltage drop induced in one of the conductors\, if the current flows through the second one. Often it can be interpreted as an effect of rectification of the non-equilibrium quant um noise of current. Here\, we investigate the Coulomb drag effect in meso scopic electrical circuits and show that it can be mediated by classical f luctuations of the circuit collective mode. Moreover\, by considering this phenomenon in the context of the full counting statistics of charge trans port we demonstrate that not only the noise power\, but also the third cum ulant of current may contribute to the drag current. We discuss the situat ions\, where this contribution becomes dominant.\n\nhttps://indico.unina.i t/event/18/contributions/218/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/218/ END:VEVENT BEGIN:VEVENT SUMMARY:Full counting statistics of quantum phase slips DTSTART;VALUE=DATE-TIME:20190621T073000Z DTEND;VALUE=DATE-TIME:20190621T080000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-219@cern.ch DESCRIPTION:Speakers: Andrew G. Semenov (P.N.Lebedev Physical Institute)\n In our talk we present a microscopic theory describing complete statistics of voltage fluctuations generated by quantum phase slips (QPS) in superco nducting nanowires. We evaluate the cumulant generating function and demon strate that shot noise of the voltage as well as the third and all higher voltage cumulants differ from zero only due to the presence of QPS. In the zero-frequency limit voltage fluctuations in superconducting nanowires ar e described by Poisson statistics just as in a number of other tunneling-l ike problems. However\, at non-zero frequencies quantum voltage fluctuatio ns in superconducting nanowires become much more complicated and are not a nymore accounted for by Poisson statistics. In the case of short supercond ucting nanowires we explicitly evaluate all finite-frequency voltage cumul ants and establish a non-trivial relation between these cumulants and the current-voltage characteristics of our system.\n\nhttps://indico.unina.it/ event/18/contributions/219/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/219/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Interference in Phase Slip Devices DTSTART;VALUE=DATE-TIME:20190621T070000Z DTEND;VALUE=DATE-TIME:20190621T073000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-238@cern.ch DESCRIPTION:Speakers: Oleg Astafiev (National Physical Laboratory\, Teddi ngton\, UK \, Department of Physics\, Royal Holloway University of London\ , Egham\, UK\, Moscow Institute of Physics and Technology\, Dolgoprudny\, Russia\, Skolkovo Institute of Science and Technology\, Moscow\, Russia)\n The Coherent Quantum Phase Slip (CQPS) effect in superconducting nanowires is exactly dual to the Josephson effect – tunneling of Cooper pairs thr ough a thin dielectric layer. CQPS has been experimentally proven for the first time in Ref. [1] and since then reproduced in different materials [2 \, 3]. CQPS is interesting from the fundamental point of view as well as f or practical applications\, particularly\, for quantum metrology as it pro mises to build quantum current standards dual to voltage standards on the Josephson effect. An important milestone in this direction is the demonstr ation of interference of a pair of flux tunneling amplitudes similarly to charge tunneling amplitudes in SQUIDs. \n We demonstrate a device exactly dual to SQUID\, which we call a charge quantum interference device (CQUID) [4]. The two nominally identical nanowires with constrictions separated b y a superconducting island are fabricated to observe the quantum interfere nce of two flux tunneling amplitudes. The effective tunneling energy depen ds on the gate induced charge on the island. In our experiment\, the CQUID is incorporated into a superconducting loop\, forming a phase-slip qubit with tunable energy. Such a circuit allows to measure the CQPS energy usin g spectroscopic methods. This is exactly dual to the charge qubit with a S QUID\, where the effective Josephson energy is tuned by an external magnet ic flux. \n Figure 1 demonstrates observed oscillations of energies of CQP S qubit with two junctions (nanowires with constrictions) as a function of gate induced charge. The oscillations are not harmonic and well described by the interference effect of two CQPS amplitudes. \n![Energy oscillati ons in CQUID due to interference of two tunneling amplitudes.][1]\n\n\n [ 1]: https://indico.unina.it/event/18/attachments/43/175/Untitled1.png\n[1] O. V. Astafiev\, et. al. Nature 484\, 355 (2012). \n[2] J. T. Peltonen\, et. al. Phys. Rev. B 88\, 220506 (2013). \n[3] J. T. Peltonen\, et. al. Ph ys. Rev. B 94\, 180508(R) (2016). \n[4] S. E. de Graaf\, et. al. Nature Ph ysics 14\, 590 (2018).\n\nhttps://indico.unina.it/event/18/contributions/2 38/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/238/ END:VEVENT BEGIN:VEVENT SUMMARY:Analytical calculation of phase bistability switching rates in dis sipative Jaynes-Cummings model DTSTART;VALUE=DATE-TIME:20190620T164500Z DTEND;VALUE=DATE-TIME:20190620T170000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-205@cern.ch DESCRIPTION:Speakers: Tomáš Novotný (Charles University\, Prague)\nWe s tudy the dynamics of a dissipative Jaynes-Cummings model subject to a stro ng resonant drive. Above a certain drive threshold there appear two metast able states in the stationary state with roughly the same field amplitude but different phases which are well captured by the bifurcation in the neo -classical approach. Their appearance is associated with the splitting of the spectrum of the corresponding Liouvillean heralding the quantum bistab ility. We focus on the analytical evaluation of the switching rates betwee n the two metastable states which we achieve by a generalized Fermi-golden -rule-like method based on a precise estimate of the character of the meta stable states. We find simple analytical expression for the rate surprisin gly of non-exponential (i.e.\, non-Arrhenius) form\, which nevertheless ma tches nearly perfectly the numerical results.\n\nhttps://indico.unina.it/e vent/18/contributions/205/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/205/ END:VEVENT BEGIN:VEVENT SUMMARY:Quasiparticle transport properties in superconductor-ferromagnet-s uperconductor trilayers DTSTART;VALUE=DATE-TIME:20190620T163000Z DTEND;VALUE=DATE-TIME:20190620T164500Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-200@cern.ch DESCRIPTION:Speakers: Zorica Popović (University of Belgrade\, Faculty of Physics)\nA quantitative theory describing the behaviour of current/volta ge characteristics (CVC) and conductances (G) for both s-wave (S) and d- wave (D) type of ballistic voltage-biased superconductor/ferromagnet (F)/ superconductor (SFS or DFD) trilayers is developed. The calculation is b ased on the nonequilibrium microscopic theory of transport in isotropic s- wave superconductor/normal metal (SNS) junctions by Kümmel\, Gunsenheimer and Nikolsky [1] in the relaxation time approximation using the time-depe ndent Bogoliubov-de Gennes equations [2-5]. The model operates for differe nt barrier thicknesses d\, the mean free path in the barrier l>d and diffe rent temperatures T. For given exchange energy h the shape of CVCs depends \, first\, on the barrier thickness\, while the presence and number of non linear structures are determined by h. The behaviour of current-voltage ch aracteristics (CVC) in SFS junctions\, such as steep rise of the current a nd negative differential conductance at small voltage\, as well as the exc hange field dependent position of the peaks\, are obtained for weak exchan ge energy h≤∆\, where ∆=∆(T) is the superconducting energy gap. Su ch behaviour is interpreted to be induced by multiple Andreev reflections (AR)\, modified in presence of h in F. For DFD junctions\, the AR suppress ion due to the presence of order parameter nodes in D\, and the presence o f h in the F barrier leads to relatively smooth CVC for any value of h and of d in contrast to the case of isotropic pairing in superconducting elec trodes (SFS case). This provides an indication of the superconductor order parameter symmetry. For DFD junctions with misoriented superconducting el ectrodes we found that at low bias the coherence in the quasiparticle tran sport could be enhanced by magnetic field in F. For θ=π/4 (d-wave superc onductor is oriented with its gap node facing the boundary with F)\, where the proximity effect is the strongest\, there is an enhancement of the cu rrent (as well as zero bias conductance)\, starting from h=0 up to a maxim um at h≈∆(T). \nWe find that conductance curves G(V) have a rich nonli near structure in low-voltage multiple AR region. At higher voltages\, the curves are almost flat\, with characteristic dips whose position are not influenced by the type of order parameter anisotropy and electrodes misori entation\, but vary only with the h in F and temperature dependent pair po tential in superconductor\, according to the simple law neV=2∆(T)∓h\, with n=0\,1\,…. We suggest that from observed dip's locations at given t emperature one could determine experimentally the value of the exchange fi eld in the barrier. We find that temperature dependence of zero bias cond uctance for h≤∆\, show a kink at some characteristic temperature T^* such that ∆(T^* )=h\, what provides another reliable experimental metho d for measurements of small exchange field.\\\\ \n\n\nReferences \n\n1. R. Kümmel\, U. Gunsenheimer\, and R. Nicolsky\, Phys. Rev. B 42\, 3992 (199 0).\n2. Z. Popović\, L. Dobrosavljević - Grujić\, and R. Zikic\, Ph ys. Rev. B 85\, 174510 (2012).\n3. Z. Popović\, L. Dobrosavljević - Grujić\, and R. Zikic\, J. Phys. Soc. Jpn. 82\, 114714 (2013).\n4. Z. P opović\, R. Zikic\, and L. Dobrosavljević - Grujić\, Prog. Theor. Exp. Phys. 2015\, 103I01 (2015).\n5. Z. Popović\, P. Miranović\, and R. Ziki c\, Phys. Status Solidi B 255\, 1700554 (2018).\n\nhttps://indico.unina.it /event/18/contributions/200/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/200/ END:VEVENT BEGIN:VEVENT SUMMARY:Spinful quantum dot junctions probed by superconductivity and ther moelectricity DTSTART;VALUE=DATE-TIME:20190620T160000Z DTEND;VALUE=DATE-TIME:20190620T163000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-207@cern.ch DESCRIPTION:Speakers: Clemens Winkelmann (Univ. Grenoble Alpes)\nWe invest igate the properties of gate-tunable single quantum dot junctions\, obtain ed by the electromigration technique\, in the spin-1/2 Kondo regime with r ather large $U/\\Gamma$ ($U$ is the on-site interaction and $\\Gamma$ the tunnel coupling). In the first part we investigate the device response in the presence of superconductivity in the leads. We tune the ground state o f the dot quantum spin from screened to unscreened\, using the gate voltag e\, the temperature and the magnetic field. In the second part\, we invest igate the thermoelectric device response in the normal state of the leads\ , in the presence of a thermal gradient. We find a 2e-periodic response of the Seebeck coefficient with respect to the quantum dot charge state\, wh ich provides a characteristic signature of the spin degeneracy of the quan tum dot levels. A sign change of the Seebeck coefficient with increasing t emperature in the oddly occupied state provides a hallmark of Kondo correl ations\, in very good agreement with NRG calculations.\n\nhttps://indico.u nina.it/event/18/contributions/207/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/207/ END:VEVENT BEGIN:VEVENT SUMMARY:Spin-dependent thermoelectric effects in superconductor/ferromagne t hybrid structures DTSTART;VALUE=DATE-TIME:20190620T153000Z DTEND;VALUE=DATE-TIME:20190620T160000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-217@cern.ch DESCRIPTION:Speakers: Detlef Beckmann (KIT\, Institute of Nanotechnology)\ nWe report on the experimental observation of spin-dependent thermoelectri c effects in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of particle-hole symmetry on the energy scale of the superconducting gap. Due to the small energy scale\, the thermoelectric effects can be quite large \, and we infer a maximum Seebeck coefficient of about 100 µV/K from our data. Nonlocal thermoelectric effects elucidate the coupling of spin and h eat transport in high-field superconductors.\n\nhttps://indico.unina.it/ev ent/18/contributions/217/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/217/ END:VEVENT BEGIN:VEVENT SUMMARY:Identifying and Controlling Sources of Decoherence In Superconduct ing Quantum Devices. DTSTART;VALUE=DATE-TIME:20190620T133000Z DTEND;VALUE=DATE-TIME:20190620T140000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-204@cern.ch DESCRIPTION:Speakers: Sergey Kubatkin (Chalmers University of Technology)\ nDespite the promises of superconducting qubits\, their performance is pre sently limited by short coherence times due to defects intrinsic to materi als. As a result\, future quantum computers would require massive error co rrection circuits\, which seem to be very challenging to build. Another mo re promising path would be to improve this coherence time\, which would re lax the constraints on the quantum error correction circuits and would thu s make a quantum computer more feasible. This task is considered one of th e main challenges in the field. Our recent results [1] gave vital clues to the long-standing problem of noise and decoherence in superconducting dev ices: a technique for on-chip Electron Spin Resonance (ESR) [2]\, allowed to identify\, for the first time\, the chemical species responsible for th e flux noise in superconducting circuits [3]. Furthermore\, the most recen t noise measurements in superconducting resonators point to the link betwe en charge and flux noise in superconducting circuits [3]: a mild sample tr eatment has lead to tenfold reduction of the surface spins\, responsible f or the flux noise\, as evidenced by ESR\, and this treatment has also lead to tenfold reduction of the low frequency noise in superconducting resona tor\, usually associated with the charge noise. The chemical identificatio n of the possible remaining sources of noise in superconducting devices al lows for an active chemical intervention\, aiming at silencing the defects and\, therefore\, improving the coherence in superconducting quantum devi ces.\n\n[1] Phys. Rev. Lett. 118\, 057703\, (2017)\n[2] Journ. of Appl. Ph ys. 112\, 123905\, (2012)\n[3] Phys. Rev. Lett. 118\, 057702\, (2017)\n[4] Nature Comms. 9\, 1143\, (2018)\n\nhttps://indico.unina.it/event/18/contr ibutions/204/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/204/ END:VEVENT BEGIN:VEVENT SUMMARY:Low temperature characterization of low-dissipation ferromagnetic Josephson junctions DTSTART;VALUE=DATE-TIME:20190620T103000Z DTEND;VALUE=DATE-TIME:20190620T104500Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-211@cern.ch DESCRIPTION:Speakers: Roberta Caruso (Università degli Studi di Napoli Fe derico II)\nFerromagnetic Josephson junctions present a rich emerging phys ics due to the coupling between ferromagnetism and superconductivity. The interplay between the two competing phases causes an oscillation of the su perconducting order parameter within the ferromagnetic barrier\, which is responsible for the appearance of a π ground state\, and of triplet corre lations in the Josephson junction [1\,2]. Because of such properties\, SFS junctions are sought to have applications in the emerging field of superc onducting spintronics [3] and in quantum and digital superconducting compu tation as phase shifters [4] or as auxiliary circuit elements for error co rrection\, readout and memory elements [5\, 6\, 7\, 8]. Currently\, their use is limited by their metallic\, highly dissipative nature. In this work we will review the properties of a specific category of SFS\, namely low dissipation spin filter junctions [9\,10]. In particular\, we will present a low temperature characterization of such devices down to 0.3K. We measu red several junction parameters as a function of thickness\, focusing our attention on critical current versus temperature dependencies at different thicknesses. We developed a model to describe the anomalous behaviour and the incomplete 0-π transition found in experimental data using short-ran ge triplet correlations. These results offer new perspectives for the stud y of the role of short-range triplet correlations in the transport propert ies of low dissipation ferromagnetic junctions.\n\nhttps://indico.unina.it /event/18/contributions/211/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/211/ END:VEVENT BEGIN:VEVENT SUMMARY:Critical current 1/f noise in graphene Josephson junction DTSTART;VALUE=DATE-TIME:20190620T100000Z DTEND;VALUE=DATE-TIME:20190620T103000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-216@cern.ch DESCRIPTION:Speakers: Elisabetta Paladino (Dipartimento di Fisica e Astron omia\, Università di Catania)\nShort ballistic graphene Josephson junctio ns (GJJ) sustain superconducting current with a strongly non-sinusoidal cu rrent-phase relation (CPR) up to a critical current threshold. The CPR\, a rising from proximitized superconductivity\, is gate-voltage tunable and e xhibits peculiar skewness observed in high-quality graphene-superconductor s heterostructures with clean interfaces. These properties make GJJ promis ing sensitive quantum probes of microscopic fluctuations underlying relati vistic transport in 2D. We demonstrate that fluctuations with 1/f power sp ectrum of the critical current of a short ballistic GJJ directly probe car rier density fluctuations of the graphene channel. Tunability with the che mical potential\, close to and far from the charge neutrality point\, and temperature dependence of the noise amplitude are clear fingerprints of th e underlying material-inherent processes. These results provide also relev ant figure of merits in view of the envisaged implementation of coherent q uantum circuits in hybrid quantum information architectures.\n\nhttps://in dico.unina.it/event/18/contributions/216/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/216/ END:VEVENT BEGIN:VEVENT SUMMARY:Tuning of dissipation in tunnel-ferromagnetic Josephson junctions DTSTART;VALUE=DATE-TIME:20190620T093000Z DTEND;VALUE=DATE-TIME:20190620T100000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-212@cern.ch DESCRIPTION:Speakers: Davide Massarotti (Dipartimento di Ingegneria Elettr ica e delle Tecnologie dell'Informazione\, Università degli Studi di Napo li Federico II)\nJosephson coupling between superconducting and ferromagne tic layers is driving new fundamental physics and innovative applications for superconducting electronics and quantum circuits [1\,2]. Examples are: the possibility to switch the ground state of a Josephson junction (JJ) f rom a 0 to a π phase state\, the existence of JJs having a doubly degener ate ground state with an average Josephson phase ψ = ±φ\, the possibili ty to carry spin-triplet supercurrent in the presence of certain types of magnetic inhomogeneity.\n\nWe will report on a comprehensive study of diss ipation in hybrid JJs composed by pure metallic ferromagnetic layers [3] o r by ferromagnetic-insulator barriers [4\,5\,6]. Transport measurements hi ghlight different dissipation sources\, which reflect different properties of the barriers and of the composition of the junctions. This study provi des the electrodynamic characterization [3\,6\,7] necessary for the possib le use of these systems in more complex circuits\, as cryogenic memories o r spintronic devices\, and suggests new solutions of ferromagnetic JJs in superconducting qubits.\n\n 1. A. A. Golubov and M. Yu Kupriyanov Nat. Mat er. 16\, 156-157 (2017).\n 2. A. K. Feofanov\, et al. Nat. Phys. 6\, 593-5 97 (2010).\n 3. D. Massarotti\, et al. Phys. Rev. B 98\, 144516 (2018).\n 4. D. Massarotti\, et al. Nat. Commun. 6\, 7376 (2015).\n 5. R. Caruso\, e t al. J. Appl. Phys. 123\, 133901 (2018).\n 6. R. Caruso\, et al. Phys. Re v. Lett. 122\, 047002 (2019).\n 7. H. Ahmad et al. in preparation.\n\nhttp s://indico.unina.it/event/18/contributions/212/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/212/ END:VEVENT BEGIN:VEVENT SUMMARY:Cross-correlated shot noise in three-terminal superconducting hybr id nanostructures DTSTART;VALUE=DATE-TIME:20190620T090000Z DTEND;VALUE=DATE-TIME:20190620T093000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-203@cern.ch DESCRIPTION:Speakers: Dmitry Golubev (Aalto University)\nWe work out a uni fied theory describing both nonlocal electron transport and cross-correlat ed shot noise in a three-terminal normal-superconducting-normal (NSN) hybr id nanostructure. We describe noise cross correlations both for subgap and overgap bias voltages and for arbitrary distribution of channel transmiss ions\nin NS contacts. We specifically address a physically important situa tion of diffusive contacts and demonstrate nontrivial behavior of nonlocal shot noise exhibiting both positive and negative cross correlations depen ding on\nthe bias voltages. For this case\, we derive a relatively simple analytical expression for cross-correlated noise power which contains only experimentally accessible parameters.\n\nhttps://indico.unina.it/event/18 /contributions/203/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/203/ END:VEVENT BEGIN:VEVENT SUMMARY:Topology- and Geometry-Induced Properties of Advanced Nanoarchitec tures DTSTART;VALUE=DATE-TIME:20190620T080000Z DTEND;VALUE=DATE-TIME:20190620T083000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-210@cern.ch DESCRIPTION:Speakers: Vladimir M. Fomin ((1) Institute for Integrative Nan osciences\, Leibniz IFW Dresden (2) Laboratory of Physics and Engineering of Nanomaterials\, Department of Theoretical Physics\, Moldova State Unive rsity )\nStudy of topological matter is one of the fascinating main roads of modern physics. The present overview is aimed at topology- and geometry -driven effects\, owing to special geometries of novel micro- and nanoarch itectures fabricated of both conventional and topologically nontrivial mat erials implemented by the high-tech techniques\, in particular\, self-orga nization [1\, 2]. I will demonstrate how topology of the quantum fields de termines electronic [3]\, excitonic [4]\, optical\, superconducting [5]\, magnetic\, thermal [6] properties of emerging nanostructured materials lea ding to their functionalization towards novel applications in advanced nan otechnologies. Self-assembled quantum volcanos\, which are singly connecte d\, surprisingly exhibit the Aharonov–Bohm behavior in experiment. This is explained by the fact that in a quantum volcano the electron wave funct ions are identical to the electron wave functions in a quantum ring from a topological point of view. Combination of a geometric potential and an in homogeneous twist renders an observation of the topology-driven effects in the electron ground-state energy in Möbius rings at the microscale into the area of experimental verification. Advances in the high-tech roll-up f abrication methods have provided qualitatively novel curved superconductor micro- and nanoarchitectures\, e.g.\, nanostructured microtubes and micro helices. Rolling up superconductor Nb nanomembranes into open tubes allows for a new\, highly correlated vortex dynamics regime that shows a three-f old increase of a critical magnetic field for the beginning of vortex moti on and a transition magnetic field between single- and many-vortex dynamic patterns. These results demonstrate pathways of tailoring nonequilibrium properties of vortices and phase slips in curved superconductor nanoarchit ectures leading to their application as tunable superconducting flux gener ators for fluxon-based information technologies. For various micro- and na noarchitectures\, we have found a possibility of efficiently engineering t he Seebeck coefficient and electric conductivity in one-dimensional stacks of quantum dots\, acoustic phonon energy dispersion in one-dimensional qu antum-dot superlattices\, cross-section-modulated nanowires\, Si wires ran ging from nanoscale to microscale\, and\, more recently\, multishell tubul ar structures\, which are promising candidates for an advancement in therm oelectric materials and devices. I gratefully acknowledge the support of t he COST Action "Nanoscale Coherent Hybrid Devices for Superconducting Quan tum Technologies" CA16218 and the German Research Foundation (DFG) under g rants #FO 956/4-1 and FO 956/5-1.\n\n[1] V. M. Fomin\, Topology-driven eff ects in advanced nanoarchitectures\, in: A. Sidorenko (Ed.)\, Functional N anostructures and Metamaterials\, Springer International Publishing\, Cham \, 2018\, 195 – 220. \n\n[2] V. M. Fomin\, Topology and geometry contr olled properties of nanoarchitectures\, Phys. Stat. Sol. – Rapid Researc h Letters 13\, 1800595 (2019). \n\n[3] V. M. Fomin (Editor)\, Physics of Q uantum Rings\, 2nd Edition\, Springer International Publishing\, Cham\, 20 18\, 586 p. \n\n[4] P. Corfdir\, O. Marquardt\, R. B. Lewis\, C. Sinito\, M. Ramsteiner\, A. Trampert\, U. Jahn\, L. Geelhaar\, O. Brandt\, V. M. Fo min\, Excitonic Aharonov–Bohm oscillations in core–shell nanowires\, A dv. Mater. 31\, 1805645 (2019).\n\n[5] R. O. Rezaev\, E. A. Posenitskiy\, E. I. Smirnova\, E. A. Levchenko\, O. G. Schmidt\, V. M. Fomin\, Voltage induced by superconducting vortices in open nanostructured microtubes\, Ph ys. Stat. Sol. – Rapid Research Letters 13\, 1800251 (2019).\n\n[6] V. M . Fomin\, Tailoring electron and phonon energy dispersion and thermal tran sport in nano- and microarchitectures\, Moldavian Journal of the Physical Sciences 17\, 121-131 (2018).\n\nhttps://indico.unina.it/event/18/contribu tions/210/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/210/ END:VEVENT BEGIN:VEVENT SUMMARY:Coherent quantum phenomena in ultimate 2D superconductors: A STM s tudy DTSTART;VALUE=DATE-TIME:20190620T073000Z DTEND;VALUE=DATE-TIME:20190620T080000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-208@cern.ch DESCRIPTION:Speakers: Dimitri Roditchev (Laboratoire de Physique et d’Et ude des Matériaux (LPEM) and Institut des Nanosciences de Paris (INSP)\, Sorbonne University\, PSL-University\, CNRS & ESPCI-Paris\, France)\nIn 1 964 V. L. Ginzburg predicted that new superconducting phases could appear in ultrathin films deposited on insulating surfaces. In 2010 superconducti vity below 2K was discovered in some crystalline atomic monolayers of Pb g rown on atomically clean Si(111) [1\,2]. Owing their peculiar electronic p roperties\, these two-dimensional materials manifest a number of intriguin g superconducting phenomena. In crystalline monolayers of Pb on Si(111) th e superconducting condensate is an intrinsic Josephson network formed by s uperconducting terraces coupled by Josephson links at individual atomic st eps [1]. The detailed atomic arrangement at each step decides the strength of the Josephson coupling. In a magnetic field\, the superconducting vort ex phase contains different kinds of vortices\, ranging from Abrikosov (Pe arl) to Josephson limits. By contrast\, amorphous monolayers of Pb are non -superconducting correlated metals. Playing with geometry of in-situ grown samples enables realizing ultimately thin lateral SNS junctions\, reveal and study Josephson proximity vortices inside their N-parts [2]. \nWhen in dividual magnetic impurities are added\, the Cooper pairs are scattered in a peculiar manner\, resulting in so-called Yu\, Shiba and Rusinov (YSR) b ound states. While in three-dimensional superconductors these states rapid ly decay around impurities on atomic scale\, superconductors with two-dime nsional electronic structure such as 2H-NbSe2 or Pb-monolayers on Si(111) host YSR bound states with spatial extents orders of magnitude larger [3]. These long-range magnetic states could be used to produce new topological phases in hybrid systems such as arrays or clusters of magnetic atoms [4] and molecules coupled through the 2D-superconducting medium.\nIn our lect ure we describe a series of recent experiments which mapped superconductiv ity\, vortices and YSR states in Pb/Si(111) and 2H-NbSe2 by scanning tunne ling microscopy and spectroscopy at ultralow temperatures. \n\n[1] Ch. Bru n\, et al. Nature Phys. 10\, 444 (2014)\n[2] D. Roditchev\, et al. Nature Phys. 11\, 332 (2015)\n[3] G. Ménard\, et al. Nature Phys. 11\, 1013 (201 5)\n[4] G. Ménard\, et al. Nature Comm. 8\, 2040 (2017)\n\nhttps://indico .unina.it/event/18/contributions/208/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/208/ END:VEVENT BEGIN:VEVENT SUMMARY:Atomic scale scanning tunneling spectroscopy with superconducting tips DTSTART;VALUE=DATE-TIME:20190620T070000Z DTEND;VALUE=DATE-TIME:20190620T073000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-206@cern.ch DESCRIPTION:Speakers: Hermann Suderow (Universidad Autonoma de Madrid)\nTh e scanning tunneling microscope (STM) allows for a rather unique control o ver matter at atomic scale. By measuring at very low temperatures\, it als o serves as a spectroscopic probe of low energy phenomena\, such as superc onductivity. As such\, the STM can measure all known features of supercond ucting tunneling\, namely density of states\, inelastic tunneling\, Andree v scattering and Josephson effect. I will review results obtained with thi s technique and discuss recent insight obtained in atomic scale Josephson junctions and in unconventional superconductors.\n\nhttps://indico.unina.i t/event/18/contributions/206/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/206/ END:VEVENT BEGIN:VEVENT SUMMARY:Unveiling the bosonic nature in an ultrashort single-electron puls e DTSTART;VALUE=DATE-TIME:20190619T163000Z DTEND;VALUE=DATE-TIME:20190619T170000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-246@cern.ch DESCRIPTION:Speakers: Everton Arrighi (Institut Neel)\nQuantum dynamics is very sensitive to dimensionality. While two-dimensional electronic system s form Fermi liquids\, one-dimensional systems - Tomonaga-Luttinger liquid s - are described by purely bosonic excitations\, even though they are ini tially made of fermions. \nWith the advent of coherent single-electron sou rces [1- 3]\, the quantum dynamics of such a liquid is now accessible at t he single-electron level. Very little is known\, however\, on the propagat ion of such single electron charge excitations.\nHere\, we investigate in a time-resolved manner the propagation of an ultrashort single-electron ch arge pulse injected into a quasi-one-dimensional quantum conductor. This a llows us to extract the collective\ncharge excitation velocity. We show th at the velocity of such a single electron pulse is found to be much faster than the Fermi velocity due to the presence of strong electron-electron i nteractions and can be tuned over more than an order of magnitude by elect rostatic confinement. In addition\, our set-up allows us to tune our syste m continuously from a clean one-channel Tomonaga-Luttinger liquid to a mul ti-channel Fermi liquid. Our results [4] are in quantitative agreement wit h a parameter-free theory and demonstrate a powerful new probe for directl y investigating real-time dynamics of fractionalisation phenomena in low-d imensional conductors.\n[1] G. Fève\, A. Mahé\, J.-M. Berroir\, T. Konto s\, B. Plaçais\, D.C. Glattli\, A. Cavanna\, B. Etienne\, Y. Jin. “An O n-Demand Coherent Single-Electron Source”. Science 316\, 1169-1172 (2007 ).\n[2] J. Dubois\, T. Jullien\, F. Portier\, P. Roche\, A. Cavanna\, Y. J in\, W. Wegscheider\, P. Roulleau and D.C. Glattli. “Minimal-excitation states for electron quantum optics using levitons.”\, Nature 502\, 659-6 63 (2013)\n[3] C. Bäuerle\, C. Glattli\, T. Meunier\, F. Portier\, P. Roc he\, P. Roulleau\, S. Takada\, and X. Waintal\, “Coherent control of sin gle electrons: a review of current progress”\, Rep. Prog. Phys (2018) DO I: 10.1088/1361-6633/aaa98a\n[4] G. Roussely\, E. Arrighi\, G. Georgiou\, S. Takada\, M. Schalk\, M. Urdampilleta\, A. Ludwig\, A. D. Wieck\, P. Arm agnat\, T. Kloss\, X. Waintal\, T. Meunier\, and C. Bauerle. Unveiling the bosons in an ultra-short single electron pulse\, Nature Communications 9\ , 2811 (2018)\n\nhttps://indico.unina.it/event/18/contributions/246/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/246/ END:VEVENT BEGIN:VEVENT SUMMARY:Elusive Bose metal is a Bosonic Topological Insulator DTSTART;VALUE=DATE-TIME:20190619T153000Z DTEND;VALUE=DATE-TIME:20190619T160000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-221@cern.ch DESCRIPTION:Speakers: Valerii Vinokur (Argonne National Laboratory)\nTrans port measurements of the superconductor-insulator transition (SIT) in diso rdered two-dimensional films and Josephson junction arrays showed the exis tence of an anomalous metallic phase that persists to low temperatures. Th e nature of this mysterious phase often referred to as “Bose metal\,” remains unclear. We develop a gauge theory of the Bose metal as the phase in which Cooper pairs and vortices are out of the Bose condensate due to s trong quantum fluctuations and form an incompressible liquid of intertwine d Aharonov-Bohm-Casher loops. As a result\, the Bose metal emerges as an i nteger (Z) bosonic topological insulator in which bulk transport is suppre ssed by topological mutual statistics interactions\, the Hall resistance v anishes\, and longitudinal charge transport is mediated by U(1)-symmetry-p rotected gapless edge modes. The transport measurements in NbTiN films acr oss the disorder- and magnetic field-driven SIT and observe a disorder and magnetic field–tuned transition from a true superconductor to a metalli c phase with saturated longitudinal resistivity.\n\nhttps://indico.unina.i t/event/18/contributions/221/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/221/ END:VEVENT BEGIN:VEVENT SUMMARY:Coherent effects in junctions based on p-wave superconductor DTSTART;VALUE=DATE-TIME:20190619T150000Z DTEND;VALUE=DATE-TIME:20190619T153000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-201@cern.ch DESCRIPTION:Speakers: Alexander Golubov (Moscow Institute of Physics and T echnology\, Dolgoprudny\, Russia\, and Faculty of Science and Technology\, University of Twente\, Enschede\, The Netherlands)\nThe famed p-wave supe rconductivity harbors a variety of exotic topological states. The practica l ways for its implementing are being extensively discussed in literature\ , and the contact of a superconductor with the topological insulator is ex pected to become the most promising candidate. There have been reports of the 4π-periodicity in such contacts\, which are a hallmark of the p-wave superconductivity. However\, the phase-sensitive measurements of the Josep hson currents that would serve as conclusive evidence of the p-wave symmet ry are still lacking. In this work we report direct observation of the Jos ephson effect in the Nb/Bi2Te2Se/Nb structures which are characterized by ballistic electronic transport across the Bi2Te2Se nanocrystals. We show t hat in the mK temperature range the investigated junctions exhibit a new t ype of oscillations of the Josephson current in magnetic field with an ult ra-short period ∼ 1 Oe corresponding to energy spectrum with the level s pacing of order of 1 µeV. We develop theoretical model explaining these o scillations in terms of fine structure of low-energy Andreev bound states. The results are consistent with emerging p-wave superconducting correlati ons induced at the Bi2Te2Se surface due to an interplay between the s-wave superconductivity in Nb and a peculiar symmetry of the topological insula tor Bi2Te2Se. This work is supported by the Russian Science Foundation (P roject No. 18-72-10118)\, the EU H2020-WIDESPREAD-05-2017-Twinning project “SPINTECH” (the Grant Agreement No. 810144) and by Dutch FOM.\n\nhttp s://indico.unina.it/event/18/contributions/201/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/201/ END:VEVENT BEGIN:VEVENT SUMMARY:Topological Superconductivity in Non-Centrosymmetric Materials DTSTART;VALUE=DATE-TIME:20190619T160000Z DTEND;VALUE=DATE-TIME:20190619T163000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-222@cern.ch DESCRIPTION:Speakers: Matthias Eschrig (Royal Holloway\, University of Lon don)\nRecent interest in the effect of intrinsic spin-orbit coupling in ma terials that exhibit an excitation gap has led to the notions of topologic al insulators and topological superconductors. Intrinsic spin-orbit coupli ng is enhanced in non-centrosymmetric materials\, as in this case already band-diagonal matrix elements contribute. We study non-centrosymmetric sup erconductors with various point group symmetries. For self-consistent orde r parameter profiles we calculate the surface density of states\, showing intricate structure of spin-polarised Andreev bound states. The topology ’s effect on the surface states and the tunnel conductance is thoroughly investigated\, and a topological phase diagram is constructed for open an d closed Fermi surfaces showing a sharp transition between the two for the cubic point group O.\n\nhttps://indico.unina.it/event/18/contributions/22 2/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/222/ END:VEVENT BEGIN:VEVENT SUMMARY:opening DTSTART;VALUE=DATE-TIME:20190619T143000Z DTEND;VALUE=DATE-TIME:20190619T150000Z DTSTAMP;VALUE=DATE-TIME:20260907T115750Z UID:indico-contribution-18-251@cern.ch DESCRIPTION:https://indico.unina.it/event/18/contributions/251/ LOCATION:Strand Hotel Terme Delfini URL:https://indico.unina.it/event/18/contributions/251/ END:VEVENT END:VCALENDAR