BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Fast and Robust Phase Gates with Trapped-Ion Hyperfine Qubits DTSTART;VALUE=DATE-TIME:20170718T133500Z DTEND;VALUE=DATE-TIME:20170718T135500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4453@indico.ific.uv.es DESCRIPTION:Speakers: Iñigo Arrazola (University of the Basque Country)\n I will present a proposal for generating fast and robust quantum phase gat es between two microwave-driven hyperfine ions\, making use of a pulsed dy namical decoupling protocol. The scheme consists of a series of pi-pulses that are applied individually to each ion\, whose internal level act as a qubit. Unlike previous proposals\, this gate uses both axial vibrational m odes as the quantum bus between both qubits. In this way\, we are able to achieve a higher gate speed. In addition\, I will argue that the proposed gate is robust against most harmful noise sources\, related with fluctuati ons of the Rabi frequency or the magnetic field. Our numerical simulations show that with state-of-the-art ion trap technology\, entangling gates wi th fidelities above 99.9% can be produced in tens of microseconds.\n\nhttp s://indico.ific.uv.es/event/2851/contributions/4453/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4453/ END:VEVENT BEGIN:VEVENT SUMMARY:Nanoscale control of antenna-coupling strength g for bright single photon sources DTSTART;VALUE=DATE-TIME:20170718T162500Z DTEND;VALUE=DATE-TIME:20170718T164500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4444@indico.ific.uv.es DESCRIPTION:Speakers: Niek F. van Hulst (ICFO - the Institute of Photonic Sciences)\nCavity QED is the art of enhancing light-matter interaction of photon emitters in cavities\, with opportunities for sensing\, quantum inf ormation and energy capture technologies. To boost emitter-cavity interact ion\, i.e. coupling strength 𝑔\, ultrahigh quality cavities have been c oncocted yielding photon trapping times of µs to ms. However\, such high- Q cavities give poor photon output\, hindering applications. To preserve h igh photon output it is advantageous to strive for highly localised electr ic fields in radiatively lossy cavities. Nanophotonic antennas are ideal c andidates combining low-Q factors with deeply localised mode volumes\, all owing large 𝑔\, provided the emitter is positioned exactly right inside the nanoscale mode volume. Here\, with nanometre resolution\, we map and tune the coupling strength between a dipole nanoantenna-cavity and a singl e molecule\, obtaining a coupling rate of 2𝑔max = 412 GHz. Together wit h accelerated single photon output\, this provides ideal conditions for fa st and pure non-classical single photon emission with brightness exceeding 10E9 photons/sec. Clearly nanoantennas\, acting as “bad” cavities\, o ffer an optimal regime for strong coupling 𝑔\, to deliver bright on-dem and and ultrafast single photon nanosources for quantum technologies.\n\nh ttps://indico.ific.uv.es/event/2851/contributions/4444/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4444/ END:VEVENT BEGIN:VEVENT SUMMARY:Characterising multi-photon quantum interference with decoy-state techniques DTSTART;VALUE=DATE-TIME:20170718T143500Z DTEND;VALUE=DATE-TIME:20170718T145500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4429@indico.ific.uv.es DESCRIPTION:Speakers: Álvaro Navarrete Rodríguez (Universidad de Vigo)\n Correct characterization of general linear optical networks is becoming a promising task due to the continuous development in some fields as quantum computation and quantum communications\, in which quantum optics is typic ally involved. Specifically\, it is of great importance in several applica tions to know the photon number statistics at the outputs of the linear ne twork as a function of the input photon number to check its quality. Altho ugh in recent years there have been some advances in multi-photon sources and photon number resolution a simple plug-and-play method for characteris ing general linear optics networks with enough accuracy is still missing. We propose a simple and practical method to estimate these photon number s tatistics that can be implemented with laser sources that generate quantum signals which are diagonal in the Fock basis in combination with threshol d single-photon detectors.\n\nhttps://indico.ific.uv.es/event/2851/contrib utions/4429/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4429/ END:VEVENT BEGIN:VEVENT SUMMARY:Measurement-Device-Independent Quantum Key Distribution with Infor mation Leakage DTSTART;VALUE=DATE-TIME:20170718T160500Z DTEND;VALUE=DATE-TIME:20170718T162500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4426@indico.ific.uv.es DESCRIPTION:Speakers: Weilong Wang (University of Vigo)\nMeasurement-devic e-independent quantum key distribution (MDI-QKD) is proposed to remove all the detection side-channels in quantum communication systems. In recent y ears\, MDI-QKD has been proven to be secure with certain assumptions and b ecome a significant step toward the practicality of QKD systems. However\, the assumption that there is no information leakage from the security zon es of the legitimate parties seems very difficult to be guaranteed in prac tice. In this work we relax this assumption by proposing a general formali sm to prove the security of MDI-QKD in the presence of information leakage . Particularly\, we analyze a specific Trojan-Horse attack on the intensit y modulator and phase modulator and the secure key rates under different a mounts of information leakage are calculated in several practical cases. O ur work provides an essential reference for experimentalists to ensure the security when implementing MDI-QKD protocols in the presence of informati on leakage.\n\nhttps://indico.ific.uv.es/event/2851/contributions/4426/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4426/ END:VEVENT BEGIN:VEVENT SUMMARY:Single-atom edgelike states via quantum interference DTSTART;VALUE=DATE-TIME:20170718T154500Z DTEND;VALUE=DATE-TIME:20170718T160500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4371@indico.ific.uv.es DESCRIPTION:Speakers: Gerard Pelegrí (Universitat Autònoma de Barcelona) \nRecent theoretical and experimental studies have shown that it is possib le to simulate\nartificial magnetic fields with ultracold atoms in optical lattices [1]. In particular\, the possibility to\nimplement chiral\, topo logically protected edge states analogous to those found in the context of \nquantum Hall physics has been demonstrated both for fermionic and bosoni c atoms [2\,3].\nIn this work\, we propose an alternative strategy to impl ement robust edgelike states (ELS) in\noptical ribbons\, which we model by regarding each of the sites as a two-dimensional harmonic trap\nof equal frequency\, with a single atom carrying l = 0 or l = 1 orbital angular mom entum (OAM)\nunits. First\, we consider a system of three in-line sites go verned by tunneling dynamics\, which can\nbe described by a few-state mode l. We show that in this system quantum interference effects give\nrise to spatial dark states (SDS)\, i.e.\, states in which one site remains unpopu lated along the time\nevolution. Then\, we show that by using the SDS as b asic building blocks\, global ELS can be created\nin arbitrarily large rib bons. These ELS are very robust against defects in the ribbon and\nperturb ations in the phase differences between the local eigenstates of the sites required to have\nquantum interference [3].\nFor the l = 0 case\, the tun neling amplitudes between sites are always real and interference\neffects are solely induced by phase differences between the populated sites. This fact allows one to\ncreate ELS within this manifold and switch between the m in a very straightforward manner by\napplying laser pulses\, as shown in the left panel of figure 1\, and also opening the possibility to\nimpleme nt similar ELS in more complex geometries.\nFor the l = 1 case\, the few-s tate description is richer because the tunneling amplitudes depend\nboth o n the spatial localization and the winding number of the local states\, an d they may become\ncomplex depending on the relative position of the sites [4]. The ELS implemented in this manifold\ncan display global chirality\, as shown in the right panel of figure 1. Another interesting possibility\ nthat this manifold offers is to simulate an extra dimension by regarding the winding number as a\nsynthetic dimension.\n\nhttps://indico.ific.uv.es /event/2851/contributions/4371/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4371/ END:VEVENT BEGIN:VEVENT SUMMARY:Bichromatically driven Kerr-like cavities and vacuum squeezing gen eration. DTSTART;VALUE=DATE-TIME:20170718T164500Z DTEND;VALUE=DATE-TIME:20170718T170500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4350@indico.ific.uv.es DESCRIPTION:Speakers: Rafael Garcés Malonda (Departament d'Òptica\, Univ ersitat de València)\nHere we theoretically analyse the generation of str ong vaccum squeezing in optomechanical\, superconducting circuits and pola riton cavities driven by a bichromatic field . This proposal has the follo wing advantages over the usual proposals with mochromatic driving: the pro cess is unrelated to bistability which is good for stability issues and th e reduction of fluctuations takes place at a non-injected frequency\, thus one obtains a squeezed vacuum state\n\nhttps://indico.ific.uv.es/event/28 51/contributions/4350/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4350/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Walking the number of quanta probability distribution DTSTART;VALUE=DATE-TIME:20170718T135500Z DTEND;VALUE=DATE-TIME:20170718T141500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4204@indico.ific.uv.es DESCRIPTION:Speakers: Eugenio Roldán Serrano (Universitat de Valencia)\nW e present schemes based on the alternation between Jaynes-Cummings (JC) an d \nanti-JC Hamiltonians for implementing quantum walks along the number o f quanta "\nline"\, i.e.\, which provides new means for quantum state mani pulation\n\nhttps://indico.ific.uv.es/event/2851/contributions/4204/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4204/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum-enhanced Landauer erasure and storage of a molecular magne tic bit DTSTART;VALUE=DATE-TIME:20170718T141500Z DTEND;VALUE=DATE-TIME:20170718T143500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4150@indico.ific.uv.es DESCRIPTION:Speakers: Fernando LUIS (Instituto de Ciencia de Materiales de Aragón\, CSIC)\nThe erasure of a bit of information encoded in any physi cal system is an irreversible operation bound to dissipate an amount of en ergy Q = kBT ln 2 [1]. As a result\, work W ≥ Q has to be applied to the physical system to restore the erased information content [2-4]. This lim it\, called Landauer limit\, sets a minimal energy dissipation inherent to any classical computation. In the pursuit of the fastest and most efficie nt means of computation\, the ultimate challenge is to produce a memory de vice executing an operation as close to this limit in the shortest time po ssible. \nHere\, we use a single crystal of Fe8 molecular nanomagnets as a spin-memory device. Each molecular cluster carries a net spin S = 10 and possesses a strong uniaxial magnetic anisotropy. The ground state correspo nds to maximum spin projections Sz = +10 and -10 along the anisotropy axis \, common to all molecules\, which define the ‘0’ and ‘1’ bit stat es (Fig. 1(a)). These states are separated by an energy barrier U/kB ≈ 2 4 K\, which hinders the spin flip and gives rise to magnetic hysteresis\, thus magnetic memory\, below approximately 1.2 K [5\,6].\n \nIn our experi ments\, the Landauer cycle is performed\, at T = 1 K\, via the application of a sequence of magnetic fields aligned along different orientations wit h respect to the magnetic anisotropy axis (Fig. 1(b)). The erasure is indu ced by a transverse magnetic field Hy\, which reduces the height of the ma gnetic energy barrier and promotes tunneling between quasi-degenerate spin projections\, thus exploiting a form of quantum annealing [7\,8]. The bit s are then recorded by applying a magnetic field Hz along the anisotropy a xis\, strong enough to polarize their magnetic moments. The cycle is then completed by reducing first Hy and then Hz back to zero. \nThe magnetic su sceptibility along z and y has been measured (Fig. 1(c)) and then integrat ed to obtain the net magnetic work required to perform the erasure and rec ording cycle. It agrees\, within experimental uncertainties\, with the Lan dauer limit. The ac susceptibility provides also information about the mag netization dynamics and\, in particular\, enables us to estimate the time needed to record each bit. This time turns out to be shorter than 0.1 micr o-seconds thanks to the very fast quantum spin dynamics induced by the tra nsverse magnetic field. The performance of our device in terms of energy-t ime cost is then orders of magnitude better than that of any existing memo ry devices to date.\nAcknowledgments\nThe research reported here was suppo rted by the Spanish MINECO (grant MAT2015-68204-R)\, the Dutch Organizatio n for Fundamental research (NWO/FOM)\, the Gobierno de Aragón (grant E98- MOLCHIP) and the European Union (advanced ERC grant Mols@Mols and COST 151 28 Molecular Spintronics project). \nReferences\n[1] R. Landauer\, IBM Jou rnal of Research and Development 5 (1961) 183.\n[2] C. H. Bennett\, Intern ational Journal of Theoretical Physics 21 (1982) 905.\n[3] C. H. Bennett\, IBM Journal of Research and Development 32 (1988) 16.\n[4] H. Leff and A. Rex\, Maxwell's demon: Information\, entropy\, computing\, Hilger and Pri nceton Univ. Press\, Europe/USA (1990).\n[5] W. Wernsdorfer\, R. Sessoli\, A. Caneschi\, D. Gatteschi and A. Cornia\, EPL 50 (2000) 552.\n[6] E. Bur zurí\, F. Luis\, O. Montero\, B. Barbara\, R. Ballou\, and S. Maegawa\, P hys. Rev. Lett. 111 (2013) 057201.\n[7] J. Brooke\, D. Bitko\, T. F. Rosen baum and G. Aeppli\, Science 284 (1999) 779.\n[8] E. Burzurí\, F. Luis\, B. Barbara\, R. Ballou\, E. Ressouche\, O. Montero\, J. Campo\, and S. Ma egawa Phys. Rev. Lett. 107 (2011) 097203.\n\nhttps://indico.ific.uv.es/ev ent/2851/contributions/4150/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4150/ END:VEVENT BEGIN:VEVENT SUMMARY:Conexión de iones en distintas trampas mediante corrientes induci das DTSTART;VALUE=DATE-TIME:20170718T131500Z DTEND;VALUE=DATE-TIME:20170718T133500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4133@indico.ific.uv.es DESCRIPTION:Speakers: Raúl Rica Alarcón (Universidad de Granada)\nLa con exión de dos iones confinados en dos trampas electromagnéticas (Paul o P enning) diferentes mediante las corrientes que estos inducen en un electro do común constituye un gran reto tecnológico que no se ha conseguido has ta la fecha. La conexión o acoplamiento daría lugar a aplicaciones de gr an interés en el ámbito de la física fundamental\, como son la detecci ón de corrientes de radiofrecuencia con sensibilidad sin precedentes o el intercambio de información cuántica entre dos iones [1\,2].\nEl proyect o TRAPSENSOR [3\,4] se inició en la Universidad de Granada con el objetiv o de construir un sistema de dos trampas Penning de 7-Tesla\, conectadas mediante un hilo conductor. En una de las trampas se almacenará un ion de 40Ca+ enfriado mediante láser\, mientras que en la otra se confinará un ion de cualquier especie cuya masa se quiere medir con precisión. La con exión entre los dos iones\, a través de las corrientes inducidas y que s e transmiten por el hilo conductor\, permitiría tanto enfriar simpatétic amente el ion desconocido\, como medir su frecuencia de oscilación utiliz ando campos externos variables [5]\, y por tanto su relación carga-masa. El desarrollo de este proyecto está generando una tecnología extrapolabl e a otras aplicaciones cuánticas. \nEn esta contribución\, presentamos el laboratorio de Trampas de Iones y Láseres de la Universidad de Granada [6] en el que se está desarrollando el proyecto TRAPSENSOR. Discutimos l os distintos enfoques que estamos utilizando para alcanzar con éxito el o bjetivo del proyecto\, lo que incluye el enfriamiento por láser de iones en trampas de Paul y Penning\, la detección de su fluorescencia\, la elec trónica asociada a la conexión de dos trampas a temperatura criogénica y la construcción de un sistema de micro-trampas Penning que permita el a coplamiento de manera efectiva. También expondremos los resultados más r elevantes obtenidos hasta la fecha. En particular\, hemos realizado experi mentos para estimar la sensibilidad de un único ion de 40Ca+ enfriado has ta el límite Doppler en una trampa de radiofrecuencia a corrientes aplica das a uno de los electrodos\, mientras que hemos conseguido el atrapamient o estable en la trampa de Penning de 7-Tesla a temperatura ambiente. \n \n Figura 1. Fotografía del sistema doble de micro-trampas Penning construid o. \nAgradecimientos\nEste proyecto está financiado por el Consejo Europe o de Investigación (ERC StG 278648-TRAPSENSOR) junto con los proyectos MI NECO/FEDER FPA2012-32076\, FPA2015-67694-P\, UNGR10-1E-501\, FIS2015-69983 -P y UNGR13-1E-1830\, y Junta de Andalucía/FEDER IE_57131.\n\nReferencias \n[1] D.J. Heinzen\, D.J Wineland\, Phys. Rev. A 42\, (1990) 2977. \n[2] N . Daniilidis\, T. Lee\, R. Clark\, S. Narayanan\, and H. Häffner\, J. Phy s. B 42\, (2009) 144012\n[3] D. Rodríguez\, Appl. Phys. B 107\, (2012) 10 31\n[4] J.M. Cornejo\, M.J. Gutiérrez\, E. Ruiz\, A. Bautista-Salvador\, C. Ospelkaus\, S. Stahl\, D. Rodríguez\, Int. J. Mass Spectrom. 410C\, (2 016) 22\n[5] L.S. Brown and G. Gabrielse\, Rev. Mod. Phys. 58 (1986) 233 \ n[6] http://trapsensor.ugr.es\n\nhttps://indico.ific.uv.es/event/2851/cont ributions/4133/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4133/ END:VEVENT BEGIN:VEVENT SUMMARY:Causality in waveguide QED DTSTART;VALUE=DATE-TIME:20170718T152500Z DTEND;VALUE=DATE-TIME:20170718T154500Z DTSTAMP;VALUE=DATE-TIME:20261017T021125Z UID:indico-contribution-541-4088@indico.ific.uv.es DESCRIPTION:Speakers: Eduardo Sánchez-Burillo (Instituto de Ciencia de Ma teriales de Aragón (CSIC-Unizar))\nCausality is one of the most fundament al principles in physics and it has strong implications. For instance\, in QFT\, the scattering matrix\, the mathematical object connecting input an d output free states\, must follow the so-called cluster-decomposition pri nciple\, which says that the scattering amplitude factorizes as a product of single-particle amplitudes for causally disconnected input states. In t his work\, we find that the cluster-decomposition principle also occurs in a non-causal system: the nonrelativistic scenario of waveguide QED\, wher e a one-dimensional photonic field interacts with some scatterers. We firs t show a Lieb-Robinson-like bond holds for the free theory\, so the system is approximately causal if there are not scatterers. We then show that th e ground state of the full model is equivalent to the vacuum far away from the scattering region\, so we can properly define free input and output s tates. We then show the Lieb-Robinson-like bond also holds for the full sy stem. Lastly\, considering that there are more stable states apart from th e ground state\, we show that the scattering amplitude for a bunch of caus ally disconnected incident photons is composed by a product of one-photon amplitudes\, with a sum over all the stable states\, so the cluster-decomp osition principle holds. We find the structure for the S-matrix in positio n space compatible with this scattering amplitude. We finally illustrate o ur results with two examples: (i) a two-level system ultrastrongly coupled to a dispersive medium and (ii) a general scatterer coupled to a waveguid e with linear dispersion relation. In the first example\, we show the clus ter properties hold. In the second one\, we find the structure for the S-m atrix in momentum space and compute how the photon-photon correlations gen erated by this S-matrix decay with the distance between the incident photo ns.\n\nhttps://indico.ific.uv.es/event/2851/contributions/4088/ LOCATION:Facultad Química (USC) Aula Química General URL:https://indico.ific.uv.es/event/2851/contributions/4088/ END:VEVENT END:VCALENDAR