Testing a discrete model for quantum spin with two sequential Stern-Gerlach detectors and photon Fock states

Despite its unparalleled success, quantum mechanics (QM) is an incomplete theory of nature. Longstanding concerns regarding its mathematical foundations and physical interpretation persist, a full century beyond its conception. Limited by these issues, efforts to move beyond QM have struggled to gain traction within the broader physics community. One approach to progress in this direction, which is deeply rooted in the tradition of physics, is the development of new models for physical systems otherwise treated by QM. One such model is presented here, which concerns the interaction of a spin system with sequences of two Stern-Gerlach detectors that may be independently rotated. Rather than employing the traditional formalism of QM, the proposed model is supported by tools from discrete mathematics, such as finite groups, set theory, and combinatorics. Equipped with this novel toolkit, an analog of Wigner's d-matrix formula is derived and shown to deviate slightly from QM. With these results, the proposed model is extended to an optical system involving photon number states passing through a beam splitter. Leveraging recent advancements in high precision experiments on these systems, we then propose a means of testing the new model using a tabletop experiment. Hence, the proposed model not only makes clear testable predictions, but also provides valuable insight into the essential principles of quantum theory.Comment: 20 pages, 6 figure

Magnetoplasmonic Interferometers and Applications

Comunicación presentada en el 2nd Early Stage Researchers Workshop in Nanoscience, celebrado en Madrid el 28 y 29 de junio de 2012.Surface plasmons polaritons (SPP) are evanescent waves that propagate along a dielectric-metal interface. They can be confined in subwavelength metal structures, i.e. below the diffraction limit, which leads to many possible applications, including miniaturized optical devices. Within that context, the development of active plasmonics is important to achieve nanophotonic devices with advanced functionalities. This requires a system where the plasmon properties can be manipulated using an external agent. Among the different control agents considered so far, the magnetic field seems a promising candidate, since it is able to modify the dispersion relation of SPP at reasonable magnetic field strengths, and with a high switching speed. This modulation comes from the non-diagonal elements of the dielectric tensor, εij, appearing when the magnetic field is turned on. For noble metals, the ones typically used in plasmonics, these elements are proportional to the applied magnetic field but, unfortunately, very small at field values reasonable for developing applications. On the other hand, ferromagnetic metals have sizeable εij values at small magnetic fields (proportional to their magnetization), but are optically too absorbent. A smart system to develop magnetic field tunable plasmonic devices is the use of multilayers of noble and ferromagnetic metals. That is the framework of the present work, where we analyze the magnetic field induced SPP wavevector modulation (Ak) in Au/Co/Au films as a function of the wavelength and its possible application as a sensor.N

Optical spectroscopy of novel nanostructures fabricated with a focussed ion beam

Diese Arbeit untersucht mit Methoden der optischen Spektroskopie neuartige photonischen Nanostrukturen die mittels fokussierten Ionenstrahl hergestellt wurden. Unter anderem werden Photolumineszenzmessungen von CdSe/ZnSe Halbleiterquantenpunkten eingebettet in dielektrische Rosonatorsäulen vorgestellt. Außerdem werden ultraschnelle Anrege-Abfrage Experimente an Schlitz-Nut Interferometer in Metall-Ferromagnet Vielschichtsystemen gezeigt

Role of Coulomb correlations for femtosecond pump-probe signals obtained from a single quantum dot

We present a theoretical analysis of femtosecond pump-probe experiments performed on a single negatively charged quantum dot. The influence of Coulomb-correlation effects as well as carrier relaxation on transient transmission change signals is investigated. Our model describes ultrafast disappearance of the fundamental trion absorption due to instantaneous Coulomb renormalizations and a delayed onset of gain at the same frequency, as found in the measurements. Going beyond previous experimental information, we predict that after spin-conserving carrier relaxation, new optical transitions exhibiting either gain or absorption should emerge that build up on a picosecond timescale. The time dependence of these new transitions provides insight into details of the carrier relaxation processes

Femtosecond surface plasmon interferometry

We demonstrate femtosecond plasmonic interferometry with a novel geometry. The plasmonic microinterferometer consists of a tilted slit-groove pair. This arrangement allows for (i) interferometric measurements at a single wavelength with a single microinterferometer and (ii) unambiguous discrimination between changes in real and imaginary parts of the metal dielectric function. The performance is demonstrated by monitoring the sub-picosecond dynamics of hot electrons in gold.Deutsche Forschungsgemeinschaft (TE770/1)National Science Foundation (U.S.) (CHE-0616939)National Science Foundation (U.S.) (CHE-0507147)European Commission (EU Network of Excellence ”PhOREMOST”)European Commission (EU Network of Excellence NMP3-SL-2008-214107-Nanomagma)European Commission (FUNCOAT CONSOLIDER INGENIO 2010 CSD2008-00023)European Commission (MAGPLAS MAT2008-06765-C02-01/NAN)European Commission (NANOMAGNETCMS- 0505/MAT/0194)European Commission (MICROSERES S-0505/TIC/0191

Enhancement of the magnetic modulation of surface plasmon polaritons in Au/Co/AuFilms

The deposition of a dielectric overlayer on top of Au/Co/Au multilayer films can significantly enhance the magnetic field induced modulation of the surface plasmon polariton (SPP) wave vector. This enhancement is analyzed as a function of the thickness of the dielectric overlayer and the associated SPP electromagnetic field confinement and redistribution. The decrease in SPP propagation distance is taken into account by analyzing an adequate figure of merit.We acknowledge funding from the EU (Grant No. NMP3-SL-2008-214107 Nanomagma), the Spanish MICINN (“MAGPLAS” Grant No. MAT2008-06765-C02-01/NAN,“FUNCOAT” CONSOLIDER INGENIO 2010 Grant Nos.CSD2008-00023, and MAT2005-05524-C02-01), the Comunidad de Madrid (“NANOBIOMAGNET” Grant No. S2009/MAT-1726 and “MICROSERES-CM” Grant No. S2009/ TIC-1476), CSIC (Grant No. 200850I187), and Deutsche Forschungsgemeinschaft (Grant No. TE770/1).Peer reviewe

Defect induced low temperature ferromagnetism in Zn1-xCoxO films

We present a detailed study on the structural, magnetic, and optical properties, as well as the electronic structure of epitaxial Co-doped ZnO films prepared by magnetron sputtering. Different preparation conditions were implemented in order to control the concentration of oxygen vacancies in the ZnO host lattice. Magnetization measurements indicate ferromagnetic behavior at low temperature for samples prepared at oxygen-poor conditions whereas the samples prepared at oxygen-rich conditions show extremely small ferromagnetic signal corroborating that ferromagnetism in Zn1−xCoxO correlates with the presence of the oxygen-related defects. X-ray absorption spectroscopy (XAS) at the Co L2, 3 edge together with optical transmittance measurements show that Co ions are present in the high-spin Co2+ (d^7) state under tetrahedral symmetry indicating a proper incorporation in the ZnO host lattice. Comparison of the O K edge XAS spectra of the samples prepared at different conditions show substantial changes in the spectral line shape which are attributed to the presence of lattice defects such as oxygen vacancies in the ferromagnetic oxygen-poor Co-doped ZnO samples. Our findings indicate that the ferromagnetic properties of Co-doped ZnO samples are strongly correlated with the presence of oxygen vacancies in the ZnO lattice supporting the spin-split impurity band model