Abstract: We present an inequality relating visibility and which-way information for a particle equipped with an internal degree of freedom travelling through a Mach-Zehnder interferometer. The inequality paints an unexpectedly intricate picture of wave-particle duality in the general case. Strikingly, in some instances which-way information becomes erased by introducing classical uncertainty in the internal degree of freedom. Furthermore, even imperfect interference visibility measured for a suitable set of inputs can be sufficient to infer absence of which-way information.

Abstract: Amplitude and phase damping is a natural decoherence mechanism, changing entangled pure states into less-entangled mixed states. We show that even local amplitude damping of one or two qubits can result in mixed states more entangled than pure states, comparing the relative entanglement entropy (REE) for a given degree of the Bell-CHSH inequality violation (i.e., nonlocality). By applying Monte-Carlo simulations, we find maximally-entangled mixed states and show their likelihood of being optimal by checking the Karush-Kuhn-Tucker conditions, which generalize the method of Lagrange multipliers for this nonlinear optimization problem. We show that the REE for mixed states can exceed that of pure states assuming nonlocality in the (0,0.82) range and maximal REEs difference of 0.4. For comparison we normalized the nonlocality measure to equal the standard entanglement measures, including the negativity for arbitrary two-qubit pure states. We also analyze the influence of the phase-damping channels on the entanglement of initially pure states, showing that the minimum of the REE for a given nonlocality can be achieved by these two channels. Our results can stimulate further search for practical protocols of quantum information processing for which mixed states are more effective than pure states.

[1] B. Horst, K. Bartkiewicz, and A. Miranowicz, Phys. Rev. A 87, 042108 (2013).

Abstract: By means of nonequilibrium Green function technique we calculated spin-dependent electrical conductance through a quantum dot coupled to one ferromagnetic and one superconducting electrodes in the Andreev reflection (AR) regime. Effects due to a competition between the Coulomb correlations on the dot and Zeeman splitting of the dot discrete level are analyzed in both linear and nonlinear transport regimes. It is presented that when a coherent spin rotation is present on the dot, Coulomb interactions may lead to a significant enhancement of the AR tunneling current. New conditions of matching of coupling strengths leading to the perfect AR transmission are formulated in the context of arbitrary Coulomb correlations on the dot. Origin of occurrence of a variety of the multipeak structure of the conductance in equilibrium as well as in nonequilibrium situation is also discussed in detail.

Abstract: We show that the direct measurement of the beam radius in Z-scan experiments using a CCD camera at the output of a 4f-imaging system allows a higher sensitivity and a better accuracy than other methods. One of the advantages is to be insensitive to pointing instability of the pulsed laser because no hard aperture is employed as in the usual Z-scan. In addition, the numerical calculations involved here and the measurement of the beam radius are simplified since we do not measure the transmittance through an aperture and it is not subject to mathematical artefacts related to a normalization process, especially when the diffracted light is very low.

Keywords: Nonlinear optics, Z-scan, diffraction, image processing, Fourier optics

Abstract: Quantum technologies rely on the ability to coherently manipulate, process and transfer information, encoded in quantum states, along quantum channels. Decoherence induced by the environment introduces errors, thus setting limits on the efficiency of any quantum-enhanced protocol or device. A fundamental bound on the ability of a noisy quantum channel to transmit quantum (classical) information is given by its quantum (classical) capacity. Generally, the longer is a quantum channel the more are the introduced errors, and hence the worse is its capacity. In this Letter we show that for non-Markovian quantum channels this is not always true: surprisingly the capacity of a longer channel can be greater than the one of a shorter channel. We introduce a general theoretical framework linking non-Markovianity to the capacities of quantum channels, and demonstrate in full generality how harnessing non-Markovianity may improve the efficiency of quantum information processing and communication.

Abstract: We propose a linear-optical scheme for heralded qubit amplification. The device is able to change the ratio between probabilities of detecting vacuum or a photonic qubit in the signal transmitted via some lossy channel by using a pair of entangled ancillae. The probability of successful amplification does not asymptotically drop to zero for infinite gain and it can be optimized if (i) some a priory knowledge of input state is known or (ii) some noise in the output signal is tolerated.

Abstract: The poster reviews several our proposals for quantum routers using linear optics and single photon qubits. The schemes are based on two-qubit gates such as controlled-phase gate and programmable phase gate.

Abstract: We discuss recent concepts of non-Markovianity of quantum evolution. The discussion is illustrated by simple examples (pure decoherence, amplitude damping and random unitary dynamics).

Abstract: As is widely known, the standard "one oscillator per one mode" quantization of free fields leads to the correct physical prediction <AB>=cos(a-b) for entanglement of linear polarizations, and violates the Bell inequality. This seems to suggest that the tensor product structure associated with the "oscillator per mode" quantization is indeed THE tensor structure associated with quantum fields. However, I will show that <AB>=cos(a-b) is typical also of fields quantized in a different way, where there is no relation at all between the number of modes and the number of oscillators.

Abstract: The coherence and entangled properties of coupled Gaussian modes of optical systems are discussed. The systems considered are (1) an atomic ensemble located inside a ring cavity, and (2) an optical lattice trapped inside a cavity with a movable mirror. We examine separately the cases of two-mode and three-mode interactions, which are distinguished by a suitable tuning of the mode frequencies. We find that the occurrence of entanglement in the system is highly sensitive to the presence of the first-order coherence between the modes. In particular, the creation of the first-order coherence between modes is achieved at the expense of entanglement between them.

Abstract: Intensive theoretical and numerical study of the nonlinear collisional spectra of the light hyper-Rayleigh scattered (HRS) by dihydrogen-noble gas (H₂-Rg) mixtures has been recently completed by adding the heaviest elements of Kr and Xe to the previously considered set of perturbers. This allowed for studying the evolution of the roto-translational spectral features with regard to the growing mass of the supermolecules included. The influence of the spatial distribution of the first hyperpolarizability property was examined and feasibility of experimental verification of the effect indicated. The anisotropic properties of the H₂-Rg interaction potential are partially taken into account for the first time in the HRS analyses.

Abstract: The contribution is focused on spectroscopic investigations of electronic levels, in particular metastable ones, in free atoms and ions.
A system consisting of a metastable atomic state and the ground state is very favorable for optical atomic frequency standards, since the levels are connected via a forbidden transition with possible application as a "clock" transition. The same system of levels may serve as a basis for construction of a quantum bit.
Within the work some recent achievements in high precision spectroscopy of metastable levels in chromium atoms, obtained with ABMR-LIRF (laser - microwave double resonance on an atomic beam) method [1, 2], are presented. A brief review of experimental investigations of thorium ion structure aimed at construction of an extremely precise optical nuclear frequency standard [3], performed in cooperation in PTB, is also given.

[1] A. Jarosz, D. Stefańska, M. Elantkowska, J. Ruczkowski, A. Buczek, B. Furmann, P. Głowacki, A. Krzykowski, Ł. Piątkowski, E. Stachowska, J. Dembczyński, High precision investigations of the hyperfine structure of metastable levels in chromium atom, J. Phys. B: At. Mol. Opt. Phys. 40: 2785-2797 (2007).
[2] A. Krzykowski, P. Głowacki, A. Jarosz Precise measurements of the hyperfine structure of the levels belonging to the terms 3d⁵4s ⁵G and ⁵P in Cr(I), Acta Phys. Pol. A, 122, 78-81 (2012).
[3] O. A. Herrera-Sancho, M. V. Okhapkin, K. Zimmermann, Chr. Tamm, E. Peik, A. V. Taichenachev, V. I. Yudin, P. Głowacki, Two-photon laser excitation of trapped ²³²Th⁺ ions via the 402-nm resonance line Phys. Rev. A 85, 033402 (2012).

Abstract: The research of a refraction law played a major role in the development of the optics since the first attempts of Ptolemy until the more accomplished results of Ibn Sahl, Snel or Descartes. However, it is necessary to wait for the beginning of the XIXth century, much later than the theory of colours of Newton and thanks to the researches on the achromatic glasses, so that emerges the concept of refractive index and so that it begins to be understood well. We propose a historical reminder and an outline of the obstacles and epistemological advances which allowed to establish it.

Abstract: We consider relations between communication complexity problems and detecting correlations (violating local realism) with no local hidden variable model. We show first universal equivalence between characteristics of protocols used in that type of problems and non-signaling correlations. We construct non linear bipartite Bell type inequalities and strong nonlocality test with binary observables by providing general method of Bell inequalities construction and showing that existence of gap between quantum and classical complexity leads to violation of these inequalities. We obtain, first to our knowledge, explicit Bell inequality with binary observables and exponential violation.

Abstract: The primary goal of a theory of liquid mixtures is to determine, using statistical mechanics, how the structure and free energy varies with the composition, and with the chemical composition of its components. Such a theory provides the key to the determination of dielectric and spectral properties, phase transitions, critical points, solubilities, immiscible regions, metastable and unstable regions, etc.

Theories proposed in the first half of the 20th century were, for the most part, lattice theories, and many of these are described in the books by Guggenheim [1] and Prigogine [2]. These early theories pre-dated molecular simulations and the availability of electronic computers, so that they were “tested” by direct comparison with experimental data. Since such comparisons, in the case of the lattice theories, involved adjustment of various parameters to experimental data, these tests were of dubious value. Once molecular simulation data became available in the early 1960’s these theories were shown to be in serious error, and can now be considered to be extinct.

Modern theory of polar liquids (the last 60 years) has followed a dual path. The first has been perturbation theory, in which the free energy and other properties of the solution of interest are related to those of a simpler solution having simple intermolecular forces, for example hard spheres or Lennard-Jones mixtures. Perturbation theory has been particularly successful for thermodynamic properties. The theory of Wertheim [3], relates the free energy of a polar or associating fluid to that of a hard body (non-associating) fluid through a clever resummation of a cluster series for the free energy. It and its later extensions are finding widespread practical application [4].

The second route to a theory of polar liquids has been integral equation theory, which yields the structure in the form of distribution functions [5]. Although less successful than the perturbation theories for thermodynamic properties, integral equation theories have been successful for other properties, in particular dielectric and spectral properties.

References
[1] E.A. Guggenheim, “Mixtures”, Clarendon Press, Oxford, 1952.
[2] I. Prigogine, “The Molecular Theory of Solutions”, North-Holland Pub. Co., Amsterdam, 1957.
[3] Wertheim, M.S. J. stat. Phys. 35, 19 (1984); ibid. 35, 35 (1984); ibid. 42, 459 (1986); ibid. 42, 477 (1986).
[4] For reviews of the theory and its extensions, and practical applications, see: Müller, E.A. and Gubbins, K.E. Ind. Engng. Chem. Research, 40, 2193 (2001); Tan, S.P., Adidharma, H. and Radosz, M., Ind. Eng. Chem. Research, 47, 8063 (2008).
[5] C.G. Gray and K.E. Gubbins, Theory of Molecular Fluids. I. Fundamentals, Chap. 5, Oxford University Press (1984); C.G. Gray, K.E. Gubbins and C.G. Joslin, Theory of Molecular Fluids. II. Applications, Chap. 9-11, Oxford University Press (2011).

Abstract: We describe how to generate an Einstein-Podolsky-Rosen (EPR) paradox between a mesoscopic mechanical oscillator and an optical pulse. We find two types of paradox, defined by whether it is the oscillator or the pulse that shows the effect Schrodinger called “steering”. Only the oscillator paradox addresses the question of mesoscopic local reality for a massive system. In that case, EPR’s “elements of reality” are defined for the oscillator, and it is these elements of reality that are falsified (if quantum mechanics is complete). For this sort of paradox, we show that a thermal barrier exists, meaning that a threshold level of pulse-oscillator interaction is required for a given thermal occupation n₀ of the oscillator. We find there is no equivalent thermal barrier for the entanglement of the pulse with the oscillator, nor for the EPR paradox that addresses the local reality of the optical system. Our work highlights the asymmetrical effect of thermal noise on quantum nonlocality.

Abstract: Physics of dielectrics started in Poznań when professor Arkadiusz Piekara took chair in Experimental Physics at the Poznań University in 1952. At the beginning a lot of effort was taken to prepare the measuring basis, that is to construct the measuring condensers, Schering bridges, resonance circuits, heterodyne beat apparatus (∆C/C ≈ 10⁻⁶), to purifying liquid dielectrics and to synthesize ferroelectrics. Later, professor Piekara got Stanisław Kielich interested in theoretical approach to the physics of dielectrics and his Master of Science dissertation in 1955 can be considered as the beginning of the work of young Poznań staff in theory of dielectrics.

Abstract: Recently the protocols of randomness amplification have been introduced secure against quantum and no-signaling adversaries. Here we present the first fully constructive proof of existence of the protocol that is secure against general no-signaling adversary and amplifies arbitrary small randomness (in standard terms of Santha-Vazirani source) in a fully device independent way. The protocol tolerates some amount of noise depending among others on the initial randomness that is to be amplified.

Abstract: Incessant run of successes of quantum mechanics suggests that quantum formalism plays decisive role in the description of physical phenomena. It leads inevitably to the problem: How does Nature create a "foot-bridge" from fragile quanta to the objective world of everyday experience? The subject of the talk will provide an answer to this fundamental issue. We will show how a crucial for quantum mechanics notion of non-disturbance due to Bohr and a natural definition of objectivity lead to a canonical spectrum broadcasting structure of a quantum system-environment state, reflecting objective information records about the system stored in the environment.

Abstract: We consider an anharmonic Kerr-like oscillator driven by a series of ultra-short coherent pulses. For such a model we discuss the both: quantum and classical dynamics of the system. We show that mean number of photons for quantum model can behave chaotically in classical sense, despite quantum character of the system. We believe that this parameter could be applied as indicator of its quantum-chaotic dynamics.

Abstract: Bi₂ZnOB₂O₆ nonlinear optical single crystals were grown by means of the Kyropoulos method from stoichiometric melt. The SHG and THG response of the Bi₂ZnOB₂O₆ crystal was studied by the Maker fringes techniques. Moreover SHG microscopy studies were carried out providing two-dimensional SHG images as a function of the incident laser polarization. The crystals have been shown to have high SHG and THG efficiency, comparable with those of well-known crystals such as BBO, KDP, KTP, which makes them very attractive materials for NLO applications. The high nonlinear optical efficiency combined with the possibility to grow high quality crystals make Bi₂ZnOB₂O₆ an excellent candidate for photonic applications.

Abstract: We conjecture new uncertainty relations which restrict correlations between results of measurements performed by two parties on a shared quantum state. The uncertainty relations bounds the sum of mutual informations in scenarios when one party measures a single observable and the other party measures one of two observables, and when each party measures one of two observables. The first uncertainty relation is stronger than Hall's derived from Maassen-Uffink uncertainty relation. The uncertainty relations are proved to hold for large classes of states and observables.

Abstract: Dispersion relation of periodic wires is periodic in reciprocal space due to the Bragg reflections. Periodicity of the structure significantly alters the dispersion even when the modulation of structural or material parameters is relatively weak. The main goal of presented work is to investigate the changes in spin wave dispersion for periodic antidot wire (ADW) in dependence on the structural parameters like: lattice constant and size of antidots. We will show that precise choice of these parameters is crucial for achieving desired properties of ADW.

We investigate numerically ADW made of permalloy (Py) with square air holes placed equidistantly along the wire, in its center. Such structure is feasible to fabricate even with a resolution in the range of few nanometers. The considered antidot wire will then operate in the frequency range of few tens of GHz. We used two different computational techniques micromagnetic simulation (OOMMF) and plane wave method to crosscheck the obtained results.

In our calculations we assumed the ideal pinning at the Py/air interfaces. In the presence of strong pinning the row of antidots divides the system into two subwires. Depending on the period a and the size of antidots s, we have controlled the following properties of the system: (1) the width of the gap, (2) the coupling between two subwires.

We acknowledge the financial support from FP7/2007-2013 (Grant Agreement no. 233552 for DYNAMAG), NCN of Poland project DEC-2012/07/E/ST3/00538 and a senior research fellowship from CSIR, India (D.K.).

Abstract: Magnonic crystals are the magnetic equivalent of photonic crystals, with spin waves as the counterpart of electromagnetic waves, playing the role of information carriers. We will present short overview of research performed on magnonic crystals offering tailored band structures for spin waves. The promising directions of magnonic crystals research and its applications will be briefly discussed.

Abstract: One of the current trends in quantum physics is the quest for controllable quantum many-body systems which can be used as quantum simulators. In particular, there is a growing interest in simulating spin and quantum magnetism. In recent years, the focus is moving from SU(2) spins towards SU(N)-symmetric models. The SU(3) systems, having their origin in nuclear physics, were a fruitful playground for quantum chaos investigations, in particular due to they reach possible behavior in the classical limit. Now it seems to be possible to realize such models experimentally with trapped ions providing a large degree of control from the experimental point of view.

Abstract: This talk summarizes our recent results in the field of quantum routing. First, we define a fully functional quantum router with emphasis on the features such router has to provide. Then we review some of the previously published schemes showing the lack for genuine linear-optical quantum router for individual photons. Subsequently we present our two proposals for linear-optical quantum routers [1,2] and discuss their advantages and disadvantages. Finally we address the experimental implementation that is currently under construction in our laboratory.

[1] K. Lemr, A. Černoch, Linear-optical programmable quantum router, Opt. Comm. 300, 282-285 (2013).
[2] K. Lemr, K. Bartkiewicz, A. Černoch, and J. Soubusta, Resource-efficient linear-optical quantum router, Phys. Rev. A 87, 062333 (2013).

Abstract: The controlled-phase gate is a versatile quantum gate. We show that the tunable version of this gate offers even more improvement to its applications.

Abstract: Quantum amplification is an important tool for quantum communications. We present a linear-optical scheme for amplification of an unknown qubit implemented by single photon. The scheme can be tuned to a regime of quantum presence detection where it reveals the presence of a photon without destroying it.

Abstract: We consider a system composed of a large number of two-level subsystems. Such models were already discussed in numerous papers not only from the point of view of contemporary physics and engineering but also biological and even social sciences. In particular, we discuss a model that is an extension of one-dimensional system, considered in previous works. We show how cellular automata formalism can be applied for investigation of such system's dynamics, and how it can be implemented in MATLAB or Octave environments.

Abstract: The optical coupler composed of two mutually interacting nonlinear quantum oscillators is discussed. This Kerr-like nonlinear coupler is excited by a series of ultra-short pulses of an external classical electromagnetic field. Assuming that the field was initially in the vacuum state for two oscillators' modes and week excitations we show that the system's dynamics remains closed within a set of three two-mode n-photon states. In consequence, our system can be treated as "nonlinear quantum scissors". Moreover, we show that the system is able to generate Bell states. When damping effects are taken into account, under a proper choice of parameters involved in the problem, some part of entanglement can be preserved in our model. For the system considered here, we can also observe the so-called sudden death of entanglement and its revival effects.

Abstract: This commemoration intertwines between various physical ideas (as presented in the title), shared within the scientific works of Professors: Stanisław Kielich, Louis Michel, Jan Mozrzymas, Joshua Zak, Marian Surma, and others. It goes from experimental studies on Cotton-Mouton effect (heavy electromagnesses in the basements of Collegium Chemicum), through symmetry considerations in phase transitions (nematics, smectics, etc., mainly breaking of symmetry, but, somehow exceptionally, also ascent), to the magnetic translation group as a mathematical tool for the Bohm-Aharonov effect (everybody knows Landau levels of a free two-dim electron gas, and the magnetic translation group serves as an equivalent for the case of itinerant electrons, with its irreducible representations labeling the levels, and the basis functions describing degenerate cyclotronic orbits). Nowadays, these ideas can be converted to "reality" within nanotechnology, e. g. magnetic quantum dots.

Abstract: The ellipsometric parameters for light reflection from a dielectric film with Kerr optical nonlinearity on a bigyrotropic magneto-electric film are theoretically investigated. The combined contributions of the cubic optical nonlinearity and the magneto-electric coupling allows to control the ellipsometric parameters and thus for example the Kerr rotation with the incoming light intensity, in particular at incidence angles close to the pseudo-Brewster angle.

Abstract: One of the possibilities to obtain efficient and stable nonlinear optical (NLO) material is to dope an amorphous polymer with organic donor-acceptor molecules forming a composite. The appropriate material for the first NLO effect as persistent second harmonic generation (SHG) requires large number of polarizable molecules embedded in polymeric matrix preventing polar orientation. The polar orientation may be induced by external electric field at the temperatures where the matrix is sufficiently mobile to allow fast alignment of the dopants. The experimental explanation of the origin of their NLO response is very difficult because optical susceptibilities are measured in condensed matter where the molecular properties are affected by the host matrix. Molecular simulations can help to explain the nature of the guest-host interaction and separate the different contribution of the material to the optical output signal. A goal of many theoretical works is to find appropriate model describing optical properties of molecules incorporated into polymeric environment.

In the presented work linear and nonlinear optical susceptibilities of guest-host polymer systems were calculated applying the hierarchic procedure . The wild variety of chromophores characterized by different size, shape and charge distribution incorporated into different polymer matrix were studied. First of all the structures of the investigated systems have been modeled by molecular dynamic simulations applying molecular mechanics CVFF force field method. The obtained structures are amorphous. Investigations of radial distribution function prove that location of chromophores in polymeric matrix is an intrinsic property of polymer. The motion of polymer chain allows a rotation of dopants under influence of an external electric field.

The electronic properties of the NLO chromophores were computed at the HF and DFT level using different exchange - correlation potentials. These properties were investigated for the isolated NLO molecules as well as for the ones in polymer environment. In the second case the first-order susceptibilities corresponding to SHG were calculated using discrete local field approach. The implemented method is very efficient to the molecules with high charge transfer effect and give the data approximately consistent with the experimental results. It was also proved that the optical response, especially NLO output signal of chromophores embedded into polymeric matrix, depends on their local environment.

Abstract: We present a general method for the quantification of the performance of quantum chemical methods over an arbitrary collection of atomic/molecular properties. Our approach relies on the Minkowski metric , graph theoretic concepts and pattern recognition techniques. The method should be of interest as a rigorous approach to the introduction of order and classification in spaces of theoretical descriptions. We show how it can be used to quantify the relative merit of ab initio and DFT methods.

Abstract: We study an entangled state of spatially separated electrons, in particular its spins, in a solid state electronic system. The ground state of conventional superconductors is a singlet state of electron Cooper pairs that can provide a natural source of entangled electrons. One of the proposals to obtain the nonlocal entanglement of electrons is to use the Cooper pairs split in the Double Quantum Dot (DQD) system using the Coulomb interaction between electrons [1]. We have analyzed an efficiency of the separation of Cooper pairs in systems, where the DQD is connected to the two superconducting leads, or to the superconducting and normal leads [2,3]. Addressing the idea of quantum communication with entangled electrons in a solid state, where ferromagnetic detectors allow for spin correlation detection, we provide, using quantum information theory, a lower bond on the spin polarization of detectors [4]. In ferromagnetic detectors the spin information is transformed into charge information, however, any real magnetic materials feature imperfect spin polarization due to presence of both spin component in density of states at the Fermi surface. We find that lower bond for the spin polarization is p > 58% for detection of entanglement using an optimal entanglement witness [4]. It provides the minimal spin polarization of ferromagnetic materials that can be useful in quantum communication.

[1] L. Hofstetter, S. Csonka, J. Nygard, and C. Schönenberger, Nature 461, 960 (2009).
[2] J. Eldridge, M. G. Pala, M. Governale, and J. König, Phys. Rev. B 82, 184507 (2010).
[3] R. Zitko, J. Lim, R. Lopez, J. Martinek, P. Simon, Phys. Rev. Lett. 108, 166605 (2012).
[4] W. Kłobus, A. Grudka, A. Baumgartner, D. Tomaszewski, C. Schönenberger, and J. Martinek, (in preparation).

Abstract: A system of two charged particles in a harmonic trap with additional magnetic field is considered. The problem is reduced to a single-particle one in relative coordinates. The ground- and lowest excited-state energies and wave functions are found. The ground state exhibits non-zero expectation value of the velocity (kinetic momentum) and the probability current density does not vanish as well. When the ground state becomes degenerate the expectation value of velocity becomes discontinuous. The effects associated with turning on of the magnetic field are studied by solving the appropriate time-dependent Schroedinger equation. No substantial differences between abrupt (discontinuous in time) and continuous switching on have been observed. Evolution of a wave packet which is initially Gaussian is also investigated. The wave packet loses its Gaussian nature and, after sufficiently large time, a system of diffractive maxima and minima is built.

Abstract: We investigate magnonic crystals in direct contact with the perfect electric conductor. The effect of metalization on the dispersion relation has been studied with the use of finite element method. The perfect conducting overlayer has been implemented in the model as an effective boundary condition. The strong nonreciprocity of spin waves dispersion relation results in appearing of band gaps at wave vectors that do not correspond to the edge of the Brillouin zone. The analysis of the spatial distribution of dynamic magnetization amplitudes elaborates the mechanism of forming of dispersion bands in this kind of structures and explains the hybridizations between magnonic bands in magnonic crystal with nonreciprocal dispersion relation.
We acknowledge the financial support from FP7/2007-2013 (Grant Agreement no. 247556 NoWaPhen) and NCN of Poland project DEC-2012/07/E/ST3/00538.

Abstract: Determination of phase transition temperatures and the identification of phases in liquid crystals (LCs) are of fundamental importance for technical applications and research of liquid-crystalline properties. Experimental methods for identifying LC phases and for determining phase transitions between them involve various approaches, like switching measurements, conoscopic observations, dielectric and electro-optical spectroscopy, conventional X-ray diffraction, or differential scanning calorimetry (DSC) [1,2]. However, some of the methods are not capable of yielding reliable results, especially in cases of helical subphases (SmC_α^*, SmC_β^* or SmC_γ^*).

In this presentation, we analyzed spectra of the second, third and fourth harmonic of electro-optical response obtained using relatively weak external electric field to detect phase transitions in liquid crystals. The effectiveness of the method will be presented using the well-known prototype antiferroelectric liquid crystal materials: MHPOBC and MHPOPB in various phases.

[1] Fukui M., Orihara H., Yamada Y., Yamamoto N. and Ishibashi Y., New Phases in the Ferroelectric Liquid Crystal MHPOBC Studied by Differential Scanning Calorimetry, Jpn. J. Appl. Phys., Part 2 28, L849 (1989).
[2] Mandal P.K., Jaishi B. R., Haase W., Dąbrowski R., Tykarska M. and Kula P., Optical microscopy, DSC and dielectric relaxation spectroscopy studies on a partially fluorinated ferroelectric liquid crystalline compound MHPO(13F)BC, Phase Trans. 79, 223 (2006).
Acknowledgments. This work was supported by the funds for science in the years 2010-2013 as a research project.

Abstract: Photon blockade, in analogy to Coulomb's or phonon blockades, is a phenomenon when a single photon in a nonlinear cavity blocks the transmission of a second photon. This effect can occur in Kerr-type systems driven by a laser due to strong nonlinear photon-photon interactions. We predict the occurrence of higher-order photon blockades where the transmission of more than two photons is effectively blocked by single- and two-photon states. This photon blockade can be achieved by tuning the frequency of the laser driving field to be equal to the sum of the Kerr nonlinearity and the cavity resonance frequency. We refer to this phenomenon as two-photon blockade or two-photon state truncation via nonlinear scissors, and can also be interpreted as photon-induced tunnelling. We also show that, for a driving-field frequency fulfilling another resonance condition and for higher strengths of the driving field, even a three-photon blockade can occur but less clearly than in the case of single- and two-photon blockades. We demonstrate how various photon blockades can be identified by analyzing photon-number correlations, coherence and entropic properties, Wigner functions, and spectra of squeezing. We show that two- and three-photon blockades can, in principle, be observed in various cavity and circuit quantum electrodynamical systems for which the standard single-photon blockade was observed without the need of using two-photon driving fields or Kerr media exhibiting higher-order nonlinear susceptibility.

[1] A. Miranowicz, M. Paprzycka, Y. Liu, J. Bajer and F. Nori, Phys. Rev. A 87, 023809 (2013).

Abstract: States with sub-Poissonian photon-number statistics obtained by post-selection from twin beams are characterized. States with Fano factors around 0.7 and mean photon numbers around 12 are experimentally reached. Their quasi-ditributions of integrated intensity attaining negative values are determined. An intensified CCD camera with quantum detection efficiency exceeding 20 % is utilized both for post-selection and characterization. Experimental results are compared with theory that provides optimum conditions for the experiment.

Abstract: I will show how to calculate the time-of-flight patterns of strongly interacting bosons confined in two-dimensional square lattice in the presence of an artificial magnetic field. I will discuss the cases with the artificial magnetic field being uniform, staggered or forming a checkerboard configuration. Effects of additional temporal modulation of the optical potential that results from application of Raman lasers driving particle transitions between lattice sites are also included. The presented time-of-flight patterns may serve as a verification of chosen gauge in experiments, but also provide important hints on unconventional, non-zero momentum condensates, or possibility of observing graphene-like physics resulting from occurrence of Dirac cones in artificial magnetic fields in systems of ultra-cold bosons in optical lattices. Also, I elucidate on differences between effects of magnetic field in solids and the artificial magnetic field in optical lattices, which can be controlled on much higher level leading to effects not possible in condensed matter physics.

Abstract: Significant progress in nanostructures fabrication technologies opens possibility of building the quantum computer, by use of metallic/semiconducting nanostructures. The main advantage over all other possible realizations of quantum computer will be fact the nanostructures fabrication technology is highly advanced and such quantum system would be scalable. Entanglement of two qubits is essential in basics quantum communication protocols and quantum cryptography. For this applications qubits have to be moved and modified - which are called flying qubits. In solid-state systems, there are possibilities of preparing such states. We investigate the system of two quantum dots coupled with superconducting that can work as effective Cooper pair splitter. Due to the nature of superconductors charge carriers – singlet state Cooper pairs, a pair of electrons which are entangled, it is possible to have two separated but spin-entangled electrons on two quantum dots. Ferromagnetic electrodes which work as a spin detectors, gives possibility of converting information about spin of electrons to electric charge, and measuring the correlation between spins, by direct current measurement that can be easily performed in comparison to current correlation measurements. Using POVM (positive-operator valued measure) operators, we define which measurements can be used to investigate spin-correlations. Characteristics of system will be presented and results related to detection of entanglement of electrons in the system, using selected entanglement witness operators that only can be detected with current measurements.

Abstract: Quantum neuron based on noise quantum channels are introduced. The aim of the project is to show computational capabilities of dissipative quantum systems, in which one can combine some ideas taken from quantum information theory and artificial neural network. Dynamics of quantum neuron model subjected to periodic interaction with an environment are analyzed. Learning procedures based on backward propagation of errors are developed. Under the condition of strong decoherence due to large coupling, one-qubit system with one-qubit environment, ability to conduct simple pattern recognition is shown.

Abstract: We summarize ten years of experiments dealing with quantum cloning and implementations of linear-optical quantum devices. We tried several concepts and several platforms for optimal cloning of photon qubits. We developed several linear-optical quantum information processing devices and we used them for cloning.

Abstract: We study influence of waveguide parameters on the second harmonic generation in periodically poled materials.

Abstract: Experimental progress on trapping and manipulating ultra-cold atoms confined in optical lattices has opened new perspectives for controlling many-body states of different quantum systems. In the simplest case such systems are described in the context of the Bose-Hubbard (BH) model. In my talk I will consider the class of extended BH models with additional three-body on-site interactions. After short introduction I will divide the talk into two parts: (i) Standard BH with additional three-body term: I will show that the shape of insulating lobes may crucially depend on the three-body interactions and in the case of attractive three-body term may lead to vanishing of the second insulating lobe [1,2]. (ii) Attractive BH model with soft-core three-body repulsion: I will show that the critical behavior of the system undergoing a phase transition from pair-superfluid to superfluid at integer filling depends on the value of the three-body repulsion. In particular, a critical exponent and the central charge governing the quantum phase transitions are shown to have repulsion dependent features. In consequence, the model extends the list of known systems violating the universality hypothesis [3].

[1] T. Sowinski, Phys. Rev. A 85, 065601 (2012).
[2] T. Sowinski, ArXiv:1307.6852 (2013).
[3] T. Sowinski, R. W. Chhajlany, O. Dutta, L. Tagliacozzo, M. Lewenstein, ArXiv:1304.4835 (2013).

Abstract: Quantum communication is one of the most intensively developing areas of science. The important step is to get entangled state of electrons in solid state device. One of the solutions is the use of Cooper pairs as a source of entangled electrons and separating them in Double Quantum Dot (DQD) system. Operation of Cooper pair splitting device is based on Coulomb interactions between electrons. We considered two systems: DQD connected to two superconducting leads and DQD connected to superconducting and normal leads. In both systems we studied a flow of electrons in a cotunneling regime (simultaneous tunneling of Cooper pairs through the whole system). We calculated Cooper pair splitting (CPS) efficiency for different ground states of quantum dots. Calculations were made with use of the 4-th order perturbation theory. We were able to show several kinds of tunneling processes that are possible in these systems, where some of them lead to a split of Cooper pairs and some lead to a tunneling through a single dot only. For the first system (two superconducting leads) the CPS efficiency close to resonance is 100%. Far away from resonance the CPS efficiency is 66.6% for singlet and 50% for the DQD without electrons. For the second system close to resonance the CPS efficiency is 100% and far away from resonance is 80% and 50% for singlet and empty state, respectively.

Abstract: The scenario of remote state preparation with shared correlated quantum state and one bit of forward communication [B. Dakic et al., Nature Physics 8, 666 (2012)] is considered. Optimisation of the transmission efficiency is extended to include general encoding and decoding strategies. The importance of use of linear fidelity is recognized. It is shown that separable states cannot exceed the efficiency of entangled states in standard "local operations plus classical communication" paradigm. It is proven however that such a surprising phenomena may naturally occur when the decoding agent has limited resources in the sense that either (i) has to use decoding which is insensitive to change of coordinate system in the plane being in question (which is the natural choice if the receive does not know the latter) or (ii) is forced to use bistochastic operations which may be imposed by physically inconvenient local thermodynamical conditions.

Abstract: In Quantum Optics the widely used definition of nonclassicality is based on the Glauber-Sudarshan P function [1]. If the P function has the properties of a classical probability density, the state is a classical mixture of coherent states. In any other case, the quantum state clearly shows quantum interference effects. In general, the P function is strongly singular and, hence, not applicable in experiments. A universal regularization resolves this problem [2], as it was demonstrated in experiments. In view of its structure [3], entanglement can also be visualized by quasiprobabilities. This requires an optimization based on the solution of the separability eigenvalue problem [4]. Its extension to the multipartite case yields multipartite entanglement witness for complex quantum states [5]. To characterize general quantum correlations, the concept of the P function was extended to a functional [6]. Its regularized version visualizes quantum correlations, even when the state is not entangled and has zero quantum discord [7].

[1] E. C. G. Sudarshan, Phys. Rev. Lett. 10, 277 (1963); R. J. Glauber, Phys. Rev. 131, 2766 (1963).
[2] T. Kiesel and W. Vogel, Phys. Rev A 82, 032107 (2010).
[3] R. F. Werner, Phys. Rev. A 40, 4277 (1989).
[4] J. Sperling and W. Vogel, Phys. Rev. A 79, 042337 (2009).
[5] J. Sperling and W. Vogel, Phys. Rev. Lett. 111, 110503 (2013).
[6] W. Vogel, Phys. Rev. Lett. 100, 013605 (2008).
[7] E. Agudelo, J. Sperling, and W. Vogel, Phys. Rev. A 87, 033811 (2013).

Abstract: The fibre bundle approach [1] has been applied to the unified description of all the eight fundamental magnetic structures and their symmetry groups [2]. On this basis the explicit formulas describing both the variety of magnetic structures and their symmetry groups have been derived. In the particular case of the spin glass state (SGS) the global magnetic coupling constant has been interpreted as a section of the corresponding fibre bundle. The fibre of this bundle makes the space of the Gaussian distributions. Thus one can say that the randomness of the distribution of both the magnetization and the individual magnetic moments in the SGS is of the Gaussian-like character. An observation was made that another kind of the fibre bundle sections make the magnetization vectors M multiplied by a certain Gaussian factor defined in R³, the last factor making the problem continuous and more physical [3, 4]. In one of the previous papers the authors have proved that an internal spontaneous magnetic field H_int is necessary for the SGS to be stable and just to exist [5]. For the angle between M and H_int equal to ϕ one can say that at ϕ=const any rotation (precession) of M around the direction of H_int makes the operation of symmetry of the SGS. Thus the magnetic symmetry group of SGS turns out to be SO(2). The role of both the H_int and the external magnetic field H_ext as well as of the average kinetic energy E_kin of the separate magnetic atoms in the explanation of the experimental temperature dependencies of susceptibility is shown. Thus the fibre bundle approach equates the method of the symmetry analysis of magnetic structures with the method of the higher dimensional embeddings of the modulated structures. The symmetry groups appearing in the method of the symmetry analysis become the structural groups of the bundles. From the other side a higher dimensional space needed to the description of a modulated structure makes here the total space of the bundle. Thus these three methods, namely the symmetry analysis, the higher dimensional embeddings and the fibre bundles are equivalent. The analogous situation is with the description of the magnetic structures with the use of the spin groups, where an additional type of symmetry is introduced. Note that the Gaussian factor introduced above plays a double role: it makes the vector M to be a field and simultaneously makes the description of the magnetic structures more physical [6, 7]. It seems that the fibre bundle approach could serve also for the description of the symmetry groups of all the other aperiodic structures, like e.g. the modulated nonmagnetic structures, quasicrystals (nonmagnetic and magnetic) etc. It is worthwhile to mention here that these different magnetic structures under consideration have been found by the authors to be related with the values of the certain topological invariants [8].

Abstract: Quantum dots are promising candidates for future quantum computing devices. They are also considered as ideal model systems to study fundamental correlations and interactions between single charges and spins. We will here present the basic transport properties of quantum dots coupled to external leads, with a special focus on the strong coupling regime where the electronic correlations can give rise to the Kondo effect. The case of the spin S=1/2 Kondo effect will be analyzed for quantum dots with both nonmagnetic and ferromagnetic leads. Moreover, we will also discuss the SU(4) Kondo effect, which can occur in double quantum dots when the system possesses both spin and orbital degeneracy.

Abstract: We compare two approaches to non-Markovian quantum evolution: one based on the concept of divisible maps and the other one based on distinguishability of quantum states. The former concept is fully characterized in terms of local generator whereas it is in general not true for the latter one. A simple example of random unitary dynamics of a qubit shows the intricate difference between those approaches. Moreover, in this case both approaches are fully characterized in terms of local decoherence rates. As a byproduct it is shown that entropy might monotonically increase even for non-Markovian qubit dynamics.

Abstract: Quantum metamaterials are optical media comprised of artificial quantum scatterers (e.g., qubits), in such a way that (1) these unit blocks maintain quantum coherence for times exceeding the characteristic travel time of an electromagnetic wave through the system, and (2) their quantum state can be directly controlled. For example, a periodic arrangement of qubits in a register of an adiabatic quantum computer can be considered as a quantum metamaterial.

The simplest case of a quantum metamaterial is a one-dimensional set of superconducting qubits in a transmission line. It was shown in experiment that a single qubit in such a line demonstrates all the expected of a pointlike quantum scatterer, with a much stronger coupling to the field than can be achieved with natural atoms in 3D space. Other implementations of quantum metamaterials (like quantum dots placed inside photonic crystals, which would operate in the optical range) are also being considered.

In my talk I will discuss some of the unusual properties of a quantum metamaterial, which stem from its being an extended quantum object, and their possible applications.

Abstract: This work contains investigation results of the structural and nonlinear optical properties of organometallic thin films and nanostructures. The films and nanostructures were successfully grown by Physical Vapor Deposition technique in high vacuum on transparent (quartz, glass) and semiconductor (n-type silica) substrates kept at room temperature during the deposition process. Selected films were annealed after fabrication in ambient atmosphere for 24 hours at the temperature in the range from 50^oC to 250^oC. Spectral properties were examined using transmission, photoluminescence, Second and Third Harmonic Generation's techniques. The experimental spectra were allowed to determine optical constant of the films. Structural properties were investigated by AFM measurements. The organometallic films and nanostructures exhibit high structural quality regardless of the annealing process, but the stability of the film can be improved by using an appropriate temperature during the annealing process. We find that the optical properties were strictly connected with the morphology and the annealing process can significantly change the structural properties of the films and lead to the formation of various nanostructures.

Abstract: We present multi-partite Hardy-type test against local realism. For n qubit systems, we prove the uniqueness and purity of the Hardy state (that is the one that satisfies Hardy conditions), and its genuine n-partite entanglement. We show an that Hardy correlations allow one to find solutions to some quantum communication problems. As an example we present a secure quantum scheme for the original Byzantine Generals problem. Our protocol is based on Hardy's paradox, which uses a set of conditions impossible for classical systems, but satisfied by a unique quantum two-particle state, and on entanglement swapping methods.

Abstract: Measures of quantum entanglement are reviewed and compared. We focus quantities characterizing entanglement which could be experimentally accessible. A quantity called 'collectibility' is proposed which can be determined in a coincidence experiment involving two copies of the state analyzed. Our approach, initially designed for the case of pure states, works also in the general case of mixed quantum states of a multi-partite system.