Memorial Session (December 5)

Date: Wednesday 2018.12.05Speaker: Prof. Ryszard Tanaś (keynote speaker)Affiliation: Nonlinear Optics Division, Physics Faculty, Adam Mickiewicz University, Poznań, PolandTitle: Memories of Prof. Stanisław KielichAbstract: In my talk I would like to remind some historical facts from the biography of Professor Stanisław Kielich related to the beginning and progress of nonlinear optics in Poznań.
Sessions on Quantum Technologies (Nov 28)
and Nonlinear Optics (Dec 5)

Date: Wednesday 2018.11.28Speaker: M.Sc. Shilan Ismael AboAffiliation: Nonlinear Optics Division, Physics Faculty, AMU, PoznańTitle: Photonphonon blockadeAbstract: Many applications in quantum technologies, such as quantum cryptography or optical quantum information processing, require light sources with a precise number of photons. Photon (phonon) blockade is the quantum phenomenon that occurs in a driven nonlinear system, in which a single photon (phonon) in the system prohibits the generation or entry of other photons (phonons) to the system. These effects are described by the subPoissonian excitationnumber statistics. Here we describe cases such that a combined photonphonon mode exhibits subPoissonian statistics, while each mode, if analyzed separately, exhibits superPoissonian statistics.

Date: Wednesday 2018.11.28Speaker: Dr. Ievgen I. ArkhipovAffiliation: Joint Laboratory of Optics of Palacky University and Institute of Physics of CAS, Olomouc, Czech RepublicTitle: Revealing nonclassicality of Gaussian states of lightAbstract: We present a method that allows one to completely reveal nonclassicality of Gaussian states of light, initially generated in optical spontaneous parametric processes, by means of an appropriately induced stimulated emission. Namely, we exploit the fact that stimulating fields in stimulated emission processes for Gaussian states play the role of displacing coherent fields, which, therefore, by no means affect nonclassicality of initially generated Gaussian states. Then, by utilizing a certain nonclassicality criterion, which is expressed in terms of integrated intensity moments of optical fields up to the second order, we show that one can truly certify the presence of quantum correlations of such Gaussian states by varying the complex amplitude of stimulating coherent fields.

Date: Wednesday 2018.11.28Speaker: Dr. Karol BartkiewiczAffiliations:Title: Measuring distance between points in Hilbert space with photons
^{1} Nonlinear Optics Division, Physics Faculty, AMU, Poznań
^{2} RCPTM, Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, Faculty of Science, Palacký University, Czech RepublicAbstract: The quantum properties of polarisationcorrelated photon pairs like, e.g., quantum entanglement, purity etc. make them a powerful resource in quantum communication, including quantum key distribution protocols. These properties and their quantifiers, which can be defined in terms of distances in Hilbert space, are usually measured indirectly by first performing complete quantum state tomography and then calculating their value from the reconstructed density matrices. In many cases this procedure requires performing more measurements than necessary to characterise the investigated quantum property and it tells little about the nature of the characterised property. I will explain how to directly measure the distance between points in Hilbert space using single photons, the maximal level of Bell inequality violation, a universal entanglement witness and the negativity of an arbitrary twophoton polarisation state by only twophoton interference of photons assorted from a few (at most four) copies of the investigated state. I will discuss the experimental challenges and limitations of this approach as well as the possible solutions within the framework of linear optics.
[1] Bartkiewicz, K., Horst, B., Miranowicz, A., “Entanglement estimation from Bell inequality violation,” Phys. Rev. A 88, 052105 (2013).
[2] Bartkiewicz, K., Lemr, K., Černoch, A., Miranowicz, A, “Bell nonlocality and fully entangled fraction measured in an entanglementswapping device without quantum state tomography,” Phys. Rev. A 95, 030102R (2017).
[3] Bartkiewicz, K., Horodecki, P., Lemr, K., Miranowicz, A., Życzkowski, K., “Method for universal detection of twophoton polarization entanglement,” Phys. Rev. A 91, 032315 (2015).
[4] Bartkiewicz, K., Beran, J., Lemr, K., Norek, M., Miranowicz, A., “Quantifying entanglement of a twoqubit system via measurable and invariant moments of its partially transposed density matrix,” Phys. Rev. A 91, 022323 (2015).
[5] Bartkiewicz, K., Chimczak, G., Lemr, K., “Direct method for measuring and witnessing quantum entanglement of arbitrary twoqubit states through HongOuMandel interference, ” Phys. Rev. A 95, 022331 (2017).
[6] Bartkiewicz, K., Chimczak., “Two methods for measuring Bell nonlocality via local unitary invariants of twoqubit systems in HongOuMandel interferometers,” Phys. Rev. A 97, 012107 (2018).
[7] Bartkiewicz, K., Lemr, K., Černoch, A., Soubusta, J., “Measuring nonclassical correlations of twophoton states,” Phys. Rev. A 87, 062102 (2013).
[8] Trávníček, V., Bartkiewicz, K., Černoch, A., Lemr. K., “Experimental measurement of a nonlinear entanglement witness by hyperentangling twoqubit states,” Phys. Rev. A 98, 032307 (2018). 
Date: Wednesday 2018.11.28Speaker: Dr. Antonin Černoch (invited speaker)Affiliation: Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, Faculty of Science, Palacký University, Olomouc, Czech RepublicTitle: Beamsplitting tricksAbstract: Abstract: Beamsplitter is a very common component of setups for quantum information experiments. The quality of measurement results strongly depends on its parameters especially on splitting ratio. In this talk some tricks how to fine tune the splitting ratio will be shown.

Date: Wednesday 2018.11.28Speaker: Dr. Grzegorz ChimczakAffiliation: Nonlinear Optics Division, Physics Faculty, AMU, PoznańTitle: Fourlevel diamondtype atom as a fieldfield couplerAbstract: Abstract: We present engineering a fully controllable effective coupling between two quantized cavity modes via an ensemble of fourlevel atoms in the diamond configuration. This controllable effective coupling makes it possible to transfer coherent superpositions of cavitymode number states from one mode to the other on demand. We also show that despite the fact that the system is complex, it is possible to describe its evolution using a simple effective Hamiltonian

Date: Wednesday 2018.11.28Speaker: M.Sc. Izabela DomagalskaAuthors: Izabela A. Domagalska ^{1}, Marcin W. Jarosik ^{2}, Radosław Szczęśniak ^{2}, Joanna K. Kalaga ^{1}Affiliations:Title: The influence of a charge asymmetry of cores on the physical state of the positively charged molecule ion.
^{1} Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra, Zielona Góra, Poland
^{2} Institute of Physics, Częstochowa University of Technology, Częstochowa, PolandAbstract: We have analyzed the dynamics of the positively charged ion of a diatomic molecule, in which the atomic cores are under the influence of an external force of harmonictype which is explicitly dependent on the amplitude and frequency. The ground state of the ion has been determined using the variational method. The influence of charge core asymmetry on such state energy and the filling of ion nodes has been calculated. We have also verified how the charge asymmetry of the cores affects the value of the Lyapunov exponent. 
Date: Wednesday 2018.11.28Speaker: Prof. Andrzej GrudkaAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Time travel and the Second Law of Thermodynamics.Abstract: One of the most surprising predictions of general relativity is possibility of time travel into one’s past. These so called closed timelike curves lead to the grandfather paradox. However Deutsch and also Bennett and Schumacher proposed quantum models which avoid this paradox. In this talk we show what are implications of these models to the Second Law of Thermodynamics.

Date: Wednesday 2018.11.28Speaker: Dr. hab. Krzysztof GrygielAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Anomalous rotational diffusion in electric fieldsAbstract: The formulae for linear electric polarization induced by harmonic electric field in liquids composed of rigid noninteracting dipolar and asymmetrictop molecules in spherical solvents are derived. The model of noninertial, anomalous rotational Brownian motion is applied. The fractional rotational diffusion equations are solved and time evolution of the electric polarizability is investigated for the case when a dcelectric field is turned off and for the stationary state case when only an acfield is present. Numerical analysis of the dispersion and absorption parts of electric polarizability is performed as well as the influence of molecular parameters on socalled ColeCole plots is investigated.

Date: Wednesday 2018.11.28Speaker: M.Sc. Kateřina JirákováAuthors: Kateřina Jiráková ^{1*}, Karol Bartkiewicz ^{2,1}, Antonín Černoch ^{3}, and Karel Lemr ^{1}^{1} RCPTM, Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, Olomouc, Czech RepublicTitle: Experimental counterfeiting of quantum money
^{2} Faculty of Physics, Adam Mickiewicz University, Poznań, Poland
^{3} Institute of Physics of Academy of Sciences of the Czech Republic, Joint Laboratory of Optics of PU and IP AS CR, Olomouc, Czech Republic
(*) Presently on leave at Faculty of Physics, Adam Mickiewicz University, Poznań, PolandAbstract: The concept of quantum money has been originally suggested by S. Wiesner in the 1970s. Its main advantage is that every attempt to copy quantum banknotes leaves the quantum states changed providing a mark on money counterfeits. According to the nocloning theorem the quantum states cannot be in general perfectly cloned (copied). However, an imperfect cloning is still possible. We present a version of an eavesdropping attack on the protocol proposed by Bozzio et al. (2018). The aim of our research is to demonstrate that cloning implemented even rarely enough that it is indistinguishable from noise is fully sufficient to acquire useful information to counterfeit quantum banknotes. We exploit the fact that completely random encoding of quantum banknotes is computationally impractical and that the bank needs to select a nonrandom but secret encoding algorithm. Data analysis or machine learning allow the attacker to discover bank’s secret and thus predict future banknotes merely on the basis of partial information gained by cloning of previous banknotes. 
Date: Wednesday 2018.11.28Speaker: Dr. Joanna Kalaga (invited speaker)Authors: J. K. Kalaga ^{1,2}, W. Leoński ^{1,2}, M. W. Jarosik ^{3}, and R. Szczęśniak ^{3}Affiliations:Title: Generation of squeezed states in a quantumchaotic system
^{1} Quantum Optics and Engineering Division, Faculty of Physics and Astronomy, University of Zielona Góra, Zielona Góra, Poland
^{2} Joint Laboratory of Optics of Palacký University and Institute of Physics of CAS, Faculty of Science, Palacký University, Olomouc, Czech Republic
^{3} Institute of Physics, Częstochowa University of Technology, Częstochowa, PolandAbstract: Analysis of quantum dynamics of the systems which classical counterparts exhibit chaotic behavior seems to be one of the most intriguing topics related to the quantum dynamics’ research. In particular, finding the methods allowing detection of the appearance of the quantum chaos is especially intriguing. We consider here the application of the normally ordered variances of the quadratures operators as a witness of quantumchaotic evolution. We discuss them in a context of the anharmonic Kerrlike oscillator excited by a series of ultrashort coherent pulses. 
Date: Wednesday 2018.11.28Speaker: M.Sc. Marcin KarczewskiAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Monogamy of Particle Statistics in Tripartite Systems Simulating Bosons and FermionsAbstract: In the quantum world, correlations can take the form of entanglement which is known to be monogamous. Following Phys. Rev. Lett. 121, 090403 (2018), we will argue that another type of correlation, indistinguishability, is also restricted by some form of monogamy. Namely, if particles A and B simulate bosons, then A and C cannot perfectly imitate fermions. The main point of this talk consists in demonstrating to what extent it is possible.

Date: Wednesday 2018.11.28Speaker: Dr. hab. Anna KowalewskaKudłaszykAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Photon blockade via squeezing

Date: Wednesday 2018.11.28Speaker: Dr. hab. Paweł KurzyńskiAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Evolution of negative probability distributionsAbstract: There is an intriguing idea that quantum theory would be recovered if standard probabilities were replaced by negative probabilities and some events were deemed unobservable. However, such approach would be able to recover only one half of quantum theory – state description and measurement. The other half of the theory describes how states change in time. In this presentation I will discuss which evolutions of negative probability distributions are allowed. It is known that the evolution of standard probability distributions is determined by stochastic matrices, which generate either simple reversible permutations, or fundamentally irreversible dynamics. On the other hand, the evolution of negative probability distributions can be described by pseudostochastic matrices, i.e., matrices whose entries are given by negative probabilities. These matrices give rise to a much richer dynamics in which there are nontrivial reversible transformations.

Date: Wednesday 2018.11.28Speaker: M.Sc. Zakarya LasmarAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: On composite behaviour of complex quantum systems: sometimes entanglement needs to be backed by interaction

Date: Wednesday 2018.11.28Speaker: Dr. hab. Karel Lemr (invited speaker)Affiliation: Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, Faculty of Science, Palacký University, Olomouc, Czech RepublicTitle: Diagnosing quantum relays by means of collective entanglement witnessesAbstract: The talk discusses the possibility to use collective entanglement witnesses, namely the collectibility, in quantum relay diagnostics. Theoretical concept as well as an experimental implementation shall be presented. The talk promotes benefits of this idea by comparing its experimental requirements with previously used methods.

Date: Wednesday 2018.11.28Speaker: Prof. Wiesław LeońskiAffiliation: Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra, Zielona Góra, PolandTitle: Quantum steering in a system of three qubits – some remarks and findings (keynote talk)Abstract: We discuss a system of three qubits and concentrate on the quantum steering effect appearing in such a system. In particular, we discuss the relations of the steering with the other form of quantum correlations, the quantum entanglement [1,2]. Additionally, we present how the interesting us effects can appear in the threemode triangle Bose–Hubbard system [3].
[1] J. K. Kalaga, W. Leoński, Quant. Inf. Process. (2017) 16:175
[2] J. K. Kalaga, W. Leoński, J. Perina Jr., Phys. Rev. A (2018) 97:042110
[3] J. K. Kalaga, W. Leoński, R. Szczęśniak Quant. Inf. Process. (2017) 16:265 
Date: Wednesday 2018.11.28Speaker: Prof. Adam MiranowiczAuthors: A. F. Kockum ^{1}, A. Miranowicz ^{1,2}, S. De Liberato ^{1,3}, S. Savasta ^{1,4}, and F. Nori ^{1,5}Affiliations:Title: Deterministic quantum nonlinear optics without photons
^{1} Theoretical Quantum Physics Laboratory, RIKEN Cluster for Pioneering Research, Wakoshi, Saitama 3510198, Japan
^{2} Faculty of Physics, Adam Mickiewicz University, 61614 Poznan, Poland
^{3} School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom
(4) Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Universita di Messina, Messina, Italy
(5) Physics Department, The University of Michigan, Ann Arbor, Michigan, USAAbstract:We show how analogs of a large number of wellknown nonlinearoptics phenomena can be realized with one or more twolevel atoms coupled to one or more resonator modes in the ultrastrongcoupling regime. Through higherorder processes, where virtual photons are created and annihilated, an effective deterministic coupling between two states of such a system can be created. In this way, analogs of threewave mixing, fourwave mixing, higherharmonic and subharmonic generation (i.e., up and downconversion), multiphoton absorption, parametric amplification, Raman and hyperRaman scattering, the Kerr effect, and other nonlinear processes can be realized. In contrast to most conventional implementations of nonlinear optics, these analogs can reach unit efficiency, only use a minimal number of photons (they do not require any strong external drive), and do not require more than two atomic levels [1,2,3].
[1] A. F. Kockum, A. Miranowicz, V. Macri, S. Savasta, F. Nori, Phys. Rev. A 95, 063849 (2017), eprint arXiv:1701.05038.
[2] R. Stassi, V. Macri, A. F. Kockum, O. Di Stefano, A. Miranowicz, S. Savasta, and F. Nori, Phys. Rev. A 96, 023818 (2017), eprint arXiv:1702.00660
[3] A. F. Kockum, A. Miranowicz, S. De Liberato, S. Savasta, and F. Nori, in press in Nature Reviews Physics, eprint arXiv:1807.11636 . 
Date: Wednesday 2018.11.28Speaker: M.Sc. Mateusz NowotarskiAuthors: Mateusz Nowotarski ^{1} and Artur Barasiński ^{1,2}Affiliations:Title: Entanglement properties of highly symmetric qudit states
^{1} Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra, Z. Szafrana 4a, 65516 Zielona Góra, Poland
^{2}RCPTM, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Sciences of the Czech Republic, 17. Listopadu 12, 772 07 Olomouc, Czech RepublicAbstract: Quantum entanglement plays an important role in quantum theory as one of the most unintuitive physical phenomenons. Because of many possible applications, characterization of quantum states is an important task. While the calculation of entanglement measures for pure twoqudit states is not challenging, it becomes significantly much more complicated in case of mixed twoqudit states. The basic approach to this problem is restriction the specific subgroup of states which obey specific symmetrical conditions. Here we discus a recently introduced highly symmetric qudit states family with incomplete permutation symmetry [1, 2] This family consists of both pure and mixed states and can be described by five real parameters. For those states we perform extensive analysis of various conditions of separability and entanglement classification. Furthermore our results can be used for any arbitrary quantum state by application of twirling operator.
[1] A. Barasiński and M. Nowotarski, Phys. Rev. A 94, 062319 (2016)
[2] A. Barasiński and M. Nowotarski, Phys. Rev. A 95, 042333 (2017) 
Date: Wednesday 2018.11.28Speaker: Dr. Małgorzata PaprzyckaAffiliation: Nonlinear Optics Division, Physics Faculty, AMU, PoznańTitle: Raman spectroscopy in the investigation of proteinsAbstract: Modern medicine widely uses exogenous collagen as good material for tissue regeneration, also as natural substrate for cell attachment and proliferation, used to create dressings and to support the treatment of burn wounds or diabetic wounds, or finally as a source of amino acids in the diet complementary to the body’s needs [1,2]. Collagen is a safe material that has a high biocompatibility and biodegradability and good cell adhesion [3]. Due to the possibility of transferring CreutzfeldJacob disease(Bovine Spongiform Encephalopathy) from animals to the human body, the interest in collagen from fish increased. The collagen we examined comes from the skin of silver carp fish (Hypophtalmichthys molitrix), and was obtained by method of hydration in an aqueous lactic acid solution [4]. The topography of the test sample was made with The Dimension® Icon™ Scanning Probe Microscope (SPM), showing its fibrillar structure, with dimensions equivalent to those shown in the literature [5]. Raman spectroscopy was used to study fish collagen using a Renishaw Ramascope 1000 spectrometer. The source of the excitations was a heliumneon laser with a wavelength of 633 nm. Analysis of Raman spectra allowed to determine the content of amino acids in collagen, including glycine, proline and hydroxyproline. It also showed the native nature of the material at 200C. The durability of the secondary structure of this material heated to about 900C and cooled was also proved. Raman spectroscopy has been presented as an effective method for testing biopolymers [6].
[1] Sanz M and all, Clinical Evaluation of a New collage matrix (mucograpf prototype) to enhance the wight of keratinized tissue In patients with fixed prosthetic restorations: a randomized prospective clinical trial. J. Clin Periodontol. 2009; 36 (10), 868876.
[2] Ghanaati S et al, Evaluation of the tissue reaction to a new bilayered collagen matrix in vivo and its translation to the clinic. Biomed Mater. 2011^{1}; 015010.
[3] Sionkowska A. Current reaserch on the blends of natural and synthetic polymers as new biomaterial: review. Progress in Polimer science, 2011; 36: 12541276.
[4] Przybylski J.E., Patent US 7285638, B2 (2007).
[5] Buehler M.J., Nature designs tough collagen: Explaining the nanostructure of collagen fibrils, Proceedings of the National Academy of Sciences Aug 2006, 103 (33) 1228512290.
[6] Paprzycka M, Scheibe B, Jurga S, Fish collage – molecular structure after thermal treatment, Fibres & Textile In Eastern Europe, 132, 2018. 
Date: Wednesday 2018.12.05Speaker: Prof. Jan Peřina Jr. (keynote speaker)Authors: J. Peřina^{1}, Jr., W. Leoński^{2}, A. Luks^{1}, V. Peřinová^{1}Affiliations:Title: Autoionization in the presence of a neighbor atom.
^{1}Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Science of the Czech Republic, Olomouc, Czech Republic
^{2} Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra, Zielona Góra, PolandAbstract: Longtime photoelectron ionization spectra of a system with an autoionizing level interacting with a neighbor twolevel atom are discussed. These spectra are typically composed of several peaks. Conditions for the occurrence of Fano and Fanolike zeros are revealed. Photoelectron ionization spectra conditioned by the measurement on the twolevel atom show oscillations at the Rabi frequency of the neighbor twolevel atom. The presence of spectral dynamical zeros in the conditioned spectra is predicted. Also entanglement between an ionized electron and that bound on the twolevel system is analyzed using negativity. Twodimensional spectral density of negativity is defined to identify spectrally local entanglement between two electrons. It reveals that entanglement is ‘concentrated’ around spectral peaks. 
Date: Wednesday 2018.11.28Speaker: Dr. hab. Jan Soubusta (invited speaker)Authors: Artur Barasiński ^{1,2}, Antonín Černoch ^{2}, Karel Lemr ^{2}, and Jan Soubusta ^{2}Affiliations:Title: Experimental testing of threequbit nonlocality.
^{1} Institute of Physics, University of Zielona Góra, Poland
^{2} Joint Laboratory of Optics of Palacky University and Institute of Physics of Czech Academy of Sciences, 771 46 Olomouc, Czech Republic
Abstract: We are used to the fact that all bipartite pure entangled quantum states violate a Bell inequality. This means that measurement results on this quantum system manifest nonlocal correlations. So far the relationship between entanglement and nonlocality is still a subject of an intense study. Recently a new measure of nonlocality was proposed [1]. It is defined as the probability, that the pure state will display nonlocal correlation when subjected to random measurements. When scanning over all possible projection measurements, we can define a nonlocal volume, which corresponds to the subspace in which the projection measurements prove nonlocality of the input state. We decided to test these relations for threequbit states, generalized GreenbergerHorneZeilinger (gGHZ) states [2]. It was recently shown that the nonlocal volume has very convenient properties. For example, for pure states this measure is monotonic with entanglement described by the gGHZ angle. The more the state is entangled, the larger is the probability to violate Bell inequalities selecting random measurements. For this purpose we first had to build an efficient experimental setup, that is capable to generate the gGHZ states. states and to carry out the optimal measurements very fast. Secondly, we have experimentally verified numerical simulations of optimal measurements proposed to detect the greatest violation of several Belltype inequalities for threepartite states [3, 4]. Finally, we have started detailed experimental mapping of the projection measurement space to get the nonlocal volume of the tested states. We hope that this both theoretical end experimental research can help to get better insight into the abstract quantities characterizing quantum states and also to the mutual relationship between them [5, 6].
[1] V. Lipinska, F. J. Curchod, A. Mattar, and A. Acin, New J. Phys. 20, 063043 (2018).
[2] D. M. Greenberger, M. A. Horne, A. Shimony, and A. Zeilinger, Am. J. Phys. 58, 1131 (1990).
[3] G. Svetlichny, Phys. Rev. D 35, 3066 (1987).
[4] J.D. Bancal, J. Barrett, N. Gisin, and S. Pironio, Phys. Rev. A 88, 014102 (2013).
[5] I. Arkhipov, A. Barasiński, and J. Svozilik, Sc. Rep. 8, 16955 (2018).
[6] A. Barasiński, Sc. Rep. 8, 12305 (2018). 
Date: Wednesday 2018.11.28Speaker: Prof. Ryszard Tanaś (keynote speaker)Affiliation: Nonlinear Optics Division, Physics Faculty, Adam Mickiewicz University, Poznań, PolandTitle: Violation of monogamy relations for negativity in a threeatom systemAbstract: Quantum correlations in multiqubit systems are subject of intensive studies because of their crucial role in quantum information processing. Probably the most popular measure of correlations is entanglement, but there are other measures that have been introduced and studied, such as quantum discord, geometric quantum discord, measurement induced disturbance and others. The simplest bipartite system in which the correlations can be studied is a system of two qubits, or two twolevel atoms. In case of twolevel atoms interacting with the reservoir of electromagnetic field modes in the vacuum, the evolution of the system can be described by the well known LehmbergAgarwal master equations. The collective evolution of the twoatom system depends on two collective parameters: collective damping 12 and dipoledipole interaction γ_{12}, which both depend on the interatomic distance. Such a system is a good testing ground for studying evolution of quantum correlations. We study a more complex system of threeatoms embedded in a common vacuum. Such a system is more difficult to describe because, for mixed states, we deal with 8×8 matrix which leads to 63 equations, and, what is even worse, there are no formulas to calculate concurrence, even if we know all the matrix elements. Fortunately, it is possible to calculate negativity, which is another measure of entanglement. Concurrence and negativity give the same values for pure states, but are different for mixed states. So, we use negativity as a measure of entanglement in a threeatom system. Master equation for the density matrix is solved, and we find evolution of the negativity in a threeatom system. The evolution depends on the collective parameters γ_{ij} and Ω_{ij}. We test, in particular, the so called monogamy relations for negativity, for chosen initial states of the system. It is shown that for some states monogamy relations are violated.

Date: Wednesday 2018.12.05Speaker: Prof. Vasily V. Temnov (keynote speaker)Affiliation: Institute of Molecules and Materials of Le Mans, CNRS, Le MansTitle: Nonlinear magnetoplasmonics and Wood’s anomaly probed by magnetic secondharmonic generationAbstract: Angular and wavelengthdependent magnetic second harmonic generation (mSHG) on periodic arrays of nickel nanodimers allowed us to identify a periodic structure acting as a metasurface (diffraction forbidden) at the fundamental frequency and diffraction grating (diffraction allowed) at the double SHG frequency and observe the purely nonlinear Wood’s anomaly. Similar measurements on magnetoplasmonic multilayers in Kretschmann configuration are used to quantify the nonlinear phasematching condition and magnetic control of surface plasmon polaritons generated at the SHG frequency.

Date: Wednesday 2018.11.28Speaker: M.Sc. Vojtěch TrávníčekAffiliation: Joint Laboratory of Optics of Palacký University, Olomouc, Czech RepublicTitle: Experimental measurement of nonlinear entanglement witness by hyperentangling twoqubit statesAbstract: We demonstrate that non–linear entanglement witnesses can be made particularly useful for en tanglement detection in hyper–entangled or multilevel states. We test this idea experimentally on the platform of linear optics using a hyper–entangled state of two photons. Instead of several simultaneous copies of twophoton entangled states, one can directly measure the witness on single copy of a hyper–entangled state. Our results indicate that hyper–entanglement can be used for quick entanglement detection and it provides a practical testbed for experiments with non–linear entanglement witnesses.

Date: Wednesday 2018.12.05Speaker: M.Sc. Vishal VashisthaAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Light channeling, bending and splitting via local modification of interfaces of a photoniccrystal slabAbstract: Photonics crystal slab (PC) consists of one, two, or three dimensions periodic array structures which are widely used for many applications in photonics such as guiding the light (waveguide), highquality factor cavity resonator, photonic crystal fibers, and so on. In general, PCs are designed by removing the certain portion of the periodic array structures socalled defect region and this defect region is used to guide the light. We study a new hybrid PC slab which consists of dielectric rods coated with a thin layer of metal cap structures, and the defect region is created by just removing the thin layer of the metal cap. In this talk, I will present the various modes which exists in the defect region, and I will present the properties of different modes while propagating the light in different shapes of the waveguide.

Date: Wednesday 2018.12.05Speaker: Dr. hab. Maciej Wiesner (invited speaker)Affiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Can surface plasmons break symmetry in topological insulators and graphene?Abstract: A monolayer graphene is a perfect material allowing for high frequency transport of electrons. Due to missing energy band gap its application in switching devices is not possible. The only way to open the band gap is symmetry breaking of a monolayer graphene.Topological insulators are famous of lack of scattering of electrons on structural defects. Topologically protected states can be observed in samples of thickness of 2 – 7 nm where contribution of bulk electrons bulk is limited. Fabrication of such thin layers requires advanced techniques like MBE. To reduce contribution of bulk electrons to surface conductivity one have to break symmetry of the topological insulator along zdirection.During this talk I will present results showing the effect of symmetry breaking in both materials due to surface plasmon generation.
Magnonics and Metamaterials (December 56)

Date: Wednesday 2018.12.05Speaker: M.Sc. Nandan Babu Kuttath PadiAuthors: N. Babu Kuttath Padi, A. Trzaskowska, S. Mielcarek, M. Zdunek, P. Graczyk, J. W. Kłos, M. KrawczykAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Magnons and phonons in CoFeB/Au multilayer structuresAbstract: Inelastic light scattering is a powerful method to study the dispersion relations of magnons and phonons. We determine the dispersion relation of thermal magnons and phonons which exist in the multilayered sample using Brillouin light scattering (BLS) spectroscopy in CoFeB/Au multilayer deposited on the silicon substrate with Ti and Au layers. In the backward scattering geometry, the dispersion relations of magnons and phonons are determined for different values of the magnetic field. The finite element method (FEM) is used for interpretation of the experimental results.
This work was supported by National Science Centre of Poland Grant No. UMO2016/21/B/ST3/00452 and the EU’s Horizon 2020 Research and Innovation Program under Marie SklodowskaCurie Grant Agreement No. 644348 (MagIC). 
Date: Wednesday 2018.12.05Speaker: Grzegorz CentałaAffiliation:Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: The effect of spin wave pinning on FMR frequency in periodic structuresAbstract: One of the greatest advantages of spin waves is high frequency associated with low energy loss, therefore spin waves are promising as prospective information carriers. However, the usability of the devices based on spin waves is dependent on the range of operating frequency. The customizable frequency range may be achieved by changes in structural parameters, hence we consider spin wave pinning as a relatively easy way to adjust the frequency. Numerical calculations were made for CoFeB stripes arranged in the horizontal plane. We checked how the change in the width, thickness, and distance between the stripes affects the FMR frequency.

Date: Thursday 2018.12.06Speaker: Dr. Gabriel D. ChavesO’FlynnAffiliation: Institute of Molecular Physics, Polish Academy of Sciences, PoznańTitle: Thermal Stability of Soft Ferromagnetic NanoringsAbstract: The thermal stability of ferromagnetic nanostructures is mostly determined by the height of the energy barrier between two micromagnetic configurations: a metastable state and the ground state. Few analytical models for the magnetization profile at the lowest barrier have been obtained. In this talk, I will present micromagnetic simulations perform to validate one of those cases: a model for magnetization reversal of ferromagnetic nanorings[1].
[1] Phys. Rev. B 73, 054413 (2006) 
Date: Thursday 2018.12.06Speaker: Dr. Emerson Coy (invited speaker)Affiliation: Institute of Molecular Physics, Polish Academy of Sciences, PoznańTitle: High temperature magneto dielectric thin films with low magnetic dampingAbstract: Here we present multiferroic (ferromagnetic/ferroelectric) thin films of highly strained Bi(Fe_{0.5}Mn_{0.5})O_{3} as the only known hightemperature magnetodielectric material with low Gilbert damping. We present the general functional properties of the material, as well as few previously unreported structural and functional properties. Finally, we will show the great potential of this perovskite for spintronic applications.

Date: Thursday 2018.12.06Speaker: Dr. Hubert GłowińskiAffiliation: Institute of Molecular Physics, Polish Academy of Sciences, PoznańTitle: Magnetization damping in polycrystalline CoFe filmsAbstract: Magnetization damping of polycrystalline thin films of the Co_{25}Fe_{75} alloy was found to be very low reaching 1×10^{3} and the intrinsic damping of this alloy is even lower achieving 5×10^{4}. Our study focuses on the influence of an adjacent layer on total damping. We found that only using Cu buffer we obtain low magnetization damping and we confirmed low value of intrinsic damping.

Date: Thursday 2018.12.06Speaker: Dr. Piotr Graczyk (invited speaker)Affiliation: Institute of Molecular Physics, Polish Academy of Sciences, PoznańTitle: Electricfielddriven enhancement of magnetization dynamics in magnetoelectric heterostructuressAbstract: We performed simulations of coupled chargespinmagnetization dynamics in magnetoelectric heterostructure which consists of two highpermittivity dielectrics separated by two conducting ferromagnetic layers. The layers are magnetized either parallel or antiparallel to each other. We show that it is possible to affect magnetization dynamics with an ac voltage applied to such heterostructure. The effect is driven by the fieldlike and antidamping spin transfer torques.

Date: Wednesday 2018.12.06Speaker: Dr. Batłomiej Graczykowski (invited speaker)Affiliation: NanoBioMedical Center, Adam Mickiewicz Univesity in Poznań, PoznańTitle: Elastic properties of few nanometers thick membranesAbstract: The performance gainoriented nanostructurization has opened a new pathway for tuning mechanical features of solid matter vital for application and maintained performance. Simultaneously, the mechanical evaluation has been pushed down to dimensions way below 1 μm. In this work, by means of microBrillouin light scattering we determine the mechanical properties, that is, Young modulus and residual stress, of polycrystalline few nanometers thick MoS_{2} membranes in a simple, contactless, nondestructive manner. The results show huge elastic softening compared to bulk MoS_{2}, which is correlated with the sample morphology and the residual stress.

Date: Thursday 2018.12.06Speaker: Dr. Joachim Graefe (invited speaker)Affiliation: Max Planck Institute for Intelligent Systems, StuttgartTitle: Nanomagnetism in the XRay SpotlightAbstract: The Xray microscopy allows the application of powerful spectroscopic techniques in length scales far smaller than possible with optical microcopy. Near Edge Xray Absorption Fine Structure (NEXAFS) gives the possibilities to the element and chemically sensitive imaging, while Xray Circular Magnetic Dichroism (XMCD) allows direct, highly sensitive detection of sample magnetization. These contrast mechanisms at spatial resolutions of below 15 nm, and even betterusing emergent techniques like ptychography, combined with the possibility of using the time structure of synchrotron light for pump and probe imaging with time resolutions of <50 ps make xray microscopy a powerful tool.
[1] W. Chao et al.: Nature 435 (2005) 1210.
[2] D. A. Shapiro et al.: Nature Photonics 8 (2014) 765.
[3] S. Woo et al.: Nature Materials 15 (2016) 501.
[4] K. Litzius et al.: Nature Physics 13 (2017) 170.
[5] S. Wintz et al.: Nature Nanotechnology 11 (2016) 948. 
Date: Thursday 2018.12.06Speaker: Dr. Paweł GruszeckiAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Reflection of spin wave beamsAbstract: Reflection of spin wave beams We present results of the theoretical investigation of the spin wave beam reflection off the ferromagnetic film’s edge and/or the gradually decreasing magnonic refractive index. In particular, we demonstrate the GoosHanchen and the mirage effects for spin waves. Furthermore, the scattering of the incident spin wave beam at the edge spin waves, which causes the excitation of secondary beams with the increased/decreased frequency, will be discussed, as well.

Date: Thursday 2018.12.06Speaker: Prof. Konstatin V. Guslienko (keynote speaker)Affiliation: Departament of Materials Physics, Faculty of Chemistry, University of the Basque Country, San SebastianTitle: Magnetic skyrmion stability and dynamicsAbstract: Magnetic skyrmion is a kind of topological soliton, a nontrivial inhomogeneous magnetization texture on the nanoscale. In this talk I focus on the skyrmion stability and spin excitations in ultrathin magnetic films and cylindrical magnetic dots. The skyrmions can be stabilized due to an interplay of the isotropic and DzyaloshinskiiMoriya exchange interactions, outofplane magnetic anisotropy and magnetostatic interaction.

Date: Thursday 2018.12.06Speaker: Dr. hab. Jarosław W. KłosAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Hartman effect for spin waves in exchange regimeAbstract: Hartman effect for spin waves in exchange regime The Hartman effect is the wave phenomenon observed for the wave package tunneling through the barrier where the evanescent solutions exist. This effect is manifested by the saturation of group delay of tunneling wave package with increasing width of the barrier. We showed the possibility of existence of the Hartman effect for the exchange spin waves. We took into account the general BarnaśMills boundary conditions in order to calculate the transmission of spin wave through the anisotropy barrier. This work was supported by National Science Centre of Poland Grant No. UMO2016/21/B/ST3/00452 and the EU’s Horizon 2020 Research and Innovation Program under Marie SklodowskaCurie Grant Agreement No. 644348 (MagIC).

Date: Wednesday 2018.12.05Speaker: Dr. Dominika KuźmaAffiliation: Institute of Nuclear Physics, Polish Academy of Sciences, KrakówTitle: Modeling of configuration switching in systems of macrospinsAbstract: We study switching mechanisms between ferromagnetic and antiferromagnetic (F – AF) configurations in systems of elliptically shaped flat nanoparticles (macrospins) under a variable applied magnetic field. Using a software based on the dynamical matrix method we compute frequencies and the corresponding spin profiles for the spin waves. Of special interest are those in the gigahertz frequency region. Limits of stability of configurations are marked by soft spin waves. We present various possibilities of enhancing recovery of the most stable AF configuration in a homogeneous external field.

Date: Wednesday 2018.12.05Speaker: M.Sc. Filip Lisiecki (invited speaker)Affiliation: Institute of Molecular Physics, Polish Academy of Sciences, PoznańTitle: Reprogrammability and scalability of magnonic Fibonacci quasicrystalsAbstract:Magnonic quasicrystals exceed the possibilities of spin waves (SW) manipulation offered by regular magnonic crystals, because of their more complex SW spectra with fractal characteristics. Here, we show the reprogrammability property of 1D Fibonacci magnonic quasicrystals, which allows controlling the SWs transmission. We demonstrate this property in the structures of different elements sizes and thus show the scalability of this system down to the nanometer scale.

Date: Wednesday 2018.12.05Speaker: Prof. Tadeusz Lulek (invited speaker)Affiliation: Division of Mathematical Physics, Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: A threemagnon qubit: an example of Galois symmetry of Bethe pseudoparticlesAbstract:We discuss a specific Bethe Ansatz solution [1,2] of the eigenproblem of the Heisenberg Hamiltonian for a magnetic isotropic ring with N = 7 nodes, at the centre k = 0 of the Brillouin zone, within the threemagnon sector r = 3, which implements an arithmetic qubit with the energy E = 5, and whose tho basis states are rigged string configurations. We demonstrate that this qubit exhibits Galois symmetry, represented by the dihedral group D6 permuting six admissible state paerameters of r = 3 Bethe pseudoparticles.
[1] T. Lulek, M. Łabuz, J. Milewski, and R. Stagraczyński, Physica B550, 294 (2018),
[2] J. Milewski, B. Lulek, T. Lulek, and R. Stagraczyński, Physica B434, 14 92014). 
Date: Thursday 2018.12.06Speaker: Prof. Igor L. Lyubchanskii (keynote speaker)Authors: Y. S. Dadoenkova,^{1,2}, N. N. Dadoenkova, ^{1,2}, M. Krawczyk ^{3}, I. L. Lyubchanskii^{2,4}Affiliations:Title: GoosHaenchen effect at Brillouin light scattering
^{1} Ulyanovsk State University, Ulyanovsk
^{2} Donetsk Institute for Physics and Engineering of the National Academy of Sciences of Ukraine
^{3} Faculty of Physics, Adam Mickiewicz University in Poznań, Poznań
^{4} Faculty of Physics, V. N. Karazin Kharkiv National University, KharkivAbstract: The lateral shift of reflected light beam, known as GoosHaenchen effect, is theoretically studied for Brillouin light scattering by acoustic phonons and spin waves for DaemonEshbach geometry [1].
[1] Yuliya Dadoenkova, Nataliya Dadoenkova, Maciej Krawczyk and Igor Lyubchanskii, GoosHänchen effect for Brillouin light scattering by acoustic phonons, Optics Letters 43 (16), 3965 – 3968 (2018). 
Date: Thursday 2018.12.06Speaker: M.Sc. Szymon MieszczakAuthors: Jarosław W.KłosAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Driving magnetization dynamics in an ondemand magnonic crystal via the magnetoelastic interactionAbstract: Using spatial light interference of ultrafast laser pulses we impulsively generate a spatial modulation of the magnetization profile in an otherwise uniformly magnetized film, inducing the onset of magnonic bandstructure and its unique spatial distribution of magnetic excitations. The magnonic behaviour is visualized by the resonant interaction of these spin wave modes with elastics waves, which are simultaneously generated with, and phaselocked to, the magnonic profile. Calculation of the spin wave modal distribution in a laterally modulated magnetization landscape, using both the Plane Wave Method and micromagnetic simulations, provide a unified picture of the nontrivial precessional dynamics observed in our experiment. This work was supported by National Science Centre of Poland Grant No. UMO2016/21/B/ST3/00452 and the EU’s Horizon 2020 Research and Innovation Program under Marie SklodowskaCurie Grant Agreement No. 644348 (MagIC).

Date: Wednesday 2018.12.05Speaker: M.Sc. Justyna RychłyAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Theoretical studies of spin wave dynamics in planar magnonic quasicrystalsAbstract:We have studied theoretically spin wave dynamics in planar magnonic quasicrystals and compared obtained results with the corresponding magnonic crystals. We have found that magnonic quasicrystals are characterized by complex spin wave spectra of a fractal nature and that spin waves of higher frequencies are localized in the bulk region of an intact system. Moreover, the lifetime of spin wave modes in magnonic crystals and magnonic quasicrystals will be presented. This work was supported by the EU’s Horizon 2020 Research and Innovation Program under Marie SklodowskaCurie Grant Agreement No. 644348 (MagIC).

Date: Wednesday 2018.12.05Speaker: Dr. Paweł Sobieszczyk (invited speaker)Authors: P. Sobieszczyk, M. Krupiński, P. Zieliński, M. MarszałekAffiliation: Institute of Nuclear Physics, Polish Academy of Sciences, KrakówTitle: Magnetization reversal mechanisms in nanopatterned thin films with perpendicular magnetic anisotropyAbstract:Fabrication and modeling of patterned thin films with perpendicular magnetic anisotropy rise great interest due to their wide applications in magnetic storage, sensors and magnonic crystals. A good representative of such systems are wellordered arrays of magnetic antidots and dots based on Co/Pd multilayers, where magnetic reversal mechanisms strongly depend on the array geometry [1, 2]. We attempt to understand and reproduce the observed magnetic properties and domain structure appearing in the arrays by micromagnetic simulations performed using Mumax3 software [3]. In particular, changes in coercivity field, magnetic anisotropy constant and magnetic domain arrangement were studied and correlated with symmetry and size of nanostructures. The calculations show how edge effects, defects and inhomogeneity affect magnetization reversal and domain wall pinning mechanism, which helps to design similar patterned systems with the specific magnetic properties.
The numerical simulations were supported in part by the PLGrid Infrastructure.
[1] M. Krupinski, D. Mitin, A. Zarzycki, A. Szkudlarek, M. Giersig, M. Albrecht and M. Marszałek, Magnetic transition from dot to antidot regime in large area Co/Pd nanopatterned arrays with perpendicular magnetization, Nanotechnology 2017, 28, 085302.
[2] C. Banerjee, Pawel Gruszecki, J. W. Klos, O. Hellwig, M. Krawczyk, and A. Barman, Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations, Phys. Rev. B 96, 024421
[3]Vansteenkiste, A.; Leliaert, J.; Dvornik, M.; Helsen, M.; GarciaSanchez, F.; Van Waeyenberge, B., The Design and Verification of Mumax3. AIP Adv. 2014, 4, 107133. 
Date: Wednesday 2018.12.05Speaker: Krzysztof SzulcAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Magnetization reversal in the array of nanobarsAbstract: We investigate remagnetization in the twodimensional array of permalloy nanobars with periodic and Fibonacci order. Hysteresis loops measured with magnetooptic Kerr effect microscopy shows particular behaviour of the structure in the magnetization reversal process. Monte Carlo simulations of macrospins in effective field and micromagnetic simulations as well as theoretical investigations of demagnetizing fields and dipolar interactions complemented experimental results explaining occurent phenomenons.

Date: Thursday 2018.12.06Speaker: Dr. Żaneta ŚwiątkowskaWarkockaAffiliation: Institute of Nuclear Physics, Polish Academy of Sciences, KrakówTitle: Laser synthesis of composite magnetic particlesAbstract: Iron or nickel and their oxide nanoparticles have received considerable attention due to their applications in magnetic, electronic, pigmental, catalyst and biomedical purposes. NiO/Ni and Fe3O4/FeO composite particles were prepared by a pulsed laser irradiation of oxide nanoparticles dispersed in liquid. The sizes of particles and their composition were controlled by tuning the laser parameters, such as laser fluence and/or irradiation time. Correlation between structure of obtained composites and their magnetic properties will be presented.

Date: Wednesday 2018.12.05Speaker: Dr. hab. Aleksandra Trzaskowska (invited speaker)Affiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Periodic nanostructures investigated using BLSAbstract: Experimental and theoretical study of the phononic band gap in the hypersonic range for thermally activated Surface Acoustic Waves will be presented. Two dimensional phononic crystals have been studied by the Surface Brillouin Light Scattering. The experimental data will be compared with results of theoretical modeling by the Finite Element Method. This work was supported by National Science Centre of Poland Grant No. UMO2016/21/B/ST3/00452.

Date: Wednesday 2018.12.05Speaker: Miłosz ZdunekAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Investigation of magnons and phonons by BLS in bilayer substituted YIG samples?Abstract: We have investigated Surface Acoustic Waves (SAWs) and Backward Volume Magnetostatic Spin Waves (BVMSWs) in bilayer substituted YIG (Yttrium Iron Garnet) samples. The bottom layer is characterised by inplane magnetisation direction, while the top layer’s magnetisation direction is outofplane. The spectra were obtained by Brillouin Light Scattering (BLS) method for different magnetic configurations. The dispersion relations for aforementioned waves has been designated by analyzing the spectral data. This work was supported by National Science Centre of Poland Grant No. UMO2016/21/B/ST3/00452.

Date: Thursday 2018.12.06Speaker: M.Sc. Mateusz ZelentAffiliation: Faculty of Physics, Adam Mickiewicz University in Poznań, PoznańTitle: Controlled motion of skyrmions in magnonic antidot latticesAbstract: Magnetic skyrmions are topologically protected nanometer sized chiral spin textures with an out of plane magnetic domain at the center. Due to their various unique features such as stability given by their topology, they are considered as potential candidates for information carriers in next generation data storage devices, like racetrack memory. Therefore, it is crucial to be able to manipulate their currentinduced motion in various directions. Magnetic antidot arrays can be used as a controller for skyrmion motion by using properly designed sequences of electrical current pulses, which marks a big leap toward skyrmion based devices, like logic gates, magnonics filters or demultiplexers.

Date: Wednesday 2018.12.05Speaker: Prof. Piotr Zieliński (keynote speaker)Authors: P. Zieliński ^{1,2}, D. Kuźma ^{1}, P. Sobieszczyk^{1}, F. Montoncello^{3}Affiliations:Title: Is a discontinuous phase transition of second order possible in magnetic systems?
^{1} Institute of Nuclear Physics, Polish Academy of Sciences, Kraków
^{2} Institute of Nuclear Physics, Cracow University of Technology, Kraków, Poland
^{3} Department of Physics and Earth Sciences, CNISM Unit, University of Ferrara, FerraraAbstract:A transition between groupsubgroup unrelated configurations is always discontinuous and often marked by a large hysteresis that impedes the switching of the configurations by varying a control parameter. This is e.g. characteristic of martensitic phase transitions. It will be shown that in some specific spin systems the hysteresis width may be reduced to zero in analogy to the second order phase transitions. Possible applications of such systems in the most efficiently switchable devices will be discussed.