Generation of indistinguishable and pure heralded single photons with tunable bandwidth

We describe a new scheme to fully control the joint spectrum of paired photons generated in spontaneous parametric down-conversion. We show the capability of this method to generate frequency-uncorrelated photon pairs that are pure and indistinguishable, and whose bandwidth can be readily tuned. Importantly, the scheme we propose here can be implemented in any nonlinear crystal and frequency band of interest.Comment: 3 pages, 3 figure

Monitoring of excessive deformation of steel structure Extra-High Voltage pylons

Reliability and security of a power transmission depends on the state of the power grid and mainly on the state of the Extra-High Voltage pylons. The paper deals with deformation analysis of existing steel structure of selected Extra-High Voltage pylons which showed excessive differences comparing to the original design. In the assessment of the situation, geodetic survey of selected pylons of power grid that showed the greatest deformation was performed. On taken images, deformation of steel structures by using the FOTOMNG system was also analyzed. The proposed method allows a modeling of the structure of the object based on precisely obtained photographic documentation of the current state. It also represents a very effective method which allows to quickly and efficiently analyze the deformation in the structure of Extra-High Voltage pylons in the critical position of the power grid. Other benefits include the possibility of repeatable and safe measurement.Web of Science62232932

Generation of tunable entanglement and violation of a Bell-like inequality between different degrees of freedom of a single photon

We demonstrate a scheme to generate noncoherent and coherent correlations, i.e., a tunable degree of entanglement, between degrees of freedom of a single photon. Its nature is analogous to the tuning of the purity (first-order coherence) of a single photon forming part of a two-photon state by tailoring the correlations between the paired photons. Therefore, well-known tools such as the Clauser-Horne-Shimony-Holt (CHSH) Bell-like inequality can also be used to characterize entanglement between degrees of freedom. More specifically, CHSH inequality tests are performed, making use of the polarization and the spatial shape of a single photon. The four modes required are two polarization modes and two spatial modes with different orbital angular momentum.Comment: 7 pages, 5 figures. Updated to be consistent with published versio

Shape of the spatial mode function of photons generated in noncollinear spontaneous parametric downconversion

We show experimentally how noncollinear geometries in spontaneous parametric downconversion induce ellipticity of the shape of the spatial mode function. The degree of ellipticity depends on the pump beam width, especially for highly focused beams. We also discuss the ellipticity induced by the spectrum of the pump beam

Quantum identification system

A secure quantum identification system combining a classical identification procedure and quantum key distribution is proposed. Each identification sequence is always used just once and new sequences are ``refuelled'' from a shared provably secret key transferred through the quantum channel. Two identification protocols are devised. The first protocol can be applied when legitimate users have an unjammable public channel at their disposal. The deception probability is derived for the case of a noisy quantum channel. The second protocol employs unconditionally secure authentication of information sent over the public channel, and thus it can be applied even in the case when an adversary is allowed to modify public communications. An experimental realization of a quantum identification system is described.Comment: RevTeX, 4 postscript figures, 9 pages, submitted to Physical Review

Bragg reflection waveguide as a source of wavelength-multiplexed polarization-entangled photon pairs

We put forward a new highly efficient source of paired photons entangled in polarization with an ultra-large bandwidth. The photons are generated by means of a conveniently designed spontaneous parametric down-conversion process in a semiconductor type-II Bragg reflection waveguide. The proposed scheme aims at being a key element of an integrated source of polarization-entangled photon pairs highly suitable for its use in a multi-user quantum-key-distribution system

Experimental estimation of the dimension of classical and quantum systems

An overwhelming majority of experiments in classical and quantum physics make a priori assumptions about the dimension of the system under consideration. However, would it be possible to assess the dimension of a completely unknown system only from the results of measurements performed on it, without any extra assumption? The concept of a dimension witness answers this question, as it allows one to bound the dimension of an unknown classical or quantum system in a device-independent manner, that is, only from the statistics of measurements performed on it. Here, we report on the experimental demonstration of dimension witnesses in a prepare and measure scenario. We use pairs of photons entangled in both polarization and orbital angular momentum to generate ensembles of classical and quantum states of dimensions up to 4. We then use a dimension witness to certify their dimensionality as well as their quantum nature. Our results open new avenues for the device-independent estimation of unknown quantum systems and for applications in quantum information science.Comment: See also similar, independent and jointly submitted work of J. Ahrens et al., quant-ph/1111.127

The Possibilities of Extraction and Use of Bentonite and Other Claystones Adsorbents in the North Bohemian and Sokolov Basin

Import 04/07/2011Tato bakalářská práce se zabývá možnostmi těžby jílovcových sorbentů v oblasti Severočeské a Sokolovské pánve České republiky a jejich aplikací a využitím v jednotlivých oborech národního hospodářství. Dalšími oblastmi, na které se práce zaměřuje je rozbor vlastností těchto sorbentů, jejich zpracování a možné využití v průběhu dalších let. Cílem práce je zhodnotit význam těchto surovin ve všech oblastech využití s ohledem na technologické, ekonomické a ekologické důsledky jejich těžby.This bachelor thesis deals with the possibility of extracting claystone sorbents in the North Bohemian and Sokolov basins of the Czech Republic and their applications and use in various fields of national economy. Other parts of this work are focused on the characteristic analysis of these sorbents, their processing and possible use in subsequent years. The goal of this work is to evaluate the signifikance and exploitation of these materials regarding to technological, economic and environmental consequences of mining.Prezenční542 - Institut hornického inženýrství a bezpečnostidobř

Acknowledgements

In the first place, I owe a great debt of gratitude to Prof. Jan Peřina, who brought me to physics and whose memorable lectures showed me into the realm of quantum optics. It has certainly been an exceptional privilege to meet and work with such a personality. I wish to acknowledge his advice, support and comments during my PhD study as well as his careful reading of the manuscript of the Thesis. I am also deeply indebted to my co-workers Miloslav Dušek, Ondřej Haderka and Robert Myška without who the quantum key distribution and quantum identification experiments could have never succeeded. I am grateful to Prof. Malvin C. Teich for giving me the opportunity to work a