Quantum uniqueness

In the classical world one can construct two identical systems which have identical behavior and give identical measurement results. We show this to be impossible in the quantum domain. We prove that after the same quantum measurement two different quantum systems cannot yield always identical results, provided the possible measurement results belong to a non orthogonal set. This is interpreted as quantum uniqueness - a quantum feature which has no classical analog. Its tight relation with objective randomness of quantum measurements is discussed.Comment: Presented at 4th Feynman festival, June 22-26, 2009, in Olomouc, Czech Republic

Applicability of QKD: TerraQuantum view on the NSA's scepticism

Quantum communication offers unique features that have no classical analog, in particular, it enables provably secure quantum key distribution (QKD). Despite the benefits of quantum communication are well understood within the scientific community, the practical implementations sometimes meet with scepticism or even resistance. In a recent publication [1], NSA claims that QKD is inferior to "quantum-resistant" cryptography and does not recommend it for use. Here we show that such a sceptical approach to evaluation of quantum security is not well justified. We hope that our arguments will be helpful to clarify the issue

Triplet-like correlation symmetry of continuous variable entangled states

We report on a continuous variable analogue of the triplet two-qubit Bell states. We theoretically and experimentally demonstrate a remarkable similarity of two-mode continuous variable entangled states with triplet Bell states with respect to their correlation patterns. Borrowing from the two qubit language, we call these correlations triplet-like.Comment: 7 pages, 5 figures. Comments are welcom

Feasibility of free space quantum key distribution with coherent polarization states

We demonstrate for the first time the feasibility of free space quantum key distribution with continuous variables under real atmospheric conditions. More specifically, we transmit coherent polarization states over a 100m free space channel on the roof of our institute's building. In our scheme, signal and local oscillator are combined in a single spatial mode which auto-compensates atmospheric fluctuations and results in an excellent interference. Furthermore, the local oscillator acts as spatial and spectral filter thus allowing unrestrained daylight operation.Comment: 12 pages, 8 figures, extensions in sections 2, 3.1, 3.2 and 4. This is an author-created, un-copyedited version of an article accepted for publication in New Journal of Physics (Special Issue on Quantum Cryptography: Theory and Practice). IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Бромування хiнoлiн-4(1Н)-oнів як ефективна стратегія у створенні нових антибактеріальних агентів

Aim. To study the reactivity of 2-methylquinolin-4(1H)-ones in the bromination reaction in order to develop target-oriented methods for the synthesis of compounds that can affect the Quorum sensing processes of various bacterial communities.Results and discussion. Features of the reactivity of 2-methylquinoline-4(1H)-ones in the bromination reaction using two halogenating reagents – molecular bromine and N-bromosuccinimide (NBS) have been studied. It has been shown that in both cases the direction of halogenation depends on the presence and nature of the substituent in position C(3) of the heterocycle. It has been found that variations in reagents, solvents, and catalysts did not lead to changes in the qualitative composition of the reaction products and only slightly affected their yields.Experimental part. The synthesis of bromo derivatives of quinoline-4(1H)-ones was carried out by acting on the initial compounds of a molecular bromine or NBS in glacial acetic acid or chloroform, respectively, in the presence of catalytic amounts of benzoyl peroxide or without it. The structure of the compounds synthesized was proven by the data of 1H NMR spectroscopy and elemental analysis.Conclusions. The features of the bromination reaction in the series of 3-substituted 2-methylquinolin-4(1H)-ones have been studied. It has been found that depending on the nature of the substituent in position C(3) of quinolone, bromination occurs on the methyl group of position C(2), or on positions C(3) and C(6) of the heterocycle. In the case of 3-benzyl-2-methylquinolin-4(1H)-one, bromination takes place on the methyl group of position C(2) of quinolone to form 3-benzyl-2-(bromomethyl)quinolin-4(1H)-one, which can be used for developing a new class of drugs designed to affect the virulence factors of microorganisms. The reactivity of 3-benzyl-2-(bromomethyl)-quinolin-4(1H)-one has been studied on the example of n-hexylamine alkylation.Received: 10.07.2020 Revised: 29.10.2020 Accepted: 14.11.2020Мета. Вивчити реакційну здатність 2-метилхiнoлiн-4(1Н)-oнiв у реaкцiї брoмувaння для цілеспрямованої розробки методів синтезу сполук, які можуть впливати нa прoцеси Quorum sensing різних бактеріальних спільнот.Результати та їх обговорення. Вивченo oсoбливoстi реaкцiйнoї здaтнoстi 2-метилхiнoлiн-4(1Н)-oнiв у реaкцiї брoмувaння з викoристaнням двoх гaлoгенувальних реaгентiв – мoлекулярнoгo брoму i N-бромосукциніміду. Показано, що в обох випадках напрямок галогенування залежить від наявності та природи замісника в положенні С(3) гетероциклу. З’ясовано, що вaрiювaння реaгентaми не впливало на змiну якiснoї кaртини прoдуктiв реaкцiй i лише незнaчною мірою позначалося нa їх вихoдах.Експериментальна частина. Синтез брoмопoхідних хінoлін-4(1Н)-oнів проводили дією на вихідні сполуки мoлекулярного брoму aбo N-брoмосукцинiмiду в середoвищi льoдяної oцтoвої кислoти або хлoрoфoрму відповідно, в присутнoстi кaтaлiтичних кiлькoстей перoксиду бензoїлу aбo без ньoгo. Структуру і склад усіх синтезованих речовин доведено даними 1Н ЯМР-спектроскопії та елементного аналізу.Висновки. Дoслiдженo oсoбливoстi брoмувaння в ряду зaмiщених за положенням 3 2-метилхiнoлiн-4(1H)-oнiв. Виявлено, щo залежно вiд прирoди зaмiсникa в пoлoженнi С(3) хiнoлoну брoмувaння вiдбувaється за метильнoю групою пoлoження С(2) aбo за пoлoженням С(3) тa С(6) гетерoциклу. У випaдку 3-бензил-2-метилхiнoлiн-4(1Н)-oну бромування вiдбувaється за метильною групою С(2) пoлoження хiнoлoну, з утворенням 3-бензил-2-(брoмометил)хiнoлiн-4(1Н)-oнy, який можна використовувати для розробки нового класу ліків, призначених впливати на фактори вірулентності мікроорганізмів. Продемонстровано синтетичні можливості 3-бензил-2-брoмометилхiнoлiн-4(1Н)-oнy на прикладі алкілування н-гексиламіну.Received: 10.07.2020 Revised: 29.10.2020 Accepted: 14.11.202

Atmospheric Channel Characteristics for Quantum Communication with Continuous Polarization Variables

We investigate the properties of an atmospheric channel for free space quantum communication with continuous polarization variables. In our prepare-and-measure setup, coherent polarization states are transmitted through an atmospheric quantum channel of 100m length on the roof of our institute's building. The signal states are measured by homodyne detection with the help of a local oscillator (LO) which propagates in the same spatial mode as the signal, orthogonally polarized to it. Thus the interference of signal and LO is excellent and atmospheric fluctuations are autocompensated. The LO also acts as spatial and spectral filter, which allows for unrestrained daylight operation. Important characteristics for our system are atmospheric channel influences that could cause polarization, intensity and position excess noise. Therefore we study these influences in detail. Our results indicate that the channel is suitable for our quantum communication system in most weather conditions.Comment: 6 pages, 4 figures, submitted to Applied Physics B following an invitation for the special issue "Selected Papers Presented at the 2009 Spring Meeting of the Quantum Optics and Photonics Section of the German Physical Society