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Sep 19, 2013
09/13

by
N. Korolkova; R. Loudon

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The impact of the operator-valued commutator on nonclassical properties of continuous polarization variables is discussed. The definition of polarization squeezing is clarified to exclude those squeezed states which do not contain any new physics beyond quadrature squeezing. We present a consistent derivation of the general nonseparability criterion for the continuous variables with the operator-valued commutator, and apply it to the polarization variables.

Source: http://arxiv.org/abs/quant-ph/0303135v2

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51

Sep 23, 2013
09/13

by
Ch. Silberhorn; N. Korolkova; G. Leuchs

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We suggest a quantum cryptographic scheme using continuous EPR-like correlations of bright optical beams. For binary key encoding, the continuous information is discretized in a novel way by associating a respective measurement, amplitude or phase, with a bit value "1" or "0". The secure key distribution is guaranteed by the quantum correlations. No pre-determined information is sent through the quantum channel contributing to the security of the system.

Source: http://arxiv.org/abs/quant-ph/0109009v3

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45

Sep 23, 2013
09/13

by
D. Mogilevtsev; T. Tyc; N. Korolkova

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In this work we investigate an influence of decoherence effects on quantum states generated as a result of the cross-Kerr nonlinear interaction between two modes. For Markovian losses (both photon loss and dephasing), a region of parameters when losses still do not lead to destruction of non-classicality is identified. We emphasize the difference in impact of losses in the process of state generation as opposed to those occurring in propagation channel. We show moreover, that correlated losses...

Source: http://arxiv.org/abs/0904.3235v1

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37

Sep 20, 2013
09/13

by
T. Opatrny; N. Korolkova; G. Leuchs

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The question of efficient multimode description of optical pulses is studied. We show that a relatively very small number of nonmonochromatic modes can be sufficient for a complete quantum description of pulses with Gaussian quadrature statistics. For example, a three-mode description was enough to reproduce the experimental data of photon number correlations in optical solitons [S. Spalter et al., Phys. Rev. Lett. 81, 786 (1998)]. This approach is very useful for a detailed understanding of...

Source: http://arxiv.org/abs/quant-ph/0204131v2

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37

Sep 22, 2013
09/13

by
D. Mogilevtsev; V. S. Shchesnovich; N. Korolkova

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In this work we describe a simple and efficient scheme for inference of photon number distribution by adding variable thermal noise to the signal. The inference remains feasible even if the scheme parameters are subject to random dynamical change.

Source: http://arxiv.org/abs/1302.3838v1

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3.0

Jun 30, 2018
06/18

by
G. Harder; D. Mogilevtsev; N. Korolkova; Ch. Silberhorn

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We present an efficient and robust method for the reconstruction of photon number distributions by using solely thermal noise as a probe. The method uses a minimal number of pre-calibrated quantum devices, only one on/off single-photon detector is sufficient. Feasibility of the method is demonstrated by the experimental inference of single-photon, thermal and two-photon states. The method is stable to experimental imperfections and provides a direct, user-friendly quantum diagnostics tool.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1409.8076

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34

Sep 18, 2013
09/13

by
D. Mogilevtsev; A. Mikhalychev; V. S. Shchesnovich; N. Korolkova

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We demonstrate that it is possible to compensate for effects of strong linear loss when generating non-classical states by engineered nonlinear dissipation. We show that it is always possible to construct such a loss-resistant dissipative gadget in which, for a certain class of initial states, the desired non-classical pure state can be attained within a particular time interval with an arbitrary precision. Further we demonstrate that an arbitrarily large linear loss can still be compensated by...

Source: http://arxiv.org/abs/1211.4435v1

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Sep 19, 2013
09/13

by
O. Glöckl; J. Heersink; N. Korolkova; G. Leuchs; S. Lorenz

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We have experimentally demonstrated polarization entanglement using continuous variables in an ultra-short pulsed laser system at telecommunication wavelengths. Exploiting the Kerr-nonlinearity of a glass fibre we generated a polarization squeezed pulse with S2 the only non-zero Stokes parameter thus S1 and S3 being the conjugate pair. Polarization entanglement was generated by interference of the polarization squeezed field with a vacuum on a 50:50 beam splitter. The two resultant beams...

Source: http://arxiv.org/abs/quant-ph/0302083v1

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9.0

Jun 27, 2018
06/18

by
D. Mogilevtsev; G. Ya. Slepyan; E. Garusov; S. Kilin; N. Korolkova

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We present a one-dimensional tight-binding chain of two-level systems coupled only through common dissipative Markovian reservoirs. This quantum chain can demonstrate anomalous thermodynamic behavior contradicting Fourier law. Population dynamics of individual systems of the chain is polynomial with the order determined by the initial state of the chain. The chain can simulate classically hard problems, such as multi-dimensional random walks.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1503.07213

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Sep 23, 2013
09/13

by
N. Korolkova; Ch. Silberhorn; O. Gloeckl; S. Lorenz; Ch. Marquardt; G. Leuchs

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We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give a brief overview of the variety of optical techniques and quantum communication applications on this basis. A new entanglement-based quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the relative interference phase which is advantageous for quantum communication applications.

Source: http://arxiv.org/abs/quant-ph/0109011v3

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Sep 23, 2013
09/13

by
S. Lorenz; Ch. Silberhorn; N. Korolkova; R. S. Windeler; G. Leuchs

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Amplitude squeezed pulsed light has been produced using a microstructured silica fibre. By spectrally filtering after the nonlinear propagation in the fibre a squeezing value of -1.7dB has been measured. A quantum key distribution scheme based on squeezed light from such microstructured fibres is proposed.

Source: http://arxiv.org/abs/quant-ph/0109018v2

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Sep 19, 2013
09/13

by
J. Heersink; T. Gaber; S. Lorenz; O. Glöckl; N. Korolkova; G. Leuchs

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We report on the generation of polarization squeezing of intense, short light pulses using an asymmetric fiber Sagnac interferometer. The Kerr nonlinearity of the fiber is exploited to produce independent amplitude squeezed pulses. The polarization squeezing properties of spatially overlapped amplitude squeezed and coherent states are discussed. The experimental results for a single amplitude squeezed beam are compared to the case of two phase-matched, spatially overlapped amplitude squeezed...

Source: http://arxiv.org/abs/quant-ph/0302100v4

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123

Jul 19, 2013
07/13

by
O. Glöckl; U. L. Andersen; S. Lorenz; Ch. Silberhorn; N. Korolkova; G. Leuchs

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We present a setup to perform sub shot noise measurements of the phase quadrature for intense pulsed light without the use of a separate local oscillator. A Mach--Zehnder interferometer with an unbalanced arm length is used to detect the fluctuations of the phase quadrature at a single side band frequency. Using this setup, the non--separability of a pair of quadrature entangled beams is demonstrated experimentally.

Source: http://arxiv.org/abs/quant-ph/0406087v1

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Sep 24, 2013
09/13

by
Ch. Silberhorn; P. K. Lam; O. Weiss; F. Koenig; N. Korolkova; G. Leuchs

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We report on the generation of a continuous variable Einstein-Podolsky-Rosen (EPR) entanglement using an optical fibre interferometer. The Kerr nonlinearity in the fibre is exploited for the generation of two independent squeezed beams. These interfere at a beam splitter and EPR entanglement is obtained between the output beams. The correlation of the amplitude (phase) quadratures are measured to be 4.0+-0.2 (4.0+-0.4) dB below the quantum noise limit. The sum criterion for these squeezing...

Source: http://arxiv.org/abs/quant-ph/0103002v1