Resonant metamaterials for contrast enhancement in optical lithography

Sabine Dobmann, Dzmitry Shyroki, Peter Banzer, Andreas Erdmann, Ulf Peschel

The transmission through ultra-thin metal films is noticeable and thus limits their potential for the formation of lithographic masks. By sub-wavelength patterning of a metal film with a post structure, a resonant metamaterial is formed, which can effectively suppress the transmission. Measurements as well as calculations identify the width of the metal islands as a critical geometrical feature. Hence, the extraordinarily low transmission effect can be explained by the resonant response of single scatterers known as Localized Surface Plasmon Resonances (LSPR). A potential application of this suppressed transmission effect to thin metal masks in optical lithography is experimentally investigated. (C) 2012 Optical Society of America

Quantum polarization tomography of bright squeezed light

C. R. Mueller, B. Stoklasa, C. Peuntinger, C. Gabriel, J. Rehacek, Z. Hradil, A. B. Klimov, G. Leuchs, Ch Marquardt, et al.

We reconstruct the polarization sector of a bright polarization squeezed beam starting from a complete set of Stokes measurements. Given the symmetry that underlies the polarization structure of quantum fields, we use the unique SU(2) Wigner distribution to represent states. In the limit of localized bright states, the Wigner function can be approximated by an inverse three-dimensional Radon transform. We compare this direct reconstruction with the results of a maximum likelihood estimation, thus finding excellent agreement.

Classifying, quantifying, and witnessing qudit-qumode hybrid entanglement

Karsten Kreis, Peter van Loock

Recently, several hybrid approaches to quantum information emerged which utilize both continuous-and discrete-variable methods and resources at the same time. In this work, we investigate the bipartite hybrid entanglement between a finite-dimensional, discrete-variable quantum system and an infinite-dimensional, continuous-variable quantum system. A classification scheme is presented leading to a distinction between pure hybrid entangled states, mixed hybrid entangled states (those effectively supported by an overall finite-dimensional Hilbert space), and so-called truly hybrid entangled states (those which cannot be described in an overall finite-dimensional Hilbert space). Examples for states of each regime are given and entanglement witnessing as well as quantification are discussed. In particular, using the channel map of a thermal photon noise channel, we find that true hybrid entanglement naturally occurs in physically important settings. Finally, extensions from bipartite to multipartite hybrid entanglement are considered.

Dynamics of optomechanical spatial solitons in dual-nanoweb structures

C. Conti, A. Butsch, F. Biancalana, P. St J. Russell

We theoretically investigate the stability and dynamics of self-channeled beams that form via nonlocal optomechanical interactions in dual-nanoweb microstructured fibers. These beams represent a class of spatial soliton.

Compensation of Nonlinear Phase Noise Using the Effective Negative Nonlinearity of a Nonlinear Amplifying Loop Mirror

Klaus Sponsel, Christian Stephan, Georgy Onishchukov, Bernhard Schmauss, Gerd Leuchs

The nonlinear amplifying loop mirror (NALM) has been explored for use as a nonlinear phase-shift compensator (NPSC). Operation conditions for a tunable effective negative nonlinearity are considered and the NALM parameter optimization is discussed for direct bit-error-ratio (BER) improvement by post-compensation after a nonlinear transmission line. In this configuration, the fundamental limits for NPSC are estimated for differential quadrature phase-shift keying (DQPSK) using a simplified model. Numerical simulations of a 20 Gb/s RZ-DQPSK transmission system confirmed the applicability of this model and showed a significant BER improvement in a realistic transmission line. Alternatively, the fiber launch power per span could be increased by 2 dB for the same BER.

Three-dimensional quantum polarization tomography of macroscopic Bell states

Bhaskar Kanseri, Timur Iskhakov, Ivan Agafonov, Maria Chekhova, Gerd Leuchs

The polarization properties of macroscopic Bell states are characterized using three-dimensional quantum polarization tomography. This method utilizes three-dimensional (3D) inverse Radon transform to reconstruct the polarization quasiprobability distribution function of a state from the probability distributions measured for various Stokes observables. The reconstructed 3D distributions obtained for the macroscopic Bell states are compared with those obtained for a coherent state with the same mean photon number. The results demonstrate squeezing in one or more Stokes observables.

Characteristics of displaced single photons attained via higher order factorial moments

Kaisa Laiho, Malte Avenhaus, Christine Silberhorn

We investigate up to the fourth order normalized factorial moments of free-propagating and pulsed single photons displaced in phase space in a phase-averaged manner. Due to their loss independence, these moments offer expedient methods for quantum optical state characterization. We examine quantum features of the prepared displaced states, retrieve information on their photon-number content and study the reliability of the state reconstruction method used.

Polarization-Entangled Light Pulses of 10(5) Photons

Timur Sh. Iskhakov, Ivan N. Agafonov, Maria V. Chekhova, Gerd Leuchs

We experimentally demonstrate polarization entanglement for squeezed vacuum pulses containing more than 105 photons. We also study photon-number entanglement by calculating the Schmidt number and measuring its operational counterpart. Theoretically, our pulses are the more entangled the brighter they are. This promises important applications in quantum technologies, especially photonic quantum gates and quantum memories.

Generation of a phase-locked Raman frequency comb in gas-filled hollow-core photonic crystal fiber

A. Abdolvand, A. M. Walser, M. Ziemienczuk, T. Nguyen, P. St J. Russell

In a relatively simple setup consisting of a microchip laser as pump source and two hydrogen-filled hollow-core photonic crystal fibers, a broad, phase-locked, purely rotational frequency comb is generated. This is achieved by producing a clean first Stokes seed pulse in a narrowband guiding photonic bandgap fiber via stimulated Raman scattering and then driving the same Raman transition resonantly with a pump and Stokes fields in a second broad-band guiding kagome-style fiber. Using a spectral interferometric technique based on sum frequency generation, we show that the comb components are phase locked. (C) 2012 Optical Society of America

Universal quantum computation with continuous-variable Abelian anyons

Darran F. Milne, Natalia V. Korolkova, Peter van Loock

We describe how continuous-variable Abelian anyons, created on the surface of a continuous-variable analog of Kitaev's lattice model can be utilized for quantum computation. In particular, we derive protocols for the implementation of quantum gates using topological operations. We find that the topological operations alone are insufficient for universal quantum computation, which leads us to study additional nontopological operations such as offline squeezing and single-mode measurements. It is shown that these in conjunction with a non-Gaussian element allow for universal quantum computation using continuous-variable Abelian anyons.