A bright, pulsed two-mode squeezer

We report the realization of a bright ultrafast two-mode squeezer based on type II parametric downconversion (PDC) in periodically poled $\mathrm{KTiOPO_4}$ (PP-KTP) waveguides. It produces a pulsed two-mode squeezed vacuum state: a photon-number entangled pair of truly single-mode pulses or, in terms of continuous variables quantum optics, a pulsed, single mode Einstein-Podolsky-Rosen (EPR) state in the telecom regime. We prove the single mode character of our source by measuring its $g^{(2)}$ correlation function and demonstrate a mean photon number of up to 2.5 per pulse, equivalent to 11dB of two-mode squeezing.Comment: 4 pages, 3 figure

From quantum pulse gate to quantum pulse shaper -- enigneered frequency conversion in nonlinear optical waveguides

Full control over the spatio-temporal structure of quantum states of light is an important goal in quantum optics, to generate for instance single-mode quantum pulses or to encode information on multiple modes, enhancing channel capacities. Quantum light pulses feature an inherent, rich spectral broadband-mode structure. In recent years, exploring the use of integrated optics as well as source-engineering has led to a deep understanding of the pulse-mode structure of guided quantum states of light. In addition, several groups have started to investigate the manipulation of quantum states by means of single-photon frequency conversion. In this paper we explore new routes towards complete control of the inherent pulse-modes of ultrafast pulsed quantum states by employing specifically designed nonlinear waveguides with adapted dispersion properties. Starting from our recently proposed quantum pulse gate (QPG) we further generalize the concept of spatio-spectral engineering for arbitrary \chitwo-based quantum processes. We analyse the sum-frequency generation based QPG and introduce the difference-frequency generation based quantum pulse shaper (QPS). Together, these versatile and robust integrated optics devices allow for arbitrary manipulations of the pulse-mode structure of ultrafast pulsed quantum states. The QPG can be utilized to select an arbitrary pulse mode from a multimode input state, whereas the QPS enables the generation of specific pulse modes from an input wavepacket with Gaussian-shaped spectrum.Comment: 21 pages, 9 figure

Direct Measurement of the Spatial-Spectral Structure of Waveguided Parametric Down-Conversion

We present a study of the propagation of higher-order spatial modes in a waveguided parametric down-conversion photon pair source. Observing the multimode photon pair spectrum from a periodically poled KTiOPO$_4$ waveguide allowed us to isolate individual spatial modes through their distinctive spectral properties. We have measured directly the spatial distribution of each mode of the photon pairs, confirming the findings of our waveguide model, and demonstrated by coincidence measurements that the total parity of the modes is conserved in the nonlinear interaction. Furthermore, we show that we can combine the advantages of a waveguide source with the potential to generate spatially entangled photon pairs as in bulk crystal down-converters.Comment: 4 pages, 5 figure

Floquet prethermalization in the resonantly driven Hubbard model

We demonstrate the existence of long-lived prethermalized states in the Mott insulating Hubbard model driven by periodic electric fields. These states, which also exist in the resonantly driven case with a large density of photo-induced doublons and holons, are characterized by a nonzero current and an effective temperature of the doublons and holons which depends sensitively on the driving condition. Focusing on the specific case of resonantly driven models whose effective time-independent Hamiltonian in the high-frequency driving limit corresponds to noninteracting fermions, we show that the time evolution of the double occupation can be reproduced by the effective Hamiltonian, and that the prethermalization plateaus at finite driving frequency are controlled by the next-to-leading–order correction in the high-frequency expansion of the effective Hamiltonian. We propose a numerical procedure to determine an effective Hubbard interaction that mimics the correlation effects induced by these higher-order terms

Nonequilibrium dynamical cluster approximation study of the Falicov-Kimball model

We use a nonequilibrium implementation of the dynamical cluster approximation (DCA) to study the effect of short-range correlations on the dynamics of the two-dimensional Falicov-Kimball model after an interaction quench. As in the case of single-site dynamical mean-field theory, thermalization is absent in DCA simulations, and for quenches across the metal-insulator boundary, nearest-neighbor charge correlations in the nonthermal steady state are found to be larger than in the thermal state with identical energy. We investigate to what extent it is possible to define an effective temperature of the trapped state after a quench. Based on the ratio between the lesser and retarded Green's function, we conclude that a roughly thermal distribution is reached within the energy intervals corresponding to the momentum-patch dependent subbands of the spectral function. The effectively different chemical potentials of these distributions, however, lead to a very hot, or even negative, effective temperature in the energy intervals between these subbands

Integration interner und externer Daten zur Früherkennung entscheidungsrelevanter Symptome

Bedingt durch die Internationalisierung der Märkte, einen sich zuspitzenden Preiswettbewerb, immer kürzere Produktlebenszyklen und nicht zuletzt durch die zunehmende Nutzung innovativer Informations- und Kommunikationstechnologien sehen sich viele Unternehmen einer erhöhten Marktdynamik und einem verschärften Wettbewerb gegenüber. Für die Konzeption von Management Support Systemen (MSS) bedeutet dies, dass neben den internen Informationen auch Informationen aus externen Quellen eingebunden, mit den internen verknüpft und hinsichtlich auffälliger Konstellationen für die Entscheidungsunterstützung aufbereitet werden müssen. Im Rahmen des von der Deutschen Forschungsgemeinschaft geförderten und kooperativ mit dem Bereich Wirtschaftsinformatik I (Prof. Dr. Dr. h. c. mult. Peter Mertens) an der Universität Erlangen-Nürnberg bearbeiteten Forschungsprojektes INTEX („Integration von Controlling- und Marktforschungsdaten in einem Expertisesystem“) wurde dazu ein Konzept entwickelt und prototypisch realisiert [MeUh01]

Integration interner und externer Daten zur Früherkennung entscheidungsrelevanter Symptome

Bedingt durch die Internationalisierung der Märkte, einen sich zuspitzenden Preiswettbewerb, immer kürzere Produktlebenszyklen und nicht zuletzt durch die zunehmende Nutzung innovativer Informations- und Kommunikationstechnologien sehen sich viele Unternehmen einer erhöhten Marktdynamik und einem verschärften Wettbewerb gegenüber. Für die Konzeption von Management Support Systemen (MSS) bedeutet dies, dass neben den internen Informationen auch Informationen aus externen Quellen eingebunden, mit den internen verknüpft und hinsichtlich auffälliger Konstellationen für die Entscheidungsunterstützung aufbereitet werden müssen. Im Rahmen des von der Deutschen Forschungsgemeinschaft geförderten und kooperativ mit dem Bereich Wirtschaftsinformatik I (Prof. Dr. Dr. h. c. mult. Peter Mertens) an der Universität Erlangen-Nürnberg bearbeiteten Forschungsprojektes INTEX („Integration von Controlling- und Marktforschungsdaten in einem Expertisesystem“) wurde dazu ein Konzept entwickelt und prototypisch realisiert [MeUh01]