Observation of Nonlocal Modulation with Entangled Photons

We demonstrate a new type of quantum mechanical correlation where phase modulators at distant locations, acting on the photons of an entangled pair, interfere to determine the apparent depth of modulation. When the modulators have the same phase, the modulation depth doubles; when oppositely phased, the modulators negate each other.Comment: 4 pages, 4 figure

Intense ultra-broadband down-conversion from randomly poled nonlinear crystals

Randomly poled nonlinear crystals are shown to be able to emit intense ultra-broadband photon-pair fields with properties comparable to those coming from chirped periodically-poled crystals. Their intensities scale linearly with the number of domains. Also photon pairs extending over intervals with durations comparable to one optical cycle can be generated in these crystals.Comment: 6 pages, 4 figure

Enhanced spontaneous raman scattering and gas composition analysis using a photonic crystal fiber

Spontaneous gas-phase Raman scattering using a hollow-core photonic bandgap fiber (HC-PBF) for both the gas cell and the Stokes light collector is reported. It was predicted that the HC-PBF configuration would yield several hundred times signal enhancement in Stokes power over a traditional free-space configuration because of increased interaction lengths and large collection angles. Predictions were verified by using nitrogen Stokes signals. The utility of this system was demonstrated by measuring the Raman signals as functions of concentration for major species in natural gas. This allowed photomultiplier-based measurements of natural gas species in relatively short integration times, measurements that were previously difficult with other systems. © 2008 Optical Society of America

Chirped quasi-phase-matching with Gauss sums for production of biphotons

We study the theory of linearly chirped biphoton wave-packets produced in two basic quasi-phase-matching configurations: chirped photonic-like crystals and aperiodically poled crystals. The novelty is that these structures are considered as definite assembles of nonlinear layers that leads to detailed description of spontaneous parametric down-conversion (SPDC) processes through the discrete Gauss sums. We demonstrate that biphoton spectra for chirped photonic crystals involving a small number of layers consist from definite well-resolved spectral lines. We also discuss the forming of broadband spectra of signal (idler) waves in SPDC for both configurations as number of layers increases as well as in dependence of chirping parameters .Comment: 7 pages, 3 figure

Narrowband Biphotons: Generation, Manipulation, and Applications

In this chapter, we review recent advances in generating narrowband biphotons with long coherence time using spontaneous parametric interaction in monolithic cavity with cluster effect as well as in cold atoms with electromagnetically induced transparency. Engineering and manipulating the temporal waveforms of these long biphotons provide efficient means for controlling light-matter quantum interaction at the single-photon level. We also review recent experiments using temporally long biphotons and single photons.Comment: to appear as a book chapter in a compilation "Engineering the Atom-Photon Interaction" published by Springer in 2015, edited by A. Predojevic and M. W. Mitchel

Photon extrabunching in ultrabright twin beams measured by two-photon counting in a semiconductor

For many years twin beams originating from parametric down-converted light beams have aroused great interest and attention in the photonics community. One particular aspect of the twin beams is their peculiar intensity correlation functions, which are related to the coincidence rate of photon pairs. Here we take advantage of the huge bandwidth offered by two-photon absorption in a semiconductor to quantitatively determine correlation functions of twin beams generated by spontaneous parametric down-conversion. Compared with classical incoherent sources, photon extrabunching is unambiguously and precisely measured, originating from exact coincidence between down-converted pairs of photons, travelling in unison. These results strongly establish that two-photon counting in semiconductors is a powerful tool for the absolute measurement of light beam photon correlations at ultrashort timescales

An intuitive approach to quantum circuit simulation

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaf 27).The study of quantum logic and quantum algorithms is still in its infancy. Quantum algorithms can potentially solve many problems much more efficiently than their classical counterparts, and research in the field is fast-paced and dynamic. The theory that motivates the creation and analyses of quantum algorithms is very complicated and often requires extensive knowledge of advanced mathematics such as complex linear algebra, modular arithmetic, and Fourier analysis. This poses much difficulty for beginners in the field. A student may better understand an algorithm by visualizing each step and observing the state of the system over time. While there are many representations of a quantum algorithm, perhaps the most intuitive is the quantum circuit realization, analogous to the classical Boolean logic circuit. In this representation, the quantum system evolves along a set of quantum "wires" that connect various quantum gates or operators. Few software packages have been written to simulate quantum logic graphically, and most lack a level of user-friendliness beneficial to the beginner. QLS (Quantum Logic Simulator) is designed to simulate basic circuits of up to 20 "quantum bits." The user may add components, simulate circuits, and view various informative outputs using an intuitive, mouse-driven interface. The research goal is divided into two main parts: simulation and user interface. On the simulation side, the simulator is robust enough to handle a wide range of possible logic circuits. This level of generality often pushes the classical computer to its limits due to the natural inefficiency of classical simulation of quantum systems [1]. QLS utilizes a variety of techniques to simulate various circuit components while maintaining generality. On the user-interface side, the simulator is designed to be intuitive, be easy-to-use, and present meaningful outputs that facilitate understanding of quantum algorithms. If successful, QLS may become a helpful teaching aid in introductory quantum logic and algorithms