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We experimentally demonstrate a time-multiplexing method for pulse-pumped heralded single-photon sources using switchable optical fiber delay lines. The optical fibers constitute a 32-channel binary-division photon buffer that can multiplex time slots into single temporal mode to enhance single-photon generation rate without increasing multi-photon noise. Relative time multiplexing using the same actively controlled variable delay realizes Hong-Ou-Mandel interferometry by two photons produced in arbitrary two time-bins. The interference dip depth in good agreement with theory verifies path length matching within the photonic coherence length and dispersion compensation of the optical fiber delay sections. We independently confirm by low-coherence interferometry that the internal optical path lengths of the optical switches are constant during the switching operations.

We demonstrate an experimental technique to generate and measure arbitrary superpositions of core modes in a multi-core fiber. Two spatial light modulators couple the fundamental mode of a single-mode fiber with multiple-core modes of the MCF to constitute a Mach-Zehnder-type multi-path interferometer. The phase tunability of each path is verified by comparing two-, three-, and four-path interference patterns with the theory. Interference fringes in the wavelength domain estimates the inter-core group index differences with a resolution of 10(-5) using a fiber length of 1 m.

We propose a multi-photon interferometer with a generalized C-SWAP operation that can estimate Tr[rho(1)rho(2)center dot center dot center dot rho(n)], a nonlinear functional of n photonic density matrices. The scheme is demonstrated for three single-photon states whose overlap is experimentally measured as the interference visibility of a control qubit encoded into photonic paths. The validity of this method is verified by comparing the visibility with the results of Hong-Ou-Mandel experiments. (C) 2013 Optical Society of America

We propose and demonstrate the scaling up of photonic graph state through path qubit fusion. Two path qubits from separate two-photon four-qubit states are fused to generate a two-dimensional seven-qubit graph state composed of polarization and path qubits. Genuine seven-qubit entanglement is verified by evaluating the witness operator. Six qubits from the graph state are used to execute the general two-qubit Deutsch-Jozsa algorithm with a success probability greater than 90%., Comment: 4 pages. Supplementary Material is included in the zip file

We propose a novel approach to optical generation of superresolution atomic state density distribution based on interaction between Lambda- type atoms and temporally-cascaded driving fields. The scheme effectively inscribes multiplication of optical intensity profiles on atomic state density distribution, which can produce arbitrary patterns beyond the diffraction limit. The degree of resolution enhancement can be increased, not depending on the intrinsic nonlinearity of the photographic medium or the number of simultaneously interacting fields unlike the previous schemes. Procedures for drawing arbitrary two-dimensional patterns and effects of atomic state decoherence are described.

We propose and experimentally demonstrate a two-photon four-qubit cluster state generator using linear optics and a single polarization-entangled photon-pair source based on spontaneous parametric down-conversion (SPDC). Our novel scheme provides greater design flexibility compared to previous schemes that rely on hyperentanglement.