Twin-photon techniques for fiber measurements

The potential of twin photons generated by parametric down-conversion for metrological applications are discussed. We present several experimental results like the measurement of chromatic dispersion and polarization mode dispersion in optical fibers.Comment: 6 pages, 5 figures, Invited paper for the Symposium on Optical Fiber Measurements, sponsored by NIST, Boulder, Co, September 15-17, 199

SiPM used as fast Photon-Counting Module and for Multiphoton Detection

We demonstrate fast counting and multiphoton detection abilities of a Silicon Photo Multiplier (SiPM). In fast counting mode we are able to detect two consecutive photons separated by only 2.3 ns corresponding to 430 MHz. The counting efficiency for small optical intensities at a wavelength of 532 nm was found to be around 8.3% with a dark count rate of 50 kHz at T=-7 degrees Celsius. Using the SiPM in multiphoton detection mode, we find a good signal discrimination for different numbers of simultaneous detected photons.Comment: 11 pages, 13 figure

Narrowband Photon Pair Source for Quantum Networks

We demonstrate a compact photon pair source based on a periodically poled lithium niobate nonlinear crystal in a cavity. The cavity parameters are chosen such that the emitted photon pair modes can be matched in the region of telecom ultra dense wavelength division multiplexing (U-DWDM) channel spacings. This approach provides efficient, low-loss, mode selection that is compatible with standard telecommunication networks. Photons with a coherence time of 8.6 ns (116 MHz) are produced and their purity is demonstrated. A source brightness of 134 pairs(s.mW.MHz)$^{-1}$ is reported. The high level of purity and compatibility with standard telecom networks is of great importance for complex quantum communication networks

Energy-time entangled qutrits: Bell tests and quantum communication

We have developed a scheme to generate, control, transmit and measure entangled photonic qutrits (two photons each of dimension d = 3). A Bell test of this source has previously been reported elsewhere [1], therefore, here we focus on how the control of the system is realized. Motivated by these results, we outline how the scheme can be used for two specific quantum protocols, namely key distribution and coin tossing and discuss some of their advantages and disadvantages.Comment: For the conference proceedings of QCMC 200

Quantum random number generation for 1.25 GHz quantum key distribution systems

Security proofs of quantum key distribution (QKD) systems usually assume that the users have access to source of perfect randomness. State-of-the-art QKD systems run at frequencies in the GHz range, requiring a sustained GHz rate of generation and acquisition of quantum random numbers. In this paper we demonstrate such a high speed random number generator. The entropy source is based on amplified spontaneous emission from an erbium-doped fibre, which is directly acquired using a standard small form-factor pluggable (SFP) module. The module connects to the Field Programmable Gate Array (FPGA) of a QKD system. A real-time randomness extractor is implemented in the FPGA and achieves a sustained rate of 1.25 Gbps of provably random bits.Comment: 6 pages, 8 figure

High efficiency coupling of photon pairs in practice

Multi-photon and quantum communication experiments such as loophole-free Bell tests and device independent quantum key distribution require entangled photon sources which display high coupling efficiency. In this paper we put forward a simple quantum theoretical model which allows the experimenter to design a source with high pair coupling efficiency. In particular we apply this approach to a situation where high coupling has not been previously obtained: we demonstrate a symmetric coupling efficiency of more than 80% in a highly frequency non-degenerate configuration. Furthermore, we demonstrate this technique in a broad range of configurations, i.e. in continuous wave and pulsed pump regimes, and for different nonlinear crystals