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control of device temperature and a frequency-selective lter[12]. In addition, the experiment setup has proved the feasibility of its use in a double pump scheme—pump light is incident from both ends of a waveguide, and photon pairs are taken out from both ends of the other waveguide(Fig.5). It is interesting to note that, although it seems a natural consequence that the number of photon pairs generated from bi-direction output mode become, in aggregate, twice as large as those of single direction output mode (pump on one end, and output from the other end), the experimental results clearly show the ratio of produc-tion rate was greater than two (Fig. 5, right. Upper and lower plots show respectively the observation results from two operation modes: quantum visibility of an entangled photo pair obtained from single direction output mode, and that of bi-directional output mode (only the photon pairs from one end are shown)). Comparison of the two plots clearly indicates a higher photon detection rate in the lower plot. is phenomenon needs further analysis in order to provide full elucidation of a causal link: a tentative explanation is that reection and interference of excitation light at the junctions between the waveguide and resonator may have the eect of increasing the eective excitation rate to a value greater than two. In any case one can say this distinctive phenomenon will have a very favorable inuence on the future development of quantum inte-grated devices.5Concluding remarksWe describe a certain aspect of R&D in photon control technologies with a main focus on the development of a quantum entanglement source. Realization of an integrated quantum entanglement source with a higher rate and pu-rity would raise high expectations over it becoming a mainstream light source for next generation quantum cryptographic technologies. Free exchange of quantum information between the quantum memory of matter and photons—although this is a highly advanced subject—would bring the realization of quantum repeater technolo-gies much closer.R&D on receiver technologies in the quantum domain FiF4Experiment on integrated quantum entanglement source. Silicon ring resonator (a) is operated in a temperature controlled environment (b) (c): Visibility of generated quantum entanglement light(a)(b)(c)555657580200400600800Coincidence count (X0 & X'0) (1/300 s)Temperature of PLC (signal photon side) (deg)0200400600Coincidence count (X0 & X'1) (1/300 s)FiF5　Silicon ring resonator experiment (bidirectional input)　Left: Schematic representation of experiment setupRight: Experimental results 　　　　　　　　　534-1 Optical Quantum Control Technologies