Study on continuous variable entanglement of pulsed light

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We have studied methods for creating continuous variable entanglement of pulsed light, and demonstrated quantum correlations beyond the classical limit. We have proposed and demonstrated a scheme to stably generate quadrature-entangled optical pulses using a ring interferometer and generated entangled light pulses at telecommunication wavelength, and verified the inseparability of the states. We experimentally demonstrated transporting continuous quantum variables of individual light pulses by using continuous-variable Bell measurements and post-processing displacement techniques. Fidelity of F=0.57±0.03 was experimentally achieved, which is higher than the bound (Fc=0.5) of the classical case in the absence of entanglement. In the experiments using high-repetition rate picosecond pulse train, we have observed-4.5 dB squeezing using a temporally shaped local oscillator pulse. Quantum correlations were verified at two measurement points separated by a distance of 4 m that is sufficient to causally separate two measurements.