Generation and detection of bright quantum entangled light pulses using adaptive optical pulse control in frequency domain

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Quantum correlation is evolved via optical nonlinearities induced by ultrashort laser pulses in optical fibers. In this study, particular emphasis was placed on the quantum correlation formation among frequency modes of ultrashort laser pulses, and generation and detection of photon-number squeezing was experimentally and theoretically studied. The following results were obtained.(1)When an optical short pulse propagates an optical fiber in the anomalous dispersion regime, negative quantum correlation is formed among photon-number density around the center of spectrum. We have theoretically revealed that the negative quantum correlation, which directly corresponds to photon-number squeezing, can be dramatically improved when the spectral phase of the input laser pulse is adaptively shaped by referring to the negative correlation of the output pulse. Moreover, we can achieve two-mode squeezing among different spectral components in the laser pulse using the similar adaptive control sche … More me. However, these have not been realized in experiments yet because of spatiotemporal coupling effect at a spectral pulse shaping device, where some frequency components couple to the fiber with extremely low efficiency.(2)Ultra-broad spectrum is generated from a photonic crystal fiber via self-phase modulation, stimulated Raman scattering and four-wave mixing when an optical pulse of which center wavelength locates near the zero dispersion wavelength of the fiber is launched The Stokes Raman component propagates the fiber with spectral shift toward longer wavelength and exhibits soliton-like nature. We experimentally observed for the first time that extremely higher photon-number squeezing is obtainable at the Stokes Raman component, From our numerical analysis, complicated quantum correlation is formed in the broad spectrum. Higher photon-number squeezing is also obtainable at anti-Stokes component.(3)Since the anti-Stokes pulse propagates the fiber by being trapped by the Stokes pulses. Such co-propagation generates quantum correlation between two pulses. Using this mechanism, we revealed that quantum correlation can construct between two pulses with different center frequency when the two pulse can propagate together in a fiber. Therefore, the fiber could be a platform to manipulate quantum correlation among pulses.(4)We repeated the similar experiments with 1.5μm ultrashort pulses generated by an Er-fiber laser source. However, due to significant excess noise caused by ASE, photon-number squeezing cannot be attained. However, we succeeded to generate quadrature squeezing with vacuum state. Therefore, Er fiber sources are still useful to generate quantum entangled state with continuous variable. Less