Quantum memories are essential for quantum information processing. Techniques have been developed for quantum memory based on atomic ensembles. The atomic memories through optical resonance usually suffer from the narrow-band limitation. The far off-resonant Raman process is a promising candidate for atomic memories due to broad bandwidths and high speeds. However, to date, the low memory efficiency remains an unsolved bottleneck. Here, we demonstrate a high-performance atomic Raman memory in 87Rb vapour with the development of an optimal control technique. A memory efficiency of above 82.0% for 6 ns~20 ns optical pulses is achieved. In particular, an unconditional fidelity of up to 98.0%, significantly exceeding the no-cloning limit, is obtained with the tomography reconstruction for a single-photon level coherent input. Our work marks an important advance of atomic memory towards practical applications in quantum information processing.

A new type of hybrid atom-light interferometer is demonstrated with atomic Raman amplification processes replacing the beam splitting elements in a traditional interferometer. This nonconventional interferometer involves correlated optical and atomic waves in the two arms. The correlation between atoms and light developed with the Raman process makes this interferometer different from conventional interferometers with linear beam splitters. It is observed that the high-contrast interference fringes are sensitive to the optical phase via a path change as well as the atomic phase via a magnetic field change. This new atom-light correlated hybrid interferometer is a sensitive probe of the atomic internal state and should find wide applications in precision measurement and quantum control with atoms and photons. [4]. They are widely used in precision measurement of a variety of physical quantities. Building on this foundation, nonconventional interferometers can be constructed with nonlinear processes such as wave splitting and recombination elements [5][6][7][8][9][10], as shown in the inset of Fig. 1.Different from the conventional interferometers with beam splitters, the involvement of nonlinear processes in the nonconventional interferometers allows the coupling between two waves of different types, and it can lead to interference fringes that are sensitive to different types of phase shifts. We thus use the word "hybrid" to label these interferometers involving different types of waves. In fact, hybrid interference also occurs via coherent interactions between atoms and light in phenomena such as quantum storage in electromagnetically induced transparency [11][12][13], gradient echo memory [14,15], and slow light [16][17][18][19][20]. However, the hybrid interference effects in these phenomena are in essence still of the same type as the conventional interference effect where the input wave is linearly split into a linear superposition of atom and light fields in the form of a polariton state [11,15]. On the other hand, a nonconventional SU(1,1) interferometer [5,9,10,21] utilizes parametric amplifiers as wave splitting and recombination elements and performs quite differently from the conventional linear interferometers. The name SU(1,1) comes from the nonlinear interaction Hamiltonian for the parametric process [5]:which amplifies an input signal field (â s ) and produces a correlated idler field (â i ) simultaneously. The idler field is coherent with the input field, thus realizing coherent wave splitting.One of the nonlinear processes described by Eq. (1) is the collective atomic Raman amplification process, which FIG. 1 (color online). Experimental sketch for the hybrid atomlight interferometer. A strong Raman write beam (W 1 , red) and a Stokes input field (S 0 , blue) in orthogonal polarization interact with a Λ-shaped atomic system to generate an amplified Stokes field (S 1 ) and a correlated atomic spin wave S a that stays in the atomic system. The amplified Stokes beam (S 1 ), after reflection (S 0 1...

To investigate the effects of dietary bile acids (BA) on growth and metabolism of lipid in grass carp (Ctenopharyngodon idella, C. idella) at high dietary lipid level, a basal diet (50 g kg -1 lipid, 5L group) was supplemented with 20 g kg -1 soybean oil (70 g kg -1 lipid, 7L group); then, 0.06 g/kg BA was added in 7L diet to form the third diet (7L+BA group). The 96 C. idella (69.86 ± 6.24 g) were divided into three groups (duplicate per group) and fed three diets, respectively, for 8 weeks, and then, growth and lipid metabolism were determined. Results showed that growth of fish in 7L+BA group was significantly higher than 5L and 7L groups. The lipid level in whole body, hepatopancreas and muscle of grass carp in 7L+BA group were significantly lower than 7L group.Relative expression of lipid catabolism genes in hepatopancreas and muscle of 7L+BA group was significantly higher than 5L group. The amount of microbiota in intestine of fish in 7L+BA group was significantly higher than the other two groups. The present results indicated that BA in 7L diet improved growth of fish by increasing protein synthesizing, decreasing lipid content in fish body and by regulating amount of microbiota in intestine of fish. K E Y W O R D S adipose triglyceride lipase, fatty acid synthase, growth performance, intestinal microbiota, lipid accumulation, protein deposition How to cite this article: Zhou JS, Chen HJ, Ji H, et al. Effect of dietary bile acids on growth, body composition, lipid metabolism and microbiota in grass carp (Ctenopharyngodon idella). Aquacult Nutr. 2018;24:802-813.

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Collective atomic excitation can be realized by the Raman scattering. Such a photon-atom interface can form an SU(1,1)-typed atom-light hybrid interferometer, where the atomic Raman amplification processes take the place of the beam splitting elements in a traditional Mach-Zehnder interferometer. We numerically calculate the phase sensitivities and the signal-to-noise ratios (SNRs) of this interferometer with the method of homodyne detection and intensity detection, and give their differences of the optimal phase points to realize the best phase sensitivities and the maximal SNRs from these two detection methods. The difference of the effects of loss of light field and atomic decoherence on measure precision is analyzed.

We theoretically study the quantum Fisher information (QFI) of the SU(1,1) interferometer with phase shifts in two arms taking account of realistic noise effects. A generalized phase transform including the phase diffusion effect is presented by the purification process. Based on this transform, the analytical QFI and the bound to the quantum precision are derived when considering the effects of phase diffusion and photon losses simultaneously. To beat the standard quantum limit with the reduced precision of phase estimation due to noisy, the upper bounds of decoherence coefficients as a function of total mean photon number are given.

We present a scheme to obtain the coherently enhanced Raman scattering in atomic vapor which is induced by a spin wave initially written by a weak write laser. The enhancement of Raman scattering is dependent on the number and the spatial distribution of the flipped atoms generated by the weak write laser. Such an enhanced Raman scattering may have practical applications in quantum information, nonlinear optics and laser spectroscopy because of its simplicity.Comment: 7 pages, 4 figures, submitted to Phys. Rev.

Coherent conversion between a Raman pump field and its Stokes field is observed in a Raman process with a strong atomic spin wave initially prepared by another Raman process operated in the stimulated emission regime. The oscillatory behavior resembles the Rabi oscillation in atomic population in a two-level atomic system driven by a strong light field. The Rabi-like oscillation frequency is found to be related to the strength of the prebuilt atomic spin wave. High conversion efficiency of 40% from the Raman pump field to the Stokes field is recorded and it is independent of the input Raman pump field. This process can act as a photon frequency multiplexer and may find wide applications in quantum information science.