We present a quantum manipulation of a traveling light pulse using double atomic coherence for two-color stationary light and quantum frequency conversion. The quantum frequency conversion rate of the traveling light achieved by the two-color stationary light phenomenon is near unity. We theoretically discuss the two-color stationary light for the frequency conversion process in terms of pulse area, energy transfer and propagation directions. The resulting process may apply the coherent interactions of a weak field to nonlinear quantum optics such as quantum nondemolition measurement.PACS number(s): 42.65.Ky, 32.80, 03.67.Dd. IntroductionCoherent interactions have been intensively studied for the last several decades in nonlinear optics to utilize weak light for enhanced light-matter interactions [1]. Because nonlinear optics should intrinsically rely on strong field interactions, using a weak field light has been a fundamental limitation in pump laser intensity [2]. Thus, coherent interactions have drawn much attention to the weak-field limited nonlinear optics. The weak field nonlinear interactions are mostly important to quantum information sciences that need repeated non-destructive measurements of physical observables and deterministic quantum switching for quantum processing [3]. So far, an optical cavity has been an essential tool to control the weak quantum light interacting with an optical medium [4]. However, applying the optical cavity to the traveling light has been a major drawback in operational bandwidth due to the trade-off between the trapping time and the transparency of the cavity.Electromagnetically induced transparency (EIT) [5] has been studied for the last fifteen years to alleviate the intensity threshold in nonlinear optics and has been successfully applied to quantum optics by utilizing nonabsorption resonance and dispersion control of an optical medium in a traveling light scheme [6][7][8][9][10]. Actually the dispersion control of EIT is of great benefit to us when using the traveling light for deterministic quantum coherent control to decelerate or even completely stop the light pulses. With a simple modification of the EIT scheme, one can obtain a giant phase shift [11], where the phase shift itself has been a major goal in nonlinear optics for switching applications as well as in quantum optics for generation of Schrodinger's cat states [12]. Here, it should be noted that the π-phase shift is an essential acquirement for the optical switching based on Mach-Zehnder interferometer and quantum superposition. The giant phase-shift in a weak field limit has been studied using stationary light phenomenon [13]. Recently, Lukin et al. demonstrated photon trapping in a hot atomic gas using identical counterpropagating control fields resulting in standing-wave grating [14]. The photon trapping as a stationary light gives a predominant property to nonlinear quantum optics particularly when an optical medium is spatially limited and highly absorptive. The stationary light phenomenon can replace...

We have performed a theoretical analysis of the photon-echo-based quantum memory realized recently in A. L. Alexander et al., Phys. Rev. Lett. 96, 043602 ͑2006͒ in the medium with linear correlation between atomic spatial coordinates and frequency detunings of the inhomogeneously broadened transition. A more general vision on the physical picture of temporal and spatial light-atoms dynamics has been obtained in the analytical solutions, taking into account the atomic phase relaxation, inhomogeneous broadening, and arbitrary parameters of the probe light pulses. We have evaluated preferable experimental conditions for the storage of incoming data light field modes where quantum memory efficiency and fidelity have been found. Physics of high efficiency in the forward geometry of the quantum memory and advantages for the realization of more universal long-lived storage on this basis are clarified.

The interaction of a surface plasmon polariton wave of the far-infrared regime propagating in a single-walled carbon nanotube with a drift current is theoretically investigated. It is shown that under the synchronism condition a surface plasmon polariton amplification mechanism is implemented due to the transfer of electromagnetic energy from a drift current wave into a terahertz surface wave propagating along the surface of a single-walled carbon nanotube. Numerical calculations show that for a typical carbon nanotube surface plasmon polariton amplification coefficient reaches huge values of the order of 10 сm, which makes it possible to create a carbon-nanotube-based spaser.

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