Phase Locked Photon Echoes for Extended Storage Time

We report a quantum optical storage time-extended near perfect photon echo protocol using a phase locking method via an auxiliary spin state, where the phase locking acts as a conditional stopper of the rephasing process resulting in extension of storage time determined by the spin dephasing process. The near perfect retrieval efficiency is owing to phase conjugate scheme, which gives the important benefit of aberration corrections when dealing with quantum images.Comment: 5 pages, 3 figure

Understanding of collective atom phase control in modified photon echoes for a near perfect, storage time extended quantum memory

A near perfect, storage time-extended photon echo-based quantum memory protocol has been analyzed by solving the Maxwell-Bloch equations for a backward scheme in a three-level system. The backward photon echo scheme is combined with a controlled coherence conversion process via control Rabi flopping to a third state, where the control Rabi flopping collectively shifts the phase of the ensemble coherence. The propagation direction of photon echoes is coherently determined by the phase matching condition between the data (quantum) and the control (classical) pulses. Herein we discuss the classical controllability of a quantum state for both phase and propagation direction by manipulating the control pulses in both single and double rephasing photon echo schemes of a three-level system. Compared with their well-understood use for two-level photon echoes, the Maxwell-Bloch equations to a three-level system have a critical limitation regarding the phase change when interacted with an arbitrary control pulse area.Comment: 11 pages, 3 figure

Phase Locked Photon Echoes for Near-Perfect Retrieval Efficiency and Extended Storage Time

Quantum storage of light in a collective ensemble of atoms plays an important role in quantum information processing. Consisting of a quantum repeater together with quantum entanglement swapping, quantum memory has been intensively studied recently. Conventional photon echoes have been limited by extremely low retrieval efficiency and short storage time confined by the optical phase decay process. Here, we report a storage time-extended near perfect photon echo protocol using a phase locking method via an auxiliary spin state, where the phase locking acts as a conditional stopper of the rephasing process resulting in extension of storage time determined by the spin dephasing process. We experimentally prove the proposed phase locked photon echo protocol in a Pr3+ doped Y2SiO5 in a quasi phase conjugate scheme, where the phase conjugate gives the important benefit of aberration corrections when dealing with quantum images.Comment: 10 pages, 4 figure

Quantum manipulation of two-color stationary light: Quantum wavelength conversion

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.Comment: 14 pages, 3 figure

Slow light enhanced photon echoes

We report a slow light-enhanced photon echo method, whose retrieval efficiency is two orders of magnitude higher than that of conventional photon echoes. The enhanced photon echo efficiency is due to lengthened interaction time given by ultraslow group velocity.Comment: 4 pages, 4 figure

Ultralong trapping of light using double spin coherence gratings

Ultralong trapping of light has been observed in an optically dense three-level solid medium interacting with a pair of counterpropagating coupling fields. Unlike the light trapping based on standing-wave gratings excited by the same frequency pair of counterpropagating light fields (M. Bajcsy et al., Nature 426, 638 (2003)), the present method uses resonant Raman optical field-excited spin coherence gratings. The observed light trapping time is two orders of magnitude longer than the expected value of the spin dephasing time, where the extended storage time has potential for quantum information processing based on nonlinear optics.Comment: 4 pages, 4 figure

Plasmon-induced photonic switching in a metamaterial

Using light-induced localized surface plasmon interactions in a metamaterial, we present a plasmonic control of light absorption for photonic switching. We discuss that the present surface plasmon-induced photonic switching is comparable with coherence swapping in a tripod optical system based on electromagnetically induced transparency. This outcome opens a door to active controls of the surface plasmons in a metamaterial for potential applications of nano photonics.Comment: 4 pages, 4 figure

Observations of photon echo enhancement in an ultraslow light regime

Using spectral hole-burning-based ultraslow group velocity in a dilute solid medium, we report enhanced photon echo efficiency three orders of magnitude higher than that in a nonslow light regime. The enhancement is due to exponentially increased absorption of an optical data pulse owing to the enhanced photon-atom interaction in an ultraslow light regime, whereas echo reabsorption is negligibly small due to group-velocity dependent population depletion.Comment: 4 pages, 4 figure

Preparation-Attack-Immune Quantum Secure Direct Communication Using Two-Fold Photon Degree of Freedom

Quite recently, enhancing security against device-attack vulnerability has been theoretically challenging but also practically important in quantum cryptographic communication. For dealing with this issue in a general and strict scenario, we design a seemingly-new kind of quantum secure direct communication (QSDC) in a linear-optical regime, which we call "preparation-attack-immune QSDC." We address that in our "naive" analysis, it is quite formidable to extract even a piece of information of the secret message, and any malicious eavesdropping attempts will be unsuccessful. The most remarkable feature is that even in the case where a powerful eavesdropper can peep at all preparation device settings, our protocol still keeps a high level of security without invoking any additional resources and physical properties. This novel advantage that we call "preparation-attack immunity" comes from the simultaneous use of the two degrees of freedom involved in a single-photon (polarization and spatial modes), which enables one to faithfully deal with the single-photon quantum superposition nature. Our idea can be generalized to other single-photon based protocols.Comment: submitte

The origin of anticorrelation for photon bunching on a beam splitter

The Copenhagen interpretation has been long-lasted, whose core concepts are in the Heisenberg's uncertainty principle and nonlocal correlation of EPR. The second-order anticorrelation on a beam splitter represents these phenomena where it cannot be achieved classically. Here, the anticorrelation of nonclassicality on a beam splitter is interpreted in a purely coherence manner. Unlike a common belief in a particle nature of photons, the anticorrelation roots in pure wave nature of coherence optics, where quantum superposition between two input fields plays a key role. This interpretation may intrigue a fundamental question of what nonclassicality should be and pave a road to coherence-based quantum information.Comment: 9 pages, 3 figure