63,141 research outputs found
Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory
No full textWe report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.</p
A solid state spin-wave quantum memory for photonic time-Bin qubits
No full textRare-earth (RE) doped crystals are promising candidates as quantum memories as they offer coherence properties comparable to those of atomic systems, but free of the drawbacks deriving from the atomic motion. The research on RE doped crystals quantum memories has been so far mostly focused on the mapping of quantum bits to optical collective excitations using the atomic frequency comb (AFC) or the gradient echo memory protocols [1-3]. However, this leads to short lived and mostly pre-determined storage. In this contribution, we report the first solid state spin-wave optical quantum memory with on-demand read-out. We also demonstrate the first spin-wave storage of time-bin qubits with conditional fidelities higher than for classical memories [4]
In situ characterization of an optically thick atom-filled cavity
No full text A means for precise experimental characterization of the dielectric susceptibility of an atomic gas inside an optical cavity is important for the design and operation of quantum light-matter interfaces, particularly in the context of quantum information processing. Here we present a numerically optimized theoretical model to predict the spectral response of an atom-filled cavity, accounting for both homogeneous and inhomogeneous broadening at high optical densities. We investigate the regime where the two broadening mechanisms are of similar magnitude, which makes the use of common approximations invalid. Our model agrees with an experimental implementation with warm caesium vapor in a ring cavity. From the cavity response, we are able to extract important experimental parameters, for instance the ground-state populations, total number density, and the magnitudes of both homogeneous and inhomogeneous broadening. </p
Coherent optical ultrasound detection with rare-earth ion dopants
No full textWe describe theoretical and experimental demonstration for optical detection of ultrasound using a spectral hole engraved in cryogenically cooled rare-earth ion-doped solids. Our method utilizes the dispersion effects due to the spectral hole to perform phase-to-amplitude modulation conversion. Like previous approaches using spectral holes, it has the advantage of detection with large étendue. The method also has the benefit that high sensitivity can be obtained with moderate absorption contrast for the spectral holes.</p
Experimental realization of light with time-separated correlations by rephasing amplified spontaneous emission
No full textAmplified spontaneous emission is a common noise source in active optical systems, it is generally seen as being an incoherent process. Here we excite an ensemble of rare earth ion dopants in a solid with a π pulse, resulting in amplified spontaneous emission. The application of a second π pulse leads to a coherent echo of the amplified spontaneous emission that is correlated in both amplitude and phase. For small optical thicknesses, we see evidence that the amplified spontaneous emission and its echo are entangled.</p
Spin-wave storage of single photon level light fields in a doped solid
No full textWe present optical storage experiments with weak coherent states and heralded single photons by using the atomic frequency comb technique in the long-lived hyperfine levels in an ensemble of Pr3+ ions doped into a solid.</p
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Photon-echo quantum memories in inhomogeneously broadened two-level atoms
No full textHere, we propose a solid-state quantum memory that does not require spectral holeburning, instead using strong rephasing pulses like traditional photon-echo techniques. The memory uses external broadening fields to reduce the optical depth and so switch off the collective atom-light interaction when desired. The proposed memory should allow operation with reasonable efficiency in a much broader range of material systems, for instance Er3+ doped crystals which have a transition at 1.5 μm. We present analytic theory supported by numerical calculations and initial experiments
Preparing narrow velocity distributions for quantum memories in room-temperature alkali-metal vapors
No full textQuantum memories are a crucial technology for enabling large-scale quantum networks through synchronization of probabilistic operations. Such networks impose strict requirements on quantum memory, such as storage time, retrieval efficiency, bandwidth, and scalability. On- and off-resonant ladder protocols on warm atomic vapor platforms are promising candidates, combining efficient high-bandwidth operation with low-noise on-demand retrieval. However, their storage time is severely limited by motion-induced dephasing caused by the broad velocity distribution of atoms composing the vapor. In this paper, we demonstrate velocity selective optical pumping to overcome this decoherence mechanism. This will increase the achievable memory storage time of vapor memories. This technique can also be used for preparing arbitrarily shaped absorption profiles, for instance, preparing an atomic frequency comb absorption feature
Stable voters in an unstable party environment : continuity and change in Italian electoral behaviour
No full textM.24981-1999 Paolo Segatti, Paolo Bellucci and Marco Maraffi. 30 cm. A previous version of this paper was presented at a symposium on Political Parties : Changing Roles in Contemporary Democracies, held at the Center for Advanced Study in the Social Sciences of the Juan March Institute, Madrid, December 15-17, 1994. -- P.1. Includes bibliographical references (p. 56-59
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