Article
Longdistance distribution of timebin entangled photon pairs over 100 km using frequency upconversion detectors
Osaka University, Suika, Ōsaka, Japan
Optics Express
(Impact Factor: 3.53).
11/2007;
15(21):1395764.
DOI: 10.1364/OE.15.013957
Source: PubMed

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ABSTRACT: Because of low power consumption and small footprint, avalanche photodiodes (APD) have been commonly applied to photon detection. Recently, high speed quantum communication has been demonstrated for high bitrate quantum key distribution. For the high speed quantum communication, photon detectors should operate at GHzclock frequencies. We propose balanced detection circuits for GHzclock operation of InGaAsAPD photon detectors. The balanced single photon detector operates with sinusoidal wave gating. The sinusoidal wave appearing in the output is removed by the subtraction from APD signal without sharp bandelimination filters. Omission of the sharp filters removes the constraint on the operating frequency of the single photon detector. We present two designs, one works with two identical APDs, the other with one APD and a lowpass filter. The sinusoidal gating enables to eliminate the gating noise even with the simple configuration of the latter design. We demonstrated the balanced single photon detector operating with 1.020GHz clock at 233 K, 193 K, and 186.5 K. The dark count probability was 4.0 x 104 counts/pulse with the quantum efficiency of 10% at 233K, and 1.6 x 104 counts/pulse at 186.5 K. These results were obtained with easily available APDs (NR8300FPC.C, RENESASS) originally developed for optical timedomain reflectmeters.Proceedings of SPIE  The International Society for Optical Engineering 01/2014; DOI:10.1117/12.2038802 · 0.20 Impact Factor 
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ABSTRACT: Last year, the first experimental tests closing the detection loophole (also referred to as the fair sampling loophole) were performed by two experimental groups, one in Vienna and the other one in UrbanaChampaign. To violate the Belltype inequalities (the Eberhard inequality in the first test and the ClauserHorne inequality in the second test), one has to optimize a number of parameters involved in the experiment (angles of polarization beam splitters and quantum state parameters). We study this problem for the Eberhard inequality in detail, using the advanced method of numerical optimization, namely, the NelderMead method.Journal of Russian Laser Research 01/2015; 36(1):216. DOI:10.1007/s1094601594716 · 0.61 Impact Factor 
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ABSTRACT: Last year the first experimental tests closing the detection loophole (also referred to as the fair sampling loophole) were performed by two experimental groups \cite{Zeilinger}, \cite{Kwiat}. To violate Belltype inequalities (the Eberhard inequality in the first test and the ClauserHorne inequality in the second test), one has to optimize a number of parameters involved in the experiment (angles of polarization beam splitters and quantum state parameters). Although these are technicalities, their optimal determination plays an important role in approaching statistically significant violations of the inequalities. In this paper we study this problem for the Eberhard inequality in very detail by using the advanced method of numerical optimization, the NelderMead method. First of all, we improve the the results of optimization for the original Eberhard model \cite{Eberhard} and the Gustina et al. work \cite{Zeilinger} ("Vienna13 experiment") by using the model of this experiment presented in Kofler et al. \cite{Zeilinger1}. We also take into account the well known fact that detectors can have different efficiencies and perform the corresponding optimization. In previous studies the objective function had the meaning of the mathematical expectation. However, it is also useful to investigate the possible level of variability of the results, expressed in terms of standard deviation. In this paper we consider the optimization of parameters for the Eberhard inequality using coefficient of variation taking into account possible random fluctuations in the setup of angles during the experiment.
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