Coincidence Detection Rate Research Articles

Quantum storage of 1650 modes of single photons at telecom wavelength

To advance the full potential of quantum networks one should be able to distribute quantum resources over long distances at appreciable rates. As a consequence, all components in such networks need to have large multimode capacity to manipulate photonic quantum states. Towards this end, a photonic quantum memory with a large multimode capacity, especially one operating at telecom wavelength, remains an important challenge. Here we optimize the preparation of atomic frequency combs and demonstrate a spectro-temporally multiplexed quantum memory in a 10-m-long cryogenically cooled erbium doped silica fibre. Our multiplexing storage has five spectral channels - each 10 GHz wide with 5 GHz separation - with up to 330 temporal modes in each, thus resulting in a simultaneous storage of 1,650 modes of heralded single photons with a 1000-fold increasing in coincidence detection rate with respect to single mode storage. Our results could pave the way for high speed quantum networks compatible with the infrastructure of fibre optical communication.

Telecom-band-integrated multimode photonic quantum memory.

Telecom-band-integrated quantum memory is an elementary building block for developing quantum networks compatible with fiber communication infrastructures. Toward such a network with large capacity, an integrated multimode photonic quantum memory at telecom band has yet been demonstrated. Here, we report a fiber-integrated multimode quantum storage of single photon at telecom band on a laser-written chip. The storage device is a fiber-pigtailed Er3+:LiNbO3 waveguide and allows a storage of up to 330 temporal modes of heralded single photon with 4-GHz-wide bandwidth at 1532 nm and a 167-fold increasing of coincidence detection rate with respect to single mode. Our memory system with all-fiber addressing is performed using telecom-band fiber-integrated and on-chip components. The results represent an important step for the future quantum networks using integrated photonics devices.

Application of anti-HCV and HCV RNA detection in intravenous drug users

Objective: To explore the diagnostic value of anti-HCV and HCV RNA so as to provide an accurate and efficient detection strategy for the diagnosis of HCV in intravenous drug users. Methods: 527 plasma samples from intravenous drug users were collected, and preliminary anti-HCV ELISA screening test was performed. A recombinant immunoblot assay (RIBA) was used as confirmatory assay for reactive antibody samples. All samples were tested for HCV RNA, followed by analysis of anti-HCV screening test, RIBA and HCV nucleic acid test results. Results: Anti-HCV ELISA results were reactive in 386 out of 527 intravenous drug users and non-reactive in 141. Among the 386 reactive antibody samples detected by RIBA, 370 cases were anti-HCV positive, 6 cases were anti-HCV indeterminate and 10 cases were anti-HCV negative. Anti-HCV ELISA and RIBA positive coincidence detection rate was 95.85% (370/386), and 70.21% (370/527) among intravenous drug users. HCV RNA was negative in all 10 anti-HCV RIBA non-reactive samples. 376 anti-HCV RIBA-positive and indeterminate samples were tested for HCV RNA, of which 56.93% (300/527) were current HCV infection, and 14.42% (76/527) were past HCV infection. Among 141 anti-HCV ELISA negative samples, the residual risk by anti-HCV ELISA screening for HCV RNA was 1.52% (8/527). HCV viral load distribution among intravenous drug users showed that the high viral load value (>10(7) IU/ml) and low viral load values (< 10(2) IU/ml) accounted for 1.95% and 2.27%, respectively, while the samples with viral load value of 1×10(2) ~ 1×10(7) IU/ mL accounted for 95.78% (295/308), and were mainly distributed in 1×10(5) ~ 1×10(6) IU/ml (37.99%). ELISA + RIBA + NAT assay detection strategies had differentiated 300 cases of current HCV infection, 76 cases of past HCV infection and 10 cases of false positive anti-HCV results, while ELISA+NAT assay detection strategies had only detected 300 cases of current HCV infection. However, of the 386 positive subjects screened for antibodies, 10 (2.59%) were undifferentiated false positives. Conclusion: Intravenous drug users are the high-risk population of HCV infection with high prevalence and high viral load. Anti-HCV screening for intravenous drug users will have a certain degree of residual risk. Therefore, anti-HCV ELISA screening and nucleic acid detection strategy can accurately diagnose the current infected patients; however, it cannot distinguish the false positive results of antibody screening.

Time Correlation and Decoherence in a Two-Particle Interferometer

A two-particle interferometer is theoretically analyzed to show how decoherence induced by interactions with the environment affects time correlations, a process we call time correlation decoherence. Specifically, on the basis of simple mathematical analysis, we show how the interaction between a bipartite entangled system and a photon bath representing the environment can efface the oscillations in the coincidence detection rate of the interferometer. We discuss the dependence of this kind of decoherence on the photon energy and density.

Analysis on clinical value of TCT and HPV testing for screening of cervical cancer

Objective To investigate the clinical value of membrane thin prep cytology (TCT) and human papilloma virus (HPV) testing for the screening of cervical cancer.Methods Two thousand voluntary outpatients with sexual life history screened for cervical cancer in our hospital from January 2011 to June 2013 were received pathological examination,TCT and HPV testing.With pathological findings as the gold standard,the coincidence detection rates of two methods for cervical precancerous lesions and cervical cancer were compared.Results Pathological examination of 357 patients were positive,the coincidence detection rate of TCT was 86.6％ (309/357).The coincidence detection rate of HPV testing was 91.0％ (325/357).Coincidence detection rate of two methods had no statistical significant difference (P ＞ 0.05).Coincidence detection rate of TCT combined with HPV testing was 100％.Conclusion TCT combined with HPV testing can significantly improve the detection rate of cervical cancer.It can early detect precancerous lesions and reduce mortality with good clinical and social value. Key words: TCT; HPV testing; Precancerous lesions; Cervical cancer

A pump enhanced source of telecom-band correlated photon pairs

Correlated photon pairs generated through spontaneous parametric downconversion have become a key resource for research into enhanced optical measurement and quantum optical information processing. A pump-enhanced χ(2) source of correlated photons in the telecom band is presented. An investigation of the pair photon coincidence detection rate measured from the source, together with the evaluation of system losses, indicated a single spatial fibre-optic mode pair production rate of 6.12 × 104 s−1 mW−1 pump power, an order of magnitude greater than was measured without enhancement. A Hong-Ou-Mandel interference experiment confirmed that the enhancement did not have any adverse effect on the spatial and frequency indistinguishability of the emitted pairs. The source comprises a symmetric and linear enhancement cavity for the pump, making it particularly suitable for generating polarisation entangled photon pairs without the need for compensating crystals 1.

Coincidence Rates for Photon Pairs in WDM Environment

We demonstrate the flexibility that a wavelength selective switch could offer to bandwidth provisioning of potential multi-user quantum key distribution networks based on entangled pair sources. We derive an analytical expression relating the coincidence detection rates of the photon pairs to the switch bandwidth characteristics. Experimentally measured coincidence rates verify the theory in three distinct network configurations.

Heralding of telecommunication photon pairs with a superconducting single photon detector

Experiments involving entangled photon pairs created via spontaneous parametric down conversion typically use wavelengths in the visible regime. The extension of a photonic quantum information link to a fiber optical network requires that entangled pairs be created at telecommunication wavelengths (1550nm), for which photon counting detector technology is inferior to visible detection, in particular, low coincidence detection rates of correlated-photon pairs. We demonstrate a correlated-photon pair measurement using the superconducting single photon detector in a heralding scheme that can be used to substantially improve the correlated-photon detection rate.

Two-photon Interference at 1550 nm Using Two Periodically Poled Lithium Niobate Waveguides

We have observed two-photon interference at 1550 nm using two periodically poled lithium niobate waveguides. Two indium-gallium-arsenide gated-mode single-photon detectors were used for coincidence detection. The measured visibility was 95% (after subtraction of accidental coincidences) with a coincidence detection rate of 0.8 kHz. The ratio of single-photon to coincidence detection rate was 30.

Generation of polarisation-entangled photon pairs at 1550 nm using two PPLN waveguides

Generation of polarisation-entangled photon pairs at 1550 nm is demonstrated using two periodically poled lithium niobate (PPLN) waveguides. In two-photon interference experiments, the coincidence detection rate was 0.53 kHz with a visibility of /spl sim/94% (after subtraction of accidental coincidences). The ratio of single-photon to coincidence detection rate is /spl sim/50.

Experimental observation of nonclassical effects on single-photon detection rates

It is often asserted that quantum effects can be observed in coincidence detection rates or other correlations, but never in the rate of single-photon detection. We observe nonclassical interference in a singles rate, thanks to the intrinsic nonlinearity of photon counters. This is due to a dependence of the effective detection efficiency on the quantum statistics of the light beam. Such measurements of detector response to photon pairs promise to shed light on the microscopic aspects of silicon photodetectors, and on general issues of quantum measurement and decoherence.

Franson's experiment using polarized photons.

A modified Franson's two-photon correlation experiment is discussed. It is shown that the interference in the coincidence detection rate is lost when it is possible to determine the path followed by one of the photons. The interference is recovered when this information is ``erased.'' The experiment is devised so that the polarization of one of the photons depends on the path followed in the interferometer. Although the path difference is greater than the coherence length, when the two paths are open the photon can be found in a polarization state represented by the superposition of the polarization states associated to the paths. This can be comprehended by considering the situation in which one of the photons is detected before the other can reach the interferometer. In this case, the second photon has to be described by two wave packets simultaneously.

Critical analysis of the empirical tests of local hidden-variable theories.

A local hidden-variable model is exhibited for the experiments by Aspect, Grangier, and Roger [Phys. Rev. Lett. 47, 460 (1981); 49, 91 (1982)] and Aspect, Dalibard, and Roger [Phys. Rev. Lett. 49, 1804 (1982)] measuring polarization correlation of optical-photon pairs. The model agrees with quantum-mechanical predictions for all measurable quantities even with ideal polarizers and detectors, and emphasizes the need of a high degree of directional correlation, besides the correlation of spin (or polarization or other quantities), in any test of locality. It is proved that homogeneous inequalities, involving only coincidence detection rates, cannot discriminate between quantum mechanics and local theories, which invalidates all previously used empirical tests. The role of supplementary assumptions, like the so-called no enhancement, for the derivation of Bell's inequalities is discussed. Finally it is conjectured that quantum mechanics might be compatible with local realism, if we assume that not all self-adjoint operators represent observables and not all density operators represent states.