Ultra-low noise quantum memory for quasi-deterministic single photons generated by Rydberg collective atomic excitations

We demonstrate the storage and retrieval of an on-demand single photon generated by a collective Rydberg excitation in an ultra-low noise Raman quantum memory located in a different cold atomic ensemble. We generate single photons on demand by exciting a cold cloud of Rubidium atoms off resonantly to a Rydberg state, with a generation probability up to 15 $\%$ per trial. We then show that the single photons can be stored and retrieved with an efficiency of 21 $\%$ and a noise floor of $p_n= 2.3(3) \times 10^{-4}$ per trial in the Raman quantum memory. This leads to a signal-to-noise ratio ranging from 11 to 26 for the retrieved single photon depending on the input photon generation probability, which allows us to observe significant antibunching. We also evaluate the performances of the Raman memory as built-in unbalanced temporal beam splitter, tunable by varying the write-in control pulse intensity. In addition, we demonstrate that the Raman memory can be used to control the single-photon waveshape. These results are a step forward in the implementation of efficient quantum-repeater links using single-photon sources

Strongly non-linear interaction between non-classical light and a blockaded Rydberg atomic ensemble

We investigate the interaction between non-classical light with a tunable multiphoton component and a highly nonlinear medium based on cold Rydberg atoms. The non-classical field emitted by a DLCZ quantum memory is stored using Rydberg electromagnetically induced transparency, experiencing strong nonlinear response due to the dipole blockade. We show that the storage efficiency in the Rydberg ensemble decreases as function of the multiphoton strength of the input field, as a result of the nonlinearity. We also show that the autocorrelation function $g^{(2)}(0)$ of the retrieved field after storage in the Rydberg state is considerably reduced, leading to the first demonstration of single photon filtering with non-classical input light. Finally, we develop a simple simulation that allows us to model the effect of our medium on the input state. This work is a step towards matter-mediated photon-photon interactions with non-classical light

Acquiring control in emerging markets: Foreign acquisitions in Eastern Europe and the effect on shareholder wealth

YesThis paper examines stock market reaction to cross-border acquisition announcements that involve Eastern European emerging-market targets. Using a unique and a manually collected dataset, we identify 125 cross-border acquisitions in which developed-market firms from France, Germany, Netherlands, and the United Kingdom acquire ownership stakes in emerging as well as developed-markets in Europe during the period January 2000 through December 2011. In line with previous findings on foreign cross-border merger and acquisitions (M&As) in emerging- markets, evidence suggests that when the target firm is located in either the Czech- Republic, Hungary, Poland, or Russia, cumulative abnormal return (CAR) to the acquiring developed-market firm shows a statistically significant increase of 1.26% over a three day event window, following the announcement. Thereby, the relative size of the acquirer to the target appears to be the only significant factor that contributes to positive acquirer returns. The result is robust to the inclusion of controls for country, industry, as well as acquirer, target, and firm specific characteristics. Moreover, cross-border M&As involving an emerging-market target result in higher value creation for the acquiring shareholders than cross-border transactions into developed-markets

CCR2-V64I polymorphism is associated with increased risk of cervical cancer but not with HPV infection or pre-cancerous lesions in African women

<p>Abstract</p> <p>Background</p> <p>Cervical cancer, caused by specific oncogenic types of human papillomavirus (HPV), is the second most common cancer in women worldwide. A large number of young sexually active women get infected by HPV but only a small fraction of them have persistent infection and develop cervical cancer pointing to co- factors including host genetics that might play a role in outcome of the HPV infection. This study investigated the role of <it>CCR2-V64I </it>polymorphism in cervical cancer, pre-cancers and HPV infection in South African women resident in Western Cape. <it>CCR2-V64I </it>polymorphism has been previously reported to influence the progression to cervical cancer in some populations and has also been associated with decreased progression from HIV infection to AIDS.</p> <p>Methods</p> <p>Genotyping for <it>CCR2-V64I </it>was done by PCR-SSP in a case-control study of 446 women (106 black African and 340 mixed-ancestry) with histologically confirmed invasive cervical cancer and 1432 controls (322 black African and 1110 mixed-ancestry) group-matched (1:3) by age, ethnicity and domicile status. In the control women HPV was detected using the Digene Hybrid Capture II test and cervical disease was detected by cervical cytology.</p> <p>Results</p> <p>The <it>CCR2-64I </it>variant was significantly associated with cervical cancer when cases were compared to the control group (P = 0.001). Further analysis comparing selected groups within the controls showed that individuals with abnormal cytology and high grade squamous intraepitleial neoplasia (HSIL) did not have this association when compared to women with normal cytology. HPV infection also showed no association with <it>CCR2-64I </it>variant. Comparing SIL positive controls with the cases showed a significant association of <it>CCR2-64I </it>variant (P = 0.001) with cervical cancer.</p> <p>Conclusions</p> <p>This is the first study of the role of <it>CCR2-V64I </it>polymorphism in cervical cancer in an African population. Our results show that <it>CCR2-64I </it>variant is associated with the risk of cervical cancer but does not affect the susceptibility to HPV infection or HSIL in South African women of black and mixed-ancestry origin. This result implies that the role of CCR2 is important in invasive cancer of the cervix but not in HPV infection or in the development of pre-cancers.</p

Relative equity market valuation conditions and acquirers’ gains

We examine whether the relative equity market valuation conditions (EMVCs) in the merging firms countries help acquirers’ managers to time the announcements of domestic and foreign target acquisitions. After controlling for several deal- and merging firms-specific features we find that acquisition activity, as well as acquirers gains, are significantly higher during periods of high-EMVCs at home, irrespective of the domicile of the target. We also find that the higher foreign acquirers’ gains that reaped during periods of high-EMVCs at home are realized by deals of targets based in the RoW (=World-G7), rather than G6 (=G7-UK) countries, which is due to the low correlation of EMVCs between the U.K. (home) and the RoW countries. Moreover, acquisition of targets domiciled in the RoW (G6) countries yield higher (lower) gains than domestic targets during periods of high-EMVCs at home. This suggests that the relative EMVCs between the merging firms’ countries allow acquirers’ managers to time the market and acquire targets at a discount, particularly in countries in which acquirers’ stocks are likely to be more overvalued than the targets’ stocks