Coherent population trapping of a single nuclear spin under ambient conditions

Coherent control of quantum systems has far-reaching implications in quantum engineering. In this context, coherent population trapping (CPT) involving dark resonances has played a prominent role, leading to a wealth of major applications including laser cooling of atoms and molecules, optical magnetometry, light storage and highly precise atomic clocks. Extending CPT methods to individual solid-state quantum systems has been only achieved in cryogenic environments for electron spin impurities and superconducting circuits. Here, we demonstrate efficient CPT of a single nuclear spin in a room temperature solid. To this end, we make use of a three-level system with a $\Lambda$-configuration in the microwave domain, which consists of nuclear spin states addressed through their hyperfine coupling to the electron spin of a single nitrogen-vacancy defect in diamond. Dark state pumping requires a relaxation mechanism which, in atomic systems, is simply provided by spontaneous emission. In this work, the relaxation process is externally controlled through incoherent optical pumping and separated in time from consecutive coherent microwave excitations of the nuclear spin $\Lambda$-system. Such a pumping scheme with controlled relaxation allows us (i) to monitor the sequential accumulation of population into the dark state and (ii) to reach a new regime of CPT dynamics for which periodic arrays of dark resonances can be observed, owing to multiple constructive interferences. This work offers new prospects for quantum state preparation, information storage in hybrid quantum systems and metrology.Comment: 13 pages including supplementary information, links to figures correcte

Coherent population trapping of a single nuclear spin under ambient conditions

Coherent control of quantum systems has far-reaching implications in quantum engineering. In this context, coherent population trapping (CPT) involving dark resonances has played a prominent role, leading to a wealth of major applications including laser cooling of atoms and molecules, optical magnetometry, light storage and highly precise atomic clocks. Extending CPT methods to individual solid-state quantum systems has been only achieved in cryogenic environments for electron spin impurities and superconducting circuits. Here, we demonstrate efficient CPT of a single nuclear spin in a room temperature solid. To this end, we make use of a three-level system with a $\Lambda$-configuration in the microwave domain, which consists of nuclear spin states addressed through their hyperfine coupling to the electron spin of a single nitrogen-vacancy defect in diamond. Dark state pumping requires a relaxation mechanism which, in atomic systems, is simply provided by spontaneous emission. In this work, the relaxation process is externally controlled through incoherent optical pumping and separated in time from consecutive coherent microwave excitations of the nuclear spin $\Lambda$-system. Such a pumping scheme with controlled relaxation allows us (i) to monitor the sequential accumulation of population into the dark state and (ii) to reach a new regime of CPT dynamics for which periodic arrays of dark resonances can be observed, owing to multiple constructive interferences. This work offers new prospects for quantum state preparation, information storage in hybrid quantum systems and metrology.Comment: 13 pages including supplementary information, links to figures correcte

Coherent Population Trapping with a controlled dissipation: applications in optical metrology

We analyze the properties of a pulsed Coherent Population Trapping protocol that uses a controlled decay from the excited state in a $\Lambda$-level scheme. We study this problem analytically and numerically and find regimes where narrow transmission, absorption, or fluorescence spectral lines occur. We then look for optimal frequency measurements using these spectral features by computing the Allan deviation in the presence of ground state decoherence and show that the protocol is on a par with Ramsey-CPT. We discuss possible implementations with ensembles of alkali atoms and single ions and demonstrate that typical pulsed-CPT experiments that are realized on femto-second time-scales can be implemented on micro-seconds time-scales using this scheme.Comment: 9 pages, 7 figure

Confirmation of the use of Latex IgM on cerebrospinal fluid for improving stage determination of Human African Trypanosomiasis

The clinical evolution of the chronic form of Human African Trypanosomiasis starts with the haematolymphatic or first stage (P1). The meningoencephalitic or second stage (P2) begins when trypanosomes reach the cerebrospinal fluid (CSF). The classical stage determination method is based on CSF cell count, CSF protein concentration and/or the presence of trypanosomes detected in CSF. However their cutoff values and the sensitivity of detection of trypanosomes in CSF remains doubtful while the appropriate treatment depends on this determination of disease stage. Thus, the classical stage determination is reconsidered using new serological tests, and results were compared to the clinical data. Thirty-eight patients were classified into 4 clinical groups according to the observed degree of severity of neuropsychiatric signs. Based on multivariate analysis to evaluate the relevance of the new serological tests as compared with clinical groups, we confirm that Latex IgM CSF, cheap and easy to perform under field conditions, may improve stage determination of the disease

Characterization of Trypanosoma brucei gambiense stocks isolated from humans by RAPD fingerprinting in Côte d'Ivoire: another evidence for multiple infections

Trypanosoma brucei gambiense was isolated twice from each of 23 patients in Côte d'Ivoire. Genetic characterization using RAPD (Random Primed Amplified Polymorphic DNA) showed additional variability within a given isoenzyme profile (zymodeme), confirming that this fingerprinting method has a higher discriminative power (faster molecular clock) than isoenzymes. RAPD confirmed also the evidence of multiple infections by different genotypes in the same patient despite a low genetic variability among Trypanosoma brucei gambiense stocks. The involvement of this phenomenon in treatment failure is discussed. Key Words: Human African Trypanosomiasis, Trypanosoma brucei gambiense, RAPD, multiple infections. African Journal of Biotechnology Vol.3(1) 2004: 94-9

Impact de la dynamique de peuplement sur la distribution des glossines et des trypanosomoses dans la boucle du Mouhoun (Burkina Faso)

In Burkina Faso, the Mouhoun river basin (formerly 'Black Volta") constitutes a historical focus of Human (HAT) and Animal (AAT) African Tryponosomoses, both transmitted by tsetse flies. Nowadays, HAT seems to have disappeared from this area, while AAT still causes severe economic losses. In order to explain these different epidemiological situations, we undertook a geographical study based on the analysis of aerial pictures between 1952 and 2007, and field surveys to collect medical, entomological, and veterinary data on trypanosomoses. Our results suggest that in this area, landscapes have been dramatically modified as a consequence of population growth, and in turn have had an impact on the number and distribution of tsetse flies. Combined with the historical medical action on HAT which probably led to the disappearance of T. b. gambiense, this environmental degradation and the development of hydrological structures provide explanations for the local disappearance of HAT, and for the maintenance of AAT. It appears necessary to extrapolate these studies to other areas in order to identify the factors explaining the presence/absence of trypanosomoses in the context of human population growth and climatic changes, in orde

Human African trypanosomiasis

Human African trypanosomiasis (sleeping sickness) occurs in sub-Saharan Africa. It is caused by the protozoan parasite Trypanosoma brucei, transmitted by tsetse flies. Almost all cases are due to Trypanosoma brucei gambiense, which is indigenous to west and central Africa. Prevalence is strongly dependent on control measures, which are often neglected during periods of political instability, thus leading to resurgence. With fewer than 12 000 cases of this disabling and fatal disease reported per year, trypanosomiasis belongs to the most neglected tropical diseases. The clinical presentation is complex, and diagnosis and treatment difficult. The available drugs are old, complicated to administer, and can cause severe adverse reactions. New diagnostic methods and safe and effective drugs are urgently needed. Vector control, to reduce the number of flies in existing foci, needs to be organised on a pan-African basis. WHO has stated that if national control programmes, international organisations, research institutes, and philanthropic partners engage in concerted action, elimination of this disease might even be possible

Competition between electric field and magnetic field noise in the decoherence of a single spin in diamond

We analyze the impact of electric field and magnetic field fluctuations in the decoherence of the electronic spin associated with a single nitrogen-vacancy (NV) defect in diamond by engineering spin eigenstates protected either against magnetic noise or against electric noise. The competition between these noise sources is analyzed quantitatively by changing their relative strength through modifications of the environment. This study provides significant insights into the decoherence of the NV electronic spin, which is valuable for quantum metrology and sensing applications.Comment: 8 pages, 4 figures, including supplementary information

: The impact of war on the evolution of sleeping sickness in west-central Cote d'Ivoire

International audienceTo evaluate the situation of sleeping sickness in west-central Cote d'Ivoire from 2000 to 2003, in view of the war which broke out in September 2002. Active surveys by medical teams and passive case detection. Between 2000 and 2003, 250 patients were diagnosed with sleeping sickness. At first it appeared that sleeping sickness prevalence had fallen since the beginning of political troubles. But this apparent drop was due to poor population coverage. Participation in medical surveys differed according to ethnic group, reflecting land use conflicts between ethnic communities. Such conflicts are common in this area, but have been exacerbated by the war. In war, assessing the importance of sleeping sickness by medical surveys only is very difficult. But detection of sleeping sickness cases by passive surveillance increased.Evaluer la situation de la maladie du sommeil dans le centre-ouest de la Cote d'Ivoire de 2000 a 2003, en tenant compte des evenements survenus depuis en septembre 2002. Enquete active realisee par des equipes medicales et detection passive des cas. Entre 2000 et 2003, 250 patients ont ete diagnostiques pour la maladie du sommeil. De prime abord la prevalence de la maladie du sommeil semblait avoir baisse depuis le debut de la guerre. Mais cette baisse apparente etait due a une faible couverture de la population. La participation dans l'enquete medicale etait differente selon le groupe ethnique, refletant les conflits entre les differentes communautes pour les terres. De tels conflits sont courants dans la zone mais ont ete exacerbes par la guerre. L'evaluation de l'importance de la maladie du sommeil durant la guerre par enquete medicale seule est tres difficile. Mais la detection de la maladie du sommeil par surveillance passive a augmente