Coherence-preserving trap architecture for long-term control of giant Rydberg atoms

We present a way to trap a single Rydberg atom, make it long-lived and preserve an internal coherence over time scales reaching into the minute range. We propose to trap using carefully designed electric fields, to inhibit the spontaneous emission in a non resonant conducting structure and to maintain the internal coherence through a tailoring of the atomic energies using an external microwave field. We thoroughly identify and account for many causes of imperfection in order to verify at each step the realism of our proposal.Comment: accepted for publication in PR

Characterizing Quantum Properties of a Measurement Apparatus: Insights from the Retrodictive Approach

Using the retrodictive approach of quantum physics, we show that the state retrodicted from the response of a measurement apparatus is a convenient tool to fully characterize its quantum properties. We translate in terms of this state some interesting aspects of the quantum behavior of a detector, such as the non-classicality or the non-gaussian character of its measurements. We also introduce estimators - the projectivity, the ideality, the fidelity or the detectivity of measurements perfomed by the apparatus - which directly follow from the retrodictive approach. Beyond their fundamental significance for describing general quantum measurements, these properties are crucial in several protocols, in particular in the conditional preparation of non-classical states of light or in measurement-driven quantum information processing

Reconstruction of non-classical cavity field states with snapshots of their decoherence

The state of a microscopic system encodes its complete quantum description, from which the probabilities of all measurement outcomes are inferred. Being a statistical concept, the state cannot be obtained from a single system realization, but can instea

Ultrahigh finesse Fabry-Perot superconducting resonator

We have built a microwave Fabry-Perot resonator made of diamond-machined copper mirrors coated with superconducting niobium. Its damping time (Tc = 130 ms at 51 GHz and 0.8 K) corresponds to a finesse of 4.6 x 109, the highest ever reached for a Fabry-Perot in any frequency range. This result opens novel perspectives for quantum information, decoherence and non-locality studies

Quantum jumps of light recording the birth and death of a photon in a cavity

A microscopic system under continuous observation exhibits at random times sudden jumps between its states. The detection of this essential quantum feature requires a quantum non-demolition (QND) measurement repeated many times during the system evolution. Quantum jumps of trapped massive particles (electrons, ions or molecules) have been observed, which is not the case of the jumps of light quanta. Usual photodetectors absorb light and are thus unable to detect the same photon twice. They must be replaced by a transparent counter 'seeing' photons without destroying them3. Moreover, the light has to be stored over a duration much longer than the QND detection time. We have fulfilled these challenging conditions and observed photon number quantum jumps. Microwave photons are stored in a superconducting cavity for times in the second range. They are repeatedly probed by a stream of non-absorbing atoms. An atom interferometer measures the atomic dipole phase shift induced by the non-resonant cavity field, so that the final atom state reveals directly the presence of a single photon in the cavity. Sequences of hundreds of atoms highly correlated in the same state, are interrupted by sudden state-switchings. These telegraphic signals record, for the first time, the birth, life and death of individual photons. Applying a similar QND procedure to mesoscopic fields with tens of photons opens new perspectives for the exploration of the quantum to classical boundary

Ultrasensitive serum interferon-α quantification during SLE remission identifies patients at risk for relapse

International audienceObjectives Maintenance of remission has become central in the management of systemic lupus erythematosus (SLE). The importance of interferon-alpha (IFN-α) in the pathogenesis of SLE notwithstanding, its expression in remission has been poorly studied as yet. To study its expression in remission and its prognostic value in the prediction of a disease relapse, serum IFN-α levels were determined using an ultrasensitive single-molecule array digital immunoassay which enables the measurement of cytokines at physiological concentrations.Methods A total of 254 SLE patients in remission, according to the Definition of Remission in SLE classification, were included in the study. Serum IFN-α concentrations were determined at baseline and patients were followed up for 1 year. Lupus flares were defined according to the Safety of Estrogens in Lupus Erythematosus: National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index Flare Index, whereas the Kaplan-Meier analysis and Cox regression analysis were used to estimate the time to relapse and to identify baseline factors associated with time to relapse, respectively.Results Of all patients in remission, 26% displayed abnormally high IFN-α serum levels that were associated with the presence of antibodies specific for ribonucleoprotein (RNP), double stranded (ds)DNA and Ro/SSA60, as well as young age. Importantly, elevated-baseline IFN-α serum levels and remission duration were associated in an independent fashion, with shorter time to relapse, while low serum levels of complement component 3 and anti-dsDNA Abs were not.Conclusion Direct serum IFN-α assessment with highly sensitive digital immunoassay permits clinicians to identify a subgroup of SLE patients, clinically in remission, but at higher risk of relapse

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Letter to the Editor gomery-Asberg Depression Rating Scale, the Brief Psychiatric Rating Scale and the SLE Disease Activity Index (SLEDAI) During the course of the study, 5 patients were admitted with SLE and catatonia. These 5 patients, all female, met the inclusion criteria. All of them (or their families on their behalf) agreed to PE. Three of the patients were teenagers who had been hospitalized for several weeks without any improvement, receiving a treatment regimen combining psychotropic medications, corticoids and immunosuppressors. Three patients exhibited life-threatening complications: 2 were severely malnourished and the third had a pulmonary infection and skin lesions due to immobility. One patient showed a severe renal involvement. The last patient was included because of resistance after 3 weeks of treatment. The mean number of PE that patients received was 7.2 (range: 3-11). We found a significant improvement for all clinical variables. Mean CRS and SLEDAI scores before PE were 15 (range: 11-16) and 18.8 (range: 12-22), respectively. Both scores dramatically decreased after PE to a mean of 1.2 (range: 0-6) and 3.4 (range: 0-12), respectively (Wilcoxon paired test: Z = -2.032, p = 0.042). In particular, 3 patients very much improved on the Clinical Global Impression Scale after the first week of PE. The biological variables paralleled clinical improvement. At follow-up, 4 patients were still doing well; in particular, all the teenagers were able to return to school with minimal treatment for SLE. The last patient (case 4) died in her local hospital as a consequence of a septic shock 3 months after discharge. To date, only a few case studies have reported the possible use of PE in neuropsychiatric SLE The consecutive patients were recruited at Pitié-Salpêtrière Hospital from 2001 to 2004. For inclusion, the diagnosis of SLE was based on the revised criteria of the American College of Rheumatolog

Systemic perturbation of cytokine and chemokine networks in Erdheim-Chester disease: a single-center series of 37 patients

Immunopathogenesis of Erdheim-Chester disease (ECD), a rare non-Langerhan