Time gating of heralded single photons for atomic memories

We demonstrate a method for time gating the standard heralded continuous- wave (cw) spontaneous parametric down-converted (SPDC) single photon source by using pulsed pumping of the optical parametric oscillator (OPO) below threshold. The narrow bandwidth, high purity, high spectral brightness and the pseudo-deterministic character make the source highly suitable for light-atom interfaces with atomic memories.Comment: Accepted for publication in Optics Letter

Factors influencing treatment selection and thirty-day mortality following chemotherapy for people with small cell lung cancer: an analysis of national audit data

Background Thirty-day mortality after treatment for lung cancer is a measure of unsuccessful outcome and where treatment should have been avoided. Guidelines recommend offering chemotherapy to individuals with small cell lung cancer (SCLC) who have poorer performance status (PS) because of its high initial response rate. However, this comes with an increased risk of toxicity and early death. We quantified real-world 30-day mortality in SCLC following chemotherapy, established the factors associated with this and compared these to the factors that influence receipt of chemotherapy. Methods We used linked national English datasets to define the factors associated with both receiving chemotherapy and 30-day mortality following chemotherapy. Results We identified 3,715 people diagnosed with SCLC, of which 2,235 (60.2%) received chemotherapy. There were 174 (7.8%) deaths within 30 days of chemotherapy. The adjusted odds of receiving chemotherapy decreased with older age, worsening PS and increasing comorbidities. Thirty-day mortality was independently associated with poor PS (PS 2 vs PS 0 adjusted OR 3.75 95% CI 1.71-8.25) and stage (extensive vs limited adjusted OR 1.68 95% CI 1.03-2.74) but in contrast was not associated with increasing age. Both chemotherapy administration and 30-day mortality varied by hospital network.Conclusions To reduce variation in chemotherapy administration predictors of 30-day mortality could be used as an adjunct to improve sub-optimal patient selection. We have quantified 30-day mortality risk by the two independently associated factors, PS and stage, so that patients and clinicians can make better informed decisions about the potential risk of early death following chemotherapy

Coupling of effective one-dimensional two-level atoms to squeezed light

A cavity QED system is analyzed which duplicates the dynamics of a two-level atom in free space interacting exclusively with broadband squeezed light. We consider atoms in a three or four-level Lambda-configuration coupled to a high-finesse optical cavity which is driven by a squeezed light field. Raman transitions are induced between a pair of stable atomic ground states via the squeezed cavity mode and coherent driving fields. An analysis of the reduced master equation for the atomic ground states shows that a three-level atomic system has insufficient parameter flexibility to act as an effective two-level atom interacting exclusively with a squeezed reservoir. However, the inclusion of a fourth atomic level, coupled dispersively to one of the two ground states by an auxiliary laser field, introduces an extra degree of freedom and enables the desired interaction to be realised. As a means of detecting the reduced quadrature decay rate of the effective two-level system, we examine the transmission spectrum of a weak coherent probe field incident upon the cavity

Quantum teleportation between light and matter

Quantum teleportation is an important ingredient in distributed quantum networks, and can also serve as an elementary operation in quantum computers. Teleportation was first demonstrated as a transfer of a quantum state of light onto another light beam; later developments used optical relays and demonstrated entanglement swapping for continuous variables. The teleportation of a quantum state between two single material particles (trapped ions) has now also been achieved. Here we demonstrate teleportation between objects of a different nature - light and matter, which respectively represent 'flying' and 'stationary' media. A quantum state encoded in a light pulse is teleported onto a macroscopic object (an atomic ensemble containing 10^12 caesium atoms). Deterministic teleportation is achieved for sets of coherent states with mean photon number (n) up to a few hundred. The fidelities are 0.58+-0.02 for n=20 and 0.60+-0.02 for n=5 - higher than any classical state transfer can possibly achieve. Besides being of fundamental interest, teleportation using a macroscopic atomic ensemble is relevant for the practical implementation of a quantum repeater. An important factor for the implementation of quantum networks is the teleportation distance between transmitter and receiver; this is 0.5 metres in the present experiment. As our experiment uses propagating light to achieve the entanglement of light and atoms required for teleportation, the present approach should be scalable to longer distances.Comment: 23 pages, 8 figures, incl. supplementary informatio

Identification and evaluation of observational measures for the assessment and/or monitoring of level of consciousness in adult palliative care patients: A systematic review for I-CAN-CARE.

BACKGROUND: The use of observational measures to assess palliative care patients' level of consciousness may improve patient care and comfort. However, there is limited knowledge regarding the validity and reliability of these measures in palliative care settings. AIM: To identify and evaluate the psychometric performance of observational level of consciousness measures used in palliative care. DESIGN: Systematic review; PROSPERO registration: CRD42017073080. DATA SOURCES: We searched six databases until November 2018, using search terms combining subject headings and free-text terms. Psychometric performance for each identified tool was appraised independently by two reviewers following established criteria for developing and evaluating health outcome measures. RESULTS: We found 35 different levels of consciousness tools used in 65 studies. Only seven studies reported information about psychometric performance of just eight tools. All other studies used either ad hoc measures for which no formal validation had been undertaken (n = 21) or established tools mainly developed and validated in non-palliative care settings (n = 37). The Consciousness Scale for Palliative Care and a modified version of the Richmond Agitation-Sedation Scale received the highest ratings in our appraisal, but, since psychometric evidence was limited, no tool could be assessed for all psychometric properties. CONCLUSION: An increasing number of studies in palliative care are using observational measures of level of consciousness. However, only a few of these tools have been tested for their psychometric performance in that context. Future research in this area should validate and/or refine the existing measures, rather than developing new tools

A Single-Photon Server with Just One Atom

Neutral atoms are ideal objects for the deterministic processing of quantum information. Entanglement operations have been performed by photon exchange or controlled collisions. Atom-photon interfaces were realized with single atoms in free space or strongly coupled to an optical cavity. A long standing challenge with neutral atoms, however, is to overcome the limited observation time. Without exception, quantum effects appeared only after ensemble averaging. Here we report on a single-photon source with one-and-only-one atom quasi permanently coupled to a high-finesse cavity. Quasi permanent refers to our ability to keep the atom long enough to, first, quantify the photon-emission statistics and, second, guarantee the subsequent performance as a single-photon server delivering up to 300,000 photons for up to 30 seconds. This is achieved by a unique combination of single-photon generation and atom cooling. Our scheme brings truly deterministic protocols of quantum information science with light and matter within reach.Comment: 4 pages, 3 figure

Pre-natal and post-natal exposure to respiratory infection and atopic diseases development: a historical cohort study

BACKGROUND: According to the hygiene hypothesis, infections in early life protect from allergic diseases. However, in earlier studies surrogate measures of infection rather than clinical infections were associated with decreased frequencies of atopic diseases. Exposure to infection indicating sub-clinical infection rather than clinical infection might protect from atopic diseases. Objective: to investigate whether exposure to acute respiratory infections within pregnancy and the first year of life is associated with atopic conditions at age 5–14 years and to explore when within pregnancy and the first year of life this exposure is most likely to be protective. METHODS: Historical cohort study: Population level data on acute respiratory infections from the routine reporting system of the former German Democratic Republic were linked with individual data from consecutive surveys on atopic diseases in the same region (n = 4672). Statistical analyses included multivariate logistic regression analysis and polynomial distributed lag models. RESULTS: High exposure to acute respiratory infection between pregnancy and age one year was associated with overall reduced odds of asthma, eczema, hay fever, atopic sensitization and total IgE. Exposure in the first 9 months of life showed the most pronounced effect. Adjusted odds ratio's for asthma, hay fever, inhalant sensitization and total IgE were statistical significantly reduced up to around half. CONCLUSION: Exposure to respiratory infection (most likely indicating sub-clinical infection) within pregnancy and the first year of life may be protective in atopic diseases development. The post-natal period thereby seems to be particularly important

Factors influencing treatment selection and thirty-day mortality following chemotherapy for people with small cell lung cancer: an analysis of national audit data

Background Thirty-day mortality after treatment for lung cancer is a measure of unsuccessful outcome and where treatment should have been avoided. Guidelines recommend offering chemotherapy to individuals with small cell lung cancer (SCLC) who have poorer performance status (PS) because of its high initial response rate. However, this comes with an increased risk of toxicity and early death. We quantified real-world 30-day mortality in SCLC following chemotherapy, established the factors associated with this and compared these to the factors that influence receipt of chemotherapy. Methods We used linked national English datasets to define the factors associated with both receiving chemotherapy and 30-day mortality following chemotherapy. Results We identified 3,715 people diagnosed with SCLC, of which 2,235 (60.2%) received chemotherapy. There were 174 (7.8%) deaths within 30 days of chemotherapy. The adjusted odds of receiving chemotherapy decreased with older age, worsening PS and increasing comorbidities. Thirty-day mortality was independently associated with poor PS (PS 2 vs PS 0 adjusted OR 3.75 95% CI 1.71-8.25) and stage (extensive vs limited adjusted OR 1.68 95% CI 1.03-2.74) but in contrast was not associated with increasing age. Both chemotherapy administration and 30-day mortality varied by hospital network. Conclusions To reduce variation in chemotherapy administration predictors of 30-day mortality could be used as an adjunct to improve sub-optimal patient selection. We have quantified 30-day mortality risk by the two independently associated factors, PS and stage, so that patients and clinicians can make better informed decisions about the potential risk of early death following chemotherapy

Generating Single Microwave Photons in a Circuit

Electromagnetic signals in circuits consist of discrete photons, though conventional voltage sources can only generate classical fields with a coherent superposition of many different photon numbers. While these classical signals can control and measure bits in a quantum computer (qubits), single photons can carry quantum information, enabling non-local quantum interactions, an important resource for scalable quantum computing. Here, we demonstrate an on-chip single photon source in a circuit quantum electrodynamics (QED) architecture, with a microwave transmission line cavity that collects the spontaneous emission of a single superconducting qubit with high efficiency. The photon source is triggered by a qubit rotation, as a photon is generated only when the qubit is excited. Tomography of both qubit and fluorescence photon shows that arbitrary qubit states can be mapped onto the photon state, demonstrating an ability to convert a stationary qubit into a flying qubit. Both the average power and voltage of the photon source are characterized to verify performance of the system. This single photon source is an important addition to a rapidly growing toolbox for quantum optics on a chip.Comment: 6 pages, 5 figures, hires version at http://www.eng.yale.edu/rslab/papers/single_photon_hires.pd