Decoherence-protected memory for a single-photon qubit

The long-lived, efficient storage and retrieval of a qubit encoded on a photon is an important ingredient for future quantum networks. Although systems with intrinsically long coherence times have been demonstrated, the combination with an efficient light-matter interface remains an outstanding challenge. In fact, the coherence times of memories for photonic qubits are currently limited to a few milliseconds. Here we report on a qubit memory based on a single atom coupled to a high-finesse optical resonator. By mapping and remapping the qubit between a basis used for light-matter interfacing and a basis which is less susceptible to decoherence, a coherence time exceeding 100 ms has been measured with a time-independant storage-and-retrieval efficiency of 22%. This demonstrates the first photonic qubit memory with a coherence time that exceeds the lower bound needed for teleporting qubits in a global quantum internet.Comment: 3 pages, 4 figure

Measurement of low turbulence levels with a thermoanemometer

The trend for decreasing the drag of aircraft is retention of laminar flow in the boundary layer over a large portion of the surface. The laminar boundary layer was studied in a low turbulence wind tunnel for low subsonic velocities. The method used and results of measurements of very low levels of turbulence are presented. Measurements were performed by a constant-resistance thermoanemometer

Erratum: The solar wind in time II: 3D stellar wind structure and radio emission

This is an erratum to the paper ‘The solar wind in time - II: 3D stellar wind structure and radio emission’, which was published in MNRAS, 483(1), 873, 2019 (Ó Fionnagáin et al. 2019)

Cool Stars and Space Weather

Stellar flares, winds and coronal mass ejections form the space weather. They are signatures of the magnetic activity of cool stars and, since activity varies with age, mass and rotation, the space weather that extra-solar planets experience can be very different from the one encountered by the solar system planets. How do stellar activity and magnetism influence the space weather of exoplanets orbiting main-sequence stars? How do the environments surrounding exoplanets differ from those around the planets in our own solar system? How can the detailed knowledge acquired by the solar system community be applied in exoplanetary systems? How does space weather affect habitability? These were questions that were addressed in the splinter session "Cool stars and Space Weather", that took place on 9 Jun 2014, during the Cool Stars 18 meeting. In this paper, we present a summary of the contributions made to this session.Comment: Proceedings of the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Eds G. van Belle & H. Harris, 13 pages, 1 figur

Monitoring alkylphenols in water using the polar organic chemical integrative sampler (POCIS): determining sampling rates via the extraction of PES membranes and Oasis beads

Polar organic chemical integrative samplers (POCIS) have previously been used to monitor alkylphenol (AP) contamination in water and produced water. However, only the sorbent receiving phase of the POCIS (Oasis beads) is traditionally analyzed, thus limiting the use of POCIS for monitoring a range of APs with varying hydrophobicity. Here a “pharmaceutical” POCIS was calibrated in the laboratory using a static renewal setup for APs (from 2-ethylphenol to 4-n-nonylphenol) with varying hydrophobicity (log Kow between 2.47 and 5.76). The POCIS sampler was calibrated over its 28 day integrative regime and sampling rates (Rs) were determined. Uptake was shown to be a function of AP hydrophobicity where compounds with log Kow < 4 were preferentially accumulated in Oasis beads, and compounds with log Kow > 5 were preferentially accumulated in the PES membranes. A lag phase (over a 24 h period) before uptake in to the PES membranes occurred was evident. This work demonstrates that the analysis of both POCIS phases is vital in order to correctly determine environmentally relevant concentrations owing to the fact that for APs with log Kow ≤ 4 uptake, to the PES membranes and the Oasis beads, involves different processes compared to APs with log Kow ≥ 4. The extraction of both the POCIS matrices is thus recommended in order to assess the concentration of hydrophobic APs (log Kow ≥ 4), as well as hydrophilic APs, most effectively. © 2017 Elsevier Lt

High-efficiency WSi superconducting nanowire single-photon detectors for quantum state engineering in the near infrared

We report on high-efficiency superconducting nanowire single-photon detectors based on amorphous WSi and optimized at 1064 nm. At an operating temperature of 1.8 K, we demonstrated a 93% system detection efficiency at this wavelength with a dark noise of a few counts per second. Combined with cavity-enhanced spontaneous parametric down-conversion, this fiber-coupled detector enabled us to generate narrowband single photons with a heralding efficiency greater than 90% and a high spectral brightness of $0.6\times10^4$ photons/(s$\cdot$mW$\cdot$MHz). Beyond single-photon generation at large rate, such high-efficiency detectors open the path to efficient multiple-photon heralding and complex quantum state engineering

Perché si muore nei romanzi: l’ipotesi della simulazione dell’ordalia

Copyright © Author(s) 2022. What is fiction about, and what is it good for? An influential family of theories sees fiction as rooted in adaptive simulation mechanisms. In this view, our propensity to create and enjoy narrative fictions was selected and maintained due to the training that we get from mentally simulating situations relevant to our survival and reproduction. We put forward and test a precise version of this claim, the “ordeal simulation hypothesis”. It states that fictional narrative primarily simulates “ordeals”: situations where a person’s reaction might dramatically improve or decrease her fitness, such as deadly aggressions, or decisions on long-term matrimonial commitments. We study mortality in fictional and non-fictional texts as a partial test for this view. Based on an analysis of 744 extensive summaries of twentieth century American novels of various genres, we show that the odds of dying (in a given year) are vastly exaggerated in fiction compared to reality, but specifically more exaggerated for homicides as compared to suicides, accidents, war-related, or natural deaths. This evidence supports the ordeal simulation hypothesis but is also compatible with other accounts

The solar wind in time – II. 3D stellar wind structure and radio emission

In this work, we simulate the evolution of the solar wind along its main-sequence lifetime and compute its thermal radio emission. To study the evolution of the solar wind, we use a sample of solar mass stars at different ages. All these stars have observationally reconstructed magnetic maps, which are incorporated in our 3D magnetohydrodynamic simulations of their winds. We show that angular-momentum loss and mass-loss rates decrease steadily on evolutionary time-scales, although they can vary in a magnetic cycle time-scale. Stellar winds are known to emit radiation in the form of thermal bremsstrahlung in the radio spectrum. To calculate the expected radio fluxes from these winds, we solve the radiative transfer equation numerically from first principles. We compute continuum spectra across the frequency range 100 MHz to 100 GHz and find maximum radio flux densities ranging from 0.05 to 2.2 μJy. At a frequency of 1 GHz and a normalized distance of d = 10 pc, the radio flux density follows 0.24 (Ω/Ω☉)0.9 (d/[10pc])-2μJy, where Ω is the rotation rate. This means that the best candidates for stellar wind observations in the radio regime are faster rotators within distances of 10 pc, such as κ1 Ceti (0.73 μJy) and χ1 Ori (2.2 μJy). These flux predictions provide a guide to observing solar-type stars across the frequency range 0.1-100 GHz in the future using the next generation of radio telescopes, such as ngVLA and Square Kilometre Array

UVMag: stellar formation, evolution, structure and environment with space UV and visible spectropolarimetry

Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence, main sequence and evolved stars. They will cast new light onto stellar physics by addressing many exciting and important questions. UVMag is currently undergoing a Research and Technology study and will be proposed at the forthcoming ESA call for M-size missions. This spectropolarimeter could also be installed on a large UV and visible observatory (e.g. NASA's LUVOIR project) within a suite of instruments.Comment: Accepted in ApSS's special volume on UV astronom