Quantum storage of photonic entanglement in a crystal.

Entanglement is the fundamental characteristic of quantum physics-much experimental effort is devoted to harnessing it between various physical systems. In particular, entanglement between light and material systems is interesting owing to their anticipated respective roles as 'flying' and stationary qubits in quantum information technologies (such as quantum repeaters and quantum networks). Here we report the demonstration of entanglement between a photon at a telecommunication wavelength (1,338 nm) and a single collective atomic excitation stored in a crystal. One photon from an energy-time entangled pair is mapped onto the crystal and then released into a well-defined spatial mode after a predetermined storage time. The other (telecommunication wavelength) photon is sent directly through a 50-metre fibre link to an analyser. Successful storage of entanglement in the crystal is proved by a violation of the Clauser-Horne-Shimony-Holt inequality by almost three standard deviations (S = 2.64 ± 0.23). These results represent an important step towards quantum communication technologies based on solid-state devices. In particular, our resources pave the way for building multiplexed quantum repeaters for long-distance quantum networks.

Quantum storage of heralded polarization qubits in birefringent and anisotropically absorbing materials.

Storage of quantum information encoded into heralded single photons is an essential constituent of long-distance quantum communication based on quantum repeaters and of optical quantum information processing. The storage of photonic polarization qubits is, however, difficult because many materials are birefringent and have polarization-dependent absorption. Here we present a simple scheme that eliminates these polarization effects, and we demonstrate it by storing heralded polarization qubits into a solid-state quantum memory. The quantum memory is implemented with a biaxial yttrium orthosilicate (Y2SiO5) crystal doped with rare-earth ions. Heralded single photons generated from a filtered spontaneous parametric down-conversion source are stored, and quantum state tomography of the retrieved polarization state reveals an average fidelity of 97.5±0.4%, which is significantly higher than what is achievable with a measure-and-prepare strategy.

Statistical distortion of supervised learning predictions in optical microscopy induced by image compression.

The growth of data throughput in optical microscopy has triggered the extensive use of supervised learning (SL) models on compressed datasets for automated analysis. Investigating the effects of image compression on SL predictions is therefore pivotal to assess their reliability, especially for clinical use. We quantify the statistical distortions induced by compression through the comparison of predictions on compressed data to the raw predictive uncertainty, numerically estimated from the raw noise statistics measured via sensor calibration. Predictions on cell segmentation parameters are altered by up to 15% and more than 10 standard deviations after 16-to-8 bits pixel depth reduction and 10:1 JPEG compression. JPEG formats with higher compression ratios show significantly larger distortions. Interestingly, a recent metrologically accurate algorithm, offering up to 10:1 compression ratio, provides a prediction spread equivalent to that stemming from raw noise. The method described here allows to set a lower bound to the predictive uncertainty of a SL task and can be generalized to determine the statistical distortions originated from a variety of processing pipelines in AI-assisted fields.

Impaired monocyte function in cancer patients: restoration with a cyclooxygenase-2 inhibitor.

Epidemiological data and animal models have provided evidence that nonsteroidal antiinflammatory drugs (NSAIDs) have an anticancer effect. However, the molecular mechanisms underlying these antineoplastic effects are not well understood. We described previously that expression levels of the chemokine receptor, CCR5, and the beta2-integrin, Mac-1, were down-regulated on primary monocytes after incubation in supernatants from human carcinoma cell lines, and that this down-regulation resulted in impaired monocyte function with respect to migration and adhesion. We now demonstrate that these impairments are also present in vivo. Monocytes from cancer patients displayed significantly reduced CCR5 levels and migration capacities in comparison to cells from healthy donors. Because migration is necessary for the antitumor activity of monocytes/macrophages, these deficits may contribute to the suppressed immune system seen in cancer patients. In a clinical study, we analyzed the effect of a selective COX-2 inhibitor, Rofecoxib, on the migration of monocytes derived from cancer patients. The results revealed significant improvement in migration equal to those levels seen in healthy donors. We conclude that in patients with cancer, the intake of Rofecoxib for 3 wk leads to significant restoration of monocyte function. These data may, at least in part, help explain the anticancer effects of NSAIDs.

Second-harmonic generation of light at 544 and 272 nm from an ytterbium-doped distributed-feedback fiber laser.

We report external cavity second-harmonic generation of light at 544 and 272 nm based on an ytterbium-doped distributed-feedback fiber laser. The nonlinear crystal used to generate light at 544 nm is LiNbO3, and the maximum output of the cavity is 845 mW, corresponding to a conversion efficiency of 55%. In a second frequency-doubling step, using a beta-BaBa2O4 crystal, we generate up to 115 mW of light at 272 nm with a conversion efficiency of 14%.