Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber.

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226-1408 nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300 nm we measure a heralded g^{(2)}(0)=0.25(6) for converted light from an input with g^{(2)}(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.

Resource-efficient frequency conversion for quantum networks via sequential four-wave mixing.

We report a resource-efficient scheme in which a single pump laser was used to achieve frequency conversion by Bragg-scattering four-wave mixing in a photonic crystal fiber. We demonstrate bidirectional conversion of coherent light between Sr+2P1/2→2D3/2 emission wavelength at 1092 nm and the telecommunication C band with conversion efficiencies of 4.2% and 37% for up- and down-conversion, respectively. We discuss how the scheme may be viably scaled to meet the temporal, spectral, and polarization stability requirements of a hybrid light-matter quantum network.

Coherent supercontinuum generation in photonic crystal fiber with all-normal group velocity dispersion.

We demonstrate supercontinuum generation in a photonic crystal fiber with all-normal group velocity dispersion. Pumping a short section of this fiber with compressed pulses from a compact amplified fiber laser generates a 200 nm bandwidth continuum with typical self-phase-modulation characteristics. We demonstrate that the supercontinuum is compressible to a duration of 26 fs. It therefore has a high degree of coherence between all the frequency components, and is a single pulse in the time domain. A smooth, flat spectrum spanning 800 nm is achieved using a longer piece of fiber.

Ultrashort pulse compression and delivery in a hollow-core photonic crystal fiber at 540 nm wavelength.

We have fabricated a bandgap-guiding hollow-core photonic crystal fiber (PCF) capable of transmitting and compressing ultrashort pulses in the green spectral region around 532 nm. When propagating subpicosecond pulses through 1 m of this fiber, we have observed soliton-effect temporal compression by up to a factor of 3 to around 100 fs. This reduces the wavelength at which soliton effects have been observed in hollow-core PCF by over 200 nm. We have used the pulses delivered at the output of the fiber to machine micrometer-scale features in copper.

Photons walking the line: a quantum walk with adjustable coin operations.

We present the first robust implementation of a coined quantum walk over five steps using only passive optical elements. By employing a fiber network loop we keep the amount of required resources constant as the walker's position Hilbert space is increased. We observed a non-Gaussian distribution of the walker's final position, thus characterizing a faster spread of the photon wave packet in comparison to the classical random walk. The walk is realized for many different coin settings and initial states, opening the way for the implementation of a quantum-walk-based search algorithm.

Pure single photon generation by type-I PDC with backward-wave amplification.

We explore a promising method of generating pure heralded single photons. Our approach is based on parametric down-conversion in a periodically-poled waveguide. However, unlike conventional downconversion sources, the photon pairs are counter-propagating: one travels with the pump beam in the forward direction while the other is backpropagating towards the laser source. Our calculations reveal that these downconverted two-photon states carry minimal spectral correlations within each photon-pair. This approach offers the possibility to employ a new range of downconversion processes and materials like PPLN (previously considered unsuitable due to its unfavorable phasematching properties) to produce heralded pure single photons over a broad frequency range.

Absolute efficiency estimation of photon-number-resolving detectors using twin beams.

A nonclassical light source is used to demonstrate experimentally the absolute efficiency calibration of a photon-number-resolving detector. The photon-pair detector calibration method developed by Klyshko for single-photon detectors is generalized to take advantage of the higher dynamic range and additional information provided by photon-number-resolving detectors. This enables the use of brighter twin-beam sources including amplified pulse pumped sources, which increases the relevant signal and provides measurement redundancy, making the calibration more robust.

Referral patterns of physicians requesting brain MRI procedures: a community-based study.

The results of the brain MRI procedures (n = 490) performed in a medium-sized community with a single MRI unit were reviewed. The non-neurologic medical practitioners ordered nearly as many brain scans as the neurospecialists (40.8% and 59.2% of the total scans respectively). The incidence of abnormal scans was 29.5% for the group of non-neurospecialists and 39.3% for the neurospecialists. A fairly large proportion (26.7%; n = 131) of the scans were requested to evaluate headaches. Twelve patients (9.2%) with headaches but without clear neurologic localizing features showed intracranial abnormalities in their MRI scans. Some of the abnormalities observed in the brain MRI scans could have been detected by a CT procedure.

Development and description of two new instruments for measuring the impact of coordinated social services for children.

The Boston Family Reunification Network provides two innovative services designed to help children return to their families as soon as possible. A team developed two new instruments to measure process and clinical outcomes of the initiatives. This article describes the instruments, the two-year development process, and the points considered during the instruments' development. Suggestions for other social welfare groups planning to create and implement outcome tools are included.

Role of the humanities in the education of health professionals.

In the education of health professionals, the study of the humanities has been generally overlooked in favour of an intensive scientific training. In recent years, however, both the establishment of the medical humanities as an academic discipline and changing medical expectations on the part of health professionals and public alike have renewed the relevance of the humanities to professional education. While sounding a cautious note on the methods of (re)incorporating the humanities into the curriculum, the article concludes by encouraging educational institutions, especially in the UK, to assist in the further development of the discipline.