15 research outputs found
Pure single photons from a trapped atom source
Single atoms or atom-like emitters are the purest source of on-demand single
photons, they are intrinsically incapable of multi-photon emission. To
demonstrate this degree of purity we have realized a tunable, on-demand source
of single photons using a single ion trapped at the common focus of high
numerical aperture lenses. Our trapped-ion source produces single-photon pulses
at a rate of 200 kHz with g, without any
background subtraction. The corresponding residual background is accounted for
exclusively by detector dark counts. We further characterize the performance of
our source by measuring the violation of a non-Gaussian state witness and show
that its output corresponds to ideal attenuated single photons. Combined with
current efforts to enhance collection efficiency from single emitters, our
results suggest that single trapped ions are not only ideal stationary qubits
for quantum information processing, but promising sources of light for scalable
optical quantum networks.Comment: 7 pages plus one page supplementary materia
Spatial mode storage in a gradient echo memory
Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate
for efficient quantum storage and for linear optical quantum computation with
time-bin multiplexing. In this paper we investigate the spatial multimode
properties of a lambda-GEM system. Using a high-speed triggered CCD, we
demonstrate the storage of complex spatial modes and images. We also present an
in-principle demonstration of spatial multiplexing by showing selective recall
of spatial elements of a stored spin wave. Using our measurements, we consider
the effect of diffusion within the atomic vapour and investigate its role in
spatial decoherence. Our measurements allow us to quantify the spatial
distortion due to both diffusion and inhomogeneous control field scattering and
compare these to theoretical models.Comment: 11 pages, 9 figure
Wavelength-scale errors in optical localization due to spin-orbit coupling of light
The precise determination of the position of point-like emitters and
scatterers using far-field optical imaging techniques is of utmost importance
for a wide range of applications in medicine, biology, astronomy, and physics.
Although the optical wavelength sets a fundamental limit to the image
resolution of unknown objects, the position of an individual emitter can in
principle be estimated from the image with arbitrary precision. This is used,
e.g., in stars' position determination and in optical super-resolution
microscopy. Furthermore, precise position determination is an experimental
prerequisite for the manipulation and measurement of individual quantum
systems, such as atoms, ions, and solid state-based quantum emitters. Here we
demonstrate that spin-orbit coupling of light in the emission of elliptically
polarized emitters can lead to systematic, wavelength-scale errors in the
estimate of the emitter's position. Imaging a single trapped atom as well as a
single sub-wavelength-diameter gold nanoparticle, we demonstrate a shift
between the emitters' measured and actual positions which is comparable to the
optical wavelength. Remarkably, for certain settings, the expected shift can
become arbitrarily large. Beyond their relevance for optical imaging
techniques, our findings apply to the localization of objects using any type of
wave that carries orbital angular momentum relative to the emitter's position
with a component orthogonal to the direction of observation.Comment: Main text 6 pages, Methods 8 pages, Extended data 9 pages,
Supplementary information 4 page
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
Memory and Transduction Prospects for Silicon T Center Devices
The T center, a silicon-native spin-photon interface with telecommunication-band optical transitions and long-lived microwave qubits, offers an appealing new platform for both optical quantum memory and microwave-to-optical telecommunication-band transduction. A wide range of quantum memory and transduction schemes could be implemented withT center ensembles with sufficient optical depth, with advantages and disadvantages that depend sensitively on the ensemble properties. In this work we characterize T center spin ensembles to inform device design. We perform the first T ensemble optical depth measurement and calculate the improvement in center density or resonant optical enhancement required for efficient optical quantum memory. We further demonstrate a coherent microwave interface by coherent population trapping and Autler-Townes splitting. We then determine the most promising microwave and optical quantum memory protocol for such ensembles. By estimating the memory efficiency both in free space and in the presence of a cavity, we show that efficient optical memory is possible with reasonable optical density forecasts. Finally, we formulate a transduction proposal and discuss the achievable efficiency and fidelity