17 research outputs found
Raman Quantum Memory with Built-In Suppression of Four-wave Mixing Noise
Quantum memories are essential for large-scale quantum information networks.
Along with high efficiency, storage lifetime and optical bandwidth, it is
critical that the memory add negligible noise to the recalled signal. A common
source of noise in optical quantum memories is spontaneous four-wave mixing. We
develop and implement a technically simple scheme to suppress this noise
mechanism by means of quantum interference. Using this scheme with a Raman
memory in warm atomic vapour we demonstrate over an order of magnitude
improvement in noise performance. Furthermore we demonstrate a method to
quantify the remaining noise contributions and present a route to enable
further noise suppression. Our scheme opens the way to quantum demonstrations
using a broadband memory, significantly advancing the search for scalable
quantum photonic networks.Comment: 6 pages, 5 figures plus Supplementary Materia
Optimized diamond inverted nanocones for enhanced color center to fiber coupling
Nanostructures can be used for boosting the light outcoupling of color
centers in diamond; however, the fiber coupling performance of these
nanostructures is rarely investigated. Here, we use a finite element method for
computing the emission from color centers in inverted nanocones and the overlap
of this emission with the propagation mode in a single-mode fiber. Using
different figures of merit, the inverted nanocone parameters are optimized to
obtain maximal fiber coupling efficiency, free-space collection efficiency, or
rate enhancement. The optimized inverted nanocone designs show promising
results with 66% fiber coupling or 83% free-space coupling efficiency at the
tin-vacancy center zero-phonon line wavelength of 619 nm. Moreover, when
evaluated for broadband performance, the optimized designs show 55% and 76% for
fiber coupling and free-space efficiencies respectively, for collecting the
full tin-vacancy emission spectrum at room temperature. An analysis of
fabrication insensitivity indicates that these nanostructures are robust
against imperfections. For maximum emission rate into a fiber mode, a design
with a Purcell factor of 2.34 is identified. Finally, possible improvements
offered by a hybrid inverted nanocone, formed by patterning into two different
materials, are investigated, and increases the achievable fiber coupling
efficiency to 71%.Comment: The following article has been accepted by Applied Physics Letters.
After it is published, it will be found at https://doi.org/10.1063/5.005033
Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.
BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700
Optimized diamond inverted nanocones for enhanced color center to fiber coupling
Nanostructures can be used for boosting the light outcoupling of color
centers in diamond; however, the fiber coupling performance of these
nanostructures is rarely investigated. Here, we use a finite element method for
computing the emission from color centers in inverted nanocones and the overlap
of this emission with the propagation mode in a single-mode fiber. Using
different figures of merit, the inverted nanocone parameters are optimized to
obtain maximal fiber coupling efficiency, free-space collection efficiency, or
rate enhancement. The optimized inverted nanocone designs show promising
results with 66% fiber coupling or 83% free-space coupling efficiency at the
tin-vacancy center zero-phonon line wavelength of 619 nm. Moreover, when
evaluated for broadband performance, the optimized designs show 55% and 76% for
fiber coupling and free-space efficiencies respectively, for collecting the
full tin-vacancy emission spectrum at room temperature. An analysis of
fabrication insensitivity indicates that these nanostructures are robust
against imperfections. For maximum emission rate into a fiber mode, a design
with a Purcell factor of 2.34 is identified. Finally, possible improvements
offered by a hybrid inverted nanocone, formed by patterning into two different
materials, are investigated, and increases the achievable fiber coupling
efficiency to 71%.Comment: The following article has been accepted by Applied Physics Letters.
After it is published, it will be found at https://doi.org/10.1063/5.005033