1,260 research outputs found
Chip-Scale, Sub-Hz Fundamental Sub-kHz Integral Linewidth 780 nm Laser through Self-Injection-Locking a Fabry-P\'erot laser to an Ultra-High Q Integrated Resonator
Today's state of the art precision experiments in quantum, gravimetry,
navigation, time keeping, and fundamental science have strict requirements on
the level and spectral distribution of laser frequency noise. For example, the
laser interaction with atoms and qubits requires ultra-low frequency noise at
multiple offset frequencies due to hyperfine atomic transitions, motional
sidebands, and fast pulse sequencing. Chip-scale integration of lasers that
meet these requirements is essential for reliability, low-cost, and weight.
Here, we demonstrate a significant advancement in atomic precision light
sources by realizing a chip-scale, low-cost, 780 nm laser for rubidium atom
applications with record-low 640 mHz (white noise floor at 0.2 Hz/Hz)
fundamental and 732 Hz integral linewidths and a frequency noise that is
multiple orders of magnitude lower than previous hybrid and heterogeneous
self-injection locked 780 nm lasers and lower noise than bulk microresonator
implementations. The laser is a Fabry-P\'erot laser diode self-injection locked
to an ultra-high Q photonic integrated silicon nitride resonator. This
performance is enabled by a 145 million resonator Q with a 30 dB extinction
ratio, the highest Q at 780 nm, to the best of our knowledge. We analyze the
impact of our frequency noise on specific atomic applications including atomic
frequency references, Rydberg quantum gates, and cold atom gravimeters. The
photonic integrated resonator is fabricated using a CMOS foundry-compatible,
wafer-scale process, with demonstrated integration of other components showing
promise for a full system-on-a-chip. This performance is scalable to other
visible atomic wavelengths, opening the door to a variety of transitions across
many atomic species and enabling low-power, compact, ultra-low noise lasers
impacting applications including quantum sensing, computing, clocks and more
Enduring mental health: Prevalence and prediction.
We review epidemiological evidence indicating that most people will develop a diagnosable mental disorder, suggesting that only a minority experience enduring mental health. This minority has received little empirical study, leaving the prevalence and predictors of enduring mental health unknown. We turn to the population-representative Dunedin cohort, followed from birth to midlife, to compare people never-diagnosed with mental disorder (N = 171; 17% prevalence) to those diagnosed at 1–2 study waves, the cohort mode (N = 409). Surprisingly, compared to this modal group, never-diagnosed Study members were not born into unusually well-to-do families, nor did their enduring mental health follow markedly sound physical health, or unusually high intelligence. Instead, they tended to have an advantageous temperament/personality style, and negligible family history of mental disorder. As adults, they report superior educational and occupational attainment, greater life satisfaction, and higher-quality relationships. Our findings draw attention to “enduring mental health” as a revealing psychological phenotype and suggest it deserves further study
Brokered Graph State Quantum Computing
We describe a procedure for graph state quantum computing that is tailored to
fully exploit the physics of optically active multi-level systems. Leveraging
ideas from the literature on distributed computation together with the recent
work on probabilistic cluster state synthesis, our model assigns to each
physical system two logical qubits: the broker and the client. Groups of
brokers negotiate new graph state fragments via a probabilistic optical
protocol. Completed fragments are mapped from broker to clients via a simple
state transition and measurement. The clients, whose role is to store the
nascent graph state long term, remain entirely insulated from failures during
the brokerage. We describe an implementation in terms of NV-centres in diamond,
where brokers and clients are very naturally embodied as electron and nuclear
spins.Comment: 5 pages, 3 figure
The fitness of African malaria vectors in the presence and limitation of host behaviour
<p>Background
Host responses are important sources of selection upon the host species range of ectoparasites and phytophagous insects. However little is known about the role of host responses in defining the host species range of malaria vectors. This study aimed to estimate the relative importance of host behaviour to the feeding success and fitness of African malaria vectors, and assess its ability to predict their known host species preferences in nature.</p>
<p>Methods
Paired evaluations of the feeding success and fitness of African vectors Anopheles arabiensis and Anopheles gambiae s.s in the presence and limitation of host behaviour were conducted in a semi-field system (SFS) at Ifakara Health Institute, Tanzania. In one set of trials, mosquitoes were released within the SFS and allowed to forage overnight on a host that was free to exhibit natural behaviour in response to insect biting. In the other, mosquitoes were allowed to feed directly on from the skin surface of immobile hosts. The feeding success and subsequent fitness of vectors under these conditions were investigated on 6 host types (humans, calves, chickens, cows, dogs and goats) to assess whether physical movements of preferred host species (cattle for An. arabiensis, humans for An. gambiae s.s.) were less effective at preventing mosquito bites than those of common alternatives.</p>
<p>Results
Anopheles arabiensis generally had greater feeding success when applied directly to host skin than when foraging on unrestricted hosts (in five of six host species). However, An. gambiae s.s obtained blood meals from free and restrained hosts with similar success from most host types (four out of six). Overall, the blood meal size, oviposition rate, fecundity and post-feeding survival of mosquito vectors were significantly higher after feeding on hosts free to exhibit behaviour, than those who were immobilized during feeding trials.</p>
<p>Conclusions
Allowing hosts to move freely during exposure to mosquitoes was associated with moderate reductions in mosquito feeding success, but no detrimental impact to the subsequent fitness of mosquitoes that were able to feed upon them. This suggests that physical defensive behaviours exhibited by common host species including humans do not impose substantial fitness costs on African malaria vectors.</p>
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