We have measured -3.5 dB (-8.1 dB corrected for losses) relative intensity squeezing between probe and conjugate beams generated by stimulated, nondegenerate four-wave mixing in hot rubidium vapor. Unlike early observations of squeezing in atomic vapors based on saturation of a two-level system, our scheme uses a resonant nonlinearity based on ground-state coherences in a three-level system. Since this scheme produces narrowband, squeezed light near an atomic resonance, it is of interest for experiments involving cold atoms or atomic ensembles.

Direct air capture (DAC) can provide an impactful, engineered approach to combat climate change by removing carbon dioxide (CO2) from the air. However, to meet climate goals, DAC needs to be scaled at a rapid rate. Current DAC approaches use engineered contactors filled with chemicals to repeatedly capture CO2 from the air and release high purity CO2 that can be stored or otherwise used. This review article focuses on two distinctive, commercial DAC processes to bind with CO2: solid sorbents and liquid solvents. We discuss the properties of solvents and sorbents, including mass transfer, heat transfer and chemical kinetics, as well as how these properties influence the design and cost of the DAC process. Further, we provide a novel overview of the considerations for deploying these DAC technologies, including concepts for learning-by-doing that may drive down costs and material requirements for scaling up DAC technologies.

We show that a simple scheme based on nondegenerate four-wave mixing in a hot atomic vapor behaves like a near-perfect phase-insensitive optical amplifier, which can generate bright twin beams with a measured quantum noise reduction in the intensity difference of more than 8 dB, close to the best optical parametric amplifiers and oscillators. The absence of a cavity makes the system immune to external perturbations, and the strong quantum noise reduction is observed over a large frequency range.PACS numbers: 42.50. Gy, 42.50.Dv Two-mode squeezed beams have become a valuable source of entanglement for quantum communications and quantum information processing [1]. These applications bring specifi requirements on the squeezed light sources. For instance, for squeeze light to be used as a quantum information carrier interacting with material system, as in an atomic quantum memory, the light field must be resonant with an atomic transition and spectrally narrow to ensure an efficient coupling between light and matter. In recent years, attention has also been brought to the problem of the manipulation of cold atomic samples with non-classical fields in order to produce non-classical matter waves [2,3,4]. In this case, the slow atomic dynamics also requires squeezing at low frequencies.The standard technique for generating nonclassical light fields is by parametric down-conversion in a crystal, with an optical parametric oscillator or an optical parametric amplifier [5,6]. While very large amounts of quantum noise reduction have been achieved in this way [7,8], controlling the frequency and the linewidth of the light remains a challenge. Only recently have sources based on periodically-poled nonlinear crystals been developed at 795 nm to couple to the Rb D1 atomic line [9,10]. On the other hand, stimulated four-wave mixing (4WM) naturally generates narrow-band light close to an atomic resonance, but its development as an efficient source of squeezed light has been hindered by fundamental limitations such as spontaneous emission. At the end of the 1990s, nondegenerate 4WM in a double-lambda scheme was identified as a possible workaround for these limitations, as described in Ref.[11] and references therein. It was not until recently that such a scheme was implemented in continuous mode in an efficient way in both the low [12,13,14] and the high [15,16] intensity regimes, where it was shown to generate twin beams where quantum correlations are not masked by competing effects.The double-lambda scheme gives rise to complex atomic dynamics and propagation properties, such as slow-light effects [17]. In this Letter, we show that in spite of this complexity, the quantum properties of the scheme can be accurately described as the combination of a perfect amplifier and a partial absorber. This model allows us to optimize the quantum noise reduction in the intensity difference of the bright twin beams and to isolate the limiting factors of this reduction. It also helps to identify regions of the parameter space where the syst...

Cytoarchitectural analyses combined with injections of the tracer horseradish peroxidase in various structures in the brain of the goldfish, Carassius auratus, have defined some of the major components of acoustic and lateral line mechanosensory circuits between the medulla and midbrain. The main acoustic receptor in Carassius, the saccule, is known to provide a major input to the dorsomedial zone of the descending octaval nucleus. The dorsomedial zone in turn projects bilaterally to the secondary octaval population (SO) and to nucleus centralis of the torus semicircularis. The SO is composed of three major subdivisions which are also present in a related otophysan, the catfish Ictalurus punctatus. The SO in Carassius projects bilaterally to nucleus centralis and to the saccular recipient zones of the ipsilateral descending octaval nucleus. By contrast, the mechanosensory lateral line receptors are known to direct most of their input to nucleus medialis. Nucleus medialis in turn projects bilaterally to nucleus praeeminentialis, nucleus ventrolateralis of the torus semicircularis, and the optic tectum, and to the contralateral nucleus medialis. We also provide evidence for a bilateral projection of nucleus medialis to the sensory trigeminal nucleus, and for a reciprocal input from the sensory trigeminal nucleus to the ipsilateral nucleus medialis.

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