Bright Light Beams Research Articles

POCUS - Thoracic Sonography in Times of Corona: What Sonographing Family Physicians Should Examine

POCUS - Thoracic Sonography in Times of Corona: What Sonographing Family Physicians Should Examine Abstract. When performing chest sonography of patients with symptoms such as respiratory infection, dyspnea and chest pain, the primary goal is to find or exclude significant diagnoses such as pneumothorax, pleural effusion, pulmonary edema, tumors, pulmonary emboli, etc. as the cause of the symptoms. If infection with SARS-CoV-2 is present, COVID-19 pneumonia can be confirmed or excluded as the cause of the symptoms with a high degree of probability based on the sonographic signs. COVID-19 pneumonia shows typical changes in the lungs, which are easily accessible to ultrasound due to their usually peripheral location. These are ubiquitous signs, such as a thickened, fragmented pleura with subpleural consolidations, multiple comet tail artifacts of varying size and thickness, some of which are coascent, broad bright light beams, and possibly small encapsulated pleural effusions. The more of these sonographic signs are present and the more pronounced they are, the sooner the patient must be hospitalized and possibly intubated. Ultrasound is also useful as a follow-up tool, together with clinical and laboratory findings.

Assumption-free measurement of the quantum state of light: Exploring the sidebands of intense fields

The quantum noise in photocurrent fluctuations usually gives incomplete information about the quantum state of spectral sideband modes of bright light beams involved in the detection. Each frequency component of the noise spectrum corresponds to two sideband modes symmetrically located around the bright optical field. In the case of the usual homodyne detection, it limits the ability to recover discriminated information of each mode involved. We theoretically show that complete reconstruction of the two-mode quantum state can be obtained by using phase-locked (coherent) resonator detection, even for non-Gaussian states. We experimentally demonstrate the technique by measuring a two-mode displaced coherent state.

Optomechanically induced entanglement

We present a special quantum phenomenon named optomechanically induced entanglement in the conventional single-cavity optomechanical system driven by a strong pump input field and a relatively weak probe input field. Bipartite entanglement between the pump and probe output fields can be achieved under realistic experimental conditions when the input pump (probe) field is blue detuned by the mechanical frequency (resonant) with respect to the cavity field. The physical origin is the mechanical oscillator displacement, which plays a role similar to the atomic coherence for the well-known electromagnetically induced transparency in the traditional \ensuremath{\Lambda}-type atomic system. This scheme provides an alternative, convenient way to generate nondegenerate entangled bright light beams by using only coherent laser fields, and may bring great facility in realistic quantum information processing protocols.

Electromagnetically Induced Entanglement.

Quantum entanglement provides an essential resource for quantum computation, quantum communication, and quantum network. How to conveniently and efficiently produce entanglement between bright light beams presents a challenging task to build realistic quantum information processing networks. Here, we present an efficient and convenient way to realize a novel quantum phenomenon, named electromagnetically induced entanglement, in the conventional Λ-type three-level atomic system driven by a strong pump field and a relatively weak probe field. Nearly perfect entanglement between the two fields can be achieved with a low coherence decay rate between the two lower levels, high pump-field intensity, and large optical depth of the atomic ensemble. The physical origin is quantum coherence between the lower doublet produced by the pump and probe fields, similar to the well-known electromagnetically induced transparency. This method would greatly facilitate the generation of nondegenerate narrow-band continuous-variable entanglement between bright light beams by using only coherent laser fields, and may find potential and broad applications in realistic quantum information processing.

Quantum state tomography of orbital angular momentum photonic qubits via a projection-based technique

While measuring the orbital angular momentum state of bright light beams can be performed using imaging techniques, a full characterization at the single-photon level is challenging. For applications to quantum optics and quantum information science, such characterization is an essential capability. Here, we present a setup to perform the quantum state tomography of photonic qubits encoded in this degree of freedom. The method is based on a projective technique using spatial mode projection via fork holograms and single-mode fibers inserted into an interferometer. The alignment and calibration of the device is detailed as well as the measurement sequence to reconstruct the associated density matrix. Possible extensions to higher-dimensional spaces are discussed.

SEEING RED: BLOOD FLOW IN A SNAKE'S SPECTACLE

When Kevin van Doorn found himself setting up an experiment to investigate how snakes' eyes are able to focus at the beginning of his PhD in Jacob Sivak's lab at the University of Waterloo, Canada, he noticed something rather unusual: the bright light beam from the equipment lit up the eye from behind and revealed an array of tiny blood vessels branching their way across the transparent skin covering the snake's eye. This see-through skin, called the spectacle, is found in all snakes and is analogous to our own eyelids, except in the case of the snake, the two halves are fused together and have become transparent. Although snake spectacles are well known, van Doorn recalls: ‘I never knew that snakes had blood vessels in their spectacle. In fact, it seems like most vision researchers and even snake researchers, herpetologists, in general had no idea.’ So, although van Doorn had initially set out to study how snakes' eyes focus, he decided to turn his attention to these blood vessels instead (p. 4190).First van Doorn wondered who else knew about these blood vessels and did some investigative work. Delving into the scientific literature, he found one brief report on the eye's vasculature dating back to 1852. With the help of Google Translate, he also found an Italian scientist describing the vessels in 1888, and then with the help of some German-speaking friends, he unearthed Manfred Lüdicke's manuscripts from the 1940s–1970s. But by and large, these vessels had fallen under the radar and were a mere curiosity.Being interested in vision, van Doorn next wondered what implications these blood vessels might have for the snake's eyesight. ‘Evolution has done a pretty good job of keeping blood vessels out of the optically transparent portion of the eye, and so from that we can infer that blood vessels in the eye generally have a negative effect on vision’, says van Doorn. What's more, Lüdicke had seen that in a snake with foveas (regions of the eye responsible for sharp vision), the overlying spectacle was less densely packed with blood vessels, suggesting that these vessels do affect vision.To investigate in more detail, van Doorn put coachwhip snakes into a small thin box made of Perspex glass. Luckily, unlike in most snakes, this small enclosure made the coachwhips feel safe enough to hunker down and stay still so that van Doorn could use a slit lamp to illuminate and magnify their eyes. van Doorn then hid behind a curtain for half an hour, while a camera attached to the slit lamp recorded the capillaries periodically dilating and contracting to allow and inhibit blood flow, respectively. On average, van Doorn found that periods of contraction lasted for 115 s, before the vessels dilated to allow blood flow to re-oxygenate the eye. Next, van Doorn crept out from his hiding place to perform some routine tasks in the background. However, given their twitchy nature, the coachwhips regarded his presence as a potential threat, and during the 8 min van Doorn spent in the lab, the coachwhips decreased the period of dilation and blood flow down from 57 s to 33.5 s. When van Doorn returned to his hiding spot, the rhythm of contraction and dilation returned to normal.Whether the snakes actively reduce blood flow in the eye or do so as a side effect of a sympathetic response induced by a threat, van Doorn doesn't know. However, either way, by reducing the amount of blood in the vessels by prolonging periods of contraction, van Doorn thinks this would allow the snake to see better, which would certainly be advantageous had a real threat been in the room.

Signature of squeezing in controlled quantum systems

We report on specific signatures of one-mode squeezing due to multipulse control over quantum dynamics. As an important example, we discuss generation of squeezed bright light beams in an optical parametric oscillator subjected to a periodic sequence of laser pulses. We show that the synchronized pulse control essentially improves the degree of integral squeezing, making it below the standard limit established for a stationary cw regime.

Validation of entanglement purification by continuous variable polarization

We investigate the possibility of characterizing two-party entanglement by measuring correlations of Stokes operators in polarized bright light beams. We adapt a general separability criterion to such operators. We then show that entanglement purification can only be singled out for a particular protocol.

Continuous variable (2, 3) threshold quantumsecret sharing schemes

We present two schemes to perform continuous variable (2, 3)threshold quantum secret sharing (QSS) on the quadrature amplitudesof bright light beams. Both schemes require a pair of entangledlight beams. The first scheme utilizes two phase sensitiveoptical amplifiers, whilst the second uses an electro-opticfeedforward loop for the reconstruction of the secret. Weexamine the efficacy of QSS in terms offidelity, as well as the signal transfer coefficients and theconditional variances of the reconstructed output state. Weshow that both schemes in the ideal case yield perfect secretreconstruction.

Bright afterglow illuminator made of phosphorescent material and fluorescent fibers

Phosphorescent oxides and fluorescent dyes were used together to create a fiber-type illuminator that glows in the dark without the need for electric power. Dye-doped polymer fibers, which were bundled at one end, were linearly arrayed in a polysiloxane resin that contained phosphorescent oxide particles. The phosphorescent resin continued to glow for a long time even after the excitation light was removed. Organic dyes in a polymer fiber were excited by the phosphorescence and emitted fluorescence toward the fiber end. Fluorescence from a number of dyes was combined in the long fiber, and, consequently a bright light beam emerged from the fiber end. Useful performance, i.e., high power density, narrow beam divergence, and long afterglow, is demonstrated by the prototype fiber illuminator.

Radiophotoluminescence of alkali-halide crystals stimulated by Bessel laser beam

A new approach to realization of optimal high-resolution reading of deep X-ray images in X-ray-sensitive materials on the base of alkali-halide crystals modified with admixtures has been suggested and investigated experimentally. A possibility to use diffraction axicons with ring aperture for forming micron bright light beams (spatially truncated Bessel beams) which can efficiently de-excite radiophotoluminescence centers lying at large depth in crystals is also presented.

Behaviour of migrating birds exposed to X-band radar and a bright light beam

Radar studies on bird migration assume that the transmitted electromagnetic pulses do not alter the behaviour of the birds, in spite of some worrying reports of observed disturbance. This paper shows that, in the case of the X-band radar 'Superfledermaus', no relevant changes in flight behaviour occurred, while a strong light beam provoked important changes. Large sets of routine recordings of nocturnal bird migrants obtained using an X-band tracking radar provided no indication of differing flight behaviour between birds flying at low levels towards the radar, away from it or passing it sideways. Switching the radar transmission on and off, while continuing to track selected bird targets using a passive infrared camera during the switch-off phases of the radar, showed no difference in the birds' behaviour with and without incident radar waves. Tracking single nocturnal migrants while switching on and off a strong searchlight mounted parallel to the radar antenna, however, induced pronounced reactions by the birds: (1) a wide variation of directional shifts averaging 8 degrees in the first and 15 degrees in the third 10 s interval after switch-on; (2) a mean reduction in flight speed of 2-3 m s-1 (15-30 % of normal air speed); and (3) a slight increase in climbing rate. A calculated index of change declined with distance from the source, suggesting zero reaction beyond approximately 1 km. These results revive existing ideas of using light beams on aircraft to prevent bird strikes and provide arguments against the increasing use of light beams for advertising purposes.