Synchronized source of indistinguishable photons for quantum networks.

We present a source of indistinguishable photons at telecom wavelength, synchronized to an external clock, for the use in distributed quantum networks. We characterize the indistinguishability of photons generated in independent parametric down-conversion events using a Hong-Ou-Mandel interferometer, and show non-classical interference with coalescence, C = 0.83(5). We also demonstrate the synchronization to an external clock within sub-picosecond timing jitter, which is significantly shorter than the single-photon wavepacket duration of ≈ 35 ps. Our source enables scalable quantum protocols over multi-node, long-distance optical networks using network-based clock recovery systems.

Evaluation of the hematological and immunological markers after the first and second doses of BNT162b2 mRNA vaccine.

OBJECTIVE: Both humoral and cellular immunity can be significantly influenced by the immunological responses to vaccination, and both responses are essential. Vaccination is the most consistent, safe, and cost-efficient practice for controlling the COVID-19 pandemic. PATIENTS AND METHODS: Blood samples were collected from participants who received two vaccine doses of COVID-19 Pfizer/BioNTech (BNT162b2) before and on days 7 and 10 after the first and second immunization. We evaluated some hematological and immunological markers responses to the 1st and 2nd doses of the BNT162b2 mRNA (Pfizer/BioNtech) vaccine. RESULTS: In healthy subjects' neutrophil and WBC counts significantly increased compared to those after the first dose. The results of all first-group participant categories demonstrated no discernible variations in lymphocyte counts. There was no change in IgM or IgG in all second-group cohorts, except for a considerable rise in IgG levels in people with a history of coronavirus infection following the second dosage compared to baseline. After the second dose, CD4+ T-cell and CD8+ T-cell levels rose in all groups compared to before the immunization and after the first dosage. Data demonstrated a substantial rise in neutrophil-lymphocyte ratio (NLR) after the second dose of the vaccine. Individuals who had previously had COVID-19 disease experienced a considerable increase in C3 and C4 levels after the first and second dosages compared to baseline. Additionally, compared to their levels after the first dosage, C4 levels increased significantly following the second dosage. Interleukin (IL)-6, IL-15, macrophage colony-stimulating factor (M-CSF), granulocyte colony stimulating factor (G-CSF), interferon gamma-induced protein 10 (IP-10/CXCL10), and macrophage inflammatory protein-1 alpha (MIP-1α/CCL3) levels were increased after boost correlated with Spike antibody levels, supporting their utility as indicators of successful humoral immunity development in response to vaccination. CONCLUSIONS: We can conclude that the Pfizer/BioNTech vaccine produced a more potent T-cell response than humoral ones.

Experimental Shot-by-Shot Estimation of Quantum Measurement Confidence.

We demonstrate the single-shot confidence estimation for individual quantum measurement outcomes using the continuous measurement theory of the quantum counting process applied to the quantum state identification problem. We experimentally obtain single-shot and average confidences for quantum measurements and show that they favorably compare to that of the idealized classical measurement. Finally, we demonstrate that single-shot confidence estimations correctly represent observed experimental outcomes for a large ensemble of measurements.

Practical quantum-enhanced receivers for classical communication.

Communication is an integral part of human life. Today, optical pulses are the preferred information carriers for long-distance communication. The exponential growth in data leads to a "capacity crunch" in the underlying physical systems. One of the possible methods to deter the exponential growth of physical resources for communication is to use quantum, rather than classical measurement at the receiver. Quantum measurement improves the energy efficiency of optical communication protocols by enabling discrimination of optical coherent states with the discrimination error rate below the shot-noise limit. In this review article, the authors focus on quantum receivers that can be practically implemented at the current state of technology, first and foremost displacement-based receivers. The authors present the experimentalist view on the progress in quantum-enhanced receivers and discuss their potential.

Experimental demonstration of the near-quantum optimal receiver.

We implement the cyclic quantum receiver based on the theoretical proposal of Roy Bondurant and demonstrate experimentally below the shot-noise limit (SNL) discrimination of quadrature phase-shift keying signals (PSK). We also experimentally test the receiver generalized for longer communication alphabet lengths and coherent frequency shift keying (CFSK) encoding. Using off-the-shelf components, we obtain state discrimination error rates that are 3 dB and 4.6 dB below the SNLs of ideal classical receivers for quadrature PSK and CFSK encodings, respectively. The receiver unconditionally surpasses the SNL for M=8 PSK and CFSK. This receiver can be used for the simple and robust practical implementation of quantum-enhanced optical communication.

Robust, high brightness, degenerate entangled photon source at room temperature.

We report on a compact, simple and robust high brightness entangled photon source at room temperature. Based on a 30-mm-long periodically-poled potassium titanyl phosphate crystal, the source produces non-collinear, type-0, phase-matched, degenerate photons at 810 nm with spectral brightness as high as ~0.41 ± 0.02 (~0.025 ± 0.02) MHz/mW/nm for multi (single) mode fiber coupling. So far, this is the highest number of degenerate photons generated using a continuous-wave laser pumped bulk crystal and detected using multimode fiber. We have studied the dependence of pump focusing on the brightness of the generated photons collected using both multimode, and single mode fibers. For a fixed pump power and crystal parameters, the SPDC source has an optimum pump waist radius producing maximum number of paired photons. Combining the crystal in a novel system architecture comprised with Sagnac interferometer and polarizing optical elements, the source produces polarization entangled photon states with high spectral brightness. Even in the absence of any phase compensation, the entangled photon states detected using single mode fiber have a Bell's parameter, S = 2.63 ± 0.02, violating the Bell's inequality by nearly 32 standard deviations and fidelity of 0.975. The compact footprint, robust design, and room temperature operation, make our source ideal for various quantum communication experiments.

Differential diagnosis of scrub typhus meningitis from tuberculous meningitis using clinical and laboratory features.

OBJECTIVES: The involvement of the central nervous system in the form of meningitis or meningoencephalitis is common in scrub typhus and is an important differential diagnosis of other lymphocytic meningitis like tuberculous meningitis (TBM). The aim of this study was to identify the clinical and laboratory parameters that may be helpful in differentiating scrub typhus meningitis from TBM. PATIENTS AND METHODS: We compared of the clinical and laboratory features of 57 patients admitted with scrub typhus meningitis or TBM during a 3-year period. Patients who had abnormal cerebrospinal fluid (CSF) and positive scrub typhus enzyme-linked immunosorbent assay serology (n=28) were included in the scrub typhus meningitis group, while the TBM group included those who satisfied the consensus diagnostic criteria of TBM (n=29). RESULTS: Compared with the TBM group, the mean duration of symptoms was less in patients with scrub typhus meningitis, who also had a lower magnitude of neurological deficits, such as altered mental status and cranial nerve and motor deficits. Patients with scrub typhus meningitis had a lower CSF white blood-cell count (WBC) than the TBM group (130.8±213 195±175 cells/mm3, P=0.002), lower CSF protein elevation (125±120 vs. 195.2±108.2mg/dl, P=0.002), and higher CSF sugar (70.1±32.4 vs. 48.7±23.4mg/dl, P=0.006). Features predictive of the diagnosis of scrub typhus meningitis included the absence of neurological impairment at presentation, blood serum glutamic-oxaloacetic transaminase>40 international units (IU)/L, serum glutamic-pyruvic transaminase>60 IU/L, total blood leukocyte count>10,000/mm3, CSF protein<100mg/dl, CSF sugar>50mg/dl, CSF WBC<100 cells/mm3. All patients with scrub typhus meningitis recovered completely following doxycycline therapy CONCLUSIONS: This study suggests that, clinical features, including duration of fever, neurological deficits at presentation and laboratory parameters such as CSF pleocytosis,CSF protein elevation, CSF sugar levels and liver enzyme values are helpful in differentiating scrub typhus meningitis from tuberculous meningits. These features with scrub IgM serology may be helpful in identifying patients with scrub meningitis and in avoiding prolonged empirical antituberculous therapy in cases of lymphocytic meningitis.

Direct transfer of classical non-separable states into hybrid entangled two photon states.

Hybrid entangled states, having entanglement between different degrees-of-freedom (DoF) of a particle pair, are of great interest for quantum information science and communication protocols. Among different DoFs, the hybrid entangled states encoded with polarization and orbital angular momentum (OAM) allow the generation of qubit-qudit entangled states, macroscopic entanglement with very high quanta of OAM and improvement in angular resolution in remote sensing. Till date, such hybrid entangled states are generated by using a high-fidelity polarization entangled states and subsequent imprinting of chosen amount of OAM using suitable mode converters such as spatial light modulator in complicated experimental schemes. Given that the entangled sources have feeble number of photons, loss of photons during imprinting of OAM using diffractive optical elements limits the use of such hybrid states for practical applications. Here we report, on a simple generic experimental scheme to generate hybrid entangled states in polarization and OAM through direct transfer of classical non-separable states of the pump beam in parametric down conversion process. As a proof of principle, using local non-separable pump states of OAM mode l = 3, we have produced quantum hybrid entangled states with entanglement witness parameter of ~1.25 ± 0.03 violating by 8 standard deviation.

Hollow Gaussian beam generation through nonlinear interaction of photons with orbital angular momentum.

Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs.

Airy beam optical parametric oscillator.

Airy beam, a non-diffracting waveform, has peculiar properties of self-healing and self-acceleration. Due to such unique properties, the Airy beam finds many applications including curved plasma wave-guiding, micro-particle manipulation, optically mediated particle clearing, long distance communication, and nonlinear frequency conversion. However, many of these applications including laser machining of curved structures, generation of curved plasma channels, guiding of electric discharges in a curved path, study of nonlinear propagation dynamics, and nonlinear interaction demand Airy beam with high power, energy, and wavelength tunability. Till date, none of the Airy beam sources have all these features in a single device. Here, we report a new class of coherent sources based on cubic phase modulation of a singly-resonant optical parametric oscillator (OPO), producing high-power, continuous-wave (cw), tunable radiation in 2-D Airy intensity profile existing over a length >2 m. Based on a MgO-doped periodically poled LiNbO3 crystal pumped at 1064 nm, the Airy beam OPO produces output power more than 8 W, and wavelength tunability across 1.51-1.97 µm. This demonstration gives new direction for the development of sources of arbitrary structured beams at any wavelength, power, and energy in all time scales (cw to femtosecond).

Efficient nonlinear generation of high power, higher order, ultrafast "perfect" vortices in green.

We report on efficient nonlinear generation of ultrafast, higher order "perfect" vortices at the green wavelength. Based on Fourier transformation of the higher order Bessel-Gauss (BG) beam generated through the combination of the spiral phase plate and axicon, we have transformed the Gaussian beam of the ultrafast Yb-fiber laser at 1060 nm into perfect vortices of power 4.4 W and order up to 6. Using single-pass second-harmonic generation (SHG) of such vortices in 5 mm long chirped MgO-doped, periodically poled congruent LiNbO3 crystal, we have generated perfect vortices at green wavelength (530 nm) with output power of 1.2 W and vortex order up to 12 at a single-pass conversion efficiency of 27%, independent of the orders. This is the highest single-pass SHG efficiency of any optical beams other than Gaussian beams. Unlike the disintegration of higher order vortices due to spatial walk-off effect in birefringent crystals, here, the use of the quasi-phase-matching process enables generation of high-quality vortices, even at higher orders. The green perfect vortices of all orders have temporal and spectral widths of 507 fs and 1.9 nm, respectively, corresponding to a time-bandwidth product of 1.02.

Generation of "perfect" vortex of variable size and its effect in angular spectrum of the down-converted photons.

The "perfect" vortex is a new class of optical vortex beam having ring radius independent of its topological charge (order). One of the simplest techniques to generate such beams is the Fourier transformation of the Bessel-Gauss beams. The variation in ring radius of such vortices require Fourier lenses of different focal lengths and or complicated imaging setup. Here we report a novel experimental scheme to generate perfect vortex of any ring radius using a convex lens and an axicon. As a proof of principle, using a lens of focal length f = 200 mm, we have varied the radius of the vortex beam across 0.3-1.18 mm simply by adjusting the separation between the lens and axicon. This is also a simple scheme to measure the apex angle of an axicon with ease. Using such vortices we have studied non-collinear interaction of photons having orbital angular momentum (OAM) in spontaneous parametric down-conversion (SPDC) process and observed that the angular spectrum of the SPDC photons are independent of OAM of the pump photons rather depends on spatial profile of the pump beam. In the presence of spatial walk-off effect in nonlinear crystals, the SPDC photons have asymmetric angular spectrum with reducing asymmetry at increasing vortex radius.

High-power, high-repetition-rate, Yb-fiber laser based femtosecond source at 355 nm.

We report on the development of a high-power, high-repetition-rate, fiber laser based source of ultrafast ultraviolet (UV) radiation. Using single-pass second-harmonic generation and subsequent sum-frequency generation (SFG) of an ultrafast ytterbium fiber at 1064 nm in 1.2 and 5 mm long bismuth triborate (BIBO) crystals, respectively, we have generated UV output power as high as 1.06 W at 355 nm with single-pass near-infrared-to-UV conversion efficiency of ∼22%. The source has output pulses of temporal and spectral widths of ∼576 fs and 1.6 nm, respectively, at 78 MHz repetition rate. For given crystals and laser parameters, we have experimentally verified that the optimum conversion efficiency of the SFG process requires interacting pump beams to have the same confocal parameters. We also present a systematic study on the power ratio of pump beams influencing the overall conversion of the UV radiation. The UV source has a peak-to-peak short-term power fluctuation of <2.2%, with a power drift of 0.76%/h associated to different loss mechanisms of the BIBO crystal at UV wavelengths. At tight focusing, the BIBO crystal has a broad angular acceptance bandwidth of (∼2 mrad·cm) for SFG of the femtosecond laser.

Frequency-doubling characteristics of high-power, ultrafast vortex beams.

We report on frequency-doubling characteristics of high-power, ultrafast optical vortex beams in a nonlinear medium. Based on single-pass second-harmonic generation (SHG) of optical vortices in 1.2 mm long bismuth triborate (BIBO) crystal, we studied the effect of different parameters influencing the SHG process in generating high-power and higher-order vortices. We observed a decrease in SHG efficiency with the order, which can be attributed to the increase of the vortex beam area with order. Like a Gaussian beam, optical vortices show focusing-dependent conversion efficiency. However, under similar experimental conditions, the optimum focusing condition for optical vortices is reached at tighter focusing with orders. We observed higher angular acceptance bandwidth in the case of optical vortices than that of a Gaussian beam; however, there is no substantial change in angular acceptance bandwidth with vortex order. We also observed that in the frequency-doubling process, the topological charge has negligible or no effect in temporal and spectral properties of the beams. We have generated ultrafast vortices at 532 nm with power as much as 900 mW and order as high as 12. In addition, we have devised a novel scheme based on linear optical elements to double the order of any optical vortex at the same wavelength.

All-periodically poled, high-power, continuous-wave, single-frequency tunable UV source.

We report on experimental demonstration of an all-periodically poled, continuous-wave (CW), high-power, single-frequency, ultra-violet (UV) source. Based on internal second-harmonic-generation (SHG) of a CW singly resonant optical parametric oscillator (OPO) pumped in the green, the UV source provides tunable radiation across 398.94-417.08 nm. The compact source comprising of a 25-mm-long MgO-doped periodically poled stoichiometric lithium tantalate (MgO:sPPLT) crystal of period Λ(SLT)=8.5 µm for OPO and a 5-mm-long, multi-grating (Λ(KTP)=3.3, 3.4, 3.6 and 3.8 µm), periodically poled potassium titanium phosphate (PPKTP) for intra-cavity SHG, provides as much as 336 mW of UV power at 398.94 nm, corresponding to a green-to-UV conversion efficiency of ∼6.7%. In addition, the singly resonant OPO (SRO) provides 840 mW of idler at 1541.61 nm and substantial signal power of 108 mW at 812.33 nm transmitted through the high reflective cavity mirrors. UV source provides single-frequency radiation with instantaneous line-width of ∼18.3 MHz and power >100 mW in Gaussian beam profile (ellipticity >92%) across the entire tuning range. Access to lower UV wavelengths requires smaller grating periods to compensate high phase-mismatch resulting from high material dispersion in the UV wavelength range. Additionally, we have measured the normalized temperature and spectral acceptance bandwidth of PPKTP crystal in the UV wavelength range to be ∼2.25°C·cm and ∼0.15 nm·cm, respectively.

IL-33 targeting attenuates intestinal mucositis and enhances effective tumor chemotherapy in mice.

Intestinal damage and severe diarrhea are serious side effects of cancer chemotherapy and constrain the usage of most such therapies. Here we show that interleukin-33 (IL-33) mediates the severe intestinal mucositis in mice treated with irinotecan (CPT-11), a commonly used cancer chemotherapeutic agent. Systemic CPT-11 administration led to severe mucosal damage, diarrhea, and body weight loss concomitant with the induction of IL-33 in the small intestine (SI). This mucositis was markedly reduced in mice deficient in the IL-33R (ST2(-/-)). Moreover, recombinant IL-33 exacerbated the CPT-11-induced mucositis, whereas IL-33 blockade with anti-IL-33 antibody or soluble ST2 markedly attenuated the disease. CPT-11 treatment increased neutrophil accumulation in the SI and adhesion to mesenteric veins. Supernatants from SI explants treated with CPT-11 enhanced transmigration of neutrophils in vitro in an IL-33-, CXCL1/2-, and CXCR2-dependent manner. Importantly, IL-33 blockade reduced mucositis and enabled prolonged CPT-11 treatment of ectopic CT26 colon carcinoma, leading to a beneficial outcome of the chemotherapy. These results suggest that inhibition of the IL-33/ST2 pathway may represent a novel approach to limit mucositis and thus improve the effectiveness of chemotherapy.

Hypo-estrogenemia in retinal vasculopathy due to primary antiphospholipid antibody syndrome.

PURPOSE: To report hypo-estrogenemic state in a case of recurrent vitreous hemorrhages due to primary antiphospholipid antibody syndrome. METHODS: Interventional case report. A 40-year-old woman presented with recurrent vitreous hemorrhages. Treated initially with laser photocoagulation followed by hormone replacement therapy. RESULTS: Cessation of vitreous hemorrhage since starting hormone replacement therapy (twenty months ago). CONCLUSIONS: This is the first documented case of hypo-estrogenemia in lupus anticoagulant retinopathy. The response of this condition to estrogen is worth exploring.

Hypo-Oestrogenaemia in retinal vasculopathy due to primary antiphospholipid antibody syndrome.

PURPOSE: To report hypo-estrogenemic state in a case of recurrent vitreous hemorrhages due to primary antiphospholipid antibody syndrome. METHODS: Interventional case report. A 40-year-old woman presented with recurrent vitreous hemorrhages. Treated initially with laser photocoagulation followed by hormone replacement therapy. RESULTS: Cessation of vitreous hemorrhage since starting hormone replacement therapy (twenty months ago). CONCLUSIONS: This is the first documented case of hypo-estrogenemia in lupus anticoagulant retinopathy. The response of this condition to estrogen is worth exploring. (Eur J Ophthalmol 2003; 13: 819-21).