424 research outputs found
Quantum-Referenced Spontaneous Emission Tomography
We present a method of tomography that measures the joint spectral phase
(JSP) of spontaneously emitted photon pairs originating from a largely
uncharacterized ``target" source. We use quantum interference between our
target source and a reference source to extract the JSP with four spectrally
resolved measurements, in a process that we call quantum-referenced spontaneous
emission tomography (Q-SpET). We have demonstrated this method on a photonic
integrated circuit for a target micro-ring resonator photon-pair source. Our
results show that spontaneously emitted photon pairs from a micro-ring
resonator are distinctively different from that of stimulated emission, and
thus cannot in general be fully characterized using classical stimulated
emission tomography without detailed knowledge of the source
High spectro-temporal purity single-photons from silicon micro-racetrack resonators using a dual-pulse configuration
Single-photons with high spectro-temporal purity are an essential resource
for quantum photonic technologies. The highest reported purity up until now
from a conventional silicon photonic device is 92% without any spectral
filtering. We have experimentally generated and observed single-photons with
98.0+-0.3 % spectro-temporal purity using a conventional micro racetrack
resonator and an engineered dual pump pulse
Quantifying Hidden Nonlinear Noise in Integrated Photonics
We present experimental and simulated results to quantify the impact of nonlinear noise in integrated photonic devices relying on spontaneous four-wave mixing. Our results highlight the need for design rule adaptations to mitigate the otherwise intrinsic reduction in quantum state purity. The best strategy in devices with multiple parallel photon sources is to strictly limit photon generation outside of the sources. Otherwise, our results suggest that purity can decrease below 40%
Integrate and scale:A source of spectrally separable photon pairs
Integrated photonics is a powerful contender in the race for a fault-tolerant quantum computer, claiming to be a platform capable of scaling to the necessary number of qubits. This necessitates the use of high-quality quantum states, which we create here using an all-around high-performing photon source on an integrated photonics platform. We use a photonic molecule architecture and broadband directional couplers to protect against fabrication tolerances and ensure reliable operation. As a result, we simultaneously measure a spectral purity of %, a pair generation rate of MHz mW, and an intrinsic source heralding efficiency of %. We also see a maximum coincidence-to-accidental ratio of . We claim over an order of magnitude improvement in the trivariate trade-off between source heralding efficiency, purity and brightness. Future implementations of the source could achieve in excess of % purity and heralding efficiency using state-of-the-art propagation losses
Effects of hand on EM absorption and antenna performances for internal handset PIFA
Cilj ovog istraĆŸivanja je analizirati uÄinke ruke na elektromagnetsku (EM) apsorpciju i funkcioniranje antene. U radu se procjenjuje EM apsorpcija pomoÄu specifiÄne brzine apsorpcije - specific absorption rate (SAR) u ljudskoj glavi i ukupne apsorbirane snage od strane korisnika. U radu se razmatraju parametri djelovanja antene ukljuÄujuÄi uÄinkovitost zraÄenja, ukupnu uÄinkovitost, pojaÄanje i ĆĄirinu frekvencijskog podruÄja. Analiza je provedena pomoÄu mobilnog telefona poloĆŸenog na obraz i s nagibom na obraz. Glavni dio istraĆŸivanja temelji se na finite-difference time-domain (FDTD) metodi. Rezultati pokazuju da su se SAR vrijednosti smanjile i da se ukupna snaga koju je korisnik apsorbirao brzo poveÄala zbog umetanja ruÄnog modela. Ruka korisnika takoÄer dovodi do znatnog smanjenja komunikacijskog uÄinka antene. Osim toga, predstavljena analiza daje neke korisne naznake za dizajn antene mobilnog telefona s obzirom na poloĆŸaj ruke.The aim of this investigation is to analyse the effects of hand on electromagnetic (EM) absorption and antenna performances. The EM absorption is evaluated by using the specific absorption rate (SAR) in the human head and total absorbed power by the user in this paper. The antenna performanceâs parameters comprising radiation efficiency, total efficiency, gain and bandwidth are considered in this investigation. The analysis was performed using mobile phone with a human head and hand model in both cheek and tilt positions. The main part of the investigation is based on the finite-difference time-domain (FDTD) method. The results show that the SAR values are decreased and total absorbed power by user increased rapidly due to insertion of hand model. The userâs hand also leads to degrade antennaâs communication performance considerably. Moreover, the presented analysis provides some useful indication to design handset antenna considering hand effects
Effects of hand on EM absorption and antenna performances for internal handset PIFA
Cilj ovog istraĆŸivanja je analizirati uÄinke ruke na elektromagnetsku (EM) apsorpciju i funkcioniranje antene. U radu se procjenjuje EM apsorpcija pomoÄu specifiÄne brzine apsorpcije - specific absorption rate (SAR) u ljudskoj glavi i ukupne apsorbirane snage od strane korisnika. U radu se razmatraju parametri djelovanja antene ukljuÄujuÄi uÄinkovitost zraÄenja, ukupnu uÄinkovitost, pojaÄanje i ĆĄirinu frekvencijskog podruÄja. Analiza je provedena pomoÄu mobilnog telefona poloĆŸenog na obraz i s nagibom na obraz. Glavni dio istraĆŸivanja temelji se na finite-difference time-domain (FDTD) metodi. Rezultati pokazuju da su se SAR vrijednosti smanjile i da se ukupna snaga koju je korisnik apsorbirao brzo poveÄala zbog umetanja ruÄnog modela. Ruka korisnika takoÄer dovodi do znatnog smanjenja komunikacijskog uÄinka antene. Osim toga, predstavljena analiza daje neke korisne naznake za dizajn antene mobilnog telefona s obzirom na poloĆŸaj ruke.The aim of this investigation is to analyse the effects of hand on electromagnetic (EM) absorption and antenna performances. The EM absorption is evaluated by using the specific absorption rate (SAR) in the human head and total absorbed power by the user in this paper. The antenna performanceâs parameters comprising radiation efficiency, total efficiency, gain and bandwidth are considered in this investigation. The analysis was performed using mobile phone with a human head and hand model in both cheek and tilt positions. The main part of the investigation is based on the finite-difference time-domain (FDTD) method. The results show that the SAR values are decreased and total absorbed power by user increased rapidly due to insertion of hand model. The userâs hand also leads to degrade antennaâs communication performance considerably. Moreover, the presented analysis provides some useful indication to design handset antenna considering hand effects
The Effect of Noise on the Response of a Vertical Cantilever Beam Energy Harvester
An energy harvesting concept has been proposed comprising a piezoelectric patch on a vertical cantilever beam with a tip mass. The cantilever beam is excited in the transverse direction at its base. This device is highly nonlinear with two potential wells for large tip masses, when the beam is buckled. For the pre-buckled case considered here, the stiffness is low and hence the displacement response is large, leading to multiple solutions to harmonic excitation that are exploited in the harvesting device. To maximise the energy harvested in systems with multiple solutions the higher amplitude response should be preferred. This paper investigates the amplitude of random noise excitation where the harvester is unable to sustain the high amplitude solution, and at some point will jump to the low amplitude solution. The investigation is performed on a validated model of the harvester and the effect is demonstrated experimentally
A Double Inverted F-Shape Patch Antenna for Dual-Band Operation
A double inverted F-shape patch antenna is presented for dual-band operation. The proposed antenna is comprised of circular and rectangular slots on a printed circuit board of 40âmmâĂâ40âmmâĂâ1.6âmm with a 50â⊠microstrip transmission line. Commercially available high frequency structural simulator (HFSS) based on the finite element method (FEM) has been adopted in this investigation. It has a measured impedance bandwidths (2â:â1 VSWR) of 18.53% on the lower band and 7.8% on the upper band, respectively. It has achieved stable radiation efficiencies of 79.76% and 80.36% with average gains of 7.82âdBi and 5.66âdBi in the operating frequency bands. Moreover, numerical simulations have been indicated as an important uniformity with measured results
Reactions of Rhenium and Manganese Carbonyl Complexes with 1,8-bis(diphenylphosphino)naphthalene: Ligand Chelation, CâH and CâP bond-cleavage Reactions
Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(Îș1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{Îș1:Îș1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(Îș2-PPh2C10H6PPh2)] (3). Compounds 1â3 are formed by ReâRe bond cleavage and PâC and CâH bond activation of the dppn ligand. Each of these three complexes have three CO groups arranged in facial fashion. Compound 1 contains a chelating cyclometalated diphenylnaphthylphosphine ligand and a terminally coordinated PPh2H ligand. Compound 2 consists of an orthometalated dppn-dioxide ligand coordinated in a Îș1:Îș1:η1-fashion via both the oxygen atoms and ortho-carbon atom of one of the phenyl rings. Compound 3 consists of an unchanged chelating dppn ligand and a terminal Cl ligand. Treatment of [Mn2(CO)8(MeCN)2] with a slight excess of dppn in refluxing toluene at 72 °C, gave the previously reported [Mn2(CO)8(ÎŒ-PPh2)2] (4), formed by cleavage of CâP bonds, and the new compound fac-[MnCl(CO)3(Îș2-PPh2C10H6PPh2)] (5), which has an unaltered chelating dppn and a terminal Cl ligand. In sharp contrast, reaction of [Mn2(CO)8(MeCN)2] with slight excess of dppn at room temperature yielded the dimanganese [Mn2(CO)9{Îș1-PPh2(C10H7)}] (6) in which the diphenylnaphthylphosphine ligand, formed by facile cleavage of one of the PâC bonds, is axially coordinated to one Mn atom. Compound 6 was also obtained from the reaction of [Mn2(CO)9(MeCN)] with dppn at room temperature. The XRD structures of complexes 1â3, 5, 6 are reported
Estimation of the SARS-CoV-2 specific reproduction number in SAARC countries: A 60-days Data-driven analysis
Novel coronavirus disease-2019 (COVID-19) was acknowledged as a global pandemic by WHO, which was first observed at the end of December 2019 in Wuhan city, China, caused by extreme acute respiratory syndrome coronavirus2 (SARS-CoV-2). According to the Weekly operation Update on COVID-19 (November 13, 2020) of the World Health Organization, more than 53 million confirmed cases are reported, including 1.3 million deaths. Various precautionary measures have been taken worldwide to reduce its transmission, and extensive researches are going on. The purpose of this analysis was to determine the initial number of reproductions (Ro) of the coronavirus of SAARC countries named Afghanistan, Bangladesh, India, Pakistan, Bhutan, Nepal, the Maldives, and Sri-Lanka for the first 60 days as the growth is exponential in the early 60 days. The reproduction numbers of coronavirus for Afghanistan, Bangladesh, India, Pakistan, Bhutan, the Maldives, Nepal, and Sri Lanka are 1.47, 3.86, 2.07, 1.43, 1.31, 3.22, 1.75, and 2.39 respectively. The basic reproduction number (R0) 3.86 for Bangladesh and 1.31 for Bhutan indicated that up to 60-days of the outbreak COVID-19, the epidemic was more severe in Bangladesh and less severe in Bhutan among all the SAARC countries. Our predictions can be helpful in planning alertness and taking the appropriate measures to monitor it
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