Single-photon light detection and ranging(lidar)offers single-photon sensitivity and picosecond timing resolution,which is desirable for high-precision three-dimensional(3 D)imaging over long distances.Despite importa...Single-photon light detection and ranging(lidar)offers single-photon sensitivity and picosecond timing resolution,which is desirable for high-precision three-dimensional(3 D)imaging over long distances.Despite important progress,further extending the imaging range presents enormous challenges because only a few echo photons return and are mixed with strong noise.Here,we tackled these challenges by constructing a high-efficiency,low-noise coaxial single-photon lidar system and developing a long-range-tailored computational algorithm that provides high photon efficiency and good noise tolerance.Using this technique,we experimentally demonstrated active single-photon 3 D imaging at a distance of up to 45 km in an urban environment,with a low return-signal level of^1 photon per pixel.Our system is feasible for imaging at a few hundreds of kilometers by refining the setup,and thus represents a step towards low-power and high-resolution lidar over extra-long ranges.展开更多
In this paper a quantum dialogue scheme is proposed by using N batches of single photons. The same secret message is encoded on each batch of single photons by the sender with two different unitary operations, and the...In this paper a quantum dialogue scheme is proposed by using N batches of single photons. The same secret message is encoded on each batch of single photons by the sender with two different unitary operations, and then the N batches of single photons are sent to the receiver. After eavesdropping check, the message is encoded on the one remaining batch by the receiver. It is shown that the intercept-and-resend attack and coupling auxiliary modes attack can be resisted more efficiently, because the photons are sent only once in our quantum dialogue scheme.展开更多
A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth betwee...A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth between the two parties. A round run for each photon makes the two parties each obtain a classical bit of information. So the efficiency of information transmission can be increased. The present scheme is practical and well within the present-day technology.展开更多
Leafy vegetable production under controlled environment using artificial lighting has many advantages over conventional greenhouses and open-field production.However,high initial investment and operation costs are res...Leafy vegetable production under controlled environment using artificial lighting has many advantages over conventional greenhouses and open-field production.However,high initial investment and operation costs are restricting the wide application of this technology.In order to design an optimal artificial lighting environment for lettuce production,effects of different combinations of light intensity,photoperiod,and light quality on growth,quality,photosynthesis,and energy use efficiency of lettuce(Lactuca sativa L.cv Ziwei)were investigated under a closed plant factory.Lettuce transplants were grown under photosynthetic photon flux density(PPFD)at 150μmol/m^(2)·s,200μmol/m^(2)·s,250μmol/m^(2)·s,and 300μmol/m^(2)·s provided by fluorescent lamps(FL)with a red to blue ratio(R:B ratio)of 1.8 and light-emitting diode(LED)lamps with R:B ratio of 1.2 and 2.2,in combination with photoperiod of 12 and 16 h/d.In order to examine the“long term”photosynthetic characteristics,net photosynthetic rates of hydroponic lettuce leaves were continuously measured for 2 d(15^(th) and 16^(th) day after transplanting)before harvest.There was no difference in leaf fresh weight(FW)between PPFD of 250μmol/m^(2)·s and 300μmol/m^(2)·s with photoperiod of 16 h/d,regardless of light quality,and same results showed in contents of nitrate,soluble sugar,and vitamin C,respectively.The results of continuous measurements of net photosynthetic rate of lettuce leaves before harvest indicated that plants grown at PPFD of 250μmol/m^(2)·s had consistently higher compared to those grown at PPFD of 300μmol/m^(2)·s.Combining the results from growth,photosynthesis,quality,and energy consumption,it can be concluded that PPFD at 250μmol/m^(2)·s with photoperiod of 16 h/d under LED with R:B ratio of 2.2 is a suitable light environment for maximum growth and high quality of commercial lettuce(cv.Ziwei)production under indoor controlled environment.展开更多
Objective To injvestigate the cerebral blood flow of patients with early syphilis Methods 99 Tc m ECD as brain perfusion imaging agent was used in single photon emission computed tomography (SPECT) for 32 p...Objective To injvestigate the cerebral blood flow of patients with early syphilis Methods 99 Tc m ECD as brain perfusion imaging agent was used in single photon emission computed tomography (SPECT) for 32 patients with early syphilis and 15 controls Visual analyses were made on every BSPECT image Results The 32 patients with early syphilis had general, patchy hypoperfusion of cerebral blood flow Fourteen of the 32 patients had 48 episodes of marked patchy hypoperfusion of rCBF The responsible areas of hypoperfusion in a patchy distribution involved the left frontal lobe (6 episodes), right frontal lobe (3), left parietal lobe (7), right parietal lobe (6), left temporal lobe (11), right temporal lobe (5), left occipital lobe (3), left basal ganglia (3), cerebellum (1), and nerve nuceus (1) No abnormality was found in the control group Conclusions Cerebral blood flow abnormalities exist in patients with early syphilis General patchy hypoperfusion on SPECT imaging is common展开更多
Single-photon avalanche diode(SPAD)arrays are solid-state detectors that offer imaging capabilities at the level of individual photons,with unparalleled photon counting and time-resolved performance.This fascinating t...Single-photon avalanche diode(SPAD)arrays are solid-state detectors that offer imaging capabilities at the level of individual photons,with unparalleled photon counting and time-resolved performance.This fascinating technology has progressed at a very fast pace in the past 15 years,since its inception in standard CMOS technology in 2003.A host of architectures have been investigated,ranging from simpler implementations,based solely on off-chip data processing,to progressively“smarter”sensors including on-chip,or even pixel level,time-stamping and processing capabilities.As the technology has matured,a range of biophotonics applications have been explored,including(endoscopic)FLIM,(multibeam multiphoton)FLIM-FRET,SPIM-FCS,super-resolution microscopy,time-resolved Raman spectroscopy,NIROT and PET.We will review some representative sensors and their corresponding applications,including the most relevant challenges faced by chip designers and end-users.Finally,we will provide an outlook on the future of this fascinating technology.展开更多
Purpose For the High Energy Photon Source(HEPS),a green-field fourth-generation storage ring light source,the prelimi-nary design report(PDR)was completed in 2018,when the accelerator physics design had been basically...Purpose For the High Energy Photon Source(HEPS),a green-field fourth-generation storage ring light source,the prelimi-nary design report(PDR)was completed in 2018,when the accelerator physics design had been basically finished.During the subsequent hardware and engineering design of the HEPS storage ring based on the PDR design,a few problems and challenges emerged,calling for modifications of the lattice.Method In this paper,we will introduce the background and reasons for the modifications and present the linear optics and simulation results for the nonlinear performance of the modified lattice of the HEPS storage ring.Result and conclusion The modified lattice satisfies the requirements from hardware and engineering design.展开更多
In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar ce...In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar cell,with a corresponding drop in efficiency.Here,using a detailed balance model,we show that limiting the emission angle of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38%with a single junction.The highest efficiencies are predicted for a thin,light trapping cell with an ideal back reflector,though the scheme is robust to a non-ideal back reflector.Comparison with a conventional planar cell geometry illustrates that limiting emission angle in a light trapping geometry not only allows for much thinner cells,but also for significantly higher overall efficiencies with an excellent rear reflector.Finally,we present ray-tracing and detailed balance analysis of two angular coupler designs,show that significant efficiency improvements are possible with these couplers,and demonstrate initial fabrication of one coupler design.展开更多
Background The diagnosis of Parkinson’s disease is presently based on non-specific symptoms. However, radionuclide dopamine transporters imaging can provide specific diagnostic tool for Parkinson’s disease. This st...Background The diagnosis of Parkinson’s disease is presently based on non-specific symptoms. However, radionuclide dopamine transporters imaging can provide specific diagnostic tool for Parkinson’s disease. This study was designed to investigate the effects of imaging of dopamine transporters with 99mTc-TRODAT-1 in early diagnosis or differential diagnosis of Parkinson’s disease.Methods Nine normal monkeys were used to establish N-methyl-4-phenyl-1, 2, 3, 6-tetra-hydropyridine (MPTP) hemi-Parkinsonian animal models, and they were subjected to imaging. Twenty-nine patients with Parkinson’s disease, 12 age-matched healthy volunteers, and 18 age-matched patients with Parkinson’s syndrome were investigated. Single photon emission computer tomography (SPECT) was performed 3 hours after intravenous injection of 740 MBq 99mTc-TRODAT-1. Striatum specific uptake of 99mTc-TRODAT-1 was calculated according to the ratio of striatum (ST) to cerebellum (CB)in dopamine transporters uptake.Results In normal monkeys, bilateral ratio of ST/CB was 2.34±0.41. After the injection of MPTP, uptake rate of 99mTc-TRODAT-1 at damaged region was much lower than that at the contralateral region, resulting in a significant difference in the ratio of ST/CB (right: ST/CB=1.73±0.35; left: ST/CB=1.90±0.30), especially in hemi-Parkinsonian model monkeys (right: ST/CB=1.29±0.17; left: ST/CB=1.80±0.33). The ratios of ST/CB were 1.57±0.17 and 1.61±0.14 for the right and left respectively in the healthy volunteers, 1.04±0.29 and 1.06±0.30 in the age-matched patients with Parkinson’s disease, and 1.56±0.17 and 1.59±0.18 in the age-matched patients with Parkinson’s disease syndrome. A significant difference was noted between group of Parkinson’s disease, normal controls and Parkinson’s disease syndrome. Conclusion The results suggest that 99mTc-TRODAT-1 dopamine transporters SPECT has clinical application value in early diagnosis or differential diagnosis of Parkinson’s disease.展开更多
基金National Key Research and Development Program of China(2018YFB0504300)National Natural Science Foundation of China(61771443)+4 种基金Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Anhui Initiative in Quantum Information TechnologiesShanghai Science and Technology Development Funds(18JC1414700)Fundamental Research Funds for the Central Universities(WK2340000083)Youth Innovation Promotion Association of CAS(2018492)。
文摘Single-photon light detection and ranging(lidar)offers single-photon sensitivity and picosecond timing resolution,which is desirable for high-precision three-dimensional(3 D)imaging over long distances.Despite important progress,further extending the imaging range presents enormous challenges because only a few echo photons return and are mixed with strong noise.Here,we tackled these challenges by constructing a high-efficiency,low-noise coaxial single-photon lidar system and developing a long-range-tailored computational algorithm that provides high photon efficiency and good noise tolerance.Using this technique,we experimentally demonstrated active single-photon 3 D imaging at a distance of up to 45 km in an urban environment,with a low return-signal level of^1 photon per pixel.Our system is feasible for imaging at a few hundreds of kilometers by refining the setup,and thus represents a step towards low-power and high-resolution lidar over extra-long ranges.
基金Project supported by the Science Foundation of Yanbian University of China （Grant No 2005-20）.
文摘In this paper a quantum dialogue scheme is proposed by using N batches of single photons. The same secret message is encoded on each batch of single photons by the sender with two different unitary operations, and then the N batches of single photons are sent to the receiver. After eavesdropping check, the message is encoded on the one remaining batch by the receiver. It is shown that the intercept-and-resend attack and coupling auxiliary modes attack can be resisted more efficiently, because the photons are sent only once in our quantum dialogue scheme.
基金Supported by the National Hi-Tech Research and Development Program of China (Grant No. 2006AA01Z419)the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90604023)+2 种基金the National Research Foundation for the Doctoral Program of Higher Education of China (Grant No. 20040013007)the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601)the Open Foundation of the State Key Laboratory of Information Security, Graduate University of the Chinese Academy of Sciences
文摘A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth between the two parties. A round run for each photon makes the two parties each obtain a classical bit of information. So the efficiency of information transmission can be increased. The present scheme is practical and well within the present-day technology.
基金supported by the National High Technology Research and Development Program(“863”Program)of China(2013AA103005).
文摘Leafy vegetable production under controlled environment using artificial lighting has many advantages over conventional greenhouses and open-field production.However,high initial investment and operation costs are restricting the wide application of this technology.In order to design an optimal artificial lighting environment for lettuce production,effects of different combinations of light intensity,photoperiod,and light quality on growth,quality,photosynthesis,and energy use efficiency of lettuce(Lactuca sativa L.cv Ziwei)were investigated under a closed plant factory.Lettuce transplants were grown under photosynthetic photon flux density(PPFD)at 150μmol/m^(2)·s,200μmol/m^(2)·s,250μmol/m^(2)·s,and 300μmol/m^(2)·s provided by fluorescent lamps(FL)with a red to blue ratio(R:B ratio)of 1.8 and light-emitting diode(LED)lamps with R:B ratio of 1.2 and 2.2,in combination with photoperiod of 12 and 16 h/d.In order to examine the“long term”photosynthetic characteristics,net photosynthetic rates of hydroponic lettuce leaves were continuously measured for 2 d(15^(th) and 16^(th) day after transplanting)before harvest.There was no difference in leaf fresh weight(FW)between PPFD of 250μmol/m^(2)·s and 300μmol/m^(2)·s with photoperiod of 16 h/d,regardless of light quality,and same results showed in contents of nitrate,soluble sugar,and vitamin C,respectively.The results of continuous measurements of net photosynthetic rate of lettuce leaves before harvest indicated that plants grown at PPFD of 250μmol/m^(2)·s had consistently higher compared to those grown at PPFD of 300μmol/m^(2)·s.Combining the results from growth,photosynthesis,quality,and energy consumption,it can be concluded that PPFD at 250μmol/m^(2)·s with photoperiod of 16 h/d under LED with R:B ratio of 2.2 is a suitable light environment for maximum growth and high quality of commercial lettuce(cv.Ziwei)production under indoor controlled environment.
文摘Objective To injvestigate the cerebral blood flow of patients with early syphilis Methods 99 Tc m ECD as brain perfusion imaging agent was used in single photon emission computed tomography (SPECT) for 32 patients with early syphilis and 15 controls Visual analyses were made on every BSPECT image Results The 32 patients with early syphilis had general, patchy hypoperfusion of cerebral blood flow Fourteen of the 32 patients had 48 episodes of marked patchy hypoperfusion of rCBF The responsible areas of hypoperfusion in a patchy distribution involved the left frontal lobe (6 episodes), right frontal lobe (3), left parietal lobe (7), right parietal lobe (6), left temporal lobe (11), right temporal lobe (5), left occipital lobe (3), left basal ganglia (3), cerebellum (1), and nerve nuceus (1) No abnormality was found in the control group Conclusions Cerebral blood flow abnormalities exist in patients with early syphilis General patchy hypoperfusion on SPECT imaging is common
基金supported in part by the Swiss National Science Foundation Grant 166289.The authors would like to thank Scott Lindner and Arin Can Ulku(EPFL AQUA)for their kind assistance.
文摘Single-photon avalanche diode(SPAD)arrays are solid-state detectors that offer imaging capabilities at the level of individual photons,with unparalleled photon counting and time-resolved performance.This fascinating technology has progressed at a very fast pace in the past 15 years,since its inception in standard CMOS technology in 2003.A host of architectures have been investigated,ranging from simpler implementations,based solely on off-chip data processing,to progressively“smarter”sensors including on-chip,or even pixel level,time-stamping and processing capabilities.As the technology has matured,a range of biophotonics applications have been explored,including(endoscopic)FLIM,(multibeam multiphoton)FLIM-FRET,SPIM-FCS,super-resolution microscopy,time-resolved Raman spectroscopy,NIROT and PET.We will review some representative sensors and their corresponding applications,including the most relevant challenges faced by chip designers and end-users.Finally,we will provide an outlook on the future of this fascinating technology.
基金supported by the High Energy Photon Source(HEPS),a major national science and technol-ogy infrastructurethe National Natural Science Foundation of China(No.11922512)+1 种基金Youth Inno-vation Promotion Association of Chinese Academy of Sciences(No.Y201904)Bureau of Frontier Sciences and Education of Chinese Academy of Sciences(No.QYZDJ-SSW-SLH001)
文摘Purpose For the High Energy Photon Source(HEPS),a green-field fourth-generation storage ring light source,the prelimi-nary design report(PDR)was completed in 2018,when the accelerator physics design had been basically finished.During the subsequent hardware and engineering design of the HEPS storage ring based on the PDR design,a few problems and challenges emerged,calling for modifications of the lattice.Method In this paper,we will introduce the background and reasons for the modifications and present the linear optics and simulation results for the nonlinear performance of the modified lattice of the HEPS storage ring.Result and conclusion The modified lattice satisfies the requirements from hardware and engineering design.
基金Thanks to D Callahan,M Sheldon and J van de Groep for insightful discussions and advice on the manuscript.The authors also found advice from O Miller on handling non-radiative recombination,R Briggs on mode structure calculations,J Zipkin on numerical methods and C Eisler on internal fluorescence yield derivations extremely helpful.The authors are grateful for technical assistance from G Vollenbroek.The Caltech researchers are supported by the‘Light-Material Interactions in Energy Conversion’Energy Frontier Research Center funded by the US Department of Energy,Office of Science,Office of Basic Energy Sciences under grant DE-SC0001293(EK and HA).EK also acknowledges the support of the Resnick Sustainability Institute.Researchers of the Center for Nanophotonics at AMOLF are supported by the research program of FOM which is financially supported by NWO and by the European Research Council.
文摘In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar cell,with a corresponding drop in efficiency.Here,using a detailed balance model,we show that limiting the emission angle of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38%with a single junction.The highest efficiencies are predicted for a thin,light trapping cell with an ideal back reflector,though the scheme is robust to a non-ideal back reflector.Comparison with a conventional planar cell geometry illustrates that limiting emission angle in a light trapping geometry not only allows for much thinner cells,but also for significantly higher overall efficiencies with an excellent rear reflector.Finally,we present ray-tracing and detailed balance analysis of two angular coupler designs,show that significant efficiency improvements are possible with these couplers,and demonstrate initial fabrication of one coupler design.
文摘Background The diagnosis of Parkinson’s disease is presently based on non-specific symptoms. However, radionuclide dopamine transporters imaging can provide specific diagnostic tool for Parkinson’s disease. This study was designed to investigate the effects of imaging of dopamine transporters with 99mTc-TRODAT-1 in early diagnosis or differential diagnosis of Parkinson’s disease.Methods Nine normal monkeys were used to establish N-methyl-4-phenyl-1, 2, 3, 6-tetra-hydropyridine (MPTP) hemi-Parkinsonian animal models, and they were subjected to imaging. Twenty-nine patients with Parkinson’s disease, 12 age-matched healthy volunteers, and 18 age-matched patients with Parkinson’s syndrome were investigated. Single photon emission computer tomography (SPECT) was performed 3 hours after intravenous injection of 740 MBq 99mTc-TRODAT-1. Striatum specific uptake of 99mTc-TRODAT-1 was calculated according to the ratio of striatum (ST) to cerebellum (CB)in dopamine transporters uptake.Results In normal monkeys, bilateral ratio of ST/CB was 2.34±0.41. After the injection of MPTP, uptake rate of 99mTc-TRODAT-1 at damaged region was much lower than that at the contralateral region, resulting in a significant difference in the ratio of ST/CB (right: ST/CB=1.73±0.35; left: ST/CB=1.90±0.30), especially in hemi-Parkinsonian model monkeys (right: ST/CB=1.29±0.17; left: ST/CB=1.80±0.33). The ratios of ST/CB were 1.57±0.17 and 1.61±0.14 for the right and left respectively in the healthy volunteers, 1.04±0.29 and 1.06±0.30 in the age-matched patients with Parkinson’s disease, and 1.56±0.17 and 1.59±0.18 in the age-matched patients with Parkinson’s disease syndrome. A significant difference was noted between group of Parkinson’s disease, normal controls and Parkinson’s disease syndrome. Conclusion The results suggest that 99mTc-TRODAT-1 dopamine transporters SPECT has clinical application value in early diagnosis or differential diagnosis of Parkinson’s disease.
