Multi-photon quantum cutting in Gd_(2)O_(2)S:Tm^(3+) to enhance the photo-response of solar cells

Conventional photoluminescence(PL)yields at most one emitted photon for each absorption event.Downconversion(or quantum cutting)materials can yield more than one photon by virtue of energy transfer processes between luminescent centers.In this work,we introduce Gd2O2S:Tm^(3+) as a multi-photon quantum cutter.It can convert near-infrared,visible,or ultraviolet photons into two,three,or four infrared photons of,1800 nm,respectively.The cross-relaxation steps between Tm^(3+) ions that lead to quantum cutting are identified from(time-resolved)PL as a function of the Tm^(3+) concentration in the crystal.A model is presented that reproduces the way in which the Tm^(3+) concentration affects both the relative intensities of the various emission lines and the excited state dynamics and providing insight in the quantum cutting efficiency.Finally,we discuss the potential application of Gd2O2S:Tm^(3+) for spectral conversion to improve the efficiency of next-generation photovoltaics.

Efficient Near-Infrared Quantum Cutting in Tm3＋/yb3＋ Codoped LiYF4 Single Crystals for Solar Photovoltaic

Downconversion （DC） with emission of two near-infrared photons about 1000 nm for each blue photon absorbed was obtained in thulium （Tm3＋） and ytterbium （Yb3＋） codoped yt- trium lithium fluoride （LiYF4） single crystals grown by an improved Bridgman method. The luminescent properties of the crystals were measured through photoluminescence excitation, emission spectra and decay curves. Luminescence between 960 and 1050 nm from yb3＋： 2Fs/2--＋2FT/2 transition, which was originated from the DC from Tm3＋ ions to Yb3＋ ions, was observed under the excitation of blue photon at 465 nm. Moreover, the energy transfer processes were studied based on the Inokuti-Hirayama model, and the results indicated that the energy transfer from Tm3＋ to Yb3＋ was an electric dipole-dipole interaction. The max- imum quantum cutting efficiency approached with 0.49mo1% Tm3＋ and 5.99mo1% Yb3＋. increasing the energy efficiency of crystalline energy part of the solar spectrum. up to 167.5% in LiYF4 single crystal codoped Application of this crystal has prospects for Si solar cells by photon doubling of the high

Near-infrared Quantum Cutting in Pr^(3+)-Yb^(3+) Co-doped Oxyfluoride Glass Ceramics Containing CaF_2 Nanocrystals

The Pr3＋-Yb3＋ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of pr3＋-yb3＋ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glass- ceramics is CaF2 nanocrystal sized at 30 nm. Energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） have proved the incorporation of Pr3＋ and Yb3＋ into CaF2 nanocrystal lattice, Near-infrared quantum cutting involving Yb3＋ 980 nm and 1 015 tun （2F5/2→2F7/2） emission has been achieved upon the excitation of the 3P0 energy level of Pr3＋ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb3＋ concentration, and the optimal quantum efficiency reaches 191%.

Concentration effect of the near-infrared quantum cutting of 1788-nm luminescence of Tm^(3+) ion in(Y_(1-x)Tm_x)_3Al_5O_(12) powder phosphor

In the present paper, the concentration effect of near-infrared quantum cutting of Tm3＋ ion in （Y1-xTmx）3Al5Ol2 powder phosphor is studied by means of experiments and calculations. In addition, the absorption spectra, visible-to-near- infrared excitation and emission spectra, and fluorescence lifetimes are measured. It is found that （Y1-xTmx）3Al5O12 powder phosphor has a strong four-photon near-infrared quantum cutting luminescence of 1788.0-nm 3F4 →3H6 fluores- cence of Tm3＋ ion, when excited by 357.0-nm light. It is also found that the up-limit of the four-photon near-infrared quantum cutting luminescence efficiency of （Yo.700Tmo.300）3Al5 O12 powder phosphor is approximately 302.19%. To the knowledge of the authors, this is the first time that a near-infrared quantum cutting efficiency up-limit exceeding 300% has been reported. The results of this manuscript are valuable in aiding the probing of the new generation Ge solar cell.

Infrared quantum cutting conversion luminescence of Tb(0.7)Yb(3):FOV

The infrared quantum cutting of oxyfluoride nanophase vitroceramics Tb（0.7）Yb（3）：FOV has been studied in the present paper. The actual quantum cutting efficiency formula calculated from integral fluorescence intensity is extended to the case of Tb（0.7）Yb（3）：FOV. The visible and the infrared fluorescence spectra and their integral fluorescence intensities are measured from static fluorescence experiment. Lifetime curve is measured from dynamic fluorescence experiment. It is found that the total actual quantum cutting efficiency n of the excited 5D4 level is about 93.7%, and that of excited （5D3, 5G6） levels is 93.5%. It is also found that the total theoretical quantum cutting efficiency upper limit ？~x^Yb of the 485.5 nm excited 5D4 level is about 121.7%, and that of 378.5 nm excited （5D3, 5G6） levels is 137.2%.

Influence of multi-photon pulses on practical differential-phase-shift quantum key distribution

The influence of multi-photon pulses on practical differcBtial-phase-shift quantum key distribution （DPS-Qt（D） is analysed. We have estimated the information which Eve obtained by PNS （photon-number splitting） attack and BS （beam splitting） attack. The result indicates that the PNS attack and BS attack will not limit the transmission distance as long as we select an appropriate mean photon number. Also, the maximum mean photon number under BS attack in practical DPS-QKD system and the set of practical assumptions about Eve＇s capabilities are presented.

Preparation of multi-photon Fock states and quantum entanglement properties in circuit QED

We demonstrate the controllable generation of multi-photon Fock states in circuit quantum electrodynamics （circuit QED）. The external bias flux regulated by a counter can effectively adjust the bias time on each superconducting flux qubit so that each flux qubit can pass in turn through the circuit cavity and thereby avoid the effect of decoherence. We further investigate the quantum correlation dynamics of coupling superconducting qubits in a Fock state. The results reveal that the lower the photon number of the light field in the number state, the stronger the interaction between qubits is, then the more beneficial to maintaining entanglement between qubits it will be.

Squeezing Effects on the Estimation Precision of Cut off Frequency

We study the behavior of quantum Fisher information for a qubit probe that is interacting with a squeezed thermal environment. We analyzed the effect of squeezing parameters on the dynamics of quantum Fisher information which affects the optimal precision of the estimation parameter. We show that the squeezed field may offer a significant role in the precise measurement of the parameter cut-off frequency which is linked to the environment correlation time. Our results may be useful in quantum metrology, communication, and quantum estimation processes.

Heisenberg＇s Versus Von Neumann＇s Indeterminism of Quantum Mechanics

Irreducible indeterminism is considered by most physicists as an ontological interpretation of quantum mechanics, which attributes inherent indeterminism to elementary paJcticles. This view was extrapolated by von Neumann from the atomocosm to the entire universe. Heisenberg proposed an epistemic interpretation, postulating that indeterminism stems from ambivalent detection systems, rather than being a characteristic of elementary particles Transformative detection that inherently affects the measured phenomena is responsible for the indeterminism in the atomocosm. As the same does not generally hold true in the macrocosm, this discrepancy has led to the notion of the Heisenberg cut. As explained by Heisenberg＇s microscope example, high-energy light can displace electrons from their atomic shells in the atomocosm, but would not induce the same effect on objects in the macrocosm, thus rendering such detection neutral. Therefore, detection systems are ambivalent in that they can be transformative under the cut and neutral otherwise. Device variation is found under and above the cut and is the essential cause of outcome variability in the macrocosm. Thus, two completely different categories of indeterminism exist simultaneously under the Heisenberg cut, but only one is found above the cut, known as measurement variations of devices. Experimental exploration of elementary paJcticle behaviors is possible only with the help of detection systems. If these systems affect particle characteristics in any way, this would be sufficient to explain the irreducible quantum mechanical indeterminism. Consequently, the true behavior of elementary particles, whether indeterminist or determinist, would never be detectable. Above the cut, on the other hand, variations in device performance are inevitable, due to reducible perturbing factors, inducing measurement wJciation of devices Heisenberg discovered a general principle of ambivalent detection systems, which can also be found in the macrocosm. In the Wilson Cloud Chamber, vapor is an ambivalent detection system, since high-energy charged particles would produce straight tracks, whereas those of lower energy would leave an irregular trace. According to the epistemic interpretation, von Neumann＇s extrapolation of irreducible quantum mechanical indeterminism to the entire universe would not be necessary, thereby avoiding the uncomfortable conclusion that the entire universe is based on indeterminism

分布式量子计算研究进展

量子比特的高效拓展是量子计算获取量子加速优势需要解决的基本问题,分布式量子计算(DQC)因其高度可行性和灵活性,成为解决量子比特拓展问题的关键技术之一。根据芯片间通信方式的不同,分布式量子计算可以分为基于量子隐形传态和基于量子线路拆分的分布式量子计算两种类型,前者主要面向容错量子计算,而后者被认为可在中等规模含噪声量子(NISQ)时代有效提升量子计算机算力。从长远角度来看,作为量子网络的主要应用之一,分布式量子计算可以更好地整合接入量子网络的海量量子计算机以解决高难度问题。首先介绍了分布式量子计算的来源和类型,在此基础上,给出了两类分布式量子计算的基本原理和发展状况,以及关注度较高的应用算法和编译优化方法。

Efficient near-infrared quantum cutting in Tb3＋,Yb3＋ codoped LuPO_4 phosphors

Tb^（3＋） and Yb^（3＋） codoped LuPO_4 phosphors were prepared by the reverse-strike co-precipitation method.The obtained LuPO_4：Tb^（3＋）,Yb^（3＋） phosphors were characterized by X-ray diffraction（XRD）,photoluminescence（PL） spectra and decay kinetics to understand the near-infrared quantum cutting（QC） phenomena.The XRD results showed that all the phosphors exhibited good crystallinity and had a pure tetragonal phase of LuPO_4.The experimental results showed that the strong green emission around 545 nm from Tb^（3＋）（~5D_4→~7F_5） and near-infrared（NIR） emission at 1003 nm from Yb^（3＋）（~2F_（5/2）→~2F_（7/2）） of LuPO_4：Tb^（3＋）,Yb^（3＋）phosphors were observed under 489 nm excitation,respectively.The Yb^（3＋） concentration dependence on luminescent properties and lifetimes of both the visible and NIR emissions were also investigated.The quenching concentration of Yb^（3＋） ions approached as high as 10 mol.%.The excellent luminescence properties of the LuPO_4：Tb^（3＋）,Yb^（3＋） indicated its potential application in improving the energy conversion efficiency of the silicon based solar cells by converting one blue photon to two NIR ones.

Efficient near-infrared quantum cutting by Ce^(3+)-Yb^(3+) couple in GdBO_3 phosphors

Ce3＋ and Yb3＋ co-activated GdBO3 phosphors were prepared by a conventional solid-state reaction method. X-ray powder diffraction, photoluminescent spectra and decay curves were used to characterize their structural and luminescent properties. An efficient near-infrared （NIR） quantum cutting （QC） from the phosphors was observed, which involved the emission of two low-energy NIR photons （around 971 nm） from an absorbed ultra-violet （UV） photon at 358 nm via a cooperative energy transfer （CET） from Ce3＋ to Yb3＋ ions. The theoretical quantum efficiency was calculated and the maximum efficiency approached up to 164% before reaching the critical concentration quenching threshold. Our results demonstrated that these phosphors might find potential application in improving the efficiency of silicon based solar cells.

Monolayer single crystal two-dimensional quantum dots via ultrathin cutting and exfoliating

Two-dimensional(2D)atomically thin quantum dots(QDs)possess extraordinary electrical and optical properties.However,fabricating high quality 2D QDs via a universal and reliable technique remains a challenge.Here,we report a simple strategy to prepare high quality,monolayer single crystal 2D QDs via ultrathin cutting 2D bulk single crystals by ultramicrotome,followed by an exfoliation process.The as-prepared 2D QDs have pristine surface,high quality,high monolayer yield and high photoluminescence quantum yield(the highest photoluminescence quantum yield of WS2 is18%),which can be used as promising,low toxic,biocompatible,and good cell-permeability fluorescent labeling agents for in vitro imaging.

基于电路切割方法的并行量子模拟方法

量子计算在解决传统计算难题方面展现了巨大潜力,但由于其高错误率和噪声问题,经典模拟成为验证其性能的重要手段。然而,量子的叠加和纠缠特性带来了模拟上的巨大挑战,尤其是在内存受限的情况下。尽管电路切割方法能够将大规模量子电路分解为更小的计算任务,减轻计算压力,先前的研究主要关注其在量子计算机上的应用,未充分考虑其在量子电路模拟中的效果。论文研究填补了这一空白,提出了基于启发式切割算法和子电路状态向量复用的优化方案,以应对模拟中的内存限制。通过引入全局计算成本的考量和整数规划模型,提出的启发式方法不仅优化了切割过程,还结合了子电路状态向量复用技术,以减少重复计算和内存占用。实验结果显示,与当前流行的电路切割方法相比,所提出方法在提升模拟速度的同时显著降低了内存需求,有效应对了量子电路模拟中的挑战。在经典量子电路的测试中总体平均加速达到了46%。

Quantum cutting in Gd_2SiO_5:Eu^(3+) by VUV excitation

The emission and excitation spectra of Gd2SiO5: Eu3+ were investigated using the VUVbeam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results werediscussed in the frame of visible quantum cutting process involved in Gd3+-Eu3+ system. Upon di-rect excitation into the 6GJ states of Gd3+, two visible photon emissions from Eu3+ were observed.Cursory evaluation proved that Gd2SiO5: Eu3+ is an efficient visible quantum cutter.

Er^(3+),Yb^(3+)共掺杂的NaYF_4荧光粉的制备及下转换发光研究

采用高温固相法合成了Er3+、Yb3+共掺杂的NaYF4荧光粉。XRD测量数据表明合成的样品为纯相。测量了样品的激发谱和发射谱,证明377 nm的紫外光通过量子剪裁的形式将能量传递给一个Yb3+,发射一个975 nm的红外光子,再从4F9/2能级跃迁到基态发射一个红外光子。测量了377 nm激发下,监测541 nm的发光寿命曲线,计算得到最大的量子效率为126.35%。通过监测Yb3+的975 nm的近红外发射,证明了Er3+的4F7/2和2H11/2能级通过下转换的形式将吸收的485 nm和519 nm的能量传递给Yb3+。这种将Er3+在可见光波段的多种光子能量传递给Yb3+发射975 nm的近红外光子的思想在以前的研究中从未被提出。

用于GaAs太阳能电池的NaYF_4中Tb^(3+)-Er^(3+)耦合对的光谱转换

观测到一种以Tb3+-Er3+进行光谱转换的量子剪裁现象。一个高能紫外光子(Tb3+的7F6→5L1)被量子剪裁成两个低能光子:一个是近红外光子(Er3+的4I9/2→4I15/2),另一个是蓝色光子(Tb3+的5D4→7F6),它们两个都可以被GaAs太阳能电池有效地吸收。量子剪裁效率高达188%,接近理论极限的200%。从Tb3+(5L1→5D4)到Er3+(4 I15/2→4 I9/2)的能量传递的能量失配是237 cm-1,比NaYF4中的声子能400 cm-1小,能量传递是近共振的。Tb3+施主间的能量迁移可以近似地用扩散模型处理,从Tb3+-Er3+对之间能量传递的初始过程发现,偶极-偶极相互作用占主导地位。

闪烁晶体的发光研究进展

概述了近年来闪烁体发光研究的进展 ,主要介绍用于未来高能物理实验的新型闪烁体发光机理研究 ,选取我们在研究BaF2 ,BaF2 ∶RE ,CeF3 以及PbWO4中的一些新进展。重点谈及三点 :(1)在BaF2 的“价带→芯带”跃迁发光研究基础上进行稀土 (Gd3 + Eu3 + )掺杂时观察到的量子剪裁以及对多光子发光的新思考 ;(2 )CeF3 晶体发光的级联能量传递中 ,Ce3 + (2 90nm发射带 )与缺陷发光中心 (340nm发射带 )间能量传递及其传递效率的温度依赖 ;(3)PbWO4晶体的发光中心研究中 ,提出以“WO2 -4+Oi”绿光中心替代“WO3 +F”中心观点的依据。同时也简介了医用闪烁体的最新进展。

Ce^(3+)和Yb^(3+)共掺杂的Y_3Al_5O_(12)可见及量子剪裁近红外发光性质

室温下观察了YAG∶Ce和YAG∶Ce,Yb材料在可见以及近红外区域的发光特性,并通过对Ce3+的5d能级辐射跃迁寿命以及Yb3+的2F5/2能级布居时间和辐射跃迁寿命的比较研究,提出了光诱导的电荷转移态以及电荷转移辐射跃迁的能量传递机制,同时借助于能级图描述了从Ce3+到Yb3+的量子剪裁近红外发光过程。

NaGdF_4:Eu^(3+)的结构和VUV荧光性质

利用水热方法合成了纯度较高的六方结构的 NaGdF4，在氧气存在条件下 950℃加热处理可以使其转变为 CaF2型立方结构。在真空紫外光激发下，六方结构的 NaGdF4∶ Eu3＋中的 Gd3＋离子吸收一个光子，并将能量分两步传递给 Eu3＋离子，发生双光子发射。立方结构的 NaGdF4∶ Eu3＋中存在有一定量的氧离子取代缺陷，使 Gd3＋离子 4f-5d跃迁移到 177nm附近，这与惰性气体放电产生的真空紫外光波长一致。