共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Takesue H. Fukuda T. Tsuchizawa T. Watanable K. Yamada Y. Tokura S. Itabashi 《Optics and Spectroscopy》2010,108(2):160-164
We report the first entanglement generation experiments using silicon waveguide. Using highly efficient spontaneous four-wave
mixing in a 1.09 cm long silicon nanowire waveguide at room temperature, we successfully generated high-purity time-bin and
polarization entangled photon pairs in the 1.5 μm band. We expect this entanglement source will solve the problems of previous
telecom-band entanglement sources. 相似文献
2.
Entangled photon-pair sources based on spontaneous parametric processes are widely used in photonic quantum information experiments. In this paper, we clarify the relationship between average photon-pair number and the visibility of two-photon interference (TPI) using those entanglement sources. We consider sources that generate distinguishable and indistinguishable entangled photon pairs, assuming coincidence measurements that use threshold detectors. We present formulas for the TPI visibility of a polarization entanglement that take account of all the high-order multi-pair emission events. Moreover, we show that the formulas can be approximated with simple functions of the average pair number when the photon collection efficiency is small. As a result, we reveal that an indistinguishable entangled pair provides better visibility than a distinguishable one. 相似文献
3.
《中国光学快报(英文版)》2016,(6)
A multichannel polarization-entangled photon-pair source in an Mg O-doped periodically poled lithium niobate(Mg O:PPLN) waveguide is proposed. Based on type I quasi-phase-matched spontaneous parametric down conversion in a single Mg O: PPLN waveguide placed inside a Sagnac interferometer and pumped by monochromatic light, a source capable of supporting tens to hundreds of channels of polarization-entangled photon pairs in fiber communication bands simultaneously can be achieved. An inherent channel switch of this source is investigated,which will be significant for future entanglement distribution networks. 相似文献
4.
自发参量下转换过程制备的纠缠光源在量子光学及其相关领域有着广泛的应用.本文利用780 nm的分布式布拉格反射镜激光二极管抽运一块长10 mm的Ⅱ类准相位匹配的周期极化铌酸锂波导,产生了偏振正交的频率反关联纠缠光子对.通过实验结果与理论的完美结合得到,当进入波导的抽运光功率为44.9 mW时,下转换双光子对的产生速率为1.87×10~7s~(-1).利用单色仪对下转换光子的频谱进行分析,得到信号和闲置光子的中心波长分别为1561.43 nm和1561.45 nm,频谱宽度为3.62 nm和3.60 nm,双光子符合包络宽度约为3.18 nm,可以得到双光子的频率纠缠度为1.131.00,表征了双光子的频率纠缠特性.利用Hong-Ou-Mandel干涉仪测量双光子的二阶量子干涉特性,测得的干涉可见度为96.1%,干涉图谱的凹陷宽度为1.47 ps. 相似文献
5.
M. Larqué A. Beveratos I. Robert-Philip 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):119-125
We report on a scheme for the creation of time-bin entangled states out of two subsequent single photons. Both photons arrive
on the same input port of a beamsplitter and the situation in which the photons leave the beamsplitter on different output
ports is post-selected. We derive a full quantum mechanical analysis of such time-bin entanglement for emitters subject to
uncorrelated dephasing processes and apply this model to sequential single photons emerging from a single semiconductor quantum
dot. Our results indicate that the visibility of entanglement is degraded by decoherence effects in the quantum dot, but can
be restored by use of CQED effects, namely the Purcell effect. 相似文献
6.
M. Genovese C. Novero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):109-113
We propose a quantum transmission based on bi-photons, which are doubly-entangled both in polarisation and phase. This scheme
finds a natural application in quantum cryptography, where we show that an eventual eavesdropper is bound to introduce a larger
error on the quantum communication than for a single entangled bi-photon communication, when he steels the same information.
Received 23 July 2001 / Received in final form 30 November 2001 Published online 24 September 2002 相似文献
7.
8.
Y. Zhang K. Kasai M. Watanabe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):361-366
We propose a novel quantum switch teleportation with a continuous variable, which can teleport a quantum state to two different
receivers alternatively, using a pair of two-mode squeezed lights as the quantum switching to manipulate the transmission
route. In this scheme, the EPR entangled beams shared by sender and receivers are produced by mixing a pair of two-mode squeezed
lights on one beamsplitter and separating them by using a polarizing beam splitter. The teleportation capability of this system
is examined by the criteria proposed by Ralph and Lam [#!ralph!#] from a small signal quantum optical point of view.
Received 20 May 2002 / Received in final form 29 July 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: zhangyun@crl.go.jp 相似文献
9.
Logic qubit plays an important role in current quantum communication. In this paper, we propose an efficient entanglement concentration protocol (ECP) for a new kind of logic Bell state, where the logic qubit is the concatenated Greenber–Horne–Zeilinger (C-GHZ) state. Our ECP relies on the nondemolition polarization parity check (PPC) gates constructed with cross-Kerr nonlinearity, and can distill one pair of maximally entangled logic Bell state from two same pairs of less-entangled logic Bell states. Benefit from the nondemolition PPC gates, the concentrated maximally entangled logic Bell state can be remained for further application. Moreover, our ECP can be repeated to further concentrate the less-entangled logic Bell state. By repeating the ECP, the total success probability can be effectively increased. Based on above features, this ECP may be useful in future long-distance quantum communication. 相似文献
10.
We report on efficient generation of 1550-nm photon pairs in a periodically poled lithium niobate waveguide using the spontaneous parametric down-conversion process. Such photon pairs are expected to find applications in fiber-based long-distance quantum communication. Pumping the waveguide with a pulsed semiconductor laser with a pulse rate of 800 kHz and a maximum average pump power of 50 μW, we obtain a coincidence rate of 600 s−1. Despite only two single-photon detectors are used, we gain some information about the photon-number distribution. Our measurements are found to be in agreement with a Poissonian photon-pair distribution, but clearly differ from the expected outcomes for both conventional and two-mode squeezed states, the latter corresponding to a thermal photon-pair distribution. The Poissonian photon-pair distribution is also explained by comparing the coherence time of the pump light and of the detected photons. An average of 0.9 generated photon pairs per pulse can thus be inferred. 相似文献
11.
We propose a scheme of entangling two photons from two separated sources. Our proposal which is inspired by the time-bin entanglement
developed recently, provides a novel alternative for revealing contradiction between quantum nonlocality and local realism
based on two independent single photon sources. 相似文献
12.
E.G. Mishchenko M. Patra C.W.J. Beenakker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):289-297
A theory is presented for the frequency dependence of the power spectrum of photon current fluctuations originating from a
disordered medium. Both the cases of an absorbing medium (“grey body”) and of an amplifying medium (“random laser”) are considered
in a waveguide geometry. The semiclassical approach (based on a Boltzmann-Langevin equation) is shown to be in complete agreement
with a fully quantum mechanical theory, provided that the effects of wave localization can be neglected. The width of the
peak in the power spectrum around zero frequency is much smaller than the inverse coherence time, characteristic for black-body
radiation. Simple expressions for the shape of this peak are obtained, in the absorbing case, for waveguide lengths large
compared to the absorption length, and, in the amplifying case, close to the laser threshold.
Received 8 August 2000 相似文献
13.
C.P. Sun X.F. Liu D.L. Zhou S.X. Yu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):85-92
To account for the phenomenon of quantum decoherence of a macroscopic object, such as the localization and disappearance of
interference, we invoke the adiabatic quantum entanglement between its collective states (such as that of the center-of-mass
(CM)) and its inner states based on our recent investigation. Under the adiabatic limit where motion of the CM does not excite
the transition of inner states, it is shown that the wave function of the macroscopic object can be written as an entangled
state with correlation between adiabatic inner states and quasi-classical motion configurations of the CM. Since the adiabatic
inner states are factorized with respect to each component of the macroscopic object, this adiabatic separation can induce
the quantum decoherence. This observation thus provides us with a possible solution to the Schr?dinger cat paradox.
Received 24 October 2000 and Received in final form 8 March 2001 相似文献
14.
H. Aschauer H.J. Briegel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):171-177
We give a proof that entanglement purification, even with noisy apparatus, is sufficient to disentangle an eavesdropper (Eve)
from the communication channel. Our proof applies to all possible attacks (individual and coherent). Due to the quantum nature
of the entanglement purification protocol, it is also possible to use the obtained quantum channel for secure transmission
of quantum information.
Received 10 August 2001 and Received in final form 26 October 2001 相似文献
15.
量子纠缠是量子信息领域的核心资源,目前利用β型硼酸钡(BBO)晶体参量下转换制备的纠缠光子对的亮度较低,它直接制约了量子通信的最远距离,已无法满足星地实用化量子通信的发展需求.利用周期极化KTiOPO4晶体,采用准相位匹配技术设计产生了一种后选择的纠缠源,测得的符合计数达到了16×103s-1 mW-1,极化对比度达到27∶1,在亮度上比基于BBO的量子纠缠光源提高了一个数量级以上.这一高亮度的纠缠源可以广泛应用于量子密钥分发、量子隐形传态以及量子计算等新兴量子信息领域,为实现全球化量子通信提供了有力的保障.
关键词:
纠缠态
准相位匹配
4晶体')" href="#">周期极化KTiOPO4晶体 相似文献
16.
In quantum communication, the channel noise and the misalignment of the reference frames between the communication parties will lead to the failure of quantum state transmission. Here an alignment-free spatial-polarization hyperentanglement transmission scheme is provided for hyperentangled photons. In this scheme, before the spatial-polarization hyperentanglement is transmitted through the fiber channel, it is first encoded as a time-bin entanglement with the same polarization. After the photons pass through the noise channel, the polarization errors caused by reference frames misalignment and channel noise can be corrected by time-bin entanglement. In principle, by implementing this scheme, the communication parties can share the original hyperentangled state, and the success probability can approach unity. The scheme is robust to random channel noise and reference frames misalignment, and the decoherence effect caused by the misalignment of the reference frames between the communication parties can be completely suppressed by implementing this scheme. 相似文献
17.
We present two polarization-based protocols for quantum key distribution. The protocols encode key bits in noiseless subspaces or subsystems and so can function over a quantum channel subjected to an arbitrary degree of collective noise, as occurs, for instance, due to rotation of polarizations in an optical fiber. These protocols can be implemented using only entangled photon-pair sources, single-photon rotations, and single-photon detectors. Thus, our proposals offer practical and realistic alternatives to existing schemes for quantum key distribution over optical fibers without resorting to interferometry or two-way quantum communication, thereby circumventing, respectively, the need for high precision timing and the threat of Trojan horse attacks. 相似文献
18.
V.A. Brazhnyi S. Stepanow 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):355-362
We consider the adsorption of a random heteropolymer onto an interface within the model of Garel et al. [#!gareletal89!#] by taking into account random self-interactions and ternary repulsive interactions between the monomers.
Within the replica trick and by using a self-consistent preaveraging procedure we map the adsorption problem onto the problem
of binding state of a quantum mechanical Hamiltonian. The analysis of the latter is treated within the variational method
based on the 2nd Legendre transform. Our study reveals a complex behaviour of the localization of the heteropolymer. In particular,
we predict a reentrant localization transition for moderate values of the asymmetry of the distribution function of the monomer
sequences along the heteropolymer.
Received 9 October 2001 and Received in final form 27 February 2002 Published online 6 June 2002 相似文献
19.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):423-431
Several examples of photon entanglement are studied in the Q representation of quantum optics. In particular, the entangled states produced in parametric downconversion are studied in
detail, and we determine the conditions for the violation of Bell's inequality. Our approach shows that photon entanglement
is related to the existence of correlations between the quantum fluctuations of the electromagnetic field associated to different
modes.
Received 10 August 2002 / Received in final form 7 November 2002 Published online 4 February 2003 相似文献
20.
van Loock P Ladd TD Sanaka K Yamaguchi F Nemoto K Munro WJ Yamamoto Y 《Physical review letters》2006,96(24):240501
We describe a quantum repeater protocol for long-distance quantum communication. In this scheme, entanglement is created between qubits at intermediate stations of the channel by using a weak dispersive light-matter interaction and distributing the outgoing bright coherent-light pulses among the stations. Noisy entangled pairs of electronic spin are then prepared with high success probability via homodyne detection and postselection. The local gates for entanglement purification and swapping are deterministic and measurement-free, based upon the same coherent-light resources and weak interactions as for the initial entanglement distribution. Finally, the entanglement is stored in a nuclear-spin-based quantum memory. With our system, qubit-communication rates approaching 100 Hz over 1280 km with fidelities near 99% are possible for reasonable local gate errors. 相似文献