共查询到20条相似文献,搜索用时 31 毫秒
1.
P. Horak H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):279-287
We propose a method to create macroscopic superpositions, so-called Schr?dinger cat states, of different motional states of
an ideal Bose-Einstein condensate. The scheme is based on the scattering of a freely expanding condensate by the light field
of a high-finesse optical cavity in a quantum superposition state of different photon numbers. The atom-photon interaction
creates an entangled state of the motional state of the condensate and the photon number, which can be converted into a pure
atomic Schr?dinger cat state by operations only acting on the cavity field. We discuss in detail the fully quantised theory
and propose an experimental procedure to implement the scheme using short coherent light pulses.
Received 26 June 2000 and Received in final form 2nd October 2000 相似文献
2.
Ran Zeng 《Optics Communications》2007,271(1):162-168
Nonclassical features of the superposition of two coherent states which are π/2 out of phase are discussed, such as sub-Poissonian photon statistics and quadrature squeezing, as well as negativity of the Wigner function. Special nonclassicality is found in the special state where the relative phase of superposition has relationship with the average photon number. The analysis of the amount of entanglement is also presented for the related two-mode entangled coherent states. 相似文献
3.
We study optical schemes for generating both a displaced photon and a displaced qubit via conditional measurement. Combining one mode prepared in different microscopic states (one-mode qubit, single photon, vacuum state) and another mode in macroscopic states (coherent state, single photon added coherent state), a conditional state in the other output mode exhibits properties of a superposition of the displaced vacuum and a single photon. We propose to use the displaced qubit and entangled states composed of the displaced photon as components for quantum information processing. Basic states of such a qubit are distinguishable from each other with high fidelity. We show that the qubit reveals both microscopic and macroscopic properties. Entangled displaced states with a coherent phase as an additional degree of freedom are introduced. We show that additional degree of freedom enables to implement complete Bell state measurement of the entangled displaced photon states. 相似文献
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S. A. Podoshvedov 《JETP Letters》2006,83(8):360-365
We generalize the scheme of conditional preparation of x(2) macroscopic entangled states [S.A. Podoshvedov, JETP 129 (2006)]. The studied system consists of a system of coupled down converters with type-I phase matching pumped simultaneously
by powerful optical fields in coherent states with one auxiliary photon in the superposition state of two input modes and
a projective measurement system. The projective measurement system involves two Hadamard gates introduced to generated output
modes followed by photodetectors. Identification of macroscopic entangled states is produced by registration of one photon.
No photon number resolving detection is required for the studied scheme.
The text was submitted by the author in English. 相似文献
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A robust scheme is presented for realizing entangled states for two atoms trapped in separate cavities connected by an optical fiber. The first atom is initially in a superposition of the excited state and an auxiliary ground state not coupled to the first cavity, while the second one is initially in the ground state coupled to the second cavity. The scheme involves two atom-cavity-fiber interactions accompanied by the monitoring of the cavity decay and atomic spontaneous emission. The two atoms evolve to an entangled state through exchanging an excitation after the first interaction. The states with the excitation failing to be transferred are eliminated when a photon is detected during the second interaction. Therefore, the scheme is insensitive to the decoherence effect and detection inefficiency. 相似文献
8.
叠加激发双模压缩真空态的量子统计特性(英文) 总被引:5,自引:3,他引:2
从激发双模压缩真空态a+mb+m|ξ>出发构造了叠加态|Ψ>,研究了|Ψ>的量子统计特性.结果表明:在一定的条件下,随着相位差的变化,叠加态|Ψ>的平均光子数出现类似于Rabi振荡的崩塌与复原现象,而且与单个激发双模压缩真空态a+mb+m|ξ>相比,在叠加态|Ψ>中光场的相位压缩和亚泊松光子统计特性都得到了加强. 相似文献
9.
Zhen-Biao Yang 《Optics Communications》2008,281(10):2849-2853
A scheme is discussed for probabilistic teleportation of a special type of two-atom pure state - an arbitrary superposition of symmetric two-atom Dicke states. The scheme follows the previous idea [S.B. Zheng, Phys. Rev. A 69 (2004) 064302], which is proposed for approximate and probabilistic teleportation of an atomic state through only a detection on the sender atom. In principle, the present scheme can achieve faithful teleportation by resorting to a very different model, which depicts the resonant interaction of a Λ-type three-level atom with a two-mode cavity field. The scheme can also be used for teleportation of an arbitrary superposition of symmetric multi-atom Dicke states. 相似文献
10.
We firstly give a nonlocal method for generating pair coherent state with two traveling wave fields in distinct districts. The experimental scheme proposed is based on a two-mode photon number matching process, which employs weak cross-Kerr media and on/off detection. Then we discuss the details for implementing this scheme, showing that it is robust against the low quantum efficiency of photon detectors and offers nearly perfect pair coherent states. Finally, we show how a two-mode Schrödinger cat state and a generalized two-mode correlated photon number state can be prepared via this matching process. 相似文献
11.
We propose a decoy state quantum key distribution scheme with odd coherent state which follows sub-Poissonian distributed photon count and has low probability of the multi-photon event and vacuum event in each pulse. The numerical calculations show that our scheme can improve efficiently the key generation rate and secure communication distance. Fhrthermore, only one decoy state is necessary to approach to the perfect asymptotic limit with infinite decoy states in our scheme, but at least two decoy states are needed in other scheme. 相似文献
12.
Neergaard-Nielsen JS Nielsen BM Hettich C Mølmer K Polzik ES 《Physical review letters》2006,97(8):083604
We report on the experimental observation of quantum-network-compatible light described by a nonpositive Wigner function. The state is generated by photon subtraction from a squeezed vacuum state produced by a continuous wave optical parametric amplifier. Ideally, the state is a coherent superposition of odd photon number states, closely resembling a superposition of weak coherent states |alpha > - |-alpha >. In the limit of low squeezing the state is basically a single photon state. Light is generated with about 10,000 and more events per second in a nearly perfect spatial mode with a Fourier-limited frequency bandwidth which matches well atomic quantum memory requirements. The generated state of light is an excellent input state for testing quantum memories, quantum repeaters, and linear optics quantum computers. 相似文献
13.
Nasir Alam Kathakali Mandal Anirban Pathak 《International Journal of Theoretical Physics》2018,57(11):3443-3456
Role of quantum interference in the origin of higher-order nonclassical characteristics of radiation field has been probed vis-à-vis a discrete and a continuous superposition of coherent states. Specifically, the possibilities of observing higher-order nonclassical properties (e.g., higher-order antibunching (HOA), higher-order sub-Poissonian photon statistics (HOSPS), higher-order squeezing (HOS) of Hong-Mandel type and Hillery type) have been investigated using a shifted symmetric cat state that reduces to Yurke-Stoler, even and odd coherent states at various limits. This shifted symmetric cat state which can be viewed as a discrete superposition of coherent states is found to show HOA and HOSPS. Similarly, higher-order nonclassical properties of a one-dimensional continuous superposition of coherent states is also studied here. The investigation has revealed the existence of HOS and HOSPS in the one-dimensional continuous superposition of coherent states studied here. Effect of non-Gaussianity inducing operations (e.g., photon addition and addition followed by subtraction) on these superposition states have also been investigated. Finally, some comparisons have been made between the higher-order nonclassical properties of discrete and continuous superposition of coherent states. 相似文献
14.
This paper discusses the amplitude-squared squeezing for the superposition of two coherent states with their phase differences being separately π/2, 3π/2, and π1, as well as for the superposition state of two pseudoclassical states. According to the analysis, it is found that the superposition state of two coherent states with their phase differences π/2 and 3π/2, and the superposition state of two pseudoclassical states both do exhibit the amplitude-squared squeezing. Also, some specific states are found to exhibit even stronger squeezing effects when relative phase of the superposition is equal to the average photon number. Amplitude-squared squeezing is dependent on the difference in phase between two coherent states. 相似文献
15.
We propose a method to prepare multipartite entangled states such as cluster states and graph states based on the cavity input-output process and single photon measurement. Two quantum gates, a controlled phase gate and a fusion gate between two atoms trapped in respective cavities, are proposed to prepare atomic cluster states and graph states with one and two dimensions. We also introduce a scheme that can generate an arbitrary multipartite photon duster state which uses two coherent states as a qubit basis. 相似文献
16.
A scheme is presented for generation of entangled states for two atoms trapped in two distant bad cavities. The scheme can work with bad cavities with the coupling strength smaller than the cavity decay rate, which is important from the viewpoint of experiment. In the scheme the atoms have no probability of being populated in the excited state and thus the atomic spontaneous emission is suppressed, which increases the probability of success. The fidelity of the entangled state is not affected by the detection eflciency. Furthermore, the scheme does not require the detection of the left-polarized photon and right-polarized photon at the same time. 相似文献
17.
ZHAO ChunRan & YE Liu School of Physics & Materials Science Anhui University Hefei China School of Physics & Electronic Information Huaibei Normal University Huaibei 《中国科学:物理学 力学 天文学(英文版)》2011,(3)
A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photo... 相似文献
18.
A scheme is proposed for generating a photon-number entangled cluster state among four modes. The scheme only uses Kerr medium
and homodyne measurement on probe coherent light fields, which can be efficiently made in quantum optical laboratories. The
photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam
is initially set in a intense coherent state superposition. It is shown that under certain conditions, the four-photon cluster
state can be generated effectively with high success probability and homodyne detection required only once, and the scheme
is feasible by current experimental technology. 相似文献
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邹艳 《原子与分子物理学报》2009,26(1):138-144
运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明:原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用. 相似文献