共查询到20条相似文献,搜索用时 31 毫秒
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利用大失谐情况下的简并喇曼过程和双光子Jaynes-Cummings模型来产生电磁场中的宏观量子叠加态,即薛定旋风谔猫态,并探讨如何用零频检测的方法来探测这些态。研究了当电磁场初态为薛定谔猫态时,对强度耦合的Jaynes-Cummings模型中原子反转的崩塌与再生现象的影响,将在以相干态为初态所产生的原子反转的崩塌区产生不同程度的再生现象。
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The cat state, known as the superposition of coherent states, has broad applications in quantum computation and quantum metrology. Increasing the number of optical cat states is crucial to implement complex quantum information tasks based on them. Here, two optical cat states are prepared simultaneously based on a nondegenerate optical parametric amplifier. By subtracting one photon from each of two squeezed vacuum states, two odd cat states with orthogonal superposition direction in phase space are prepared simultaneously, which have similar fidelity of 60% and amplitude of 1.2. Compared with the traditional method to generate two odd optical cat states based on two degenerate optical parametric amplifiers, only one nondegenerate optical parametric amplifier is applied in this experiment, which saves half of the quantum resources of nonlinear cavities. The presented results make a step toward preparing the four-component cat state, which has potential applications in fault-tolerant quantum computation. 相似文献
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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
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The detection of microwave states is complicated by strong thermal noise, which is inevitably introduced by linear amplifiers. We show how to extract from measured data normally or anti-normally ordered moments of photon creation and annihilation operators, the set of which contains complete information on the quantum state of an electromagnetic field. Equations for the evolution of the quantum state are derived in terms of moments. Using this approach, we consider in detail issues of decoherence and thermalization of microwave quantum states. Results are illustrated using the examples of Fock, coherent, squeezed, thermal, and even and odd coherent states (Schrödinger cat states). 相似文献
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We present several examples where prominent quantum properties are transferred from a microscopic superposition to thermal states at high temperatures. Our work is motivated by an analogy of Schr?dinger's cat paradox, where the state corresponding to the virtual cat is a mixed thermal state with a large average photon number. Remarkably, quantum entanglement can be produced between thermal states with nearly the maximum Bell-inequality violation even when the temperatures of both modes approach infinity. 相似文献
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叠加多模薛定谔猫态纠缠光场的不等幂次高次差压缩 总被引:1,自引:1,他引:0
利用多模压缩态理论研究了由多模复共轭相干态、多模复共轭虚相干态和多模真空态的线性叠加所组成的三态叠加多模薛定谔猫态纠缠光场的广义非线性不等幂次高次差压缩特性.结果发现:①真空场对此猫态光场的不等幂次高次差压缩效应没有影响;②在一定条件下,此猫态光场的两个正交相位分量可分别呈现出不等幂次高次差压缩效应;③而在另外的条件下,此猫态光场的两个正交相位分量则可同时出现上述的不等幂次高次差压缩效应,这是一种与测不准关系相悖的现象,称此种现象为"双边差压缩"效应. 相似文献
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薛定谔猫态是一类重要的非经典光场,实验上可以通过真空压缩态减光子的方案获得.本文从理论上研究了实验条件对制备薛定谔猫态的影响,主要考虑了包括压缩态的压缩度和纯度、单光子探测器的效率及噪声以及零拍探测器的效率等诸多因素的影响.理想情况下通过减光子方案制备得到的薛定谔猫态为奇光子数态,其相空间原点的Wigner函数为负值是其非经典特性的重要判据,而保真度可以度量制备态与理想猫态之间的相似程度.在压缩态为非纯态以及单光子探测器为商用低效率阈值探测器的情况下,计算了制备猫态的保真度、Wigner函数及其相空间原点处W(0)的表达式,分析了实验条件对薛定谔猫态制备的影响,为制备高质量的薛定谔猫态提供了理论指导. 相似文献
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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
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Zhang-qi Yin 《Contemporary Physics》2017,58(2):119-139
The question whether quantum mechanics is complete and the nature of the transition between quantum mechanics and classical mechanics have intrigued physicists for decades. There have been many experimental breakthroughs in creating larger and larger quantum superposition and entangled states since Erwin Schrödinger proposed his famous thought experiment of putting a cat in a superposition of both alive and dead states in 1935. Remarkably, recent developments in quantum optomechanics and electromechanics may lead to the realisation of quantum superposition of living microbes soon. Recent evidence also suggests that quantum coherence may play an important role in several biological processes. In this review, we first give a brief introduction to basic concepts in quantum mechanics and the Schrödinger’s cat thought experiment. We then review developments in creating quantum superposition and entangled states and the realisation of quantum teleportation. Non-trivial quantum effects in photosynthetic light harvesting and avian magnetoreception are also discussed. At last, we review recent proposals to realise quantum superposition, entanglement and state teleportation of micro-organisms, such as viruses and bacteria. 相似文献
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描述了简并V型三能级原子与单模相干态光场的Raman相互作用,获得了处于激发态单态的原子与相干态光场相互作用的结果.利用探测原子与光场的相互作用将原子和光场制备成最大缠结态,并注入待测原子,通过原子与腔模构成的Bell基矢演化,对腔场进行选择性探测,获得探测原子相互作用后可能的量子状态,然后对待测原子与腔场进行联合探测,接着对探测原子的量子状态实施幺正变换,就将探测原子制备到待测原子的初始量子态上,从而实现未知原子态的隐形传送. 相似文献
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In this paper we re-investigate the core of Schrödinger’s “cat paradox”. We argue that one has to distinguish clearly between superpositions of macroscopic cat states |?〉 + |?〉 and superpositions of entangled states |?, ↑〉 + |?, ↓〉 which comprise both the state of the cat (?=alive, ?=dead) and the radioactive substance (↑=not decayed, ↓=decayed). It is shown, that in the case of the cat experiment recourse to decoherence or other mechanisms is not necessary in order to explain the absence of macroscopic superpositions. Additionally, we present modified versions of two quantum optical experiments as experimenta crucis. Applied rigorously, quantum mechanical formalism reduces the problem to a mere pseudo-paradox. 相似文献
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We propose a scheme to implement the Deutsch-Jozsa algorithm by using Schroedinger cat states in cavity quantum electron-dynamics (QED). The scheme is based on the Raman interaction of a degenerate three-level A-type atom with a coherent state in a cavity. By using Schroedinger cat states, the atomic spontaneous emission can be minimized and the Hadamard transformation in our scheme is not needed. 相似文献
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A matrix method is presented for treating the dynamical phases, adiabatic phases and nonadiabatic phases of quantum superposition states. It is effective for any parameter-varying Hamiltonian system. As two examples, the evolution of mass-varying harmonic oscillator and the evolution of coherent states under parameter-varying displaced operator have been studied, Some new phenomena are obtained in the first case and the possible producing of so-called Schr?dinger's cat state by geometric phases is pointed out. The quantum state useful for the quantum optical verification of Berry's phase is introduced. 相似文献
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A matrix method is presented for treating the dynamical phases, adiabatic phases and nonadiabatic phases of quantum superposition states. It is effective for any parameter-varying Hamiltonian system. As two examples, the evolution of mass-varying harmonic oscillator and the evolution of coherent states under parameter-varying displaced operator have been studied, Some new phenomena are obtained in the first case and the possible producing of so-called Schr?dinger's cat state by geometric phases is pointed out. The quantum state useful for the quantum optical verification of Berry's phase is introduced. 相似文献
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《Nuclear Physics B》1997,506(3):685-694
We present an approach to the computation of the non-abelian statistics of quasiholes in quantum Hall states, such as the Pfaffian state, whose wavefunctions are related to the conformal blocks of minimal model conformal field theories. We use the Coulomb gas construction of these conformal field theories to formulate a plasma analogy for the quantum Hall states. A number of properties of the Pfaffian state follow immediately, including the Berry phases, which demonstrate the quasiholes' fractional charge, the abelian statistics of the two-quasihole state, and equal-time ground state correlation functions. The non-abelian statistics of multi-quasihole states follows from an additional assumption. 相似文献