共查询到20条相似文献,搜索用时 125 毫秒
1.
利用坐标本征矢|x〉在Fock空间的展开式,导出了算符λ■+μ■在Fock空间的本征矢|ψ〉,并证明了其正交完备性.结果表明,得到的|ψ〉既是完备的,又是正交的,完全可以作为一个表象使用.当λ和μ分别取1和0时,|ψ〉约化为坐标本征态|x〉,而当λ和μ分别取0和1时,|ψ〉约化为动量本征态|p〉.因此,|ψ〉所构成的表象是介于坐标表象和动量表象之间的中介表象. 相似文献
2.
利用有序算符乘积内的积分技术(IWOP),建立了一种称之为相干纠缠态的两粒子体系的新表象,研究了这种新表象的性质,从理论上探讨了这种相干纠缠态的产生方法.结果表明:本文建立的这种p1-p2与a1+a2的共同本征态|p,β,既具有相干态的特性,又体现了纠缠态的特征,具有超完备性,完全可以作为一个表象使用. 物理上可以用光分束器来实现|p,β>,让分束器的两个输入端分别输入理想单模压缩态|p=0>2=exp[1-2a+22]|0>2和真空态|0>1,再经过对激光场一定的调制作用即可得到|p,β>态. 相似文献
3.
运用有序算符内积分(IWOP)技术,构建了(x)2—p1和.(x)1—P2的共同本征态|η〉,并分析了该新纠缠表象的Schmidt分解形式.另外,我们还得到纠缠态|η>的共轭态|ξ〉,同时计算了它们的内积.最后我们给出了新双模压缩算符S2=μ∫d2η/π|μη〉〈η|的显式,并分析了其压缩特性. 相似文献
4.
利用坐标本征矢∣x>在Fock空间的展开式,导出了算符λ(x)+μ(p)在Fock空间的本征矢∣ψ>,并证明了其正交完备性.结果表明,得到的∣ψ>既是完备的,又是正交的,完全可以作为一个表象使用.当λ和μ分别取1和0时, ∣ψ>约化为坐标本征态∣x>,而当λ和μ分别取0和1时, ∣ψ>约化为动量本征态∣p>.因此,∣ψ>所构成的表象是介于坐标表象和动量表象之间的中介表象. 相似文献
5.
本文讨论了光学参量频率转换过程中对相干态的演化问题, 获得了对相干态时间演化的解析表达式及在位形空间的波函数, 发现通过适当调节系统元件及相互作用时间, 对相干态在位形空间中的波包能呈现出量子涡态特性, 并且与这样涡态相关的波函数具有修正Bessel-Gaussian形式的结构, 即非高斯型波函数. 在相干态表象下, 这一量子化涡态是两模湮没算符平方和的本征态. 这一讨论揭示了产生量子化涡态的另一可实现方案. 相似文献
6.
用二次量子化和不可约张量方法,对j壳层引入对准旋-角动量为(1/2,j)阶不可约张量的产生-湮没算符b_(qm)~(1/27),由此耦合成准旋-角动量标量算符Y(x,k)=(bb)~(x,k)·(bb)~(x,k),并用其本征值对费密子j-j耦合态进行分类.计算表明:对j=9/2,11/2,13/2,当x十k≥3,Y(x,k)与准旋、角动量共同本征态能对耦合态完全分类.对多数(x,k)值,y(x,k)本身就能对耦合态完全分类.列出了对j=9/2耦合态完全分类的主要结果.
关键词: 相似文献
7.
利用有序算符乘积内的积分技术(IWOP),建立了一种称之为相干纠缠态的两粒子体系的新表象,研究了这种新表象的性质,从理论上探讨了这种相干纠缠态的产生方法.结果表明:本文建立的这种 p1- p2与 a1+ a2的共同本征态| p, β〉,既具有相干态的特性,又体现了纠缠态的特征,具有超完备性,完全可以作为一个表象使用. 物理上可以用光分束器来实现|<
关键词:
IWOP技术
相干纠缠态表象
分束器 相似文献
8.
利用多组态Dirac-Fock方法,本文研究了高电荷态类锂等电子序列(Z=31~40)离子1s22p激发态的精细结构. 考虑高关联轨道的电子关联影响以及Breit相互作用、量子电动力学效应和原子核运动效应等高阶修正,计算了2P1/2和2P3/2精细能级的本征能量,能级劈裂结果与已有理论计算一致. 结果表明,类锂离子1s22p态精细结构劈裂满足高电荷态的等电子序列标度规律(~ Z4);发现离子空间尺寸随着原子序数增加收缩,相对论轨道1s1/2和2p3/2的径向电荷密度分布趋向于原子核. 相似文献
9.
外尔于1918年引入的规范变换实际上是相位变换而非真正的尺度变换,但规范不变性、规范理论等概念都沿袭了下来。我们发现,针对由量子化条件[x,p]=ih而来的量子体系之本征值问题存在规范变换,或者说尺度变换,x→x/α,p→αp,该变换保体系的能量谱不变。量子谐振子、氢原子问题及一类多体问题的精确解析解证实了这一点。量子化条件[x,p]=ih看来是个对量子力学很强的约束,不止于能量的量子化。这个规范变换提醒我们相空间的体积及其量子化才是物理的关键,这也是量子力学和统计物理在潜意识里一直沿用却未予关注的思路。有趣的是,从量子谐振子体系的相空间表述似乎不能导向这个结论。如同规范理论所断言的电磁学量在给定坐标系下的数值表征与标度无关,我们认为量子体系的物理量,如能量谱等,在给定坐标系下的数值表征亦应与标度无关。此尺度变换与德布罗意关系相恰。 相似文献
10.
产生算符和湮灭算符是二次量子化方法中的基本算符,它们可通过对占有数表象中的基矢或波函数的作用而定义。有些著述中往往把这两种形式的算符混淆,因而引起误解和混乱。 下面以玻色子为例进行讨论。 (一)占有数表象中,对基矢作用的产生算符a-i~+与湮灭算符ai 对力学量b的占有数表象的基矢,定义产生算符a-i~+与湮灭算符ai为 上式的物理意义非常明确。它们代表基矢间的变换关系。i态的产生算符a-i~+作用到分布为 nl, n2,…ni…的态上,得到一个i态粒子数为ni+1的新态。a-i~+作用的效果使i态上多了个粒子,所以称a-i~+为i态的产生算符。 算… 相似文献
11.
This paper investigates the entanglement evolution of a two-qubit anisotropic Heisenberg XYZ chain in the presence of Dzyaloshinskii-Moriya interaction.The time evolution of the concurrence is studied for the initial pure entangled states cos θ |00 + sin θ |11 and cos |01 + sin |10 at zero temperature.The influences of Dzyaloshinskii-Moriya interaction D,anisotropic parameter and environment coupling strength γ on entanglement evolution are analysed in detail.It is found that the effect of noisy environment obviously suppresses the entanglement evolution,and the Dzyaloshinskii-Moriya interaction D acts on the time evolution of entanglement only when the initial state is cos |01 + sin |10.Finally,a formula of steady state concurrence is obtained,and it is shown that the stable concurrence,which is independent of different initial states and Dzyaloshinskii-Moriya interaction D,depends on the anisotropic parameter and the environment coupling strength γ. 相似文献
12.
We construct four linear composite operators for a two-particle
system and give common eigenvectors of those operators. The
technique of integration within an ordered product (IWOP) of
operators is employed to prove that those common eigenvectors are
complete and orthonormal. Therefore, a new two-mode intermediate
momentum-coordinate representation which involves quantum
entanglement for a two-particle system is proposed and applied to
some two-body dynamic problems. Moreover, the pure-state density
matrix | ξ 1 ,ξ 2 > C,DC,D< ξ 1 ,ξ 2 | is a Radon
transform of Wigner operator. 相似文献
13.
We have considered two distant mesoscopic superconducting quantum
interference device (SQUID) rings A and B in the presence of two-mode
nonclassical state fields and investigated the correlation of the
supercurrents in the two rings using the normalized correlation
function $C_{\rm AB}$. We show that when the parameter $\alpha$ is
very small for the separable state with the density matrix $\hat
{\rho } = (\left| {\alpha , - \alpha } \right\rangle \left\langle
{\alpha , - \alpha } \right| + \left| { - \alpha ,\alpha }
\right\rangle \left\langle { - \alpha ,\alpha } \right|) / 2$ and
entangled coherent state (ECS) $\left| u \right\rangle = N_1 (\left|
{\alpha , - \alpha } \right\rangle + \left| { - \alpha ,\alpha }
\right\rangle )$ fields, the dynamic behaviours of the normalized
correlation function $C_{\rm AB}$ are similar, but it is quite
different for the entangled coherent state $\left| {u}'
\right\rangle = N_2 (\left| {\alpha , - \alpha } \right\rangle -
\left| { - \alpha ,\alpha } \right\rangle )$ field. When the
parameter $\alpha $ is very large, the dynamic behaviours of $C_{\rm
AB}$ are almost the same for the separable state, entangled coherent
state $\left| u \right\rangle $ and $\left| {u}' \right\rangle $
fields. For the two-mode squeezed vacuum state field the maximum of
$C_{\rm AB}$ increases monotonically with the squeezing parameter
$r$, and as $r \to \infty $, $C_{\rm AB} \to 1$. This means that the
supercurrents in the two rings A and B are quantum mechanically
correlated perfectly. It is concluded that not all the quantum
correlations in the two-mode nonclassical state field can be
transferred to the supercurrents; and the transfer depends on the
state of the two-mode nonclassical state field prepared. 相似文献
14.
A potential scheme is proposed for generating cluster states of many atoms in cavity quantum electradynamics (QED), in which an unorthodox encoding is employed with the ground state being qubit [0〉 while two closely spaced upper states being qubit |1〉. Throughout the scheme the cavities can be in thermal states but axe only virtually excited. We show how to create the cluster states by performing a two-step hut no single-qubit operation. Discussion is also carried out on the experimental feasibility of our scheme. 相似文献
15.
A potential scheme is proposed for generating cluster states of many
atoms in cavity quantum electradynamics (QED), in which an unorthodox
encoding is employed with the ground state being qubit $\left\vert
0\right\rangle $ while two closely spaced upper states being qubit
$\left\vert 1\right\rangle $. Throughout the scheme the cavities can
be in thermal states but are only virtually excited. We show how to
create the cluster states by performing a two-step but no
single-qubit operation. Discussion is also carried out on the
experimental feasibility of our scheme. 相似文献
16.
Based on the displacement-squeezing related squeezed
coherent state representation ≤ft\vert z\right\rangle _{g} and
using the technique of integration within an ordered product of
operators, this paper finds a generalized Fresnel operator, whose
matrix element in the coordinate representation leads to a
generalized Collins formula (Huygens--Fresnel integration
transformation describing optical diffraction). The generalized
Fresnel operator is
derived by a quantum mechanical mapping from z to sz-rz^{\ast } in the %
≤ft\vert z\right\rangle _{g} representation, while ≤ft\vert
z\right\rangle _{g} in phase space is graphically denoted by an
ellipse. 相似文献
17.
We study amplitude-squared squeezing of the Hermitian operator Z θ=Z 1
cosθ+Z 2 sin θ, in the most general superposition state
, of two coherent states
and
. Here operators Z 1,2 are defined by
, a is annihilation operator, θ is angle, and
complex numbers C 1,2 , α, β are arbitrary and only
restriction on these is the normalization condition of the state
. We define the condition for a state
to be amplitude-squared squeezed for the operator Z θ
if squeezing parameter
, where N=a +a and
. We find
maximum amplitude-squared squeezing of Z θ in the superposed
coherent state
with minimum value 0.3268 of the
parameter S for an infinite combinations with α- β= 2.16
exp [±i(π/4) + iθ/2],
and with
arbitrary values of (α+β) and θ. For this minimum
value of squeezing parameter S, the expectation value of photon number can
vary from the minimum value 1.0481 to infinity. Variations of the parameter
S with different variables at maximum amplitude-squared squeezing are also
discussed. 相似文献
18.
Phase space analysis of quantum states is a newly developed topic in quantum optics. In this work we present Wigner phase space distributions for the two-mode binomial state produced by quantum entanglement between a vacuum state and a number state in a beamsplitter. By using two new binomial formulas involving two-variable Hermite polynomials and the so-called entangled Wigner operator, we find that the analytical Wigner function for the binomial state |ξ〉q ≡ D(ξ) |q, 0〉 is related to a Laguerre polynomial, i.e.,
$ W\left (\sigma _{,}\gamma \right ) =\frac {(-1)^{q}e^{-\left \vert \gamma \right \vert ^{2}-\left \vert \sigma \right \vert ^{2}}}{\pi ^{2}}L_{q}\left (\left \vert \frac {-\varsigma (\sigma -\gamma )+\sigma ^{\ast }+\gamma ^{\ast }} {\sqrt {1+|\varsigma |^{2}}}\right \vert ^{2}\right ) $and its marginal distributions are proportional to the module-square of a single-variable Hermite polynomial. Also, the numerical results show that the larger number sum q of two modes lead to the stronger interference effect and the nonclassicality of the states |ξ〉q is stronger for odd q than for even q. 相似文献
19.
A very long lifetime exciton emission with non-single exponential decay characteristics has been reported for single InA-s/GaAs quantum dot(QD) samples,in which there exists a long-lived metastable state in the wetting layer(WL)through radiative field coupling between the exciton emissions in the WL and the dipole field of metal islands.In this article we have proposed a new three-level model to simulate the exciton emission decay curve.In this model,assuming that the excitons in a metastable state will diffuse and be trapped by QDs,and then emit fluorescence in QDs,a stretchedlike exponential decay formula is derived as I(t)=At~(β-1)e~(-(rt)β),which can describe well the long lifetime decay curve with an analytical expression of average lifetime 相似文献
20.
We study the entanglement dynamics of an anisotropic two-qubit Heisenberg XYZ system in
the presence of intrinsic decoherence. The usefulness of such a system for performance of
the quantum teleportation protocol T0\mathcal{T}_0
and entanglement teleportation protocol T1\mathcal{T}_1
is also investigated. The results depend on the initial conditions and the parameters of
the system. The roles of system parameters such as the inhomogeneity of the magnetic field
b and the spin-orbit interaction parameter D, in
entanglement dynamics and fidelity of teleportation, are studied for both product and
maximally entangled initial states of the resource. We show that for the product and
maximally entangled initial states, increasing D amplifies the effects of
dephasing and hence decreases the asymptotic entanglement and fidelity of the
teleportation. For a product initial state and specific interval of the magnetic field
B, the asymptotic entanglement and hence the fidelity of teleportation
can be improved by increasing B. The XY and XYZ Heisenberg systems
provide a minimal resource entanglement, required for realizing efficient teleportation.
Also, in the absence of the magnetic field, the degree of entanglement is preserved for
the maximally entangled initial states $\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1}
{{\sqrt 2 }}\left( {\left| {\left. {00} \right\rangle \pm } \right|\left. {11} \right\rangle } \right)} \right.$\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1}
{{\sqrt 2 }}\left( {\left| {\left. {00} \right\rangle \pm } \right|\left. {11} \right\rangle } \right)} \right.. The
same is true for the maximally entangled initial states
$\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1}
{{\sqrt 2 }}\left( {\left| {\left. {01} \right\rangle \pm } \right|\left. {10} \right\rangle } \right)} \right.$\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1}
{{\sqrt 2 }}\left( {\left| {\left. {01} \right\rangle \pm } \right|\left. {10} \right\rangle } \right)} \right., in the
absence of spin-orbit interaction D and the inhomogeneity parameter
b. Therefore, it is possible to perform quantum teleportation protocol
T0\mathcal{T}_0
and entanglement teleportation T1\mathcal{T}_1,
with perfect quality, by choosing a proper set of parameters and employing one of these
maximally entangled robust states as the initial state of the resource. 相似文献
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