共查询到20条相似文献,搜索用时 250 毫秒
1.
We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent ■ squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one-and two-arm.Compared with the case of one-arm phase shift,the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough.Furthermore,we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula.In addition,we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1) interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses. 相似文献
2.
3.
The probe gain with and without inversion in a four—level atomic model:light amplification at a short wavelength 下载免费PDF全文
We propose a new four-level atomic model for achieving light
amplification at a short wavelength, where direct incoherent
pumping into the top level is avoided by the advantage of
coherent pumping. In this model, the lower level of the probe
transition is an excited state but not the usual ground state.
By analytical as well as numerical calculations, we find that the
probe gain, either with or without population inversion, which depends
on the relation between spontaneous decay rates $\g_{42}$ and $\g_{21}$, can be achieved with proper parameters. We note that the Raman scattering
gain always plays an important role in achieving the probe amplification. 相似文献
4.
利用量子技术增强Sagnac效应提高陀螺输出精度具有重要的研究意义, 是实现全自主导航的重要途径. 以相干态激光作为输入光源的光学陀螺因真空零点波动使其输出精度限制于散粒噪声极限而难以提高. 为减小真空波动的影响, 提出在激光输入的分束器的另一输入端输入压缩真空光并结合平衡零拍探测技术的方法增强Sagnac效应. 理论分析表明Sagnac效应性能得到有效提升: 干涉输出的灵敏度检测极限和动态范围均随着压缩程度的增加而呈指数级增长. 该方法只需对经典光学陀螺做少量改动就可实现, 是提高光学陀螺输出精度的一种新方法. 相似文献
5.
The influence of nonparaxiality on the spectral behavior in Young's experiment illuminated by partially coherent light 下载免费PDF全文
Starting from the Rayleigh--Sommerfeld diffraction integral, this
paper studies the spectral behavior in Young's experiment
illuminated by nonparaxial partially coherent light and compares
with the paraxial case, where the influence of nonparaxiality of
partially coherent light on the spectral shifts and spectral
switches is stressed. It is shown that there is a spectral shift in
the nonparaxial case relative to the paraxial one and the critical
position changes, at which the spectral switch occurs. The ratio of
the waist width to the central wavelength w0/λ0 and
relative spatial correlation length \De affect the spectral
difference. The smaller w0/λ0 is, the larger the
difference between the nonparaxial and paraxial results appears. The
effect of relative spatial correlation length Δ is relatively
small. 相似文献
6.
Generation of unconventional geometric phase gates in ion trap-optical cavity system by squeezed operators 下载免费PDF全文
Based on squeezed operators this paper has implemented an ideal
unconventional geometric quantum gate (GQG) in ion trap-optical
cavity system by radiating the trapped ions with the cavity field of
frequency wc and an external laser field of frequency
wL. It can ensure that the gate time is shorter than
the coherence time for qubits and the decay time of the optical
cavity by appropriately tuning the ionic transition frequency
w0, the frequencies of the cavity mode wc and
the vibrational mode ν. It has also realized the unconventional
GQG under the influence of the cavity decay based on the
squeezed-like operators and found that the present scheme works well
for the smaller cavity decay by investigating the corresponding
fidelity and success probability. 相似文献
7.
Coherent interaction and action-counteraction theory in small polaron systems,and ground state properties 下载免费PDF全文
Zhi-Hua Luo 《中国物理 B》2022,31(11):117104-117104
Based on the coherent interaction and action-counteraction principles, we investigate the ground state properties for small polaron systems, the coherent-squeezed fluctuation correction, and the anomalous lattice quantum fluctuation, with the new variational generator containing correlated squeezed-coherent coupling and quantum entanglement. Noting that $-2t $ is the T.B.A. energy, for the coherent interaction effect, we find the ground-state energy $E_0$ to be $-2.428t$, in which the coherent squeezed fluctuation correction $-A_0 t$ is $-0.463t $ (where $ t $ is the hopping integral, $\omega $ is the phonon frequency), with the electron-one-phonon coupling constant $g=$1 and the electron-two-phonon coupling constant $g_{1}=-0.1$. However, as a result of the action-counteraction effect, $\tilde{{E}}_{0} $ is $-2.788t$, but $-\tilde{{A}}_{0} t$ is $-0.735t$. As to the polaron binding energy $(E_{\rm P} )$, for the coherent interaction effect, $E_{\rm P} $ is $-1.38\omega $, but for the action-counteraction effect, $\tilde{{E}}_{\rm P}$ is $-1.88\omega $. In particular, the electron-two-phonon interaction noticeably enlarges the coherent interaction and the coherent squeezed quantum fluctuation correction. By intervening with the quantum entanglement, the evolutions of the squeezed coherent state and the lattice quantum fluctuation begin to take control. At that time, we encounter a new quantum phase coherence phenomenon — the collapse and revival of inversion repeatedly for the coherent state in the entangled evolution. 相似文献
8.
The transfer of the quantum correlation from two-mode nonclassical state field to the supercurrents in two distant SQUID rings 下载免费PDF全文
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
9.
Berihu Teklu 《Optics Communications》2006,261(2):310-321
We seek to investigate, employing stochastic differential equations, the squeezing and statistical properties of the cavity mode of a degenerate parametric oscillator driven by coherent light and coupled to a squeezed vacuum reservoir. Contrary to the case of the squeezed vacuum reservoir, it is found that the driving coherent light has no effect on the squeezing properties of the cavity mode. However, both the squeezed vacuum reservoir and the driving coherent light increase the mean photon number of the cavity mode. 相似文献
10.
利用低频光通信波段真空压缩态光场可实现基于光纤的量子精密测量.本文利用简并光学参量振荡器实验制备出1550 nm低频真空压缩态光场.在分析频段10—500 kHz范围内压缩态光场的压缩度均达3 dB.用实验制备的1550 nm真空压缩态光场填补光纤马赫-曾德尔干涉仪的真空通道,实现了量子增强型光纤马赫-曾德尔干涉仪,完成了突破标准量子极限的相位调制频率为500 kHz的低频信号测量.与光纤马赫-曾德尔干涉仪相比,测量信噪比提高了2 dB. 相似文献
11.
The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived the analytic expressions for the time evolutions of atomic population difference W, modulus B of the Bloch vector, and entropy E. We find that the time evolutions of these quantities are periodic with a period of π. The maxima of W and B appear at the scaled interaction time points τ- = kπ(k = 0, 1, 2,...). At these time points, E = 0, which shows that the atom and the field are not entangled. Between these time points, E ≠ 0, which means that the atom and the field are entangled. When the field is initially in a coherent state, near the maxima, the envelope of W is a Gaussian function with a variance of 1/(4n^-)(n^- is the mean number of photons). Under the envelope, W oscillates at a frequency of n^-/π. When the field is initially in a thermal state, near the maxima, W is a Lorentz function with a width of 1/n^-. 相似文献
12.
Salvador Garcia 《advances in applied mathematics and mechanics.》2009,1(4):546-572
The lid-driven square cavity flow is investigated by numerical
experiments. It is found that from $ \mathrm{Re} $$=$ $5,000 $ to $
\mathrm{Re}
$$=$$ 7,307.75 $ the solution is stationary, but at $
\mathrm{Re}$$=$$7,308 $ the solution is time periodic. So the
critical Reynolds number for the first Hopf bifurcation localizes
between $ \mathrm{Re} $$=$$ 7,307.75 $ and $ \mathrm{Re} $$=$$ 7,308
$. Time periodical behavior begins smoothly, imperceptibly at the
bottom left corner at a tiny tertiary vortex; all other vortices
stay still, and then it spreads to the three relevant corners of the
square cavity so that all small vortices at all levels move
periodically. The primary vortex stays still. At $ \mathrm{Re}
$$=$$ 13,393.5 $ the solution is time periodic; the long-term
integration carried out past $ t_{\infty} $$=$$ 126,562.5 $ and the
fluctuations of the kinetic energy look periodic except slight
defects. However, at $ \mathrm{Re} $$=$$ 13,393.75 $ the solution is
not time periodic anymore: losing unambiguously, abruptly time
periodicity, it becomes chaotic. So the critical Reynolds number for
the second Hopf bifurcation localizes between $ \mathrm{Re} $$=$$
13,393.5 $ and $ \mathrm{Re} $$=$$ 13,393.75 $. At high Reynolds
numbers $ \mathrm{Re} $$=$$ 20,000 $ until $ \mathrm{Re} $$=$$
30,000 $ the solution becomes chaotic. The long-term integration is
carried out past the long time $ t_{\infty} $$=$$ 150,000 $,
expecting the time asymptotic regime of the flow has been reached.
The distinctive feature of the flow is then the appearance of drops:
tiny portions of fluid produced by splitting of a secondary vortex,
becoming loose and then fading away or being absorbed by another
secondary vortex promptly. At $ \mathrm{Re}
$$=$$ 30,000 $ another phenomenon arises—the abrupt appearance at
the bottom left corner of a tiny secondary vortex, not produced by
splitting of a secondary vortex. 相似文献
13.
基于Braunstein与Kimble的连续变量量子隐形传态方案,通过调节输出端位移因子可以优化单模压缩相干态和单模压缩真空态量子隐形传态的保真度;分析了单模压缩态的压缩参数对保真度的影响。 相似文献
14.
Application of α——β——γ filtering to real-time atmosphere methane concentration measurement 下载免费PDF全文
A real time $\alpha$--$\beta$--$\gamma$ filtering technique is applied to
the monitoring of atmosphere CH可调二极管激光吸收光谱 谐波检测 物理光学 激光技术 tunable diode laser
absorption spectroscopy, multi-pass cell, harmonic detection Project supported by the National Natural Science Foundation of China (Grant No 10274080) and the
National High Technology Research and Development Program of China (Grant No 2003AA641010). 8/5/2005 12:00:00 AM 2005-08-052006-01-19 A real time α-β-γ filtering technique is applied to the monitoring of atmosphere CH4 based on a tunable diode laser spectrum system operating at 1.654μm. This technique is developed for improving the sensitivity and precision of CH4 concentration measurement with slow concentration change. The effectiveness of this technique is evaluated by performing CH4 concentration measurement and using it to monitor the varying methane level in the atmosphere. It was proved that signal noise ratio enhancement factor is 4.25. The comparison between this filter and moving average is also included in this article. It indicates the advantage of the α-β-γ real time filter. 相似文献
15.
Masahito Hayashi 《Communications in Mathematical Physics》2011,304(3):689-709
In a unified viewpoint in quantum channel estimation, we compare the Cramér-Rao and the mini-max approaches, which gives the
Bayesian bound in the group covariant model. For this purpose, we introduce the local asymptotic mini-max bound, whose maximum is shown to be equal to the asymptotic limit of the mini-max bound. It is shown that the local asymptotic
mini-max bound is strictly larger than the Cramér-Rao bound in the phase estimation case while both bounds coincide when the
minimum mean square error decreases with the order
O(\frac1n){O(\frac{1}{n})} . We also derive a sufficient condition so that the minimum mean square error decreases with the order
O(\frac1n){O(\frac{1}{n})} . 相似文献
16.
In this article, we assume that there exist the pseudoscalar $D\bar{D}_{s0}^*(2317)$ and $D^*\bar{D}_{s1}^*(2460)$ molecular states $Z_{1,2}$ and construct the color singlet-singlet molecule-type interpolating currents to study their masses with the QCD sum rules. In calculations, we consider the contributions of the vacuum condensates up to dimension-10 and use the formula $\mu=\sqrt{M_{X/Y/Z}^{2}-(2{\mathbb{M}}_{c})^{2}}$ to determine the energy scales of the QCD spectral densities. The numerical results, $M_{Z_1}=4.61_{-0.08}^{+0.11}\,\text{GeV}$ and $M_{Z_2}=4.60_{-0.06}^{+0.07}\,\text{GeV}$, which lie above the $D\bar{D}_{s0}^*(2317)$ and $D^*\bar{D}_{s1}^*(2460)$ thresholds respectively, indicate that the $D\bar{D}_{s0}^*(2317)$ and $D^*\bar{D}_{s1}^*(2460)$ are difficult to form bound state molecular states, the $Z_{1,2}$ are probably resonance states. 相似文献
17.
The q-analogues of two-mode squeezed states are introduced by virtue of deformation quantization methods and the technique of integration within an ordered product (IWOP) of operators. Some new completeness relations about these squeezed states composed of the bra and ket which are not mutually Hermitian conjugates are obtained. Furthermore, the antibunching effects of the two-mode squeezed vacuum state S's(τ) │00) are investigated. It is found that, in different ranges of the squeezed parameter τ, both modes of the state exhibit the antibunching effects and the two modes of the state are always nonclassical correlation. 相似文献
18.
Generation of atomic Greenberger-Horne-Zeilinger states and cluster states through cavity-assisted interaction 下载免费PDF全文
This paper proposes a scalable scheme to generate n-atom GHZ states and cluster states by using the basic building block, i.e., a weak coherent optical pulse [α) being reflected successively from a single-atom cavity. In the schemes, coherent state of light is used instead of single photon source, homodyne measurement on coherent light is done kastead of single photon detection, and no need for individually addressing keeps the schemes easy to implement from the experimental point of view. The successful probabilities of our protocols approach unity in the ideal case. 相似文献
19.
Phase estimation of phase shifts in two arms for an SU(1,1) interferometer with coherent and squeezed vacuum states 下载免费PDF全文
We theoretically study the quantum Fisher information(QFI) of the SU(1,1) interferometer with phase shifts in two arms by coherent ? squeezed vacuum state input, and give the comparison with the result of phase shift only in one arm.Different from the traditional Mach–Zehnder interferometer, the QFI of single-arm case for an SU(1,1) interferometer can be slightly higher or lower than that of two-arm case, which depends on the intensities of the two arms of the interferometer.For coherent ? squeezed vacuum state input with a fixed mean photon number, the optimal sensitivity is achieved with a squeezed vacuum input in one mode and the vacuum input in the other. 相似文献
20.
Josephson vortices and intrinsic Josephson junctions in the layered iron-based superconductor Ca10(Pt3As8)((Fe0.9Pt0.1)2As2)5 下载免费PDF全文
Qiang-Tao Sui 《中国物理 B》2022,31(9):97403-097403
Modulated electronic state due to the layered crystal structures brings about moderate anisotropy of superconductivity in the iron-based superconductors and thus Abrikosov vortices are expected in the mixed state. However, based on the angular and temperature dependent transport measurements in iron-based superconductor Ca$_{10}$(Pt$_3$As$_8$)((Fe$_{0.9}$Pt$_{0.1}$)$_2$As$_2$)$_5$ with $T_{\rm c} \simeq 12$ K, we find clear evidences of a crossover from Abrikosov vortices to Josephson vortices at a crossover temperature $T^{\star} \simeq 7 $ K, when the applied magnetic field is parallel to the superconducting FeAs layers, i.e., the angle between the magnetic field and the FeAs layers $\theta = 0^\circ$. This crossover to Josephson vortices is demonstrated by an abnormal decrease (increase) of the critical current (flux-flow resistance) below $T^{\star}$, in contrast to the increase (decrease) of the critical current (flux-flow resistance) above $T^{\star}$ expected for Abrikosov vortices. Furthermore, when $\theta$ is larger than $0.5^\circ$, the flux-flow resistance and critical current have no anomalous behaviors across $T^{\star}$. These anomalous behaviors can be understood in terms of the distinct transition from the well-pinned Abrikosov vortices to the weakly-pinned Josephson vortices upon cooling, when the coherent length perpendicular to the FeAs layers $\xi_\bot$ becomes shorter than half of the interlayer distance $d/2$. These experimental findings indicate the existence of intrinsic Josephson junctions below $T^{\star}$ and thus quasi-two-dimensional superconductivity in Ca$_{10}$(Pt$_3$As$_8$)((Fe$_{0.9}$Pt$_{0.1}$)$_2$As$_2$)$_5$, similar to those in the cuprate superconductors. 相似文献