共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Quantum correlations of pulses of optical parametric oscillator synchronously pumped above threshold
V. A. Averchenko Yu. M. Golubev K. V. Filonenko C. Fabre N. Treps 《Optics and Spectroscopy》2011,110(6):925-935
The quantum analysis of radiation from a degenerate optical parametric oscillator synchronously pumped above its oscillation
threshold is presented. It is shown that pulses of signal and pump fields at the output of the oscillator have the following
properties: quantum fluctuations of the fields are independent in each individual pulse, but correlated in pulses of the pulse
train with a temporal step multiple of the pulse period. The number of essentially correlated pulses is on the order of the
oscillator cavity finesse. Cross-correlations between the pump and signal pulses are established above the oscillation threshold.
These correlations lead to a significant quantum effect in the integral characteristics of the fields. A theoretical analysis
revealed that the spectrum of field fluctuations measured using a balanced homodyne detection technique of phase quadratures
of the fields with a pulsed local oscillator reveals quantum noise suppression in the vicinity of frequencies that are multiples
of the pulse repetition rate. 相似文献
3.
N. Kaiser 《The European Physical Journal A - Hadrons and Nuclei》2010,46(3):373-378
We calculate the one-photon loop radiative corrections to the neutral pion-pair photoproduction process p-g ?p-p0p0\pi^-\gamma \ensuremath \rightarrow\pi^-\pi^0\pi^0 . At leading order this reaction is governed by the chiral pion-pion interaction. Since the chiral p+ \pi^{+}_{}
p- \pi^{-}_{}
? \rightarrow
p0 \pi^{0}_{}
p0 \pi^{0}_{} contact vertex depends only on the final-state invariant mass it factors out of all photon loop diagrams. We give analytical
expressions for the multiplicative correction factor R ~ a/2p\ensuremath R\sim \alpha/2\pi arising from eight classes of contributing one-photon loop diagrams. An electromagnetic counterterm has to be included in
order to cancel the ultraviolet divergences generated by the photon loops. Infrared finiteness of the virtual radiative corrections
is achieved (in the standard way) by including soft photon radiation below an energy cut-off l \lambda . The radiative corrections to the total cross-section vary between +2% and -2% for center-of-mass energies from threshold
up to 7mp\ensuremath 7m_{\pi} . We study also the radiative corrections to the p0p0\ensuremath \pi^0\pi^0 mass spectrum. 相似文献
4.
We suggest a protocol for quantum key distribution—a technology allowing two distant parties to create an unconditionally
secure cryptographic key. For the creation of the key we suggest to use laser pulses weakened to the single-photon level of
duration T, the pulse carrying the value “1” being shifted in time by T/2 compared to the pulse carrying the value “0”. The overlap of the pulses provides their non-orthogonality and, therefore,
impossibility to discriminate between them with certainty. Besides the signal pulses the protocol uses coherent decoy pulses,
having longer duration than the signal ones and providing a more effective protection from a wide class of attacks. Security
of the protocol is based on interferometric control of the pulse coherence at the receiving station. We analyze the security
of the protocol against a number of intercept-resend attacks and on the basis of this analysis substantiate the necessity
of decoy state implementation. 相似文献
5.
W. Cui Z. R. Xi Y. Pan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):479-485
We theoretically analyze the entanglement generation and
dynamics by coupled Josephson junction qubits. Considering a
current-biased Josephson junction (CBJJ),
we generate maximally entangled states. In particular, the entanglement
dynamics is considered as a function of the decoherence
parameters, such as the temperature, the ratio
r
≡
wc\omega_c/w0\omega_0 between the reservoir cutoff frequency
wc\omega_c and the system oscillator frequency w0\omega_0,
and the energy levels split of the superconducting circuits in the
non-Markovian master equation. We analyzed the entanglement sudden
death (ESD) and entanglement sudden birth (ESB) by the non-Markovian
master equation. Furthermore, we find that the larger the ratio r
and the thermal energy k
BT
, the shorter the decoherence. In this
superconducting qubit system we find that the entanglement can be
controlled and the ESD time can be prolonged by adjusting the
temperature and the superconducting phases Fk\Phi_k which split the
energy levels. 相似文献
6.
C. S. Fischer T. Goecke R. Williams 《The European Physical Journal A - Hadrons and Nuclei》2011,47(2):28
Using the Dyson-Schwinger and Bethe-Salpeter equations, we calculate the hadronic light-by-light scattering contribution to
the anomalous magnetic moment of the muon am\ensuremath a_\mu , using a phenomenological model for the gluon and quark-gluon interaction. We find am=(84 ±13)×10-11\ensuremath a_\mu=(84 \pm 13)\times 10^{-11} for meson exchange, and am = (107 ±2 ±46)×10-11\ensuremath a_\mu = (107 \pm 2 \pm 46)\times 10^{-11} for the quark loop. The former is commensurate with past calculations; the latter much larger due to dressing effects. This
leads to a revised estimate of am=116 591 865.0(96.6)×10-11\ensuremath a_\mu=116 591 865.0(96.6)\times 10^{-11} , reducing the difference between theory and experiment to ≃ 1.9s \sigma . 相似文献
7.
We study theoretically electronic transport through a contact of a quantum wire with 2D or 3D leads and find that if the contact
is not smooth and adiabatic then the conduction is strongly suppressed below a threshold voltage V
T
, while above V
T
the dc current $
\bar I
$
\bar I
is accompanied by coherent oscillations of frequency f = $
\bar I
$
\bar I
/e. The effect is related to interelectronic repulsion and interaction of dc current with the Friedel oscillations near a sharp
contact. In short conducting channels of length L < L
0 ≅ ℏV
F
/eV
T
and at high temperatures T > T
0 ≅ eV
T
/k
B the effect is destroyed by fluctuations. 相似文献
8.
V. Yu. Topolov 《Physics of the Solid State》2012,54(3):478-484
The specific features of the phase coexistence in crystals of (Bi1 − z
Pb
z
)FeO3 multiferroic solid solutions with a significantly distorted perovskite unit cell below the Curie temperature T
C have been investigated. Some examples of the evolution of the Pm[`3]m = R3cPm\bar 3m = R3c, R3c-C2/m, and R3c-Pbnm heterophase structures and different scenarios of mechanical stress relaxation in the presence of several types of twin domains
of the R3c phase have been analyzed. The Pm[`3]m = R3cPm\bar 3m = R3c heterophase structures in the temperature intervals [T
C-150 K; T
C] (z = 0.025) and [T
C-185 K; T
C] (z = 0.050) have been interpreted. The results have been systematized using the diagrams relating twin structures and phase
boundaries at 0 ≤ z ≤ 0.100. 相似文献
9.
F.?Huang A.?Sibirtsev J.?Haidenbauer S.?Krewald U.?-G.?Mei?ner 《The European Physical Journal A - Hadrons and Nuclei》2010,44(1):81-92
A global analysis of the world data on differential cross-sections and polarization asymmetries of backward pion-nucleon scattering
for invariant collision energies above 3GeV is performed in a Regge model. Including the Na\ensuremath N_{\alpha} , Ng\ensuremath N_{\gamma} , Dd\ensuremath \Delta_{\delta} and Db\ensuremath \Delta_{\beta} trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable u , in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below
3GeV. Our analysis suggests a G39\ensuremath G_{39} -resonance with a mass of 2.83GeV as member of the Db\ensuremath \Delta_{\beta} -trajectory from the corresponding Chew-Frautschi plot. 相似文献
10.
Using chiral perturbation theory we calculate for pion Compton scattering the isospin-breaking effects induced by the difference
between the charged and neutral pion mass. At one-loop order this correction is directly proportional to mp±2-mp02\ensuremath{m_{\pi^\pm}^2-m_{\pi^0}^2} and free of (electromagnetic) counterterm contributions. The differential cross-section for charged pion Compton scattering
p-g? p-g\ensuremath{\pi^-\gamma \rightarrow \pi^-\gamma} gets affected (in backward directions) at the level of a few permille. At the same time the isospin-breaking correction leads
to a small shift of the pion polarizabilities by d(ap- bp) @ 1.3 ·10-5\ensuremath{\delta(\alpha_\pi- \beta_\pi) \simeq 1.3 \cdot 10^{-5}} fm^3. In case of the low-energy gg? p0p0\ensuremath{\gamma\gamma \rightarrow \pi^0\pi^0} reaction isospin breaking manifests itself through a cusp effect at the p+p-\ensuremath{\pi^+\pi^-} threshold. We give an improved estimate for it based on the empirical p \pi
p \pi -scattering length difference a0-a2\ensuremath{a_0-a_2} . 相似文献
11.
12.
We study effects of static inter-qubit interactions on the stability of the Grover quantum search algorithm. Our numerical and analytical results show existence of regular and chaotic phases depending on the imperfection strength
e\varepsilon
. The critical border
ec\varepsilon_c
between two phases drops polynomially with the number of qubits n
q
as
ec ~ nq-3/2\varepsilon_c \sim n_q^{-3/2}
. In the regular phase
(e < ec)(\varepsilon < \varepsilon_c)
the algorithm remains robust against imperfections showing the efficiency gain
ec / e\varepsilon_c / \varepsilon
for
e >~2-nq/2\varepsilon \gtrsim 2^{-n_q/2}
. In the chaotic phase
$(\varepsilon > \varepsilon_c)$(\varepsilon > \varepsilon_c)
the algorithm is completely destroyed. 相似文献
13.
Nian-quan Jiang Hong-yi Fan Shuai Wang Jun-hua Chen Long-Ying Tang Wen-Jing Gu Gen-Chang Cai 《International Journal of Theoretical Physics》2011,50(11):3610-3615
The usual Virial theorem is expressed through the coordinate and the force,
2áT? = áX\fracdVdX? = -áXF?2\langle T\rangle =\langle X\frac{dV}{dX}\rangle =-\langle XF\rangle ,
F=-\fracdVdXF=-\frac{dV}{dX}, XF is the work done by the force F, T is the kinetic energy. In this paper we extend the usual discussion on the Virial theorem about coordinate-force variables
to the case of angular displacement-torque variables. By virtue of introducing the entangled state representation and the
bosonic operator realization of the Hamiltonian of quantum pendulum system we derive the Virial theorem for angular variable
and torque. 相似文献
14.
A method for the determination of the noise spectral density in a high-temperature microwave SQUID operating in the hysteresis regime is developed. Under these conditions, the reflection coefficient serves as an output signal. It is shown that if a directional coupler used for extracting the reflected wave is placed as close to the SQUID loop as possible, the magnetometer can be designed as a microwave integrated circuit with a noise flux spectral density SF 1/2 < 10 - 5 F0 /\textHz\text0\text.5 ,\textwhere F\text0 S_\Phi ^{1/2} < 10^{ - 5} \Phi _0 /{\text{Hz}}^{{\text{0}}{\text{.5}}} ,{\text{where }}\Phi _{\text{0}} , is the magnetic flux quantum. 相似文献
15.
L. Museur A.V. Kanaev M.C. Castex L. Moussavizadeh R. von Pietrowski T. Möller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):73-78
Charge-transfer reactions are observed in a photoluminescence study of NF3\rm NF_3-doped free krypton clusters. They show up in emissions from Kr+F-\rm Kr^{+}F^{-}free excimers ejected from the clusters, and from excited Kr2+F-\rm Kr_2^{+}F^{-}and Kr2+(NF3)m-{\rm Kr}_2^{+}({\rm NF}_3)_m^{-} (m 3(m\geq 1) solvated in the clusters. The results show that reaction dynamics in clusters differs considerably from that in the gas and solid phases. 相似文献
16.
Todd A. Oliynyk 《Communications in Mathematical Physics》2010,295(2):431-463
We prove the existence of a large class of one parameter families of solutions to the Einstein-Euler equations that depend
on the singular parameter e = vT/c{\epsilon=v_T/c}
(0 < e < e0){(0< \epsilon < \epsilon_0)}, where c is the speed of light, and v
T
is a typical speed of the gravitating fluid. These solutions are shown to exist on a common spacetime slab
M @ [0,T)×\mathbb T3{M\cong [0,T)\times \mathbb {T}^3}, and converge as
e\searrow 0{\epsilon \searrow 0} to a solution of the cosmological Poisson-Euler equations of Newtonian gravity. Moreover, we establish that these solutions
can be expanded in the parameter e{\epsilon} to any specified order with expansion coefficients that satisfy e{\epsilon}-independent (nonlocal) symmetric hyperbolic equations. 相似文献
17.
M. Siomau S. Fritzsche 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):397-403
We study entanglement dynamics of the three-qubit system
which is initially prepared in pure Greenberger-Horne-Zeilinger
(GHZ) or W state and transmitted through one of the Pauli channels
sz\sigma_z, sx\sigma_x, sy\sigma_y or the depolarizing channel.
With the help of the lower bound for three-qubit concurrence we show
that the W state preserves more entanglement than the GHZ state in
transmission through the Pauli channel sz\sigma_z. For the Pauli
channels sx\sigma_x, sy\sigma_y and the depolarizing channel,
however, the entanglement of the GHZ state is more resistant against
decoherence than the W-type entanglement. We also briefly discuss
how the accuracy of the lower bound approximation depends on the
rank of the density matrix under consideration. 相似文献
18.
The calculations developed in this paper aim at determining the optimal conditions of a NQR experiment when a transition is monitored by means of a pulse train with pulses of identical duration and signal acquisition after each pulse; coherences are assumed to vanish by effective transverse relaxation prior to every new pulse. These calculations demonstrate that, as in NMR, a steady state is effectively reached for any value of the recycle time. However, by contrast with NMR, it is shown that, for optimal data averaging under steady state conditions, the recycle time T can be kept as low as possible (the only limitation is the acquisition time). Nutation curves (signal amplitude versus pulse length) calculated in the steady state case are shown to depend strongly on the ratio T/T 1 (T 1: longitudinal relaxation time). The signal growth as a function of T/T 1under averaging of the first transients has been evaluated as well as the number of pulses necessary for reaching a steady state. 相似文献
19.
S. G. Kadmensky D. E. Lyubashevsky 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(4):457-461
Anisotropy in the angular distributions of cascade-evaporation neutrons in center-of-mass systems emitting their fission fragments
is analyzed in the context of the quantum theory of fission. It is emphasized that such anisotropy is caused not by bending
but by wriggling oscillations of the fissioning nucleus in the vicinity of its point of scission; these lead to the appearance
of high-value spins of primary fission fragments [(J)\vec]1\vec J_1 and [(J)\vec]2\vec J_2 oriented in a plane perpendicular to direction [(n)\vec]0\vec n_0 of the axis of symmetry of the fissioning nucleus at the instant of scission. This direction coincides with the asymptotic
direction of the emission of fission fragments with a high degree of accuracy. The analytical dependences of the anisotropy
coefficient on the orbital momentum l and total spin j in angular distributions of cascade-evaporation neutrons are calculated using the methods developed in analyzing angular
distributions of cascade-evaporation gamma quanta. The proper spin of a neutron is shown to have almost no effect on the aforesaid
anisotropy coefficient due to the weak dependence of the neutron transmission coefficient T
lj
([`(e)]\bar \varepsilon ) on the values of j. 相似文献
20.
J. Stanzel F. Burmeister M. Neeb 《Applied Physics A: Materials Science & Processing》2010,100(1):21-29
We have studied the dynamics of photoexcited tungsten cluster anions Wn-\mathrm{W}_{n}^{-} (n=3,4,…,14) by means of time-resolved two-photon photodetachment spectroscopy. At an excitation energy of h
ν
pump=1.56 eV the photoinduced dynamics is mainly dominated by fast electronic relaxation processes. For the smallest clusters,
i.e., W3-\mathrm{W}_{3}^{-}, W4-\mathrm{W}_{4}^{-}, and W5-\mathrm{W}_{5}^{-}, individual relaxation channels have been identified and resolved on a timescale well below 100 fs. The time constants for
the decay of nascent and secondary electrons have been deduced from a Bloch model. Complete thermalization takes place for
all clusters on a timescale of ∼1 ps. 相似文献