共查询到17条相似文献,搜索用时 562 毫秒
1.
Nonadiabatic effects on population transfer of two Bose-Einstein condensates induced by atomic interaction
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We investigate the stimulated Raman adiabatic passage for Bose-Einstein condensate (BEC) states which are trapped in different potential wells or two ground states of BEC in the same trap. We consider that lasers are nearly resonant with the atomic transitions. The difference of population transfer processes between BEC atoms and usual atoms is that the atomic interaction of the BEC atoms can cause some nonadiabatic effects, which may degrade the process. But with suitable detunings of laser pulses, the effects can be remedied to some extent according to different atomic interactions. 相似文献
2.
YUZhao-Xiao JIAOZhi-Yong 《理论物理通讯》2001,36(2):240-244
It is shown that the atomic tunneling current and the Shapiro-like steps strongly depend on the initial number of atoms in each condensate and the initial phase difference between the two condensates which are initially in even(odd) coherent states.The nonlinearity of interatomic interactions in the two condensates may lead to the atomic tunneling current and Shapiro-like step between the two condensates.It is found that the interatomic nonlinear interactions can induce the atomic tunneling current and Shapiro-like step between two condensates even though there does not exist the interspecies Josephson-like tunneling coupling.The static atomic tunneling current flows in positive or negative direction,which depends on the phase difference of the two-species condensates. 相似文献
3.
Nonadiabatic effects on population transfer of two Bose-Einstein condensates induced by atomic interaction
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We investigate the stimulated Raman adiabatic passage for Bose-Einstein condensate (BEG) states which are trapped in different potential wells or two ground states of BEG in the same trap. We consider that lasers are nearly resonant with the atomic transitions. The difference of population transfer processes between BEG atoms and usual atoms is that the atomic interaction of the BEG atoms can cause some nonadiabatic effects, which may degrade the process. But with suitable detunings of laser pulses, the effects can be remedied to some extent according to different atomic interactions. 相似文献
4.
Two-colour coherent control of multiphoton ionization: a comparison between long-range and short-range potential model atoms
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Using the numerical solution of the time-dependent Schr\"odinger
equation of a one-dimensional model atom in a two-colour laser field,
we have investigated the effects of the potential models on coherent
control of atomic multiphoton ionization. It is found that the
photoelectron spectra are obviously different for the long-range
(Coulomb-like) and short-range (with no excited bound states)
potential model atoms, which are produced by two-colour coherent
control of atomic multiphoton ionization in a few laser cycles. Our
results indicate that two-colour coherent control of atomic
multiphoton ionization can be observed in simulations, depending on
the choice of the model potentials. 相似文献
5.
This paper investigates the squeezing properties of an atom laser
without rotating-wave approximation in the system of a binomial states
field interacting with a two-level atomic Bose--Einstein condensate.
It discusses the influences of atomic eigenfrequency, the interaction
intensity between the optical field and atoms,parameter of the binomial
states field and virtual photon field on the squeezing properties.
The results show that two quadrature components of an atom laser can be
squeezed periodically. The duration and the degree of squeezing an atom
laser have something to do with the atomic eigenfrequency and the parameter
of the binomial states field, respectively. The collapse and revival
frequency of atom laser fluctuation depends on the interaction intensity
between the optical field and atoms. The effect of the virtual photon field
deepens the depth of squeezing an atom laser. 相似文献
6.
Tunnelling of Two-Level Atoms in Two-Photon Mazer: Atomic Coherence Effect and Statistics of Cavity Fields
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Tunnelling of a two-level atom is investigated in the two-photon mazer when the atom is initially prepared in a coherent superposition state and the cavity in various quantum states. For a strong coherent field, the tunnelling exhibits more regular oscillations but less remarkable switch effect than that in the one-photon mazer. It is discovered that in the presence of atomic coherence, the transmission probabilities in the ultracold regime are significantly different when the cavity field is initially in coherent, squeezed vacuum, even cat and odd cat states, respectively. 相似文献
7.
Stationary entanglement between two spatially separated atoms driven by a coherent laser field
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This paper studies quantum entanglement between two spatially
separated atoms driven by a coherent laser field in the dissipative
process of spontaneous emission. It is shown that the entanglement
strongly depends on the detuning of the laser frequency from atomic
transition frequency, the interatomic separation and the Rabi
frequency of the coherent laser field. A considerable amount of
steady state entanglement can be obtained near Δ=-α
(i.e., the dipole--dipole interaction and the detuning cancel out
mutually) for small atomic separation and large Rabi frequency of
the coherent laser field. 相似文献
8.
We have studied the evolutions of the population transfer, tunnelling current and antibunching effects between spin-(+1) and spin-(-1) in the case of the strong laser pulses. It is found that the population transfer and tunnelling current exhibit periodical oscillation. For the same Rabi frequency, the larger the atom number, the longer the oscillation period is. For the spin-(-1) component, when the atomic numbers are N=4 and 10, the antibunching effect can appear. For different atomic numbers, the appearing regions are very different. For spin component +1, the antibunching effect can always appear for different atomic numbers. 相似文献
9.
Internal Josephson-like tunnelling in two-component Bose--Einstein condensates affected by sign of the atomic interaction and external trapping potential
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This paper studies the Josephson-like tunnelling in two-component
Bose--Einstein condensates coupled with microwave field,
which is in respond to various attractive and repulsive atomic interaction
under the various aspect ratio of trapping potential. It is very
interesting to find that the dynamic of Josephson-like tunnelling can
be controlled from fast damped oscillations to nondamped oscillation,
and relative number of atoms changes from asymmetric occupation to
symmetric occupation correspondingly. 相似文献
10.
A space-dependent atomic superfluid current with an explicit analytical expression and its role in Bose–Einstein condensates are studied. The factors determining the intensity and oscillating amplitude of the space-dependent atomic superfluid current are explored in detail. Research findings reveal that the intensity of the current can be regulated by setting an appropriate configuration of the trap and its oscillating amplitude can be adjusted via Feshbach resonance. It is numerically demonstrated that the space-dependent atomic superfluid current can exert great influence on the spatial distribution of condensed atoms, and even force condensed atoms into very complex distributional states with spatial chaos. 相似文献
11.
Interference of an atomic Bose-Einstein condensate interacting
with a laser field in a double-well potential with dissipation is
investigated. If properly selecting the laser field and the
initial states of the atoms in the two wells, we find that the
intensity exhibits revivals and collapses. The fidelity of
interference is affected by the total number of atoms in the two wells and dissipation. 相似文献
12.
We have investigated quantum statistical behaviors of photons and atoms in interaction of an atomic Bose-Einstein condensate with quantized laser field. When the quantized laser field is initially prepared in a superposition state which exhibits holes in its photon-number
distribution, while the atomic field is initially in a Fock state,
it is found that there is energy exchange between photons and atoms.
For the input and output states, the photons and atoms may exhibit the
sub-Poissonian distribution. The input and output laser fields may
exhibit quadrature squeezing, but for the atomic field, only the output
state exhibits quadrature squeezing. It is shown that there exists the
violation of the Cauchy-Schwartz inequality, which means that the
correlation between photons and atoms is nonclassical. 相似文献
13.
YU Zhao-Xian JIAO Zhi-Yong 《理论物理通讯》2001,(10)
We have investigated quantum statistical behaviors of photons and atoms in interaction of an atomic Bose Einstein condensate with quantized laser field. When the quantized laser field is initially prepared in a superposition state which exhibits holes in its photon-number distribution, while the atomic field is initially in a Fock state, it is found that there is energy exchange between photons and atoms. For the input and output states, the photons and atoms may exhibit the sub-Poissonian distribution. The input and output laser fields may exhibit quadrature squeezing, but for the atomic field, only the output state exhibits quadrature squeezing. It is shown that there exists the violation of the Cauchy-Schwartz inequality, which means that the correlation between photons and atoms is nonclassical.`` 相似文献
14.
Harro G. Andresen 《Zeitschrift für Physik A Hadrons and Nuclei》1969,223(1):71-102
The conventional atomic beam preparation technique for hydrogen maser operation consists of a six pole magnetic field focussing in combination with adiabatically changing magnetic fields in the transition region between focusser and maser cavity, which results in a state selected, polarized ensemble of hydrogen atoms. Hydrogen maser operation with state selected, but unpolarized atoms has the advantage to reduce considerably the sensitivity of hydrogen maser frequency on coherently excited, low frequency,Δm F =±1 Zeeman transitions. The influence of the magnetic field pattern in the transition region on the energy level population probabilities for the focussed hydrogen beam has been analysed. Atomic beam preparation techniques using non-adiabatically changing magnetic field configurations in the transition region are described. The dependence of hydrogen maser oscillation on the energy level population within the atomic beam is theoretically investigated and the results are used for the analysis of the experimentally achieved atomic beam populations. It has been shown that a pulsed magnetic spin guidance field in the transition region, which switches between adiabatically changing magnetic field configurations and a sudden magnetic field reversal, results in an ensemble of hydrogen atoms with vanishing time averaged polarization, which does not deteriorate the conventionally achieved maser oscillation amplitude. 相似文献
15.
16.
V. F. Elesin 《Journal of Experimental and Theoretical Physics》2005,101(5):795-810
A theory of coherent resonance tunneling of electrons in a two-well nanostructure (TWNS) in the presence of a strong electromagnetic field is developed. The TWNS consists of two identical tunnel-coupled quantum wells to which a dc electric field is applied. Radiative transitions occur between two levels that arise due to the interwell interference and the dc electric field. The wavefunctions and polarization currents in the TWNS are found in the case of a strong electromagnetic field, and the oscillation power is determined as a function of the coherent pumping current and the parameters of the structure. It is shown that oscillations are possible in the relevant terahertz band, with fine frequency tuning by a dc field. It is found that the interference of electrons between quantum wells plays a crucial role. This interference significantly suppresses the effect of the electromagnetic field on the resonance tunneling and enhances the oscillation up to the highest possible level. It is proved that there exists an optimal regime of strong-field oscillations without inverse population and saturation, which are inherent in conventional lasers. 相似文献
17.
V. P. Krainov 《Journal of Experimental and Theoretical Physics》2003,96(3):430-435
The Weibel instability increment is analytically derived for plasma produced at the barrier-suppression ionization of atoms and atomic ions by a superintense femtosecond laser pulse. The cases of linear and circular polarization are considered. Relativistic effects are discussed. It is found that the instability increment is larger for the circular polarization than for the linear polarization. This increment can attain the plasma frequency. Barrier-suppression ionization decreases the increment compared with the case of tunneling ionization. Relativistic effects also decrease the value of the increment. Estimates of the produced maximum quasistatic magnetic field are given. 相似文献