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Dynamic Properties for BEC in an Optical Cavity with Atom-Photon Nonlinear Interaction
摘要： In this paper we investigate the dynamics of physical properties of the system introduced in Dimer et al. (Phys. Rev. A 75, 013804, 2007) and Zhao et al. (Phys. Rev. A 90, 023622, 2014) consisting of an ensemble of four-level atoms in Bose-Einstein condensate (BEC) state and a single-mode quantized field in which nonlinear interaction is taken into account. In fact, we start with a four-level atom and then explain how this model can be reduced to an effective two-level one via the adiabatic elimination. Also, our presentation is free of any classical approximation and so it is fully quantized. In this regard, we introduce the dynamical Hamiltonian of the system in terms of angular momentum operators and use the Dicke model to achieve the state of atomic sub-system. After obtaining the analytical solution of the state vector associated with the quantized BEC-field system, various physical properties such as atomic population inversion, quantum statistics of the field, squeezing in atomic and field subsystems as well as the degree of entanglement between the “BEC atoms” and the “photons” are numerically evaluated. It is shown that, the nonlinear interaction and other involved parameters in the presented model can dramatically affect the dynamics of the system. The collapse-revival phenomenon in the population inversion, Mandel parameter and atomic squeezing is a superb feature of the system which can be controlled by tuning the chosen parameters. Meanwhile, we propose an efficient way for the generation of sub-Poissonian and squeezed fields as well as squeezed atoms via nonlinear interaction of quantized filed with atomic BEC. In addition, it is found that, after the onset of interaction the system is always entangled. Altogether, under particular conditions, the approximated sudden death and then revival of entanglement can be observed.
关键词： Entanglement,Bose-Einstein condensate,Atomic population inversion,Atomic squeezing,Collapse-revival phenomenon
更新于2025-09-23 15:22:29
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Dark–bright solitons in spinor polariton condensates under nonresonant pumping
摘要： By adopting a mean-field Gross-Pitaevskii description of spinor polariton Bose-Einstein condensates under nonresonant pumping, we investigate the static and dynamical properties of dark-bright (DB) solitons. We derive the equation of motion for the center of mass of the DB solitons' center analytically by using the Hamiltonian approach. The resulting equation captures how the combination of the open-dissipative character and the spin degrees of freedom of a polariton Bose-Einstein condensate affects the properties of DB solitons, i.e. DB solitons relax by blending with the background at a finite time. In this case, we also determine the lifetime of the DB solitons. Further numerical solutions of the modified dissipative two-component Gross-Pitaevskii equations are in excellent agreement with the analytical results. In the presence of the Langevin noise, we demonstrate that the DB solitons can still propagate for a long time, which is sufficient for their experimental observations within current facilities.
关键词： polariton Bose-Einstein condensate,dark-bright solitons,mean-field method,stochastic GP equations
更新于2025-09-23 15:22:29
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Tuning of non-paraxial effects of the Laguerre-Gaussian beam interacting with the two-component Bose–Einstein condensates
摘要： We present the theory of microscopic interaction of the spin-orbit coupled focused Laguerre-Gaussian beam with the two-component Bose–Einstein condensate, composed of two hyperfine states of 87Rb in a harmonic trap. We have shown that Raman Rabi frequency distributions over the inter-component coupling identify phase separation coupling strength. A significant enhancement of side-band transitions due to non-paraxial nature of vortex beam is observed for particular values of inter-component coupling around 1.25 and 0.64 in unit of 5.5 nm for 105 and 106 number of atoms, respectively. The uncertainty in the estimation of these coupling strengths is improved with the focusing angles of the beam. We discuss an experimental scheme to verify this non-paraxial effect on ultra-cold atoms.
关键词： Laguerre-Gaussian beam,Bose–Einstein condensate,non-paraxial effects
更新于2025-09-23 15:22:29
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Quantum Rotation Sensing with Dual Sagnac Interferometers in an Atom-Optical Waveguide
摘要： We describe a Sagnac interferometer suitable for rotation sensing, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap. The atom wave packets are split and recombined by standing-wave Bragg lasers, and the trapping potential steers the packets along circular trajectories with a radius of 0.2 mm. Two conjugate interferometers are implemented simultaneously to provide common-mode rejection of noise and to isolate the rotation signal. With interference visibilities of about 50%, we achieve a rotation sensitivity comparable to Earth’s rate in about 10 min of operation. Gyroscope operation was demonstrated by rotating the optical table on which the experiment was performed.
关键词： Sagnac Interferometers,Quantum Rotation Sensing,Rotation Sensitivity,Atom-Optical Waveguide,Bose-Einstein Condensate
更新于2025-09-23 15:21:01
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Polariton condensation in photonic crystals with high molecular orientation
摘要： We study Frenkel exciton-polariton Bose–Einstein condensation in a two-dimensional defect-free triangular photonic crystal with an organic semiconductor active medium containing bound excitons with dipole moments oriented perpendicular to the layers. We ?nd photonic Bloch modes of the structure and consider their strong coupling regime with the excitonic component. Using the Gross– Pitaevskii equation for exciton polaritons and the Boltzmann equation for the external exciton reservoir, we demonstrate the formation of condensate at the points in reciprocal space where photon group velocity equals zero. Further, we demonstrate condensation at non-zero momentum states for transverse magnetic-polarized photons in the case of a system with incoherent pumping, and show that the condensation threshold varies for different points in the reciprocal space, controlled by detuning.
关键词： organic semiconductors,photonic crystalls,photonics,exciton polaritons,Bose–Einstein condensate
更新于2025-09-23 15:21:01
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Non-linear relaxation of interacting bosons coherently driven on a narrow optical transition
摘要： We study the dynamics of a two-component Bose-Einstein condensate (BEC) of 174Yb atoms coherently driven on a narrow optical transition. The excitation transfers the BEC to a superposition of states with di?erent internal and momentum quantum numbers. We observe a crossover with decreasing driving strength between a regime of damped oscillations, where coherent driving prevails, and an incoherent regime, where relaxation takes over. Several relaxation mechanisms are involved: inelastic losses involving two excited atoms, leading to a non-exponential decay of populations; Doppler broadening due to the ?nite momentum width of the BEC and inhomogeneous elastic interactions, both leading to dephasing and to damping of the oscillations. We compare our observations to a two-component Gross-Pitaevskii (GP) model that fully includes these e?ects. For small or moderate densities, the damping of the oscillations is mostly due to Doppler broadening. In this regime, we ?nd excellent agreement between the model and the experimental results. For higher densities, the role of interactions increases and so does the damping rate of the oscillations. The damping in the GP model is less pronounced than in the experiment, possibly a hint for many-body e?ects not captured by the mean-?eld description.
关键词： coherent driving,Bose-Einstein condensate,narrow optical transition,Gross-Pitaevskii model,relaxation mechanisms
更新于2025-09-23 15:21:01
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Four-wave mixing in spin-orbit coupled Bose-Einstein condensates
摘要： We describe possibilities of spontaneous, degenerate four-wave mixing (FWM) processes in spin-orbit coupled Bose-Einstein condensates. Phase matching conditions (i.e., energy and momentum conservation laws) in such systems allow one to identify four different configurations characterized by involvement of distinct spinor states in which such a process can take place. We derived these conditions from first principles and then illustrated dynamics with direct numerical simulations. We found, among others, the unique configuration, where both probe waves have smaller group velocity than pump wave and proved numerically that it can be observed experimentally under proper choice of the parameters. We also reported the case when two different FWM processes can occur simultaneously. The described resonant interactions of matter waves is expected to play important role in the experiments of BEC with artificial gauge fields. Beams created by FWM processes are important source of correlated particles and can be used the experiments testing quantum properties of atomic ensembles.
关键词： four-wave mixing,Bose-Einstein condensate,Spin-orbit coupling
更新于2025-09-23 15:19:57
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Geometric phase transferred from photonic mode to atomic BEC
摘要： A process of geometric phase generation in a composite matter-field system is considered. Two atomic modes correspond to different localizations of a single Bose–Einstein condensate (BEC). One of the trapping localizations is formed by a photonic mode of a ring cavity. The photonic mode is governed by an external harmonic field source, by dissipation and by the number of localized atoms due to their non-resonant interaction with photons. This interaction gives rise to entanglement between the BEC and the photonic mode. By varying the intensity and frequency of the external source, it is possible to create a geometric phase for the optical mode. Because of the entanglement between the state of atomic and photonic modes, geometric phase acquired by the latter causes modification of the BEC state. This modification can be revealed by studying the tunneling between the atomic localizations.
关键词： Bose–Einstein condensate,Geometric phase,Two-mode approximation
更新于2025-09-19 17:15:36
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Controlled creation of a singular spinor vortex by circumventing the Dirac belt trick
摘要： Persistent topological defects and textures are particularly dramatic consequences of superfluidity. Among the most fascinating examples are the singular vortices arising from the rotational symmetry group SO(3), with surprising topological properties illustrated by Dirac’s famous belt trick. Despite considerable interest, controlled preparation and detailed study of vortex lines with complex internal structure in fully three-dimensional spinor systems remains an outstanding experimental challenge. Here, we propose and implement a reproducible and controllable method for creating and detecting a singular SO(3) line vortex from the decay of a non-singular spin texture in a ferromagnetic spin-1 Bose–Einstein condensate. Our experiment explicitly demonstrates the SO(3) character and the unique spinor properties of the defect. Although the vortex is singular, its core fills with atoms in the topologically distinct polar magnetic phase. The resulting stable, coherent topological interface has analogues in systems ranging from condensed matter to cosmology and string theory.
关键词： Bose–Einstein condensate,spinor systems,superfluidity,topological defects,SO(3) vortices
更新于2025-09-19 17:13:59
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Generation of various classes of entangled states in a two-mode Bose–Einstein condensate under the influence of interatom collisions
摘要： In this paper, we generate some new classes of entangled states of a bimodal Bose–Einstein condensate (BEC), a pair of tunnel-coupled BEC, in the presence of two- and three-body elastic as well as mode-exchange collisions. The Hamiltonian of the considered system is very complicated, moreover, it can be fortunately transformed into a simple form using a two-mode displacement operator. After introducing the general form of the time evolved state, various classes of entangled states are generated. Indeed, the influence of different orders of tunneling strengths on the generated entangled states has been studied. Depending on the tunneling strength constants, two-, three- and four-partite entangled states are generated, all of which are superposition states of macroscopic number of BEC atoms. Considering three-particle collision dramatically changes the generated entangled states. Moreover, in particular cases, the resulted states are non-entangled. Also, we show that tunneling and collisional interactions can be manipulated to generate a pair of atomic entangled coherent states (quasi-Bell states). In addition, it is observed that the degree of entanglement for two-partite entangled states can be tuned via the number of BEC atoms, i.e. the corresponding concurrences tend to their maximum value by increasing the atoms in both modes of system.
关键词： interatom collision,Bose–Einstein condensate,concurrence,entangled state
更新于2025-09-16 10:30:52