本文证明了在均匀电场中氢原子的激发态（斯塔克态）具有磁荷，磁荷的大小由Dirac-Saha型关系式给出：$$ {eg\over \hbar c} = \sqrt 3 n $$提出了一种制备这种态并检测其磁荷的实验方法。
英文摘要：
It is shown that the excited states of hydrogen atom in a uniform electric field (Stark States) posess magnetic charge whose magnitude is given by a Dirac-Saha type relation: $$ {eg\over \hbar c} = \sqrt 3 n $$ An experiment is proposed to fabricate such states and to detect their magnetic charge.
Ultracold atom-traps on a chip enhances the practical application of atom traps in quantum information processing, sensing, and metrology. Plasmon mediated near-field optical potentials are promising for trapping atoms. The combination of plasmonic nanostructures and ultracold atoms has the potential to create a two dimensional array of neutral atoms with lattice spacing smaller than that of lattices created from interfering light fields -- the optical lattices. We report the design, fabrication and characterization of a nano-scale array of near-field optical traps for neutral atoms using plas…
We compute the conservative van-der-Waals forces between two atoms, one of which is initially excited, in the limit of identical atoms. Starting with the perturbative calculation of the interaction between two dissimilar atoms, we show that a time-dependent approach in the weak-interaction approximation is essential in considering the identical atoms limit in the perturbative regime. In this limit we find that, at leading order, the van-der-Waals forces are fully-resonant and grow linearly in time, being different upon each atom. The resultant net force upon the two-atom system is related to t…
The transient Casimir-Polder force on a two-level atom introduced into a three-dimensional, inhomogeneous, generally non-reciprocal environment is evaluated using non-Markovian Weisskopf-Wigner theory in the strong and weak coupling regimes. Ground-state and excited atoms are considered as two separate initial-value problems, and both the short-time and long-time atomic population and force are evaluated. The results are compared with various Markov approximation of the Weisskopf-Wigner theory, and with previous Markov results from the Heisenberg picture.
We generalize the theoretical modeling of collective atomic super- and subradiance to the multilevel case including spontaneous emission from several excited states towards a common ground state. We show that in a closely packed ensemble of $N$ atoms with $N-1$ distinct excited states each, one can find a new class of non-radiating dark states,, which allows for long-term storage of $N-1$ photonic excitations. Via dipole-dipole coupling only a single atom in the ground state is sufficient in order to suppress the decay of all $N-1$ other atoms. By means of some generic geometric configurations…
When a resonant photon traverses a sample of absorbing atoms, how much time do atoms spend in the excited state? Does the answer depend on whether the photon is ultimately absorbed or transmitted? In particular, if it is $\textit{not}$ absorbed, does it cause atoms to spend any time in the excited state, and if so, how much? In an experiment with ultra-cold Rubidium atoms, we simultaneously record whether atoms are excited by incident ("signal") photons and whether those photons are transmitted. We measure the time spent by atoms in the excited state by using a separate, off-resonant "probe" l…
We suggest a regular method of achieving an extremely long lifetime of a collective singly excited state in a generic small-size ensemble of N identical atoms. The decay rate Γ_N of such a `superdark' state can be as small as Γ_N \propto Γ(r/λ)^{2(N-1)} (Γis the radiative decay rate of an individual atom, r and λare the system size and the wavelength of the radiation, respectively), i.e., considerably smaller than in any of the systems suggested up to now. The method is based on a special fine tuning of the atomic Hamiltonian: namely, on a proper position-dependent adjustment of atomic transit…
One-dimensional (1D) subwavelength atom arrays display multiply excited subradiant eigenstates which are reminiscent of free fermions. So far, these states have been associated with subradiant states with decay rates $\propto N^{-3}$, with N the number of atoms, which fundamentally prevents detection of their fermionic features by optical means. In this Letter, we show that free-fermion states generally appear whenever the band of singly excited states has a quadratic dispersion relation at the band edge and, hence, may also be obtained with radiant and even superradiant states. 1D arrays have…
Number-resolved imaging of excited-state atoms using a scanning autoionization microscope
我们报道了一种对激发态原子进行原子数分辨成像的扫描显微镜技术。紧密聚焦的激光束导致局部自电离，并且产生的离子被电子计数。扫描穿过云的光束建立了激发原子密度分布的图像，可以在每个空间采样点获得完整的计数统计数据，总体检测效率为21%。我们应用这种技术的测量空间不均匀的电场的空间分辨率为50？m，对电场梯度的灵敏度为0.04 V cm $^{-2}$。
We study the Casimir-Polder potential of a multilevel alkali-metal atom near an optical nanofiber. We calculate the mean potential of the atom in a fine-structure level. We perform numerical calculations for the Casimir-Polder potentials of the ground state and a few low-lying excited states of a rubidium atom. We show that, unlike the potential of the ground state, which is negative and attractive, the potential of a low-lying excited state may take positive values, oscillate around the zero value with a decaying amplitude, and become repulsive in some regions of atom-to-surface distances. We…
The scalar and tensor components of the electric quadrupole (E2) polarizabilities of the first two excited states of all the alkali-metal atoms are determined. To validate the calculations, we have evaluated the ground state E2 polarizabilities of these atoms and compared them with the literature values. We could not find the ground state E2 polarizability value for Fr in the literature to compare with our result. The dominant parts of these quantities are estimated by combining the precisely calculated E2 transition matrix elements of many low-lying transitions with the experimental energies,…
Van der Waals interaction and spontaneous decay of an excited atom in a superlens-type geometry
在宏观量子电动力学的框架下，研究了由左手材料和理想镜组成的平面磁电两层系统附近受激二能级原子所经历的共振范德华势.结果表明，忽略材料的吸收导致非物理的结果，与发散值的潜在远离表面。在适当的条件下，该装置被发现具有表面附近的屏障，其可用于悬浮颗粒或用作捕获或冷却机制。最后，讨论了自发衰变问题[J.Kästel和M. Fleischhauer，Phys. Rev. A \textbf{68}，011804（R）（2005）]。不考虑吸收被证明是彻底伪造的衰变率的原子位置的依赖。
Interaction between Rydberg atoms can significantly modify Rydberg excitation dynamics. Under a resonant driving field the Rydberg-Rydberg interaction in high-lying states can induce shifts in the atomic resonance such that a secondary Rydberg excitation becomes unlikely leading to the Rydberg blockade effect. In a related effect, off-resonant coupling of light to Rydberg states of atoms contributes to the Rydberg anti-blockade effect where the Rydberg interaction creates a resonant condition that promotes a secondary excitation in a Rydberg atomic gas. Here, we study the light-matter interact…
The collective effect of large amounts of atoms exhibit an enhanced interaction between light and atoms. This holds great interest in quantum optics, and quantum information. When a collective excited state of a group of atoms during Rabi oscillation is varying, the oscillation exhibits rich dynamics. Here, we experimentally observe a size-reduction effect of the Rydberg collective state during Rabi oscillation in cold atomic dilute gases. The Rydberg collective state was first created by the Rydberg quantum memory, and we observed a decreased oscillation frequency effect by measuring the time…
In this tutorial we provide a short review of attosecond pulse characterization techniques and a pedagogical account of a recently proposed method called Pulse Analysis by Delayed Absorption (PANDA) [Pabst and Dahlström, Phys. Rev. A, 94, 13411 (2016)]. We discuss possible implementations of PANDA in alkali atoms using either principal quantum number wave packets or spin-orbit wave packets. The main merit of the PANDA method is that it can be used as a pulse characterization method that is free from atomic latency effects, such as scattering phase shifts and long-lived atomic resonances. Final…
We consider the resonant Casimir-Polder interaction of an excited alkali-type atom which has a single (electric dipole) transition with a Chern insulator. The Chern insulator has a nonzero, time reversal symmetry breaking Hall conductance, leading to an additional contribution to the resonant Casimir-Polder interaction which depends on the coupling between the Hall conductance and the circular polarization state of the atomic transition. We find that the resonant Casimir-Polder shift can be significantly enhanced for de-excitation frequencies near values associated with the van Hove singularit…
