We give numerical estimates of various unstable stationary solutions of the Gross--Pitaevskii equation in an axially symmetric set up with a linear trapping potential along the symmetry axis, and a quadratic trapping along the radial direction. These represent topological coherent modes of Bose--Einstein condensates in a gravito optical surface trap (GOST). Despite their instability, we find that many of these solutions decay sufficiently slow, so that they could be realized experimentally.
We investigate an atomic three-level $Λ$-system which is exposed to two counterpropagating laser fields (inducing Raman transitions) and which is closed by a magnetic hyperfine field tuned to be in resonance with the transition between the two ground states. The influence of a homogeneous gravitational field is included in a full quantum treatment of the internal and external dynamics of the atom. It is shown that the combined influence of the gravitational field and the lasers lead for specific momentum values with a very high probability to a transition of the Landau-Zener type. This is acco…
We study the lifetime of an atom trapped in an optical vertical lattice in proximity of a massive surface using a complex scaling approach. We analyze how the presence of the surface modifies the known lifetimes of Wannier-Stark states associated to Landau-Zener tunnelling. We also investigate how the existence of a hypothetical short-distance deviation from Newton's gravitational law could affect these lifetimes. Our study is relevant in order to discuss the feasibility of any atomic- interferometry experiment performed near a surface. Finally, the difficulties encountered in applying the com…
We explore the energy dynamics of a two dimensional (2D) trapped Bose-Einstein condensate (BEC) excited by a moving red-detuned laser potential (RDLP). The trap is a combination of a power-law (PL) potential cutoff by a hard-wall box potential (HWBP). It is found that by a restricted measurment of the energy within the boundaries of the HWBP, the energy demonstrates oscillations indicative of solitons. It is then demonstrated, that the geometry of the PL potential influences the lifetime of these oscillations, i.e., the lifetime of the ensuing solitons inside the HWBP. We argue that the energy…
We report on the trapping of single Rb atoms in tunable arrays of optical tweezers in a cryogenic environment at $\sim 4$ K. We describe the design and construction of the experimental apparatus, based on a custom-made, UHV compatible, closed-cycle cryostat with optical access. We demonstrate the trapping of single atoms in cryogenic arrays of optical tweezers, with lifetimes in excess of $\sim6000$ s, despite the fact that the vacuum system has not been baked out. These results open the way to large arrays of single atoms with extended coherence, for applications in large-scale quantum simula…
We report on single Barium ions confined in a near-infrared optical dipole trap for up to three seconds in absence of any radio-frequency fields. Additionally, the lifetime in a visible optical dipole trap is increased by two orders of magnitude as compared to the state-of-the-art using an efficient repumping method. We characterize the state-dependent potentials and measure an upper bound for the heating rate in the near-infrared trap. These findings are beneficial for entering the regime of ultracold interaction in atom-ion ensembles exploiting bichromatic optical dipole traps. Long lifetime…
An optical tweezer composed of a strongly focused single-spatial-mode Gaussian beam of a red-detuned 1064-nm laser can confine a single-cesium (Cs) atom at the strongest point of the light intensity. We can use this for coherent manipulation of single-quantum bits and single-photon sources. The trapping lifetime of the atoms in the optical tweezers is very short due to the impact of the background atoms, the laser intensity fluctuation of optical tweezer and the residual thermal motion of the atoms. In this paper, we analyzed the influence of the background pressure, the trap frequency of opti…
A cryogenic neutral-atom platform with full optical access and 2-hour trap lifetime
Max-Planck-Institut für Quantenoptik（马克斯·普朗克量子光学研究所）；Fakultät für Physik, Ludwig-Maximilians-Universität München（慕尼黑大学物理学院）；Munich Center for Quantum Science and Technology（慕尼黑量子科学与技术中心）
We present the results of numerical simulations of the dynamical behavior of trajectories of ultra cold neutrons (UCN) in a magnetic trap. The main goal of our simulations was to optimize the trap parameters in order to minimize the characteristic times for removing from the trap those untrapped neutrons with relatively long escape times (cleaning the trap). Our results demonstrate that, by a proper choice of the trap parameters cleaning times can be reduced to 15 sec, or even less. Many other dynamical characteristics of the neutrons in the trap, including the conservation of the adiabatic in…
We study the electromagnetic coupling and concomitant heating of a particle in a miniaturized trap close to a solid surface. Two dominant heating mechanisms are identified: proximity fields generated by thermally excited currents in the absorbing solid and time-dependent image potentials due to elastic surface distortions (Rayleigh phonons). Estimates for the lifetime of the trap ground state are given. Ions are particularly sensitive to electric proximity fields: for a silver substrate, we find a lifetime below one second at distances closer than some ten micrometer to the surface. Neutral at…
For several decades, ions have been trapped by radio frequency (RF) and neutral particles by optical fields. We implement the experimental proof-of-principle for trapping an ion in an optical dipole trap. While loading, initialization and final detection are performed in a RF trap, in between, this RF trap is completely disabled and substituted by the optical trap. The measured lifetime of milliseconds allows for hundreds of oscillations within the optical potential. It is mainly limited by heating due to photon scattering. In future experiments the lifetime may be increased by further detunin…
Neutral atom qubits with Rydberg-mediated interactions are a leading platform for developing large-scale coherent quantum systems. In the majority of experiments to date, the Rydberg states are not trapped by the same potential that confines ground state atoms, resulting in atom loss and constraints on the achievable interaction time. In this work, we demonstrate that the Rydberg states of an alkaline earth atom, ytterbium, can be stably trapped by the same red-detuned optical tweezer that also confines the ground state, by leveraging the polarizability of the Yb$^+$ ion core. Using the previo…
Atom chips made of superconducting material can generate magnetic traps with significantly reduced noise. Recently, several designs for superconducting chips have been theoretically analyzed and experimentally tested, for cases with many vortices considered as an average vortex density. Here we show theoretically, for the first time, how the magnetic field of a $\it single$ vortex, pinned by a superconducting nano-disc of radius $\sim$100 nm and combined with an external bias field parallel to the disc surface, yields a closed 3D trap for cold atoms. The size of the trap, and its height above …
We present a novel technique for measuring the characteristics of a magneto-optical trap for cold atoms by monitoring the spontaneous emission from trapped atoms coupled into the guided mode of a tapered optical nanofiber. We show that the nanofiber is highly sensitive to very small numbers of atoms close to its surface. The size and shape of the MOT, determined by translating the cold atom cloud across the tapered fiber, is in excellent agreement with measurements obtained using the conventional method of fluorescence imaging using a CCD camera. The coupling of atomic fluorescence into the ta…
We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $5-130 μ$m from the microchip surface. The coherence lifetime in the chip trap is independent of atom-surface distance within our measurement accuracy, and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum informatio…
Thulium atoms are trapped in a magneto-optical trap using a strong transition at 410 nm with a small branching ratio. We trap up to $7\times10^{4}$ atoms at a temperature of 0.8(2) mK after deceleration in a 40 cm long Zeeman slower. Optical leaks from the cooling cycle influence the lifetime of atoms in the MOT which varies between 0.3 -1.5 s in our experiments. The lower limit for the leaking rate from the upper cooling level is measured to be 22(6) s$^{-1}$. The repumping laser transferring the atomic population out of the F=3 hyperfine ground-state sublevel gives a 30% increase for the lif…
By integrating the techniques of laser cooling and trapping with those of cavity quantum electrodynamics (QED), single Cesium atoms have been trapped within the mode of a small, high finesse optical cavity in a regime of strong coupling. The observed lifetime for individual atoms trapped within the cavity mode is $τ\approx 28$ms, and is limited by fluctuations of light forces arising from the far-detuned intracavity field. This initial realization of trapped atoms in cavity QED should enable diverse protocols in quantum information science.
There has been a recent surge of interest and progress in creating subwavelength free-space optical potentials for ultra-cold atoms. A key open question is whether geometric potentials, which are repulsive and ubiquitous in the creation of subwavelength free-space potentials, forbid the creation of narrow traps with long lifetimes. Here, we show that it is possible to create such traps. We propose two schemes for realizing subwavelength traps and demonstrate their superiority over existing proposals. We analyze the lifetime of atoms in such traps and show that long-lived bound states are possi…
Several errors in Refs. [1, 2] are corrected related to the optical trapping potentials for a state-insensitive, compensated nanofiber trap for the D2 transition of atomic Cesium. Section I corrects our basic formalism in Ref. [1] for calculating dipole-force potentials. Section II corrects erroneous values for a partial lifetime and a transition wavelength in Ref. [1]. Sections III and IV present corrected figures for various trapping configurations considered in Refs. [1] and [2], respectively.
We have developed a compact setup which enables loading a magneto-optical trap (MOT) in ultra-high vacuum (UHV) environment. Nearly $1 \times 10^{8}$ atoms of $^{87}Rb$ are trapped in the MOT at $\sim 2 \times 10^{-10}$ Torr base pressure in the chamber. After the MOT loading, we have successfully demonstrated working of quadrupole magnetic trap in this chamber with a lifetime of $\sim 8 $ s
We demonstrate trapping and quantum state control of single Cesium atoms in a 532 nm wavelength bottle beam trap. The three dimensional trap is formed by crossing two unit charge vortex beams. Single atoms are loaded with 50% probability directly from a magneto-optical trap. We achieve a trapping lifetime of up to 6 s, and demonstrate fast Rabi oscillations with a coherence time of $T_2\sim 43 \pm 9\rm ms$.
Ultra-cold atoms trapped in an optical dipole trap and prepared in a coherent superposition of their hyperfine ground states, decohere as they interact with their environment. We demonstrate than the loss in coherence in an "echo" experiment, which is caused by mechanisms such as Rayleigh scattering, can be suppressed by the use of a new pulse sequence. We also show that the coherence time is then limited by mixing to other vibrational levels in the trap and by the finite lifetime of the internal quantum states of the atoms.
Optical trapping of selected species of radioactive atoms has great potential in precision measurements for testing fundamental physics such as EDM, PNC and parity violating beta-decay asymmetry correlation coefficients. We report trapping of 10^4 radioactive ^{82}Rb atoms (t_{1/2}=75 s) with a trap lifetime of ~55 seconds in an optical dipole trap. Transfer efficiency from the magneto-optical trap was ~14%. We further report the evidence of spontaneous spin polarization of the atoms in optical dipole trap loading. This advancement is an important step towards a new generation of precision J-b…
