Strontium Atoms Research Articles

L-changing through very-long-range interactions in high-n, n∼300, Rydberg-Rydberg collisions

SynopsisState-changing in thermal-energy collisions between strontium atoms in high-n, n∼300, n1F3 Rydberg states is studied in an atomic beam and analyzed using classical trajectory Monte Carlo simulations. The L-changing cross section is large, ∼10-4 cm2, much greater than the corresponding “hard-sphere” cross section.

Parallel quantum random number generation based on spontaneous emission of alkaline earth

We propose a parallel quantum random number generator based on spontaneous emission of strontium atoms. By directly detecting the spontaneously emitted photons in different directions, two strings of true random bits with no apparent correlation at rates up to 5.12 Mb s−1 are simultaneously extracted. Via post-processing, both output sequences pass the NIST tests. Taking advantage of the random directions of the emitted photons, the presented scheme has great scalability to be extended to arbitrary multiple channels without limitations of devices’ demultiplexing configurations.

Sr atom interferometry with the optical clock transition as a gravimeter and a gravity gradiometer

We characterize the performance of a gravimeter and a gravity gradiometer based on the 1S0–3P0 clock transition of strontium atoms. We use this new quantum sensor to measure the gravitational acceleration with a relative sensitivity of after 150 s of integration time, representing the first realisation of an atomic interferometry gravimeter based on a single-photon transition. Various noise contributions to the gravimeter are measured and characterized, with the current primary limitation to sensitivity seen to be the intrinsic noise of the interferometry laser itself. In a gravity gradiometer configuration, a differential phase sensitivity of 1.53 rad was achieved at an artificially introduced differential phase of rad. We experimentally investigated the effects of the contrast and visibility based on various parameters and achieved a total interferometry time of 30 ms, which is longer than previously reported for such interferometers. The characterization and determined limitations of the present apparatus employing 88Sr atoms provides a guidance for the future development of large-scale clock-transition gravimeters and gravity gradiometers with alkali-earth and alkali-earth-like atoms (e.g. 87Sr, Ca, Yb, Cd).

SAGE: A proposal for a space atomic gravity explorer

The proposed mission "Space Atomic Gravity Explorer" (SAGE) has the scientific objective to investigate gravitational waves, dark matter, and other fundamental aspects of gravity as well as the connection between gravitational physics and quantum physics using new quantum sensors, namely, optical atomic clocks and atom interferometers based on ultracold strontium atoms.

An ultrastable laser system at 689 nm for cooling and trapping of strontium

We present a 689-nm cavity-based laser system for cooling and trapping strontium atoms. The laser is stabilized to a high-finesse cavity by the Pound–Drever–Hall technique, exhibiting a frequency stability in the $$10^{-14}$$ range for averaging times up to 100 s. A cavity drift of 8 kHz per day is mapped out and compensated. At short times, the laser exhibits a linewidth of a few kilohertz. With this laser system, we realize a magneto-optical trap of strontium operated on the narrow inter-combination transition yielding sub-microkelvin temperatures, and demonstrate absorption spectroscopy on the strontium inter-combination line.

Synthesis, a structural and thermoanalytical study of Ca1-xSrxMoO4 ceramic

For the first time, nano- and micro-sized double-mixed Ca1-xSrxMoO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0) ceramics have been successfully synthesized by an aqueous sol-gel synthesis method in the sol-gel process using tartaric acid as a ligand. An additional novelty of this work was to show the pathways of chemical reactions that occurred under the heat-treatment of the as-prepared Ca–Sr–Mo–O tartrate gel precursors. The structural, morphological, textural and chemical properties of both the tartrate gel precursors and alkaline earth metal molybdates were obtained by thermal analysis (TG/DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and RAMAN spectroscopy (RS). The mechanism of thermal decomposition of both the tartaric acid and metal tartrates between all multicomponent Ca1-xSrxMoO4 samples was established and qualitatively compared. Moreover, in support of data from the TGA/DSC curves the quantitative distribution of intermediate products in the gel precursors during the heat-treatment was also estimated. In addition, theoretically determined data of the carbon residues were compared with the corresponding mass change from the TGA curve as a match by suggested reaction mechanism. By combining thermoanalytical investigation with the X-ray diffraction of samples heat-treated at a different temperature the relation of a final composition and its crystallite size with the thermal decomposition process of volatile components was estimated. Scanning electron microscopy was used for both the characterization of surface morphology and estimation of the particle size in the ceramic. FT-IR spectroscopy was applied in order to estimate the possible differences between multicomponent Ca1-xSrxMoO4 systems taking into account the size of crystallites and the nature of surface morphology. Finally, the Raman spectroscopic technique confirmed the initial composition of the elements in the synthesized ceramic and clearly showed that the distribution of both calcium and strontium atoms corresponds to the product, which is composed of a single-phase crystalline compound.

Building up an optical clock

Atomic Physics Arrays of optical tweezers can be used to trap atoms, which can then be manipulated individually. Such arrays have shown promise in quantum simulation of many-body systems. Norcia et al. now demonstrate that they can also be used as a platform for optical clocks. The researchers lined up 10 optical tweezers in a one-dimensional array, where each tweezer held either one or zero atoms of strontium. The atoms were subjected to laser light whose frequency was tuned to a clock transition in strontium. By monitoring the number of atoms in each tweezer, the researchers measured a long coherence time of a few seconds. Increasing the number of tweezers should improve the figures of merit of this platform. Science , this issue p. [93][1] [1]: /lookup/doi/10.1126/science.aay0644

Structural stability of SrZrO3 perovskite and improvement in electronic and optical properties by Ca and Ba doping for optoelectronic applications: a DFT approach

ABSTRACTA detailed theoretical study, based on density functional theory (DFT) with GGA-PBE, of electronic, optical and structural properties of calcium (Ca) and barium (Ba)-doped SrZrO3, is presented. The doping influence on the electronic structure and consequently optical properties are analysed and explained with TDOS and PDOS. Structural parameters vary by partial replacement of strontium (Sr) atom with Ca and Ba in SrZrO3, separately, and PDOS modify themselves with the development of new states at symmetry points and as a result reduction in the electronic band gap is observed. We have also noticed that the indirect band gap of pure SrZrO3 is altered to the direct band gap after doping. The optical properties of the pure and doped SrZrO3 are interrelated with their electronic determinations. The considerable change in the band structure and optical properties by doping of Ca and Ba assert that the doped material is a more attractive contestant for optoelectronic device applications as compared to pure SrZrO3.

Seconds-scale coherence on an optical clock transition in a tweezer array.

Coherent control of high-quality factor optical transitions in atoms has revolutionized precision frequency metrology. Leading optical atomic clocks rely on the interrogation of such transitions in either single ions or ensembles of neutral atoms to stabilize a laser frequency at high precision and accuracy. We demonstrate a platform that combines the key strengths of these two approaches, based on arrays of individual strontium atoms held within optical tweezers. We report coherence times of 3.4 seconds, single-ensemble duty cycles up to 96% through repeated interrogation, and frequency stability of 4.7 × 10-16 (τ/s)-1/2 These results establish optical tweezer arrays as a powerful tool for coherent control of optical transitions for metrology and quantum information science.

Acousto-optic modulators for a controlled frequency shift of light beams in optical and microwave cold-atom frequency standards

A series of specialised acousto-optic modulators/frequency shifters based on paratellurite (TeO2) single crystals is developed for systems of laser cooling and frequency stabilisation of laser sources in optical and microwave frequency standards based on cold strontium, rubidium and caesium atoms. The methods of calculation and optimisation of the main parameters of acousto-optic modulators are considered; their basic technical characteristics are experimentally investigated in the spectral range of optical radiation 460 – 900 nm and in the frequency shift range of 5 – 400 MHz. The modulators have a high diffraction efficiency, low power consumption and the ability to work with linearly and randomly polarised optical radiation.

Charge dynamics of a molecular ion immersed in a Rydberg-dressed atomic lattice gas

Charge dynamics in an ultra-cold setup involving a laser dressed atom and an ion is studied here. This transfer of charge is enabled through molecular Rydberg states that are accessed via a laser. The character of the charge exchange crucially depends on the coupling between the electronic dynamics and the vibrational motion of the atoms and ion. The molecular Rydberg states are characterized and a criterion for distinguishing coherent and incoherent regimes is formulated. Furthermore the concept is generalized to the many-body setup as the ion effectively propagates through a chain of atoms. Aspects of the transport such as its direction can be controlled by the excitation laser. This leads to new directions in the investigation of hybrid atom-ion systems that can be experimentally explored using optically trapped strontium atoms.

Laser cooling with adiabatic transfer on a Raman transition

Sawtooth Wave Adiabatic Passage (SWAP) laser cooling was recently demonstrated using a narrow-linewidth single-photon optical transition in atomic strontium and may prove useful for cooling other atoms and molecules. However, many atoms and molecules lack the appropriate narrow optical transition. Here we use such an atom, 87Rb, to demonstrate that two-photon Raman transitions with arbitrarily-tunable linewidths can be used to achieve 1D SWAP cooling without significantly populating the intermediate excited state. Unlike SWAP cooling on a narrow transition, Raman SWAP cooling allows for a final 1D temperature well below the Doppler cooling limit (here, 25 times lower); and the effective excited state decay rate can be modified in time, presenting another degree of freedom during the cooling process. We also develop a generic model for Raman Landau–Zener transitions in the presence of small residual free-space scattering for future applications of SWAP cooling in other atoms or molecules.

Changes of the slab structure of constitution scandate SrLaScO4 at the isovalent substitution of strontium atoms

Changes of the slab structure of constitution scandate SrLaScO4 at the isovalent substitution of strontium atoms

Fast and dense magneto-optical traps for strontium

We improve the efficiency of sawtooth-wave-adiabatic-passage (SWAP) cooling for strontium atoms in three dimensions and combine it with standard narrow-line laser cooling. With this technique, we create strontium magneto-optical traps with $6\times 10^7$ bosonic $^{88}$Sr ($1\times 10^7$ fermionic $^{87}$Sr) atoms at phase-space densities of $2\times 10^{-3}$ ($1.4\times 10^{-4}$). Our method is simple to implement and is faster and more robust than traditional cooling methods.

Effect of magnesium doping on band gap and optical properties of SrZrO3 perovskite: A first-principles study

In this paper we present the First-principles calculations, established on the density functional theory (DFT) by using generalized gradient approximation (GGA) and ultra-soft pseudo-potential (USP), study to investigate Magnesium (Mg) doping outcome on the different properties of SrZrO3. The impacts on electronic structure and hence optical properties from Mg-doping have been explored and are reviewed in detail by implementing the conception of TDOS and PDOS. Replacement of Strontium (Sr) atom by Mg tunes the electronic band structure quite significantly with the emergence of new states at Gamma point. Due to this SrZrO3 indirect band gap is transformed to the direct one for Mg-doped SrZrO3. The density of states for Mg-doped in SrZrO3 relocate themselves at slightly lower energies and there is strong interaction between Mg-atom and its surrounding atoms is observed. Furthermore, at the conduction band bottom and partial density of states of SrZrO3 change appreciably and hence we conclude that the electronic band structure is affected by Mg-doping. The optical properties of the un-doped and doped SrZrO3 are investigated and are correlated with electronic structure. The enormous variation in optical properties and band gap (i.e indirect to direct) by doping of Mg declares this material as attractive contender for optoelectronic materials.

2000-Times Repeated Imaging of Strontium Atoms in Clock-Magic Tweezer Arrays.

We demonstrate single-atom resolved imaging with a survival probability of 0.99932(8) and a fidelity of 0.99991(1), enabling us to perform repeated high-fidelity imaging of single atoms in tweezers thousands of times. We further observe lifetimes under laser cooling of more than seven minutes, an order of magnitude longer than in previous tweezer studies. Experiments are performed with strontium atoms in 813.4nm tweezer arrays, which is at a magic wavelength for the clock transition. Tuning to this wavelength is enabled by off-magic Sisyphus cooling on the intercombination line, which lets us choose the tweezer wavelength almost arbitrarily. We find that a single not retroreflected cooling beam in the radial direction is sufficient for mitigating recoil heating during imaging. Moreover, this cooling technique yields temperatures below 5 μK, as measured by release and recapture. Finally, we demonstrate clock-state resolved detection with average survival probability of 0.996(1) and average state detection fidelity of 0.981(1). Our work paves the way for atom-by-atom assembly of large defect-free arrays of alkaline-earth atoms, in which repeated interrogation of the clock transition is an imminent possibility.

A simple atomic beam oven with a metal thermal break.

We report the design and construction of a simple, easy to machine high temperature oven for generating an atomic beam in laser cooling experiments. This design eliminates the problem of thermal isolation of the oven region from the rest of the vacuum system without using a glass or ceramic thermal break. This design simplifies the construction and operation of high temperature ovens for elements having low vapor pressure. We demonstrate the functionality of such a source for strontium (Sr) atoms. We generate a high flux of Sr atoms for use in laser cooling and trapping experiments. The optimization of the design of the metal thermal break is done using a finite element analysis.

Sr4Pt10In21 – the first representative of the Ho4Ni10In21 type with a divalent cation

Abstract Rod-shaped single crystals of Sr4Pt10In21 were prepared from the elements in glassy-carbon crucibles in a high-frequency furnace. The structure of Sr4Pt10In21 was refined from single-crystal X-ray diffractometer data: C2/m, Ho4Ni10Ga21 type, a = 2322.62(7), b = 450.27(2), c = 1958.09(7) pm, β = 133.191(3)°, wR = 0.0464, 3200 F 2 values and 107 variables. The three-dimensional [Pt10In21]δ− polyanionic network is stabilized through substantial Pt–In (269–313 pm Pt–In) and In–In (294–362 pm In–In) bonding. All platinum atoms have slightly distorted tri-capped trigonal prismatic coordination and the two crystallographically independent strontium atoms are located in penta-capped pentagonal prisms.

Analyzing a single-laser repumping scheme for efficient loading of a strontium magneto-optical trap

We demonstrate enhanced loading of strontium atoms into a magneto-optical trap using a repumping scheme from the metastable state via the doubly-excited state $5\mathrm{s}5\mathrm{p}\,^3\mathrm{P}_2 \rightarrow 5\mathrm{p}^2\,^3\mathrm{P}_2$ at $481~\mathrm{nm}$. The number of trapped atoms is increased by an order of magnitude. The frequency and intensity dependence of the atom number enhancement, with respect to the non-repumping case, is well reproduced by a simple rate equation model, which also describes single-laser repumping schemes reported previously. The repumping scheme is limited by a weak additional loss channel into the long-lived $5\mathrm{s}5\mathrm{p}\,^3\mathrm{P}_0$ state. For low repumping intensities, the signature of a halo formed by magnetically trapped atoms in the metastable state is found.

Destruction of high- n ( n∼300 ) Rydberg atoms in Rydberg-Rydberg collisions

The destruction of high-$n, n\ensuremath{\sim}300$, strontium atoms contained in a hot atomic beam through Rydberg-Rydberg collisions is examined. The Rydberg atoms are initially created, under blockade conditions, in a localized volume and their subsequent motions lead to creation of a string of Rydberg atoms. The Rydberg atoms, however, are formed with a thermal distribution of velocities resulting in Rydberg-Rydberg collisions which lead to their destruction. The experimental data are interpreted using classical trajectory Monte Carlo techniques that simulate the excitation of the Rydberg atoms together with their subsequent motions. Using calculated collisional ionization cross sections and blockade radii, the model yields results in good agreement with experiment. The results highlight the important role collisional destruction can play when attempting to study (long-range) Rydberg-Rydberg interactions in a hot atomic beam.