Laser-excited Rydberg Atoms Research Articles

レーザー励起リドベルグ原子を用いた量子もつれ状態の生成とその量子情報への応用

レーザー励起リドベルグ原子を用いた量子もつれ状態の生成とその量子情報への応用

A Rydberg quantum simulator

Following Feynman and as elaborated on by Lloyd, a universal quantum simulator (QS) is a controlled quantum device which reproduces the dynamics of any other many particle quantum system with short range interactions. This dynamics can refer to both coherent Hamiltonian and dissipative open system evolution. We investigate how laser excited Rydberg atoms in large spacing optical or magnetic lattices can provide an efficient implementation of a universal QS for spin models involving (high order) n-body interactions. This includes the simulation of Hamiltonians of exotic spin models involving n-particle constraints such as the Kitaev toric code, color code, and lattice gauge theories with spin liquid phases. In addition, it provides the ingredients for dissipative preparation of entangled states based on engineering n-particle reservoir couplings. The key basic building blocks of our architecture are efficient and high-fidelity n-qubit entangling gates via auxiliary Rydberg atoms, including a possible dissipative time step via optical pumping. This allows to mimic the time evolution of the system by a sequence of fast, parallel and high-fidelity n-particle coherent and dissipative Rydberg gates.

Ionization of Rydberg atoms of sodium by 360–4400 eV alkali-metal ions

Impact ionization by singly charged ions from Rydberg $\mathrm{Na}(24d)$ and $\mathrm{Na}(25s)$ states has been investigated over the reduced velocity region $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{v}=0.5--2.2.$ The ions of ${\mathrm{Na}}^{+},$ ${\mathrm{K}}^{+},$ and ${\mathrm{Li}}^{+}$ were accelerated to energies from 360 to 4400 eV and used to bombard the laser-excited Rydberg atoms. Electrons released in the ionization of Rydberg atoms were collected from the collision volume and registered by a channel electron multiplier. Measured relative ionization cross sections from $\mathrm{Na}(24d)$ and $\mathrm{Na}(25s)$ states show maxima at $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{v}=1.6--1.7$ and agree moderately well with classical-trajectory Monte Carlo calculations.

Electrostatic cage “Stark barrel” for rapidly switching a uniform electric field through arbitrary angles

A cylindrical arrangement of electrodes, together with control electronics, is described that provides uniform electric fields over cm3 volumes in a vacuum, whose angle and magnitude can be switched on a μs time scale. Full 360° field rotation is achieved, and the device allows access for particle or light beams from all sides. Both numerical and analytic descriptions of the general fields are given. Extension to full three-dimensional field control and other variations are described. The device, which was originally designed for crossed-beam collision experiments with keV energy ions and laser-excited Rydberg atoms in field-directed Stark states or coherent-elliptic states, may be more generally useful in atom trapping and cold collisions or in materials and surface science.

Non-covalent binary interactions between some organic acids and bases

Very-low-energy electron attachment to homogeneous and mixed pyridine, phenol and cyclohexanol dimers is studied by means of collisions with laser-excited Rydberg atoms and several new dipole-bound anions are observed. The corresponding structures and binding energies of their neutral parents are determined by model calculations of the intermolecular interactions between these polar closed-shell molecules. In the case of the phenol–pyridine dimer, a valence negative ion is observed. The geometry of its neutral parent is obtained from both abinitio and model calculations.

Electron attachment to isolated nucleic acid bases

Uracil, thymine, and adenine anions were produced in charge-exchange collisions with laser-excited Rydberg atoms. Anion creation rates for uracil and thymine exhibit Rydberg electron energy dependences which are interpreted as due to the creation of both dipole-bound and conventional (valence) anions while only dipole-bound anions are observed for adenine.

Absolute cross sections for charge capture from Rydberg targets by slow highly charged ions.

A crossed beam experiment has been used to measure absolute charge capture cross sections in collisions of slow highly charged xenon ions with laser excited Rydberg atoms. The cross sections were measured for scaled projectile velocities {ital nv}{sub {ital p}} from 1.0 to 6.0, for projectile charges of 8, 16, 32, and 40, where {ital n} is the principal quantum number of the target electron. Experimental cross sections are compared with predictions of classical models.

From 1/r to 1/r2 potentials: Electron exchange between Rydberg atoms and polar molecules.

Several new molecular anions, in their dipole-bound ground states, have been created by charge exchange between polar molecules and laser-excited Rydberg atoms. Measurement of electron-binding energies, by means of electric field detachment, as function of known molecular dipole moments gives the first experimental estimation of the minimum molecular dipole required to bind an electron.

Formation of negative clusters by electron attachment in the thermal energy range

Different experimental approaches for the production of negatively charged van der Waals clusters are reviewed, with emphasis on crossing beam techniques. Laser excited Rydberg atoms constitute a source of electrons with tunable well-defined energy in the thermal range (5-300 meV). Different mechanisms occuring in the cluster anions are considered: creation, dissociation, electron autodetachment, evaporation, internal energy exchanges and solvation effects in homogenous and inhomogenous molecular clusters.

Formation of water and ammonia cluster anions by electron transfer from laser excited Rydberg atoms

Using a laser excited Rydberg atomic beam as a very low energy (10-270 meV) electron source, we have investigated the experimental conditions for observation of water (from dimer to 40-mer) and ammonia cluster anions. From simple model calculations, estimates of the small water cluster adiabatic electron affinities have been determined as well as the orders of magnitude of autodetachment lifetimes and attached electron critical energies.

Electron transfer collisions between sulfur dioxide clusters and laser-excited Rydberg atoms

Electron attachment to SO2 clusters is studied in a pulsed crossed beam apparatus, using laser-excited nf Rydberg atoms as a low energy electron source. The results are interpreted as an attachment to a dimer subcluster followed by a rapid impulsive dissociation of the nascent dimer anion. The remaining cluster anions possess a large amount of internal energy. At low principal quantum numbersn, the influence of the Rydberg ionic core leads to an important evaporation process interpreted with simple model calculations.

Very low energy electron attachment to SF6 clusters

Electron attachment to SF6 clusters has been studied in the 6–110 meV range with a crossed pulsed beam experiment using laser excited Rydberg atoms. The width of the very low energy resonance varies with the cluster size.

Electron transfer from laser excited rydberg atoms to molecules. Absolute rate constants at low and intermediate principal quantum numbers

Using mass spectrometric detection of positive and negative ions, we have investigated ionizing reactions of Ne(ns,nd) Rydberg atoms, efficiently excited by resonant two-photon excitation of metastable Ne(3s3P2) atoms, with electron attaching moleculesBC (BC=SF6, CCl4, CS2, O2) at thermal collision energies. Absolute rate constants have been determined in the range of low and intermediate principal quantum numbersn(5≦n≲30) by utilizing the photoionization signal caused by room temperature black-body radiation and the loss of Ne(3s3P2) atoms, associated with the laser excitation. Substantially differentn-dependences of the electron transfer cross section have been found for the larger molecules (BC = SF6, CCl4) and the smaller molecules (BC = CS2, O2). Simple model calculations have been performed to gain new insight into the dynamics of the electron transfer process; forBC = SF6, our results at lown(5 ≦n ≦ 10) suggest that internal energy conversion in the Coulombic complex Ne+ — SF 6 − is important for the formation of the detected ions.

Improvement in Detection Limit of Electric Field Measurement Using Optogalvanic Signals by Laser Excited Rydberg Atoms

Optogalvanic signals, caused by laser-excited Rydberg atoms, were measured to estimate the electric field in a DC glow discharge in helium. With a careful analysis of the various factors limiting the detection limit and an experiment to check the analysis, the detection limit of an electric field of 21.5 V/mm was obtained which was limited by the laser spectral width.

Generation of pure gallium ion beams by field ionization of laser-excited rydberg atoms

Gallium atoms (10 8−10 11 cm −3) effused from an oven were excited stepwise from their 4p ground state to a Rydberg state np (20 ≤ n ≤ 52) by two pulsed dye lasers ( ∼ 2–10 ns, ∼ 10–100 μJ). About 50 ns after the laser irradiation, a pulsed electric field (0 kV/cm) was applied to the Rydberg atoms to ionize and accelerate the resulting ions. Thus, a pulsed gallium ion beam of purity >99.99% was obtained with a maximum total electric charge of ∼ 2 pC and a pulse width of ∼ 200 ns full width at half maximum.

Generation of pure ion beams by field ionization of laser-excited Rydberg atoms

Sodium atoms (108–1011 cm−3) effused from an oven were stepwise excited from their ground state to a Rydberg state ns or nd (20≤n≤26) by two pulsed dye lasers (∼5–10 ns, ∼100 μJ, ∼1.6-mm-diam spot). The laser energy density necessary to saturate the excitation processes from the ground state to the Rydberg state is ∼ several mJ/cm2. About 50 ns after the laser irradiation, a pulsed electric field (0.5–5.5 kV/cm) was applied to the Rydberg atoms to ionize them and accelerate the resulting ions. Thus, a pulsed sodium ion beam of purity >99.99% was obtained with a maximum total electric charge of ∼5 pC and a pulse width of ∼120 ns full width at half maximum. The total electric charge of the ion beam is estimated including the effect of space-charge field of the beam ions, and is in good agreement with the experimental values.

Ion beam generation by field ionization of laser-excited Rydberg atoms

Sodium atoms (108–1011 cm−3) effused from an oven where excited by two pulsed dye lasers (∼8–15 ns, ∼100 μJ) from the ground state 3s, via an intermediate state 3p, to a Rydberg state ns or nd (20≤n≤25). About 50 ns after the laser irradiation, a pulsed electric field (0.5–5.5 kV/cm) was applied to the Rydberg atoms to ionize them and accelerate the resulting ions. Thus, a pulsed ion beam was obtained with a maximum total electric charge of ∼5 pC, corresponding to a peak current of ∼25 μA with an output pulse of ∼200 ns full width at half-maximum.