J. Verdú

Strong magnetic coupling of an ultracold gas to a superconducting waveguide cavity.

Placing an ensemble of 10;{6} ultracold atoms in the near field of a superconducting coplanar waveguide resonator with a quality factor Q approximately 10;{6}, one can achieve strong coupling between a single microwave photon in the coplanar waveguide resonator and a collective hyperfine qubit state in the ensemble with g_{eff}/2pi approximately 40 kHz larger than the cavity linewidth of kappa/2pi approximately 7 kHz. Integrated on an atomchip, such a system constitutes a hybrid quantum device, which also can be used to interconnect solid-state and atomic qubits, study and control atomic motion via the microwave field, observe microwave superradiance, build an integrated micromaser, or even cool the resonator field via the atoms.

Calculation of electrostatic fields using quasi-Green's functions: application to the hybrid Penning trap

Penning traps offer unique possibilities for storing, manipulating and investigating charged particles with high sensitivity and accuracy. The widespread applications of Penning traps in physics and chemistry comprise e.g. mass spectrometry, laser spectroscopy, measurements of electronic and nuclear magnetic moments, chemical sample analysis and reaction studies. We have developed a method, based on the Greens function approach, which allows for the analytical calculation of the electrostatic properties of a Penning trap with arbitrary electrodes. The ansatz features an extension of Dirichlets problem to nontrivial geometries and leads to an analytical solution of the Laplace equation. As an example we discuss the toroidal hybrid Penning trap designed for our planned measurements of the magnetic moment of the (anti)proton. As in the case of cylindrical Penning traps, it is possible to optimize the properties of the electric trapping fields, which is mandatory for high-precision experiments with single charged particles. Of particular interest are the anharmonicity compensation, orthogonality and optimum adjustment of frequency shifts by the continuous Stern-Gerlach effect in a quantum jump 5 Author to whom any correspondence should be addressed. 6 This article comprises part of the PhD thesis of S Kreim.

Determination of the electron’s mass from g-factor experiments on 12C5+ and 16O7+

Abstract We present a derivation of the electron’s mass from our experiment on the electronic g factor in 12C5+ and 16O7+ together with the most recent quantum electrodynamical predictions. The value obtained from 12C5+ is me=0.0005485799093(3) u, that from oxygen is me=0.0005485799092(5) u. Both values agree with the currently accepted one within 1.5 standard deviations but are four respectively two-and-a-half times more precise. The contributions to the uncertainties of our values and perspectives for the determination of the fine-structure constant α by an experiment on the bound-electron g factor are discussed.

Precision studies in traps: Measurement of fundamental constants and tests of fundamental theories

Experiments on single atomic particles confined in Penning ion traps have contributed significantly to the improvements of fundamental constants and to tests of the theory of Quantum Electrodynamics for free and bound electrons. The most precise value of the fine structure constant as well as the electron mass have been derived from trap experiments. Numerous atomic masses of interest for fundamental questions have been determined with precisions of 10 � 9 or below. Further progress is envisaged in the near future.

The magnetic moment anomaly of the electron bound in hydrogen-like oxygen 16O7+

The measurement of the g-factor of the electron bound in a hydrogen-like ion is a high-accuracy test of the theory of quantum electrodynamics (QED) in strong fields. Here we report on the measurement of the g-factor of the bound electron in hydrogen-like oxygen (16O7+). In our experiment a single highly charged ion is stored in a Penning trap. The electronic spin state of the ion is monitored via the continuous Stern?Gerlach effect in a quantum non-demolition measurement. Quantum jumps between the two spin states (spin up and spin down) are induced by a microwave field at the spin precession frequency of the bound electron. The g-factor of the bound electron is obtained by varying the microwave frequency and counting the number of spin flips. The comparison of our experimental values for the g-factor of the bound electron with the theoretical values shows excellent agreement and confirms the recent non-perturbative QED calculations.

HITRAP: A Facility for Experiments with Trapped Highly Charged Ions

HITRAP is a planned ion trap facility for capturing and cooling of highly charged ions produced at GSI in the heavy-ion complex of the UNILAC-SIS accelerators and the ESR storage ring. In this facility heavy highly charged ions up to uranium will be available as bare nuclei, hydrogenlike ions or few-electron systems at low temperatures. The trap for receiving and studying these ions is designed for operation at extremely high vacuum by cooling to cryogenic temperatures. The stored highly charged ions can be investigated in the trap itself or can be extracted from the trap at energies up to about 10 keV/q. The proposed physics experiments are collision studies with highly charged ions at well-defined low energies (eV/u), high-accuracy measurements to determine the g-factor of the electron bound in a hydrogen-like heavy ion and the atomic binding energies of few-electron systems, laser spectroscopy of HFS transitions and X-ray spectroscopy.

Theory of the coplanar-waveguide Penning trap

A novel planar Penning trap is presented, which results from the projection of the well-known three-dimensional cylindrical trap onto the surface of a chip. The introduced trap is also a coplanar-waveguide cavity, similar to those used in circuit quantum electrodynamics experiments with superconducting two-level systems. It opens up the possibility of integrating a single trapped electron, or geonium atom, into quantum circuits. The trap is an elliptical Penning trap, with the magnetic field parallel to the chips surface. A design procedure is described, which permits the compensation of electric anharmonicities up to sixth order. This should render possible the observation of a single trapped electron and the accurate measurement of its eigenfrequencies, a sine qua non requirement for a useful planar geonium technology.

Penning Trap Measurement of the Magnetic Moment of the Antiproton

The measurement of the magnetic moment (or g‐factor) of the antiproton and of the proton is a sensitive test of CPT invariance. In our experiment we will store and detect a single (anti)proton in a cryogenic Penning trap. The g‐factor will be measured by detection of quantum jumps via the continuous Stern‐Gerlach effect. Most of the experimental techniques to be used have been already successfully employed by our group for the measurement of the g‐factor of the bound electron in hydrogen‐like ions. However, the magnetic moment of the proton is smaller than that of the electron by a factor of 658. Our hybrid trap design combines cylindrical electrodes with a toroidal ferromagnetic ring electrode. With this novel trap, spin‐flip transitions of the (anti)proton can be detected by observation of tiny differences in the axial frequency by a phase‐sensitive method. With our apparatus, we envisage to determine the g‐factor of the (anti)proton with an accuracy of 10−9 or better.

The g Factor of Hydrogenic Ions: A Test of Bound State QED

We present a new experimental value for the magnetic moment of the electron bound in hydrogenlike carbon (12C5+): g exp = 2.001 041 596 (5). The experiment was carried out on a single 12C5+ ion stored in a Penning trap. The high accuracy was made possible by spatially separating the induction of spin flips and the analysis of the spin direction. Experiment and theory test the bound-state QED contributions to the gJ factor of a bound electron to a precision of 1%. We discuss also implications of the experiment on the knowledge of the electron mass.

A Possible New Value for the Electron Mass from g-Factor Measurements on Hydrogen-Like Ions

The mass of the electron in atomic units (me) represents the largest error contribution in an experiment to determine the g-factor of the electron bound in hydrogen-like carbon. Recent progress in the calculation reduces the uncertainty of the theoretical value to such a low value that me can be determined from a comparison of experimental and theoretical g-factors. The present preliminary value of the electron mass agrees with the accepted value but reduces the uncertainty by about a factor 2.