A measurement using a one-electron quantum cyclotron gives the electron magnetic moment in Bohr magnetons, g/2 = 1.001 159 652 180 73 (28) [0.28 ppt], with an uncertainty 2.7 and 15 times smaller than for previous measurements in 2006 and 1987. The electron is used as a magnetometer to allow lineshape statistics to accumulate, and its spontaneous emission rate determines the correction for its interaction with a cylindrical trap cavity. The new measurement and QED theory determine the fine structure constant, with α −1 = 137.035 999 084 (51) [0.37 ppb], and an uncertainty 20 times smaller than for any independent determination of α.The electron magnetic moment µ is one of the few measurable properties of one of the simplest of elementary particles -revealing its interaction with the fluctuating QED vacuum, and probing for size or composite structure not yet detected. What can be accurately measured is g/2, the magnitude of µ scaled by the Bohr magneton, µ B = e /(2m). For an eigenstate of spin S,with g/2 = 1 for a point electron in a renormalizable Dirac description. QED predicts that vacuum fluctuations and polarization slightly increase this value.Physics beyond the standard model of particle physics could make g/2 deviate from the Dirac/QED prediction (as internal quark-gluon substructure does for a proton). The 1987 measurement that provided the accepted g/2 for nearly 20 years [1] was superceded in 2006 by a measurement that used a one-electron quantum cyclotron [2]. Key elements were quantum jump spectroscopy and quantum non-demolition (QND) measurements of the lowest cyclotron and spin levels [3], a cylindrical Penning trap cavity [4] (Fig. 2), inhibited spontaneous emission [5], and a one-particle self-excited oscillator (SEO) [6]. This Letter reports an improved measurement that has a 2.7 and 15 times lower uncertainty than the 2006 and 1987 measurements, respectively, and confirms a 1.8 standard deviation shift of the 1987 value (Fig. 1a). The interaction of the electron and its surrounding trap cavity is probed by measuring g/2 and the electron's spontaneous emission rate as a function of magnetic field, thereby determining the corrections needed for good agreement between measurements at different fields. The electron is also used as its own magnetometer to accumulate quantum-jump lineshape statistics over days, making it possible to compare methods for extracting the resonance frequencies.The new measurement and recently updated QED theory [7] determine α with an uncertainty 20 times smaller than does any independent method (Fig. 1b). The uncertainty in α is now limited a bit more by the need for *

Measurements with a one-electron quantum cyclotron determine the electron magnetic moment, given by g/2 = 1.001 159 652 180 73(28)[0.28ppt], and the fine structure constant, α −1 = 137.035 999 084 (51)Announcements of these measurements [Phys. Rev. Lett. 97, 030801 (2006); 100, 120801 (2008)] are supplemented here with a more complete description of the one-electron quantum cyclotron and the measurement methods, a discussion of the cavity control of the radiation field, a summary of the analysis of the measurements, and a fuller discussion of the uncertainties.

A new measurement resolves cyclotron and spin levels for a single-electron quantum cyclotron to obtain an electron magnetic moment, given by g/2=1.001 159 652 180 85 (76) [0.76 ppt]. The uncertainty is nearly 6 times lower than in the past, and g is shifted downward by 1.7 standard deviations. The new g, with a quantum electrodynamics (QED) calculation, determines the fine structure constant with a 0.7 ppb uncertainty--10 times smaller than for atom-recoil determinations. Remarkably, this 100 mK measurement probes for internal electron structure at 130 GeV.

We investigate the dynamics of single and multiple ions during transport between and separation into spatially distinct locations in a multizone linear Paul trap. A single 9Be+ ion in a ~2 MHz harmonic well was transported 370 μm in 8 μs, corresponding to 16 periods of oscillation, with a gain of 0.1 motional quanta. Similar results were achieved for the transport of two ions. We also separated chains of up to 9 ions from one potential well to two distinct potential wells. With two ions this was accomplished in 55 μs, with excitations of approximately two quanta for each ion. Fast transport and separation can significantly reduce the time overhead in certain architectures for scalable quantum information processing with trapped ions.

Large-scale quantum information processors must be able to transport and maintain quantum information, and repeatedly perform logical operations. Here we demonstrate a combination of all the fundamental elements required to perform scalable quantum computing using qubits stored in the internal states of trapped atomic ions. We quantify the repeatability of a multi-qubit operation, observing no loss of performance despite qubit transport over macroscopic distances. Key to these results is the use of different pairs of 9 Be + hyperfine states for robust qubit storage, readout and gates, and simultaneous trapping of 24 Mg + "re-cooling" ions along with the qubit ions.The long term goal for experimental quantum information processing is to realize a device involving large numbers of qubits and even larger numbers of logical operations [1,2]. These resource requirements are defined both by the algorithms themselves, and the need for quantum error-correction, which makes use of many physical systems to store each qubit [1,3]. The required components for building such a device are robust qubit storage, single and two-qubit logic gates, state initialization, readout, and the ability to transfer quantum information between spatially separated locations in the processor [2,4,5]. All of these components must be able to be performed repeatedly in order to realize a large scale device.One experimental implementation of quantum information processing uses qubits stored in the internal states of trapped atomic ions. A universal set of quantum logic gates has been demonstrated using laser addressing [6,7,8], leading to a number of small-scale demonstrations of quantum information protocols including teleportation, dense-coding, and a single round of quantum error-correction [6]. A major challenge for this implementation is now to integrate scalable techniques required for large-scale processing.A possible architecture for a large-scale trapped-ion device involves moving quantum information around the processor by moving the ions themselves, where the transport is controlled by time varying potentials applied to electrodes in a multiple-zone trap array [5,9,10]. The processor would consist of a large number of processing regions working in parallel, with other regions dedicated to qubit storage (memory). A general prescription for the required operations in a single processing region is the following (illustrated in Fig. 1), which includes all of the elements necessary for universal quantum computation [11]. (1) Two qubit ions are held in separate zones, allowing individual addressing for single qubit gates, state readout, or state initialization. (2) The ions are then combined in a single zone, and a two-qubit gate is performed. (3) The ions are separated, and one is moved to another region of the trap array. (4) A third ion is brought into this processing region from another part of the device. In this work we implement in a repeated fashion all of the steps which must be performed in a single processing region in order to rea...