Fabrication techniques usually applied to microelectromechanical systems (MEMS) are used to reduce the size and operating power of the core physics assembly of an atomic clock. With a volume of 9.5 mm 3 , a fractional frequency instability of 2.5ϫ 10 −10 at 1 s of integration, and dissipating less than 75 mW of power, the device has the potential to bring atomically precise timing to hand-held, battery-operated devices. In addition, the design and fabrication process allows for wafer-level assembly of the structures, enabling low-cost mass-production of thousands of identical units with the same process sequence, and easy integration with other electronics.

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Using the techniques of microelectromechanical systems, we have constructed a small low-power magnetic sensor based on alkali atoms. We use a coherent population trapping resonance to probe the interaction of the atoms’ magnetic moment with a magnetic field, and we detect changes in the magnetic flux density with a sensitivity of 50pTHz−1∕2 at 10Hz. The magnetic sensor has a size of 12mm3 and dissipates 195mW of power. Further improvements in size, power dissipation, and magnetic field sensitivity are immediately foreseeable, and such a device could provide a hand-held battery-operated magnetometer with an atom shot-noise limited sensitivity of 0.05pTHz−1∕2.

The notion of wave-particle duality may be quantified by the inequality V 2 + K 2 ≤ 1, relating interference fringe visibility V and path knowledge K. With a single-photon interferometer in which polarization is used to label the paths, we have investigated the relation for various situations, including pure, mixed, and partially-mixed input states. A quantum eraser scheme has been realized that recovers interference fringes even when no which-way information is available to erase. 03.65.Bz, 07.60.Ly Wave-particle duality (WPD) dates back to Einstein's seminal paper on the photoelectric effect [1], and is a striking manifestation of Bohr's complementarity principle [2] (for a formal definition see Ref.[3]). The familiar phrase "each experiment must be described either in terms of particles or in terms of waves" emphasizes the extreme cases and disregards intermediate situations, in which particle and wave aspects coexist. Theoretical investigations [4,5], supplemented by a few experimental studies [6,7], have led to a quantitative formulation of WPD [Eq. (1) below]. Here we report an experiment using a single-photon Mach-Zehnder interferometer in which polarization marks the path. We investigated the entire scope of the duality relation, for pure, mixed, and partially-mixed input states, and found absolute agreement at the percent level [8]. We also realized a novel quantum eraser scheme, whereby interference is recoverable although no which way (WW) information was available to erase. In view of the kinematical equivalence of all binary degrees of freedom, our results are directly applicable whenever an interfering particle is entangled with a 2-state quantum system.To quantify WPD, one needs quantitative, measurable characteristics for the wave-like and particle-like behavior of quanta. In an interferometer, the former is naturally quantified by the Visibility V of the observed interference fringes. The quantification of the latter is based on the Likelihood L of correctly guessing the path taken by a particular quantum -the better one can guess, the more pronounced are the particle aspects. A random guess gives L = 1 2 , whereas L = 1 indicates that the way is known with certainty. The actual WW Knowledge K is given by K = 2L − 1, with 0 ≤ K ≤ 1. In an asymmetric interferometer one way is more likely than the other to begin with (L a priori >

Laser-cooled neutral atoms from a low-velocity atomic source are guided via a magnetic field generated between two parallel wires on a glass substrate. The atoms bend around three curves, each with a 15-cm radius of curvature, while traveling along a 10-cm-long track. A maximum flux of 2 · 10 6 atoms/sec is achieved with a current density of 3 · 10 4 A/cm 2 in the 100 × 100-µm-cross-section wires. The kinetic energy of the guided atoms in one transverse dimension is measured to be 42 µK. PACS numbers: 03.75.B, 32.80.P Just as optical waveguides play a central role in many aspects of modern optics, from communications to integrated optics, atom waveguides are likely to be an enabling technology for future atom-optics-based science. In particular, well-characterized atom waveguides may make possible inertial and rotation measurements of exquisite sensitivity via large-enclosed-area atom interferometers [1]. One of the first guides for atoms was based on optical forces, where hollow glass fibers guide light, and the light in turn guides atoms [2,3].Atom guiding using magnetic forces from current-carrying wires has been demonstrated more recently [4,5]. From the point-of-view of using atom-guides to pursue precision metrology goals [6] much benefit can be derived from patterning the waveguides on a rigid substrate. First, beamsplitters can be precisely and reproducibly fabricated.Second, the enclosed area of an interferometer can be precisely controlled. Third, the use of well-established lithographic techniques means that progress on individual optical elements (a beamsplitter, or a monochromator, for instance) can be rapidly extended to multi-component experiments. Mirrors based on micro-patterned wires have already been introduced [7]. We report magnetic guiding by a pair of parallel wires produced on a glass substrate by photolithography and subsequent electro-plating. Intricate two-dimensional guiding structures are easily produced by this manufacturing technique; in the present case, it allows us to demonstrate guiding around curves in a 10 cm long