Entanglement-based technologies, such as quantum information processing, quantum simulations, and quantum-enhanced metrology, have the potential to revolutionise our way of computing and measuring and help clarifying the puzzling concept of entanglement itself. Ultracold atoms on atom chips are attractive for their implementation, as they provide control over quantum systems in compact, robust, and scalable setups. An important tool in this system is a potential depending on the internal atomic state. Coherent dynamics in this potential combined with collisional interactions allows entanglement generation both for individual atoms and ensembles. Here, we demonstrate coherent manipulation of Bose-condensed atoms in such a potential, generated in a novel way with microwave near-fields on an atom chip. We reversibly entangle atomic internal and motional states, realizing a trapped-atom interferometer with internal-state labelling. Our system provides control over collisions in mesoscopic condensates, paving the way for on-chip generation of many-particle entanglement and quantum-enhanced metrology with spin-squeezed states.
We present a nano-scale photoelectron source, optimized towards ultrashort pulse durations and well-suited for time-resolved diffraction experiments. A tungsten tip, mounted in a suppressor-extractor electrode configuration, allows the generation of 30 keV electron pulses with an estimated pulse duration of 37 fs at the gun exit. We infer the pulse duration from particle tracking simulations, which are in excellent agreement with experimental measurements of the electron-optical properties of the source. We furthermore demonstrate femtosecond laser-triggered operation. Besides the short electron pulse duration, a tip-based source is expected to feature a large transverse coherence as well as a nanometric emittance.
Electrons travelling in free space have allowed to explore fundamental physics like the wave nature of matter [1,2], the Aharonov-Bohm [3,4] and the Hanbury Brown-Twiss effect [5]. Complementarily, the precise control over the external degrees of freedom of electrons has proven pivotal for wholly new types of experiments such as high precision measurements of the electron's mass [6] and magnetic moment [7,8] in Penning traps. Interestingly, the confinement of electrons in the purely electric field of an alternating quadrupole [9] has rarely been considered. Recent advances in the development of planar chipbased ion traps [10][11][12] suggest that this technology can be applied to enable entirely new experiments with electron beams guided in versatile potentials. Here we demonstrate the transverse confinement of a low energy electron beam in a linear quadrupole guide based on microstructured planar electrodes and driven at microwave frequencies. A new guided matter-wave system will result, with applications ranging from electron interferometry to novel non-invasive electron microscopy.Furthermore, together with advanced electron sources it appears feasible to prepare and guide electrons in the transverse motional ground state in close analogy to light guided in single-mode optical fibres, as we discuss at the end of this letter. Appropriately structuring the guide will allow the (coherent) splitting and recombination of an electron beam as needed in matter-wave interferometry experiments.To these ends it is highly desirable to shape the confining electromagnetic potential on small length scales. This can typically be done on the order of the distance between the trap centre and the field-generating electrodes. Hence, miniaturized traps with micro-structured electrodes allow for small and complex geometries. These have enabled quantum manipulation experiments both with neutral atoms in magnetic chip-traps [13] and with ions in Paul traps [14][15][16]. In analogy, microstructured Penning traps, combining a static magnetic field with the electric field generated by a planar electrode geometry, have been demonstrated for the three-dimensional confinement of electrons [17]. To avoid the rather complicated dynamics in a magnetic field, we guide a propagating electron beam by means of a purely electric alternat- ing quadrupole field. This has so far only been realized with macroscopic structures [18], which impedes shaping the potential on a microscopic scale. We show in this letter that a planar electrode configuration is, besides its potential to generate complex waveguiding elements, an ideal choice to realize an electron guide as it is compatible with planar microwave transmission line technology to feed the structure.The confinement of charged particles in a linear radiofrequency guide relies on the time-averaged action of an alternating electric field E(r, t) = E(r) cos(Ωt) [9,19]. In the ideal case, E(r) is a pure quadrupole field generated by applying an alternating voltage with amplitude V to electrodes at a di...
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