arXiv subjects

Peter Hommelhoff

Publications and source records attributed to Peter Hommelhoff.

78 records · Page 5Linked to original sources

arXiv2010

Microwave guiding of electrons on a chip

Electrons travelling in free space have allowed to explore fundamental physics like the wave nature of matter, the Aharonov-Bohm and the Hanbury Brown-Twiss effect. 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 and magnetic moment in Penning traps. Interestingly, the confinement of electrons in the purely electric field of an alternating quadrupole has rarely been considered. Recent advances in the development of planar chip-based ion traps 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.

quant-ph↗

arXiv2010

Strong-field above-threshold photoemission from sharp metal tips

We present energy-resolved measurements of electron emission from sharp metal tips driven with low energy pulses from a few-cycle laser oscillator. We observe above-threshold photoemission with a photon order of up to 9. At a laser intensity of 2*10^11 W/cm^2 suppression of the lowest order peak occurs, indicating the onset of strong-field effects. We also observe peak shifting linearly with intensity with a slope of around -1.8eV / (10^12 W/cm^2). We attribute the magnitude of the laser field effects to field enhancement taking place at the tip's surface.

quant-ph↗

arXiv2006

A spatially and temporally localized sub-laser-cycle electron source

We present an experimental and numerical study of electron emission from a sharp tungsten tip triggered by sub-8 femtosecond low power laser pulses. This process is non-linear in the laser electric field, and the non-linearity can be tuned via the DC voltage applied to the tip. Numerical simulations of this system show that electron emission takes place within less than one optical period of the exciting laser pulse, so that an 8 fsec 800 nm laser pulse is capable of producing a single electron pulse of less than 1 fsec duration. Furthermore, we find that the carrier-envelope phase dependence of the emission process is smaller than 0.1% for an 8 fsec pulse but is steeply increasing with decreasing laser pulse duration.

quant-ph↗

arXiv2006

Quantum Information Processing in Optical Lattices and Magnetic Microtraps

We review our experiments on quantum information processing with neutral atoms in optical lattices and magnetic microtraps. Atoms in an optical lattice in the Mott insulator regime serve as a large qubit register. A spin-dependent lattice is used to split and delocalize the atomic wave functions in a controlled and coherent way over a defined number of lattice sites. This is used to experimentally demonstrate a massively parallel quantum gate array, which allows the creation of a highly entangled many-body cluster state through coherent collisions between atoms on neighbouring lattice sites. In magnetic microtraps on an atom chip, we demonstrate coherent manipulation of atomic qubit states and measure coherence lifetimes exceeding one second at micron-distance from the chip surface. We show that microwave near-fields on the chip can be used to create state-dependent potentials for the implementation of a quantum controlled phase gate with these robust qubit states. For single atom detection and preparation, we have developed high finesse fiber Fabry-Perot cavities and integrated them on the atom chip. We present an experiment in which we detected a very small number of cold atoms magnetically trapped in the cavity using the atom chip.

quant-ph↗

arXiv2005

A Femtosecond Nanometer Free Electron Source

We report a source of free electron pulses based on a field emission tip irradiated by a low-power femtosecond laser. The electron pulses are shorter than 70 fs and originate from a tip with an emission area diameter down to 2 nm. Depending on the operating regime we observe either photofield emission or optical field emission with up to 200 electrons per pulse at a repetition rate of 1 GHz. This pulsed electron emitter, triggered by a femtosecond oscillator, could serve as an efficient source for time-resolved electron interferometry, for time-resolved nanometric imaging and for synchrotrons.

quant-ph↗

arXiv2004

Coherence in Microchip Traps

We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $5-130 μ$m from the microchip surface. The coherence lifetime in the chip trap is independent of atom-surface distance within our measurement accuracy, and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum information processing, we propose to use microwave near-fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.

quant-ph↗