Microwave Guiding of Electrons on a Chip

Abstract

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...

Hybrid quantum systems with trapped charged particles

“…Strontium ions, for example, have been trapped with a superconducting Niobium planar chip trap [83]. Two-dimensional trapping of electrons with rf fields was recently demonstrated, resulting in guiding electrons along a given trajectory [84]. To date, how-ever, electrons have been almost exclusively trapped in three-dimensional Penning traps, with the exception of [85].…”

Control of atomic Rydberg states using guided electrons

“…Hence, the key requirement for our scheme is the availability and control of electrons confined to move in one direction with a well defined momentum. In this respect, the recent development of chip-based systems, in which low-energy beams of free electrons are guided above the chip surface [31,32], are particularly promising. A major advantage of this type of device is that the electrons are not embedded within the chip and, hence, their coupling to adjacent Rydberg atoms would not be significantly influenced either by the chip material (e.g.…”

“…1). This method links to current experimental and theoretical efforts that aim to explore the coupling of quantum devices to solid state systems [17][18][19][20][21][22][23][24][25][26][27][28][29][30] and highlights the possibility to produce state changes of localized Rydberg atoms through electrons propagating in quantum wires or waveguides [31,32]. This approach can potentially find applications in the study and control of quantum many-body phenomena such as interaction-induced excitation transfer [33][34][35] and also in quantum information processing protocols that rely on the switching of interacting Rydberg states.…”

Light generation via quantum interaction of electrons with periodic nanostructures

“…In this respect, existing devices such as the high-resolution electron energy loss spectrometer (HREELS) or certain kinds of low-energy electron microscopes (LEEM) can be utilized as electron beam sources. Another alternative is using microwave guiding of electrons [48], a method that has shown very high quality control over electron trajectories in the relevant energy range.…”