We have investigated electron beam transport at an elevated forevacuum pressure of tens of Pascals of helium. The continuous electron beam (6–14 keV, 300 mA) is generated by a forevacuum-pressure plasma-cathode electron source utilizing a hollow-cathode discharge. A beam-plasma discharge is generated in the beam transport zone, which is characterized by increased plasma density in the region of the most intense beam-plasma interaction. We find that the location and distribution of the beam-plasma discharge depend on the electron beam energy and current density. Under certain conditions, we observe that the beam plasma is stratified, with a periodic variation of plasma density and luminosity along the direction of electron beam propagation.

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Cooper pair splitters are promising candidates for generating spin-entangled electrons. However, the splitting of Cooper pairs is a random and noisy process, which hinders further synchronized operations on the entangled electrons. To circumvent this problem, we here propose and analyze a dynamic Cooper pair splitter that produces a noiseless and regular flow of spin-entangled electrons. The Cooper pair splitter is based on a superconductor coupled to quantum dots, whose energy levels are tuned in and out of resonance to control the splitting process. We identify the optimal operating conditions for which exactly one Cooper pair is split per period of the external drive and the flow of entangled electrons becomes noiseless. To characterize the regularity of the Cooper pair splitter in the time domain, we analyze the g ð2Þ function of the output currents and the distribution of waiting times between split Cooper pairs. Our proposal is feasible using current technology, and it paves the way for dynamic quantum information processing with spinentangled electrons.

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