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Optical interferometers use the wave nature of light to make measurements with extremely high accuracy. Researchers have also created interferometers that exploit the wave nature of electrons, including some that use graphene, a single-atom-thick sheet of carbon that allows electron waves to propagate with little disruption from environmental noise. Now a team has demonstrated a fully adjustable electron interferometer on graphene [1]. Researchers expect the device to be useful for some types of quantum computers.

An optical interferometer splits a light beam into two beams, sends those beams along different paths, and then recombines them to create interference effects that reveal any subtle differences between the two paths of the beams. Interferometers for electrons will be useful for quantum computers whose quantum bits involve electrons in specific quantum states in 2D nanoscale devices. Performing logic operations on these bits can be accomplished with interferometers.

The beam splitter is a critical piece of an interferometer. Graphene-based electron beam splitters in the past have not provided full control over the amplitudes of the two output beams, which would allow researchers more flexibility in designing interferometers for specific purposes. Spurred by a new understanding of certain electron tunneling effects in graphene, Preden Roulleau of the University of Paris and colleagues set out to build a beam splitter capable of this higher level of control and then to put it into an interferometer.

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