Surface-acoustic-wave single-electron interferometry

We propose an experiment to observe interference of a single electron as it is transported along two parallel quasi-one-dimensional channels trapped in a single minimum of a traveling periodic electric field. The experimental device is a modification of the surface-acoustic-wave-based quantum processor. Interference is achieved by creating a superposition of spatial wave functions between the two channels and inducing a relative phase shift via either a transverse electric field or a magnetic field. The interference can be used to estimate the decoherence time of an electron in this type of solid-state device.

Figure 1

A Mach Zender interferometer. A single particle at a time is sent horizontally towards the first beamsplitter. We label the state of the particle in the upper and lower arms of the interferometer ∣0⟩ and ∣1⟩, respectively. A phase shift is introduced into the upper arm. The two paths are directed to interfere at a second beamsplitter. Particle detectors determine from which direction the particle exits the interferometer.

Figure 2

Interference patterns showing reduction in visibility as decoherence increases, as well as divergence of the two detector curves if the beamsplitter is not 50:50. The upper figure is for $\theta =\pi ∕4$, the lower one for $\theta =\pi ∕8$.

Figure 3

Single-electron interferometer. A surface acoustic wave propagates from left to right. Single electrons are transported by the SAW along 1D channels defined by surface electrodes parallel to the direction of SAW propagation. By lowering the potential between two channels (by a suitable gap in the surface electrodes), an electron may coherently tunnel laterally like in a beamsplitter. Biasing the channels relative to each other induces a phase gate.

Figure 4

Configuration for measuring the decoherence rate. By varying the central gate bias, the gaps in the central barrier are opened and closed in such a manner that the path length can be varied, hence varying the time the electron is in superposition between the upper and lower channels.