Ania Claire Bleszynski

Imaging a single-electron quantum dot.

Images of a single-electron quantum dot were obtained in the Coulomb blockade regime at liquid He temperatures using a cooled scanning probe microscope (SPM). The charged SPM tip shifts the lowest energy level in the dot and creates a ring in the image corresponding to a peak in the Coulomb-blockade conductance. Fits to the line shape of the ring determine the tip-induced shift of the energy of the electron state in the dot. SPM manipulation of electrons in quantum dots promises to be useful in understanding, building, and manipulating circuits for quantum information processing.

Imaging Electron Interferometer

An imaging interferometer was created in a two-dimensional electron gas by reflecting electron waves emitted from a quantum point contact with a circular mirror. Images of electron flow obtained with a scanning probe microscope at liquid He temperatures show interference fringes when the mirror is energized. A quantum phase shifter was created by moving the mirror via its gate voltage, and an interferometric spectrometer can be formed by sweeping the tip over many wavelengths. Experiments and theory demonstrate that the interference signal is robust against thermal averaging.

Imaging coherent electron flow in a two-dimensional electron gas

Images of coherent electron ow through a two-dimensional electron gas in a GaAs/AlGaAs heterostructure from a quantum point contact (QPC) were obtained at liquid He temperatures by using a scanning probe microscope with a charged tip that backscatters electrons. Near the QPC, at distances less than 500 nm, the images show angular lobes of electron ow in patterns determined by the quantum modes of the QPC. At greater distances, narrow branches of electron ow are observed, formed by the cumulative e;ects of small-angle scattering. In addition, the images show fringes spaced by half the Fermi wavelength, evidence that the electron ow is coherent. These observations agree well with theoretical simulations of electron ow. ? 2003 Published by Elsevier Science B.V.

Imaging Electrons in a Single‐Electron Quantum Dot

A scanning probe microscope (SPM) can be used to image a single‐electron quantum dot at liquid‐He temperatures by recording the Coulomb blockade conductance as a charged SPM tip is scanned above. The Coulomb blockade produces a ring in the image as the first electron is added to the dot. If the tip is sufficiently close to the surface, simulations show one may be able to extract the shape of the electron wave function inside the dot from Coulomb blockade conductance images with a resolution exceeding the size of the tip perturbation.