Physicists have just realized a channel transferring a single electron between two quantum dots distant of 4 micrometers without losing the information stored on the latter. A single electron trapped in a semiconductor nanostructure is a memory elementary magnetic to store a bit of quantum information. This memory is well protected by its environment solid, but if one wishes to use it to communicate and compute, must still be able to move this information by preserving. So far, this was only possible on the scale of a few hundred nanometers and required the control complex quantum dots networks coupled by tunneling.
Physicists at the Institute in collaboration with Japanese and German researchers have to design and build a device to transfer information stored on the spin of an electron only between two distant quantum dots 4 microns. For this, they carried out a channel empty electron between two semiconductor boxes and powered in a channel the electron stored in one of two boxes with an acoustic wave of area. The transfer time, of the order nanosecond, is then fast enough so that the information carried by the electron is not destroyed by the mechanisms of relaxation. This work is published in the journal Nature Nanotechnology.
Illustration of the transfer of a single electron assisted by a wave acoustic surface metal grids, a few tens of nanometer width are used to define two quantum dots connected by a one-dimensional channel in which spreads the electron. To achieve their quantum dots, researchers deposited fine gold grids on the surface of a gallium arsenide layer and aluminum deposited on a gallium arsenide (GaAs) substrate. They trap and electrons moving freely at the interface between the two materials semiconductors with the potential electrostatic created by the grids. This device also allows them to perform in situ an electrometer allowing them to simultaneously measure the presence of an electron in the box and its spin state.
Previous work had already allowed physicists to keep spin information stored on a single electron trapped for a few milliseconds. To transfer the electron between two boxes, the researchers used the same principle grid electrostatic to achieve a quasi one-dimensional electron channel and empty between two static quantum dots separated and 4 micrometers. The electron then moves into quantum dots in movement generated in the channel by piezoelectric effect by sending controlled surface acoustic wave at a frequency of 2.6 GHz.
The electron then moves to the speed sound and puts 1.3 ns to spend a quantum dot to another. The complete process of information transfer using single electrons then returns to store information in the spin initially trapped electron in the first quantum dot static injecting it into a quantum dot moving to the transfer to the second static box. Finally, the spin of the electron is measured in this second quantum box. By repeating this procedure about ten thousand times, physicists quantified the fidelity of the transfer of information. This is currently approaching 65%. It is limited for the moment by spin depolarization process mainly active during the injection between static and moving quantum dots.
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