Real-time detection of single-electron tunneling using a quantum point contact

Vandersypen, L. M. K.; Elzerman, J. M.; Schouten, R. N.; Willems van Beveren, L. H.; Hanson, R.; Kouwenhoven, L. P.
November 2004
Applied Physics Letters;11/8/2004, Vol. 85 Issue 19, p4394
Academic Journal
We observe individual tunnel events of a single electron between a quantum dot and a reservoir, using a nearby quantum point contact (QPC) as a charge meter. The QPC is capacitively coupled to the dot, and the QPC conductance changes by about 1% if the number of electrons on the dot changes by one. The QPC is voltage biased and the current is monitored with a current–voltage (I–V) convertor at room temperature. We can resolve tunnel events separated by only 8 μs, limited by noise from the I–V convertor. Shot noise in the QPC sets a 25 ns lower bound on the accessible timescales.


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