Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 12: Spin controlled transport I

HL 12.9: Vortrag

Dienstag, 24. März 2009, 12:00–12:15, BEY 81

Weak Value of electrons spin in a double quantum dot — •Alessandro Romito1, Yuval Gefen1, and Yaroslav Blanter21Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel — 2Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft

The measurement of an observable in quantum mechanics is described by the projection postulate. In contrast, a weak measurement (i.e. a continuos measurement performed by a weakly coupled detector) allows us to weakly disturb the system, while acquiring only partial information about the state of the system. It has been shown that a weak measurement performed on pre and post-selected states consistently defines a new kind of value, the " weak value", of the measured quantum variable [1]. Weak values may lie well beyond the range of strong values and may happen to be complex.

Here we present the first proposal to observe the weak value of electron spin in a double quantum dot with a quantum point contact to be used as a detector. The required control on the electons' spin state has been demonstrated experimentally. Anomalously large values of the electronic spin are predicted, as well as negative values for the total spin. We also show how to incorporate the adverse effect of decoherence into this procedure.

[1] Y. Aharonov, D. Z. Albert, L. Vaidman, Phys. Rev. Lett. 60, 1351-1354 (1988).

[2] A. Romito, Y. Gefen, and Ya. Blanter, Phys. Rev. Lett. 100, 056801 (2008).

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