Universal fine-structure eraser for quantum dots
A. Fognini (Kavli institute of nanoscience Delft, TU Delft - QN/Zwiller Lab)
A. Ahmadi (University of Waterloo)
S. J. Daley (University of Waterloo)
M.E. Reimer (University of Waterloo)
V. Zwiller (Kavli institute of nanoscience Delft, AlbaNova University Center, TU Delft - QN/Zwiller Lab)
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Abstract
We analyze the degree of entanglement measurable from a quantum dot via the biexciton-exciton cascade as a function of the exciton fine-structure splitting and the detection time resolution. We show that the time-energy uncertainty relation provides means to measure a high entanglement even in presence of a finite fine-structure splitting when a detection system with high temporal resolution is employed. Still, in many applications it would be beneficial if the fine-structure splitting could be compensated to zero. To solve this problem, we propose an all-optical approach with rotating waveplates to erase this fine-structure splitting completely which should allow obtaining a high degree of entanglement with near-unity efficiency. Our optical approach is possible with current technology and is also compatible with any quantum dot showing fine-structure splitting. This bears the advantage that for example the fine-structure splitting of quantum dots in nanowires and micropillars can be directly compensated without the need for further sample processing.