Dynamics in quantum dots: Smallest measurable processes recorded individually

(Nanowerk News) Colloquially, the term “quantum jump” is used to describe a tremendous development. In fact, it is the smallest change of state that can still be traced. Physicists from the Collaborative Research Center 1242 at the University of Duisburg-Essen (UDE) have now succeeded in measuring every single jump by optical means and drawing conclusions about the dynamics of the electrons inside a quantum dot.
The journal Physical Review Letters reports on this ("Optical Detection of Single-Electron Tunneling into a Semiconductor Quantum Dot").
The experimental setup included a quantum dot – i.e. a solid structure of only about 10,000 atoms – next to a reservoir with electrons. About 100 times per second an electron jumps back and forth between this structure and the reservoir.
It can jump into a high or low energy state into the quantum dot and change inside from top to bottom. For the first time, the researchers were able to observe this change through these tiny jumps.
measuring dynamics in quantum dots
Illustration of the measuring method. (Image: M. P. Geller, UDE)
"This measurement of every single quantum jump is the maximum information that can be extracted from a quantum system, because there aren’t any other or faster processes that can be measured”, explains Dr. Martin Paul Geller from the Collaborative Research Center 1242 Non-Equilibrium Dynamics of Condensed Matter in the Time Domain.
For the project, the team of experimental physicists collaborated with colleagues from theoretical physics in the working group of Professor Dr. Jürgen König (UDE). The theoretical physicists statistically analyzed the data and for the first time could made statements about the dynamics of the electrons in the quantum dot.
"In principle, we worked with a highly-sensitive optical and fast microscope that has still much room for improvement”, says Geller describing the measurement technology that has been refined by the researchers. Further optimization could outperform any electrical measurement in speed and spatial resolution.
Source: Universität Duisburg-Essen
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