A new method to produce indistinguishable and coherent electrons has been developed by scientists in France. The researchers have created a small, electron-emitting chip and used it to produce two single electrons emitted from different sources that are in the same quantum state. This technique is a key step for developing electron-based quantum-information-processing techniques.
Electrons are fermions and so must obey Pauli's exclusion principle that prevents identical fermions from occupying the same state, which leads to anticorrelations or "antibunching". Although this was recognized decades ago, it has proved difficult to perform such an antibunching experiment because electron beams are not coherent – there are many electrons in any system and they all interfere with each other, as well as the environment.
This is what encouraged Erwann Bocquillon and Gwendal Féve at the Ecole Normale Supérieure in Paris, along with colleagues from the Laboratory for Photonics and Nanostructures near Paris and from the Ecole Normale Supérieure de Lyon, to see if indistinguishable electrons could be generated by independent sources, as is done in optics. "We now understand how electrons move in a system – a very fundamental issue – a lot better. Of course, it is also important to produce such electrons to encode quantum information in the future, but we were most interested in the fundamental proof of concept, in this case," explains Féve.
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