Lunchlecture VVTP by Leo Kouwenhoven

Technical University Delft 28-11-2014

As a part of the celebration of the birthday of the VVTP (Association for Applied Physics), Leo Kouwenhoven gave a lecture about his research on the Majoranas. He started his lecture with making sure the entire audience knew the definition of a Majorana. A Majorana is a particle that is also its own antiparticle. This property in itself is not that special, because there are more particles that are their own antiparticles, think about photons (light particles). The special thing about Majoranas is that they’re a member of the class of fermions, whereas all other particles that are their own antiparticles are members of the class bosons. ‘Mathematically’ you could write for the Majorana particle:

 γ* = γ

The Majorana must have no energy, no charge and no spin to exist, and is therefore also named the niks-particle (niks = nothing in dutch). Another way of describing the Majorana is saying that it’s a superposition of an electron and a hole. He demonstrated a way to view the Majorana to us, by using a figure similar to the one below:leo1

Where all the black circles are electrons and the white circles are holes. You must see this as a train of electrons that can all step to the right and to the left. If you take the superposition of the two states, namely the one with the hole on the right and the one with the hole on the left, you get the bottom figure, which is an analog for a Majorana.


After this theoretical background he talked about his research and about the question whether the Majorana particle has actually been detected. He said to be “pretty sure” he found the Majorana, but also noted that there’s not been an error analysis, so to be  sure*, is going to take some time. Right now the signatures of the Majorana are found and confirmed by other research groups, and the combination of experiments is so far only consistend with the Majoranas. He closed his talk with an important future application of the Majorana, which is the quantum computer. This would be a computer where a bit doesn’t have to be 0 or 1, but can also be both, and this computer would therefore be extremely fast in calculation. At the very moment, companies such as Microsoft are interested in Leo’s work, because they realize that we could be standing on the edge of a major breakthrough in (quantum)computerscience.

Kasper Spoelstra –

*5σ sure means that you have a probability of 99.9999% of being right.


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