Will a Dutch discovery lead to understanding dark matter and a real quantum computer? UPDATE APR 17

April 16, 2012 by Amara D. Angelica
Indium Antemonide

The mysterious Majorana fermion has been detected in a nanowire, Dutch scientists claim (credit: TU Delft)

UPDATE APR 17, 2012: “One, however, has to be cautious because while this experiment from Delft has provided the likely necessary evidence for the existence of the Majorana, the sufficient conditions are more difficult to achieve and may take more time.” — Sankar Das Sarma, University of Maryland (press release). Also see: “Zero bias conductance peak in Majorana wires made of semiconductor-superconductor hybrid structures” C.H. Lin, J.D. Sau, and S. Das Sarma, arXiv:1204.3085 (at arXiv.org), Apr 13, 2012.

It’s not every day that we can report a discovery of a tiny particle that may solve one of the biggest problems in the Universe and also lead to the first quantum computer that actually works.

What’s even better: a particle not detected at the huge CERN Large Hadron Collider — but in a tiny nanowire.

Here’s the story: in the 1930s, Italian physicist Ettore Majorana deduced from quantum theory the possibility that there must be a very special particle — later called the “Majorana fermion” — that would be right on the border between matter and antimatter.

Fast-forward to February 2012, whcn nanoscientist Leo Kouwenhoven caused a lot of excitement among scientists by leaking preliminary results of his research at a scientific congress. On April 12, Kouwenhoven went public in Science Express, saying his team at at TU Delft’s Kavli Institute and the Foundation for Fundamental Research on Matter (FOM Foundation) — and also financed by Microsoft — had created a nanoscale electronic device in which a pair of Majorana fermions magically (my word) “appear” at either end of a nanowire.

The recipe was simple: take one nanowire (made by colleagues from Eindhoven University of Technology) and add a superconducting material and a strong magnetic field.

Majorana Fermions

This is not a scene from Tron: Legacy. Two Majorana fermions (orange balls) are formed at the end of the nanowire. Electrons enter the nanowire from the Gold contact, and meet the Majorana fermion on the way. If the electron has the wrong energy, it is reflected back into the contact. If it has the right energy, it can go through the Majorana fermion via a special interaction. (Credit: TU Delft)

On dark matter and quantum computers

So what good are they? Well, one theory assumes that dark matter, which is thought to form about 73 percent of the Universe, is composed of Majorana fermions. So we may have just discovered dark matter. Maybe.

Also, Majorana fermions could be fundamental building blocks for a future quantum computer that would be exceptionally stable and barely sensitive to external influences. This would avoid the central problem with all current quantum computers: the dreaded decoherence.

Kouwenhoven’s team hopes to use a scheme called “topological quantum computation” that could evade decoherence at the hardware level by storing quantum information non-locally.

Two conclusions if this works: a Nobel Prize for Kouwenhoven and total domination by Microsoft. Oh boy.

The case of the disappearing physicist

Is the man in the center in this 1950 photo from Argentina actually Majorana (left and right images)? (Credit: Corriere della Sera)

The Italian physicist Ettore Majorana was a brilliant theorist who showed great insight into physics at a young age. He discovered a hitherto unknown solution to the equations from which quantum scientists deduce elementary particles: the Majorana fermion.

Practically all theoretic particles that are predicted by quantum theory have been found in the last decades, with just a few exceptions, including the enigmatic Majorana particle and the well-known Higgs boson.

But Ettore Majorana the person is every bit as mysterious — and elusive — as the particle. In 1938 he withdrew all his money and disappeared during a boat trip from Palermo to Naples. Whether he killed himself, was murdered or lived on under a different identity is still not known. No trace of Majorana was ever found.

But on June 7, 2011 Italian media reported that the Carabinieri‘s RIS had analyzed a photograph of a man taken in Argentina in 1955, finding ten points of similarity with Majorana’s face. So what did Ettore discover in Argentina? Tune in tomorrow. (Actually, I have no idea, but I’m sure something mysterious will turn up — send your tips to editors@kurzweilai.net.)

Ref.: V. Mourik, et al., Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices, Science, 2012; [DOI:10.1126/science.1222360]

Amara D. Angelica is Editor of KurzweilAI