quantised conductance of the zero-bias peak delta tu delft
Hao Zhang: 'We quantised conductance of the zero-bias peak.' (Photo; TU Delft)

28 March 2018. “We have final, definite proof of the Majorana.” The timeline ‘The Quest for the Majorana’ on the website of QuTech is a thrilling read. This week, the quantum scientists, the group of Professor Leo Kouwenhoven at QuTech and Microsoft, added a new important chapter.

The researchers found the tell-tale signature of quantised conductance, definitely proving that Majorana exists.  Their findings were published this week in Nature. The elusive Majorana particle may be the key to very fast and powerful quantum computers. TU Delft researchers sighted Majorana particles for the first time in 2012, but obtaining irrefutable evidence has proven a tough challenge.

In 1937, Ettore Majorana predicted a new, fundamental particle that was later named after him: the Majorana particle. The particle has the property of being its own antiparticle. In a TU Delft press release, researcher Hao Zhang explains: “this is very special as usually there is an opposite property in the antiparticle, such as charge: the antiparticle of the electron is the positron.”

Majorana quasiparticles appear in materials in extremely restricted conditions. When a nanowire made from a semiconductor is connected to a superconductive material, researchers see a so-called zero-bias peak in the case of certain electric and magnetic fields. This signal is the main characteristic of the presence of Majoranas.

This perfect quantisation of the Majorana conductance is the final proof of the existence of the Majoranas

In the first experiment of 2012, the zero-bias peak was noisy and difficult to see. This made the Majorana appearance debatable. In the years that followed, researchers worked very hard on improving the theory, materials and the experimental fabrications.

Now the researchers in Delft combine all the improvements in an experiment to show the  ‘quantised conductance of the zero-bias peak’. This perfect quantisation of the Majorana conductance is the final proof of the existence of the Majoranas.

This experiment closes a chapter in the quest for Majorana particles and opens a new chapter in working towards quantum information processing based on their properties. Their unique physical characteristics make the Majorana particles much more stable than most other qubits.