Search for high order non-Abelian excitations

Quantum statistics, spin and symmetry of the wavefunction are central to the quantum mechanical understanding of the world. All known particles have so-called Abelian statistics, meaning that result of several consecutive particle exchanges does not depend on the order of the exchanges. Recently it has been proposed that particles with non-Abelian statistics can be realized in some exotic systems, and signatures of simplest non-Abelian particles – Majorana fermions – have been reported. The main driving force in the search for these elusive excitations, apart from scientific curiosity, is a possibility to realize a fault tolerant quantum computer. Qubits based on Majorana fermions are not computationally universal (one cannot perform all the operations with these fault tolerant qubits alone), and the main objective of this proposal is to develop a new system where more computationally complete higher order non-Abelian excitations can be realized.

Project lead

Dr. Maxim Savchenko

Current progress

The beauty of solid state physics is an ability to create structures that host (quasi-) particles that behave and have properties of our own choice. It is similar to the most fundamental branch of science – particle physics, where people study the basic laws of nature and smallest building blocks of the word. But here we are able to turn this word upside down and create particles that have, e.g., zero or even negative effective mass, where negatively charged electrons start to attract to each other or have fractional charge (just remember that it is only inside the created structure). One of the current most intriguing challenges in solid state physics is the demonstration of non-Abelian statistics, so when created particles not just have unusual properties but interact with each other in a forbidden for all particles in real 3D world way. Such particles obey non-Abelian statistics when, roughly speaking, A+B is not equal to B+A. It creates new challenges for study and understanding of such unusual world but also creates unprecedented opportunities for, e.g., development a platform for fault-tolerant quantum computations. There are several promising ways of how (or in which system) to create such non-Abelian particles, one of them in which I am working on is an introduction of superconductivity (that, in general, people know how to do) to the helical one-dimensional channel (that people also know how to create). The final step left is the combination of these two entities. For this I am developing a hybrid structure the central part of which is the high-quality two-dimensional electron gas. By applying a perpendicular magnetic field, I move the system to the quantum Hall regime when one-dimensional edge channels are formed. If one applies slightly different top gate voltage to two regions of the system it can results in the opposite spin orientation of the edge channels under the gates, and the helical channel can be formed on the border between these regions. The final fabrication step and challenge here is to introduce superconductivity to this helical channel by placing two additional made of usual superconductor material contacts on top of the channel. Although the steps mentioned seem to be clear it is not the case and one needs to develop and work out each fabrication step that takes a lot of efforts but the stakes are high.