Scientists in the Netherlands have created Majorana particles and measured their properties in short nanowires with great control

Researchers and engineers from QuTech and Eindhoven University of Technology have created Majorana particles and measured their properties with great control.

These Majoranas are so-called ‘poor man’s Majoranas’ based on two quantum dots in a nanowire, which could be scaled up to a larger chain of quantum dots with more resilient Majorana behaviour.

Majorana particles are one of several promising candidates for stable quantum bits, the building blocks of quantum computers.

Quantum computers are a revolutionary technology, which have the potential to solve certain problems much faster than classical computers. That is because they use quantum bits, or qubits, which can represent both a 0 and a 1 at the same time.

This allows quantum computers to perform multiple calculations simultaneously. The implementation of quantum computers and qubits holds significant potential for various fields, including drug discovery, financial modelling, and cryptography.

See also: Progress towards fast-charging lithium-metal batteries

the majorana particle

First author Tom Dvir, a postdoctoral researcher at QuTech – the quantum technology institute of the TU Delft and TNO, said: “Majorana particles can be made into a type of qubit and have garnered attention due to their unique properties.

“Unlike conventional qubits, which are based on the properties of individual particles like electrons, qubits based on Majorana particles are more resilient against certain types of quantum errors, which is a major challenge in the development of scalable quantum computers.”

His colleague and co-first author Guanzhong Wang added: “The desirable properties of the Majorana particles, and their exotic nature that allows us to observe new scientific phenomena, motivated a large research effort, initially by academia and later also by industry.

“Research so far was predominantly based on material synthesis, aiming at engineering the right material properties so that devices made from them are immediately operable when cooled down to low temperatures.”

The new approach shifts the focus to electrical control, meaning that we observe and adjust the device while at low temperatures to bring forward the right conditions for Majoranas to appear.

Wang continued: “Unlike regular qubits, Majoranas always appear in pairs and each pair forms a delocalised electron. That means that one part of the Majorana particle can reside on one end of a nanowire, and the second part on the other end.

“To manipulate the Majorana particle we need to affect both ends at the same time. This makes them attractive for quantum computation because if one part is affected by noise, the other half will remain unscathed.”

The researchers start by producing two quantum dots close to each other, separated by a short semiconductor/ superconductor nanowire.

The quantum dots are electrically connected to each other in two ways. The first is by electrons hopping between both dots. The second involves pairs of electrons that simultaneously enter and leave the semiconductor/ superconductor nanowire.

The researchers have shown a new method to precisely control both processes, key to the formation of the Majorana particles.

The results are published in Nature.

Image: Artistic impression of the Kitaev chain in two coupled quantum dots (white with black arrows) wherein the larger green arrows represent the Majorana part of the system and the small white dots with arrows represent the electrons and their spin. © Bar Dvir.