KAIST physicists propose a Josephson trijunction for generating and moving Majorana states
A theoretical study shows how a three-junction node in a magnetic field can create, move and fuse Majorana states, steps needed for braiding in topological qubits.
Researchers from the Department of Physics at the Korea Advanced Institute of Science and Technology (Daejeon, South Korea) described a way to manipulate mobile Majorana bound states. The authors are Kyungtae Kim, June-Young M. Lee, Hyeongseop Kim and H.-S. Sim. The paper was published in Nature Communications on 7 November 2026. nature.com
Nature Communicationsnature.comOpen source ↗ The proposed element is a trijunction: three Josephson junctions meeting on a topological insulator in a perpendicular magnetic field.
Majorana bound states are zero-energy localized states in topological superconductors and obey non-Abelian braiding statistics. According to the authors, manipulating mobile states is essential for braiding them and operating topological qubits. This includes on-demand generation, propagation and fusion.
Two dynamics at the trijunction centre
The superconducting phases at the trijunction centre evolve so that they cross a boundary between topological and non-topological phase domains. Depending on which boundary is crossed, the trijunction shows one of two distinct dynamics: source/sink or path.
At a source/sink boundary, two Majorana states are generated pairwise at the centre, and one of them is ejected into a Josephson junction. The reverse process can also happen: two states collide and annihilate in a pair. nature.com
Nature Communicationsnature.comOpen source ↗ At a path boundary, a Majorana state moves from a Josephson junction to the trijunction centre, or the other way round, without involving other Majorana states.
Fusion and braiding in a trijunction network
The authors state that these two dynamics make it possible to perform fusion and braiding of Majorana states in a network of trijunctions. They illustrate this with a double trijunction setup.
In that setup, according to the paper, non-Abelian state evolutions associated with Majorana states can be manipulated without dynamical control of the setup. They can be detected by Josephson emission spectroscopy. The work presents a scheme for such operations; the available description does not report an experimental realisation of it.
