With their superior properties, topological qubits could help achieve a breakthrough in the development of a quantum computer designed for universal applications. So far, no one has yet managed to unambiguously demonstrate a quantum bit, or qubit for short, of this type in a laboratory. However, scientists at Forschungszentrum Jülich have now come a long way to make this a reality. For the first time, they succeeded in integrating a topological insulator into a conventional superconducting qubit. Just in time for “World Quantum Day” on April 14, their new hybrid qubit graced the cover of the journal’s latest issue. Nano-letters.
Quantum computers are considered the computers of the future. By using quantum effects, they promise to provide solutions to very complex problems that cannot be handled by conventional computers in a realistic time frame. However, the widespread use of these computers is still a long way off. Current quantum computers typically contain only a small number of qubits. The main problem is that they are very error prone. The larger the system, the more difficult it is to completely isolate it from its environment.
Many hopes are therefore based on a new type of quantum bit: the topological qubit. This approach is pursued by several research groups as well as companies such as Microsoft. This type of qubit has the particularity of being topologically protected; the particular geometric structure of superconductors as well as the particular properties of their electronic materials guarantee the conservation of quantum information. Topological qubits are therefore considered particularly robust and largely insensitive to external sources of decoherence. They also appear to allow fast switching times comparable to those achieved by the conventional superconducting qubits used by Google and IBM in current quantum processors.
However, it is not yet clear whether we will ever succeed in actually producing topological qubits. Indeed, there is still a lack of a suitable material basis to experimentally generate the special quasi-particles necessary for this. These quasiparticles are also known as Majorana states. Until now, they could only be demonstrated unambiguously theoretically, but not experimentally. Hybrid qubits, as first constructed by the research group led by Dr. Peter Schüffelgen at the Peter Grünberg Institute (PGI-9) at the Forschungszentrum Jülich, now open up new possibilities in this field. They already contain topological materials at crucial points. Therefore, this new type of hybrid qubit offers researchers a new experimental platform to test the behavior of topological materials in highly sensitive quantum circuits.