'The computer models used up to now led to an unmanageably large number of spurious results. A novel computer model developed by Noa Marom's group at Carnegie Mellon University, USA, together with Vladimir Strocov from PSI, was used to interpret the complex experimental data.

'But to continue with this analogy: we still didn't know which cooking pot would give us the best results for this recipe.'Ī central concern of the current research project was therefore the comparison of two 'cooking pots.' The researchers investigated two different semiconductors and their natural oxide layer: on the one hand indium arsenide and on the other indium antimonide.Īt SLS, the PSI researchers used an investigation method called soft X-ray angle-resolved photoelectron spectroscopy - SX-ARPES for short. 'Over the course of the last decade, recipes to create Majorana fermions have already been studied and refined by research groups around the world,' Aeppli continues. They could therefore act as information carriers, ergo as quantum bits in a quantum computer. Majorana fermions are topological states. 'Now, if suitable semiconductor and superconductor materials are chosen, these electrons should give rise to special quasiparticles called Majorana fermions at the ends of the nanowires.' 'The collective, asymmetric distribution of electrons generated in these nanowires can be physically described as so-called quasiparticles,' says Gabriel Aeppli, head of the Photon Science Division at PSI, who was also involved in the current study. Computer simulations for optimising these components predict that the crucial, quantum mechanical electron states are only located at the interface between the semiconductor and the superconductor and not between the semiconductor and its oxide layer. The rest of the wire is not coated so that a natural oxide layer forms there. On their outer surface, in the longitudinal direction, the top half of the wires is coated with a thin layer of a superconductor. These have a diameter of only 100 nanometres and are 1,000 nanometres (i.e., 0.0001 centimetres) long. Specifically, ultra-thin, short wires made of a semiconductor material could be considered for this purpose. It is known that thin-film systems of certain semiconductors and superconductors could lead to exotic electron states that would act as such topological qubits. Quasiparticles in semiconductor nanowires Quantum bits in topological materials would then be topological qubits. However, the mathematical language developed for this can also be applied to other physical properties of materials. Topology is originally a field of mathematics that explores, among other things, how geometric objects behave when they are deformed. Topological materials became more widely known through the Nobel Prize in Physics in 2016. These would be something completely new that no research group has yet been able to create. The researchers hope to obtain such immunity with so-called topological quantum bits. This would allow us to use just a few qubits to achieve a slim, functioning quantum computer.' 'We want to help create a new kind of qubit that is immune to leakage of information. 'Microsoft's approach, which we are now collaborating on, is quite different,' Schröter continues. But this means that the total number of qubits needed for an operational quantum computer quickly rises into the millions. 'Most types of qubits unfortunately lose their information quickly you could say they are forgetful qubits.' There is a technical solution to this: Each qubit is backed up with a system of additional qubits that correct any errors that occur. He was a researcher at PSI until April 2021, when he moved to the Max Planck Institute of Microstructure Physics in Halle, Germany. 'Computer bits that follow the laws of quantum mechanics can be achieved in different ways,' explains Niels Schröter, one of the study's authors. To find out how these could be created, an international team of researchers has carried out measurements at the Swiss Light Source SLS at PSI. So-called topological quantum bits are a novel type that might prove to be superior. Quantum bits, or qubits for short, form the basis of quantum computers. They hold the promise of speeding up certain calculations and simulations by orders of magnitude compared to classical computers. For the most part, these are still in the research phase. By now, the future of computing is inconceivable without quantum computers.

Microsoft big quantum error after all