February 20, 2025<\/p>\n
3 min read<\/p>\n<\/div>\n
Microsoft Claims Quantum-Computing Breakthrough\u2014but Some Physicists Are Skeptical<\/p>\n
With its \u2018topological\u2019 quantum computers, Microsoft aims to reach useful scales faster than competing technologies<\/p>\n<\/div>\n
By Davide Castelvecchi<\/a> & Nature magazine<\/a> <\/p>\n Microsoft has unveiled its Majorana 1 quantum chip.<\/p>\n<\/div>\n \u00a9 John Brecher for Microsoft<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/div>\n Microsoft has announced that it has created the first \u2018topological qubits\u2019 \u2014 a way of storing quantum information that the firm hopes will underpin a new generation of quantum computers<\/a>. Machines based on topology<\/a> are expected to be easier to build at scale than competing technologies, because they should better protect the information from noise. But some researchers are sceptical of the company\u2019s claims.<\/p>\n The announcement came in a 19 February press release containing few technical details \u2014 but Microsoft says it has disclosed some of its data to selected specialists in a meeting at its research centre in Santa Barbara, California. \u201cWould I bet my life that they\u2019re seeing what they think they\u2019re seeing? No, but it looks pretty good,\u201d says Steven Simon, a theoretical physicist at the University of Oxford, UK, who was briefed on the results.<\/p>\n At the same time, the company published intermediate results \u2014 but not the proof of the existence of topological qubits \u2014 on 19 February in Nature<\/i>.<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing<\/a>. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n Topological states are collective states of the electrons in a material that are resistant to noise, much like how two links in a chain can be shifted or rotated around each other while remaining connected.<\/p>\n The Nature<\/i> paper describes experiments on a superconducting \u2018nanowire\u2019 device made of indium arsenide. The ultimate goal is to host two topological states called Majorana quasiparticles<\/a>, one at each end of the device. Because electrons in a superconductor are paired, an extra, unpaired electron will be introduced, forming an excited state. This electron exists in a \u2018delocalized\u2019 state, which is shared between the two Majorana quasiparticles.<\/p>\n The paper reports measurements suggesting that the nanowire does indeed harbour an extra electron. These tests \u201cdo not, by themselves\u201d guarantee that the nanowire hosts two Majorana quasiparticles, the authors warn.<\/p>\n According to the press release, the team has carried out follow-up experiments in which they paired two nanowires and put them in a superposition of two states \u2014 one with the extra electron in the first nanowire, and the other with the electron in the second nanowire. \u201cWe\u2019ve built a qubit and shown that you can not only measure parity in two parallel wires, but a measurement that bridges the two wires,\u201d says Microsoft researcher Chetan Nayak.<\/p>\n \u201cThere\u2019s no slam dunk to know immediately from the experiment\u201d that the qubits are made of topological states, says Simon. (A claim of having created Majorana states, made by a Microsoft-funded team based in Delft, the Netherlands, was retracted in 2021<\/a>.) The ultimate proof will come if the devices perform as expected once they are scaled up, he adds.<\/p>\n Some researchers are critical of the company\u2019s choice to publicly announce the creation of a qubit without releasing detailed evidence. \u201cIf you have some new results not connected to this paper, why don\u2019t you wait until you have enough material for a separate publication?” says Daniel Loss, a physicist at the University of Basel, Switzerland. \u201cWithout seeing the extra data from the qubit operation, there is not much one can comment,\u201d says Georgios Katsaros, a physicist at the Institute of Science and Technology Austria in Klosterneuburg.<\/p>\n \u201cWe are committed to open publication of our research results in a timely manner while also protecting the company\u2019s IP [intellectual property],\u201d says Nayak.<\/p>\n Microsoft has also shared a roadmap for scaling up its topological machines and demonstrating that they can perform quantum calculations2<\/sup><\/a>. Vincent Mourik, a physicist at the Helmholtz Research Centre in J\u00fclich, Germany, whose concerns helped to lead to the earlier retraction, is sceptical of the whole concept. \u201cAt a fundamental level, the approach of building a quantum computer based on topological Majorana qubits as it is pursed by Microsoft is not going to work.\u201d<\/p>\n \u201cAs we perform more types of measurements, it will become harder to explain our results with non-topological models,\u201d says Nayak. \u201cThere may not be one single moment when everyone will be convinced. But non-topological explanations will require more and more fine-tuning.\u201d<\/p>\n This article is reproduced with permission and was <\/i>first published<\/i><\/a> on February 19, 2025<\/i>.<\/p>\n<\/div>\n![\"Close-up](\"https:\/\/static.scientificamerican.com\/dam\/m\/282603ad446e57c2\/original\/Majorana_1.jpg?m=1740061951.711&w=600\")
On supporting science journalism<\/h2>\n
Superconducting wire<\/h2>\n
Early announcement<\/h2>\n