Microsoft’s Quantum Computing Breakthrough, Explained
Last month, Microsoft announced an advancement in quantum computing that could be a pivotal step forward, if proven accurate.
A Microsoft research team claims to have developed “the world’s first quantum processor powered by topological qubits.” The company also states they are on track to build a prototype of a scalable quantum computer within years, rather than decades, and that they have created “a new state of matter,” a topoconductor, in the process. Alongside this, Microsoft, along with quantum computing company PsiQuantum, was chosen by the U.S. government’s Defense Advanced Research Projects Agency (DARPA) to develop under-explored approaches to quantum computing.
The Microsoft chip, named Majorana 1 after the Italian physicist whose theories it’s based on, joins a series of efforts by IBM, Google, Nokia Bell Labs, and others to develop the core mechanisms that will run quantum computers. This is challenging because quantum computing uses the principles of quantum mechanics, requiring advanced engineering at the subatomic level.
There’s a considerable upside to developing computers that surpass the limitations of today’s classical computers. Since computing’s rise in the late 1940s, the operating core of computers has remained consistent: Computer chips store, manipulate, and operate according to our instructions using bits, the 0/1 binary logic of all computers. Scott Aaronson, professor of theoretical computer science at the University of Texas at Austin, points out that modern machines are simply “millions of times faster with millions of times more memory.”
This progress has followed semiconductor pioneer Gordon Moore’s prediction, known as Moore’s Law, that chip density, and thus computing speed, would double every two years. Moore anticipated his law would hold through 1985, though it has largely continued to the present day. According to the Center for Strategic and International Studies, “The computing power of a single integrated circuit today is roughly two billion times what it was in 1960.”
Yet classical computation has inherent limits. Physicist Richard Feynman first outlined one such limitation in the early 1980s. His work in quantum thermodynamics, electron-photon interactions, and liquid helium led him to realize that solving complex equations with classical computers was impossible. The issue lies in scale; quantum computing requires vast input numbers that even the fastest classical computers cannot handle efficiently.
However, Feynman and others recognized that quantum mechanics could offer a solution. If a processor could operate on the laws of quantum mechanics, it could potentially overcome these limitations.
Instead of using bits of 0s and 1s found in classical computers, quantum computers use quantum bits (qubits). These qubits behave in the unique way of electrons, photons, and other quantum particles. A qubit can exist in multiple states simultaneously (superpositions), not simply 0 or 1, but anywhere in between. They can also be linked, so a change in one qubit affects the others. As the MIT Technology Lab notes, a connected group of qubits “can provide way more processing power than the same number of binary bits.”
Chetan Nayak, technical fellow and corporate vice president of quantum hardware at Microsoft, explains that quantum computers are not “just … like classical computers but faster.” “Quantum computers are an entirely different modality of computing.”
Nor do quantum computers simply try “every possible answer in parallel”—another common misconception, according to Aaronson. Instead, quantum computing is a “choreograph” of potential states for each qubit, where “paths leading to [the] wrong answer … cancel each other out” and “paths leading to the right answer should reinforce each other.”
This could usher in a new era of problem-solving, as envisioned by Feynman and others. For Aaronson, quantum computing’s greatest promise resides in “simply the simulation of quantum mechanics itself … to learn about chemical reactions … design new chemical processes, new materials, new drugs, new solar cells, new superconductors.” DARPA sees potential applications, including “faster automation, improved target recognition and more precise, lethal weapons,” as well as more robust cybersecurity, according to Defense News.
However, the quantum states of qubits are highly sensitive. Disturbances, such as changes in light, temperature, or vibrations, can alter their superpositions and result in errors. This tendency of qubits towards “decoherence” has been a significant challenge for quantum computing research. Current quantum processors are prone to noise and are error-prone.
Microsoft’s approach might offer an advantage over its competitors. Topological qubits have a physical construction that builds in quantum stability. But they are difficult to build and measure. Nayak notes that Microsoft’s qubit project is “the longest-running R&D program in Microsoft history.” As of last September, IBM and Google had developed 127- and 72-qubit processors, respectively, compared to Microsoft’s 8. If Nayak’s team successfully builds a larger, more stable processor, it could be a step forward in quantum computing, much like the transistor was for classical computing.
The key question is whether Microsoft has, in fact, built such a processor. On the same day that Nature published the company’s peer-reviewed paper, Microsoft released a press release and met with researchers to review the Nature paper and announce the team’s progress since the paper’s submission last year.
The press release was optimistic, stating: “Majorana 1: the world’s first Quantum Processing Unit (QPU) powered by a Topological Core, designed to scale to a million qubits on a single chip… With the core building blocks now demonstrated … we’re ready to move from physics breakthrough to practical implementation.” The announcement strongly suggested that Microsoft had built a topoconductor.
Aaronson wrote on his blog, Shtetl-Optimized, “Microsoft is unambiguously claiming to have created a topological qubit, and they just published a relevant paper in Nature, but their claim to have created a topological qubit has not yet been accepted by peer review.”
Henry Legg, a physicist at the University of St. Andrews, stated, “The optimism is definitely there, but the science isn’t there.” This may be an overly optimistic proclamation on Microsoft’s part. Regardless, Aaronson has not been this excited about quantum computing in his 25-year career. “This past year or two is the first time I’ve felt like the race to build a scalable fault-tolerant quantum computer is actually underway.”
