Materials incorporated into quantum qubit platform

"Our hope for quantum computation is that it will aid chemists, materials scientists and engineers working on the design and manufacturing of new materials that are so important to our daily lives," said Michael Manfra, scientific director of Microsoft Quantum Lab West Lafayette and the Bill and Dee O'Brien Distinguished Professor of Physics and Astronomy, professor of materials engineering, and professor of electrical and computer engineering at Purdue. "The promise of quantum computation is in accelerating scientific discovery and its translation into useful technology. For example, if quantum computers reduce the time and cost to produce new lifesaving therapeutic drugs, that is real societal impact."

The Microsoft Quantum Lab West Lafayette team advanced the complex layered materials that make up the quantum plane of the full device architecture used in the tests. Microsoft scientists working with Manfra are experts in advanced semiconductor growth techniques, including molecular beam epitaxy, that are used to build low-dimensional electron systems that form the basis for quantum bits, or qubits. They built the semiconductor and superconductor layers with atomic layer precision, tailoring the material's properties to those needed for the device architecture.

Manfra, a member of the Purdue Quantum Science and Engineering Institute, credited the strong relationship between Purdue and Microsoft, built over the course of a decade, with the advances conducted at Microsoft Quantum Lab West Lafayette. In 2017 Purdue deepened its relationship with Microsoft with a multiyear agreement that includes embedding Microsoft employees with Manfra's research team at Purdue.

"This was a collaborative effort by a very sophisticated team, with a vital contribution from the Microsoft scientists at Purdue," Manfra said. "It's a Microsoft team achievement, but it's also the culmination of a long-standing partnership between Purdue and Microsoft. It wouldn't have been possible without an environment at Purdue that was conducive to this mode of work -- I attempted to blend industrial with academic research to the betterment of both communities. I think that's a success story."

Quantum science and engineering at Purdue is a pillar of the Purdue Computes initiative, which is focused on advancing research in computing, physical AI, semiconductors and quantum technologies.

"This research breakthrough in the measurement of the state of quasi particles is a milestone in the development of topological quantum computing, and creates a watershed moment in the semiconductor-superconductor hybrid structure," Purdue President Mung Chiang said. "Marking also the latest success in the strategic initiative of Purdue Computes, the deep collaboration that Professor Manfra and his team have created with the Microsoft Quantum Lab West Lafayette on the Purdue campus exemplifies the most impactful industry research partnership at any American university today."

Most approaches to quantum computers rely on local degrees of freedom to encode information. The spin of an electron is a classic example of a qubit. But an individual spin is prone to disturbance -- by relatively common things like heat, vibrations or interactions with other quantum particles -- which can corrupt quantum information stored in the qubit, necessitating a great deal of effort in detecting and correcting errors. Instead of spin, topological quantum computers store information in a more distributed manner; the qubit state is encoded in the state of many particles acting in concert. Consequently, it is harder to scramble the information as the state of all the particles must be changed to alter the qubit state.

In the Nature paper, the Microsoft team was able to accurately and quickly measure the state of quasi particles that form the basis of the qubit.

"The device is used to measure a basic property of a topological qubit quickly," Manfra said. "The team is excited to build on these positive results."

"The team in West Lafayette pushed existing epitaxial technology to a new state-of-the-art for semiconductor-superconductor hybrid structures to ensure a perfect interface between each of the building blocks of the Microsoft hybrid system," said Sergei Gronin, a Microsoft Quantum Lab scientist.

"The materials quality that is required for quantum computing chips necessitates constant improvements, so that's one of the biggest challenges," Gronin said. "First, we had to adjust and improve semiconductor technology to meet a new level that nobody was able to achieve before. But equally important was how to create this hybrid system. To do that, we had to merge a semiconducting part and a superconducting part. And that means you need to perfect the semiconductor and the superconductor and perfect the interface between them."

While work discussed in the Nature article was performed by Microsoft employees, the exposure to industrial-scale research and development is an outstanding opportunity for Purdue students in Manfra's academic group as well. John Watson, Geoffrey Gardner and Saeed Fallahi, who are among the coauthors of the paper, earned their doctoral degrees under Manfra and now work for Microsoft Quantum at locations in Redmond, Washington, and Copenhagen, Denmark. Most of Manfra's former students now work for quantum computing companies, including Microsoft. Tyler Lindemann, who works in the West Lafayette lab and helped to build the hybrid semiconductor-superconductor structures required for the device, is earning a doctoral degree from Purdue under Manfra's supervision.

"Working in Professor Manfra's lab in conjunction with my work for Microsoft Quantum has given me a head start in my professional development, and been fruitful for my academic work," Lindemann said. "At the same time, many of the world-class scientists and engineers at Microsoft Quantum have some background in academia, and being able to draw from their knowledge and experience is an indispensable resource in my graduate studies. From both perspectives, it's a great opportunity."