Credit Ian C. Bates for The New York Times
SAN FRANCISCO — Microsoft is putting its considerable financial and engineering muscle into the experimental field of quantum computing as it works to build a machine that could tackle problems beyond the reach of today’s digital computers.
There is a growing optimism in the tech world that quantum computers, superpowerful devices that were once the stuff of science fiction, are possible — and may even be practical. If these machines work, they will have an impact on work in areas such as drug design and artificial intelligence, as well as offer a better understanding of the foundations of modern physics.
Microsoft’s decision to move from pure research to an expensive effort to build a working prototype underscores a global competition among technology companies, including Google and IBM, which are also making significant investments in search of breakthroughs.
In the exotic world of quantum physics, Microsoft has set itself apart from its competitors by choosing a different path. The company’s approach is based on “braiding” particles known as anyons — which physicists describe as existing in just two dimensions — to form the building blocks of a supercomputer that would exploit the unusual physical properties of subatomic particles.
Leading researchers acknowledge that barriers still remain to building useful quantum machines, both at the level of basic physics and in developing new kinds of software to exploit certain qualities of devices known as qubits that hold out the possibility of computing in ways not possible for today’s digital systems.
Unlike conventional transistors, which can be only on or off at any one time, representing a digital 1 or 0, qubits can exist in superposition, or simultaneously in both states. If qubits are placed in an “entangled” state — physically separated but acting as though they are deeply intertwined — with many other qubits, they can represent a vast number of values simultaneously. A quantum computer would most likely consist of hundred or thousands of qubits.
Microsoft began funding research in the field in 2005 when it quietly set up a laboratory known as Station Q under the leadership of the mathematician Michael Freedman.
Microsoft now believes that it is close enough to designing the basic qubit building block that the company is ready to begin engineering a complete computer, said Todd Holmdahl, a veteran engineering manager who will direct the Microsoft effort. Over the years, he has led various Microsoft projects, including its Xbox video game machine and the yet-to-be-released HoloLens augmented reality system.
“Once we get the first qubit figured out, we have a road map that allows us to go to thousands of qubits in a rather straightforward way,” Mr. Holmdahl said.
There is still a debate among physicists and computer scientists over whether quantum computers that perform useful calculations will ever be created.
A variety of alternative research programs are trying to create qubits using different materials and designs. The Microsoft approach, known as topological quantum computing, is based on a field that took on new energy when this year’s Nobel Prize in Physics was awarded to three scientists who had done fundamental work in forms of matter that may exist in just two dimensions.
Mr. Holmdahl’s project will also include the physicists Leo Kouwenhoven of Delft University, Charles M. Marcus of the University of Copenhagen, David Reilly of the University of Sydney and Matthias Troyer of E.T.H. Zurich.
They will all become Microsoft employees as part of the Artificial Intelligence and Research Group that Microsoft recently created under the leadership of one of its top technical employees, Harry Shum.
Microsoft’s newly hired physicists say the decision to try to build a topological quantum computer comes after scientific advances made in the last two years that give the scientists growing confidence that the company will be able to create more stable qubits.
“The magic recipe involves a combination of semiconductors and superconductors,” Dr. Marcus said. The researchers recently made a “remarkable breakthrough” in their ability to control the materials used to form qubits, he said. Most of the competing approaches involve cooling quantum computers to near absolute zero temperatures.
So far, there are relatively few proven algorithms that could be used to solve problems more quickly than today’s digital computers. One early effort, known as Shor’s algorithm, would be used to factor numbers, giving hope that quantum computers might be used in the future for breaking codes.
That would potentially have world-shaking consequences because modern electronic commerce is built on cryptographic systems that are largely unbreakable using conventional digital computers. Other proposed approaches might allow faster searching of databases or perform machine learning algorithms, which are being used to make advances in computer vision and speech recognition.
More immediately, however, these tools might advance the basic understanding of physics, a possibility the physicist Richard P. Feynman mentioned when he speculated about the idea of a quantum computer in 1982.
For his part, Dr. Kouwenhoven said, “My dream application for a quantum computer would be a machine that could solve problems in quantum physics.”