Computing Breakthrough: First Logical Quantum Processor

Harvard University, Cambridge, MA

A team led by quantum expert Mikhail Lukin (right) has achieved a breakthrough in quantum computing. Dolev Bluvstein, a Ph.D. student in Lukin’s lab, was first author on the paper. (Image: Jon Chase/Harvard Staff Photographer)

Harvard researchers have realized a key milestone in the quest for stable, scalable quantum computing, an ultra-high-speed technology that will enable game-changing advances in a variety of fields, including medicine, science, and finance.

The team, led by Mikhail Lukin, the Joshua and Beth Friedman University Professor in Physics and Co-Director of the Harvard Quantum Initiative, has created the first programmable, logical quantum processor, capable of encoding up to 48 logical qubits, and executing hundreds of logical gate operations.

Published in Nature, the work was performed in collaboration with Markus Greiner, the George Vasmer Leverett Professor of Physics; colleagues from MIT; and QuEra Computing, a Boston company founded on technology from Harvard labs.

The system is the first demonstration of large-scale algorithm execution on an error-corrected quantum computer, heralding the advent of early fault-tolerant, or reliably uninterrupted, quantum computation.

Lukin described the achievement as a possible inflection point akin to the early days in the field of artificial intelligence: the ideas of quantum error correction and fault tolerance, long theorized, are starting to bear fruit.

“I think this is one of the moments in which it is clear that something very special is coming,” Lukin said. “Although there are still challenges ahead, we expect that this new advance will greatly accelerate the progress toward large-scale, useful quantum computers.”

Denise Caldwell of the National Science Foundation agrees. “This breakthrough is a tour de force of quantum engineering and design,” said Caldwell, acting Assistant Director of the Mathematical and Physical Sciences Directorate, which supported the research through NSF’s Physics Frontiers Centers and Quantum Leap Challenge Institutes programs. “The team has not only accelerated the development of quantum information processing by using neutral atoms, but opened a new door to explorations of large-scale logical qubit devices, which could enable transformative benefits for science and society as a whole.”

To date, the best computing systems have demonstrated one or two logical qubits, and one quantum gate operation — akin to just one unit of code — between them. With their logical quantum processor, the researchers now demonstrate parallel, multiplexed control of an entire patch of logical qubits, using lasers. This result is more efficient and scalable than having to control individual physical qubits.

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