Clearing significant hurdle to quantum computing

Neng-Chun Chiu (from left), Simon Hollerith, Luke Stewart, Mikhail Lukin, Jinen (Tim) Guo, Mohamed Abobeih, and Elias Trapp.

Veasey Conway/Harvard Staff Photographer

Science & Tech
Clearing significant hurdle to quantum computing

Harvard physicists working to develop game-changing tech demonstrate 3,000 quantum-bit system capable of continuous operation

Kermit Pattison

Harvard Staff Writer

September 25, 2025 5 min read

One often-repeated example illustrates the mind-boggling potential of quantum computing: A machine with 300 quantum bits could simultaneously store more information than the number of particles in the known universe.

Now process this: Harvard scientists just unveiled a system that was 10 times bigger and the first quantum machine able to operate continuously without restarting.

In a paper published in the journal Nature, the team demonstrated a system of more than 3,000 quantum bits (or qubits) that could run for more than two hours, surmounting a series of technical challenges and representing a significant step toward building the super computers, which could revolutionize science, medicine, finance, and other fields.

“We demonstrated the continuous operation with a 3,000-qubit system,” said Mikhail Lukin, Joshua and Beth Friedman University Professor and co-director of the Quantum Science and Engineering Initiative, and senior author of the new paper. “But it’s also clear that this approach will work for much larger numbers as well.”

The Harvard-led collaboration included researchers from MIT and was jointly headed by Lukin, Markus Greiner, George Vasmer Leverett Professor of Physics, and Vladan Vuletic, Lester Wolfe Professor of Physics at MIT. The team conducts research in collaboration with QuEra Computing, a startup company spun out from Harvard-MIT labs.

Conventional computers encode information — from a video on your phone to the words and images on this page — in bits with a binary code. Quantum computers use subatomic particles in individual atoms and take advantage of counterintuitive properties of quantum physics to achieve far more processing power.

Binary conventional bits store information as zeros or ones. Qubits can be zero, one, or both at the same time — and this linear combination of amplitudes is the key to the power of quantum computing.

In conventional computers, doubling the number of bits doubles the processing power; in quantum computers, adding qubits exponentially increases the power because of a process called quantum entanglement.

But realizing large quantum systems has posed major challenges.

Systems of neutral atoms (those with no electrical charge because they have equal numbers of protons and electrons) have emerged as one of the most promising platforms for quantum computers.

But one stubborn problem has been “atom loss” — qubits escaping and losing their coded information. This shortcoming has limited experiments to one-shot efforts in which researchers must pause, reload atoms, and begin again.

“We’re showing a way where you can insert new atoms as you naturally lose them without destroying the information that’s already in the system.”
Elias Trapp

In the new study, the team devised a system to continually and rapidly resupply qubits using “optical lattice conveyor belts” (laser waves that transport atoms) and “optical tweezers” (laser beams that grab individual atoms and arrange them into grid-like arrays). The system can reload up to 300,000 atoms per second.

“We’re showing a way where you can insert new atoms as you naturally lose them without destroying the information that’s already in the system,” said Elias Trapp, the paper co-author and a Ph.D. student in the Kenneth C. Griffin School of Arts and Sciences studying physics. “That really is solving this fundamental bottleneck of atom loss.”

The new system operated an array of more than 3,000 qubits for more than two hours — and in theory, the researchers said, could continue indefinitely. Over two hours, more than 50 million atoms had cycled through the system.

Lukin added, “This new kind of continuous operation of the system, involving the ability to rapidly replace lost qubits, can be more important in practice than a specific number of qubits.”

In follow-up experiments, the team plans to apply this approach to perform computations.

Neng-Chun Chiu, study lead author and a Harvard Griffin Ph.D. student in physics, said: “What really makes us stand out is the combination of three things — the scale, preserving the quantum information, and making the whole process fast enough to be useful.”

The new study advances a fast-developing frontier of research. In fact, this week a team from Caltech published a 6,100-qubit system, but it could only run for less than 13 seconds.

In another paper also published in Nature this month, the Harvard-MIT team demonstrated an architecture for reconfigurable atom arrays to simulate exotic quantum magnets.

“We can literally reconfigure the atomic quantum computer while it’s operating. Basically, the system becomes a living organism.”
Mikhail Lukin

The approach allows the connectivity of the processor to be changed during the process of computation. In contrast, most existing computer chips — like the ones in your cellphone or desktop — have fixed connectivity.

“We can literally reconfigure the atomic quantum computer while it’s operating,” said Lukin. “Basically, the system becomes a living organism.”

In a third paper published in Nature this week, the team demonstrates a quantum architecture with new methods for error correction. With this new body of research, Lukin believes that it is now possible to envision quantum computers that can execute billions of operations and continue running for days.

“Realizing this dream is now in our direct sight for the first time, ever,” he said. “One can really see a very direct path towards realizing it.”

The researchers received federal funding from the U.S. Department of Energy, the Intelligence Advanced Research Projects Activity, the Army Research Office, the Defense Advanced Research Projects Agency, and the National Science Foundation.