Harvard physicists have developed a new quantum system that could solve one of the field’s toughest challenges, quantum error correction, marking what they call a foundation for scalable quantum computers.

In a Nature paper published Monday, researchers report a system that can detect and suppress errors below a critical threshold, a milestone toward reliable, large-scale quantum computation.

“For the first time, we combined all essential elements for a scalable, error-corrected quantum computation in an integrated architecture,” said Mikhail Lukin, co-director of Harvard’s Quantum Science and Engineering Initiative. “These experiments… create the scientific foundation for practical large-scale quantum computation.”

The team demonstrated a “fault-tolerant” setup using 448 atomic qubits, employing entanglement, entropy removal, and “quantum teleportation” to transfer quantum states without physical contact. 

Lead author Dolev Bluvstein, now a Caltech professor, called the system “conceptually scalable,” adding, “It’s becoming clear that we can build fault-tolerant quantum computers.”

The collaboration, which included MIT researchers and partners from QuEra Computing and the Joint Center for Quantum Information and Computer Science, represents a key step in the decades-long quest to control fragile quantum information. “By realizing and testing these fundamental ideas in a lab, you really start seeing light at the end of the tunnel,” Lukin said.

Classical computers process information in bits of 0s and 1s, while quantum computers use qubits, atoms or particles that can exist in multiple states at once. This property, known as entanglement, allows exponential scaling: a 300-qubit system could store more information than all particles in the universe. Such power promises advances in cryptography, AI, and material science, but unstable qubits have long plagued progress.

The Harvard system adds multiple layers of error correction, suppressing errors below the threshold where adding more qubits helps rather than hurts performance. “We really focused on understanding the core mechanisms for enabling scalable, deep-circuit computation,” said co-author Alexandra Geim, a physics Ph.D. candidate.

Using neutral rubidium atoms manipulated by lasers, the team’s method builds on years of experimental refinement. Other global efforts use ions or superconducting qubits, but Google Quantum AI’s Hartmut Neven called the Harvard-led advance “a significant step toward our shared goal of building a large-scale, useful quantum computer.”

The work follows a September paper where the same group operated a system of over 3,000 qubits for two hours. Lukin said this latest milestone shows that “this big dream that many of us had for several decades, for the first time, is really in direct sight.”

Citations:

Pattison, Kermit. “A potential quantum leap — Harvard Gazette.” Harvard Gazette, 12 November 2025, https://news.harvard.edu/gazette/story/2025/11/a-potential-quantum-leap/. Accessed 15 November 2025.