Researchers at Harvard have made an important advance in quantum computing by developing the first programmable, logical quantum processor. The team, led by Professor Mikhail Lukin, created a system that can encode up to 48 logical qubits and execute hundreds of logical gate operations.
Logical qubits are bundles of error-corrected physical qubits that can reliably store information, overcoming decoherence issues with individual qubits. Building controllable logical qubits has been a central challenge in quantum computing thus far. Most existing systems can only demonstrate operations on unstable physical qubits still highly prone to errors.
The new processor demonstrates that arrays of logical qubits can be manipulated in parallel using lasers, which is more efficient than controlling individual physical qubits. The achievement builds on years of work at Harvard on a quantum computing architecture using neutral atom arrays suspended in vacuum chambers and cooled to near absolute zero.
According to Lukin, this research marks meaningful progress in realizing long-standing ideas like quantum error correction that have been theoretical for decades. However, he acknowledged practical, large-scale quantum computers still face engineering hurdles. The team’s neutral atom array method shows promise but remains difficult to manufacture and scale up.
While logical qubits can now be controlled, operations must still be cycled manually. The next steps will be demonstrating more types of logical gate operations and making the system run continuous algorithms autonomously. Further research is also needed to develop interconnects between qubits and reduce logical error rates.
The researchers collaborated with colleagues at MIT and startup company QuEra Computing, which is commercializing innovations from Harvard labs. An NSF official called the work a “tour de force” in quantum engineering. However, they cautioned that realizing transformative societal benefits from quantum computing remains a distant goal.
This achievement provides evidence that the dream of practical quantum computers is scientifically achievable with sufficient engineering effort. Logical qubits can be controlled using established techniques like laser manipulation. While realizing a universal, scalable quantum computer may take decades, this research suggests the basic components are sound.
For now, extensive work remains to improve qubit interconnects, error correction, and algorithm design. But tools like neutral atom arrays provide a promising platform for incremental progress. With continued research, quantum processors could eventually impact fields like drug design, machine learning, and climate modeling where quantum advantages are possible. However, hype over near-term applications should be tempered.
