Google cuts quantum errors 40-fold in step toward practical use

Alphabet's (GOOGL)(GOOG) Google said it has demonstrated a new technique that reduces errors in a critical component of quantum computing by about 40-fold, marking progress toward building machines powerful and reliable enough to solve problems beyond the reach of conventional computers.

The findings, published Oct. 15 in the scientific journal Science, show that a process called "magic state cultivation" works on Google's Willow quantum processor. The technique achieved a record 99.99% accuracy rate for a specialized quantum state needed to perform certain advanced calculations, researchers Emma Rosenfeld and Craig Gidney of Google Quantum AI said in a blog post.

The development addresses a major obstacle to commercial quantum computing: the enormous amount of hardware required to prevent errors. Quantum computers use quantum bits, or qubits, which can represent and process information in ways that ordinary computer bits cannot. However, qubits are extremely sensitive to disturbances, making reliable calculations difficult without extensive error correction.

Why "magic states" are key

One particularly expensive part of error correction involves producing so-called "magic states." These are specially prepared quantum states that enable certain operations required for a fully functional quantum computer. Unlike conventional computing resources, magic states are consumed when used and must be continually replenished.

Google said some previous estimates suggested that producing these states could consume as much as 95% of a quantum computer's capacity, leaving only a small fraction available for useful calculations. Reducing that burden could make future quantum computers substantially smaller and less expensive to operate.

The company's cultivation technique addresses the problem by starting with an imperfect quantum state and repeatedly checking it for errors. Attempts that fail the checks are discarded, allowing the system to produce states with much higher reliability. On Google's Willow processor, the method reduced errors by approximately 40 times compared with states that hadn't undergone cultivation.

Engineering challenges, breakthroughs

The research also required Google to overcome problems with how quantum errors are measured. The team discovered that electrical fluctuations and temperature changes were distorting its testing methods, producing results that initially appeared inconsistent with established physics. Researchers subsequently modified the hardware controls and developed a new way to measure the accuracy of their technique.

Another achievement involved transferring the improved quantum states between two different error-correction systems, known as color codes and surface codes. These are alternative methods of protecting quantum information from errors. Demonstrating that the states could survive the transition suggests that cultivation could eventually be integrated into larger quantum computing systems.

For Alphabet (GOOG)(GOOGL) investors, the findings represent progress toward overcoming one of the technical and economic barriers to commercial quantum computing. More efficient error correction could ultimately reduce the number of physical qubits needed to perform useful calculations, potentially lowering the cost and complexity of building commercially viable machines. Quantum computers could eventually have applications in materials science, chemistry and other fields involving calculations that are prohibitively difficult for conventional computers.

However, the results don't mean Google has developed a commercially practical quantum computer. The company acknowledged that it still needs to demonstrate the technique at a much larger scale, and significant engineering challenges remain. The 40-fold improvement applies specifically to the preparation of magic states, rather than the overall performance or error rate of the entire processor.

The research strengthens Google's position in the race to develop fault-tolerant quantum computing, a term describing machines capable of carrying out long, complex calculations despite errors in their underlying hardware.

While the achievement could eventually improve the economics of quantum computing, Google hasn't provided a timetable for commercialization or quantified any potential revenue impact. For investors, the immediate significance is technological progress rather than a near-term contribution to Alphabet's earnings.