Alphabet (GOOGL.US)-owned Google said it has demonstrated a new technology that can reduce the error rate of a key quantum computing process by about 40 times, marking progress toward building machines powerful and reliable enough to solve problems beyond the reach of traditional computers.
Researchers Emma Rosenfeld and Craig Gidney said in a Google Quantum AI blog post that research results published on October 15 in the scientific journal Science show that a process called "magic state cultivation" can run on Google's Willow quantum processor. The technology achieved a record 99.99% accuracy in preparing the specialized quantum states needed for certain advanced computations.
This advance addresses a major obstacle to commercial quantum computing: the massive amount of hardware required to prevent errors. Quantum computers use quantum bits, or qubits, which represent and process information in ways ordinary computer bits cannot. But qubits are extremely sensitive to interference, and reliable computation is difficult without extensive error correction.
Why "magic states" matter
One especially expensive part of error correction involves preparing so-called "magic states." These are specially prepared quantum states that can support certain operations needed by a fully functional quantum computer. Unlike traditional computing resources, magic states are consumed when used and must be continuously replenished.
Google said previous estimates suggested that preparing these states could consume as much as 95% of a quantum computer's computing power, leaving only a small portion for useful computation. Reducing this burden could allow future quantum computers to be significantly smaller and less expensive to operate.
Google's cultivation technique addresses this 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 a much more reliable state. On Google's Willow processor, the method reduced errors by about 40 times compared with uncultivated states.
Engineering challenges and breakthroughs
The research also required Google to overcome problems in the way quantum errors are measured. The team found that electrical fluctuations and temperature changes distorted its testing methods, producing results that initially appeared inconsistent with established physics. The researchers then modified hardware controls and developed a new method to measure the accuracy of their technique.
Another achievement was transferring the improved quantum state between two different error-correction systems, color codes and surface codes. These two systems are alternative ways to protect quantum information from errors. Proving that these states can survive after transfer suggests the cultivation technique could eventually be integrated into larger quantum computing systems.
For Alphabet investors, these findings mean progress in overcoming 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 computations, potentially lowering the cost and complexity of building commercially viable machines. Quantum computers may eventually be used in materials science, chemistry and other fields involving computations that are extremely difficult for traditional computers.
However, these results do not mean Google has developed a commercially practical quantum computer. The company acknowledged that the technology still needs to be validated at a larger scale, and major engineering challenges remain. The 40-fold improvement specifically applies to the preparation of magic states, not to the processor's overall performance or error rate.
The research strengthens Google's position in the race to develop fault-tolerant quantum computing. Fault-tolerant quantum computing refers to machines that can perform long, complex computations despite errors in the underlying hardware. Although this achievement could eventually improve the economics of quantum computing, Google has not provided a commercialization timeline or quantified any potential revenue impact. For investors, the immediate significance lies in technological progress, not in a contribution to Alphabet's near-term earnings.
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