Mathematician Gil Kalai remains one of the most prominent skeptics in the field of quantum computing. During a recent conversation with Yuval Boger, Kalai explained his theory regarding why large-scale, functional quantum computers may never become a reality.
At the core of his argument are two main points. First, he proposes that noise within quantum systems is inherently correlated. He suggests that these correlated errors are not just a technical hurdle but a fundamental barrier that prevents the stable fault tolerance required for quantum computing. According to Kalai, these errors will consistently defeat correction attempts regardless of improvements in hardware.
Second, Kalai points to the limitations of current noisy intermediate-scale quantum devices. He argues that even without assuming new models of noise, computational complexity theory dictates that these systems cannot achieve a true quantum advantage. He suggests that the results produced by these machines stay within a low-level complexity class that classical computers can simulate effectively.
While critics argue that recent experiments and error-correction milestones demonstrate progress, Kalai maintains that many of these claims lack the necessary rigor. He notes that if his theory holds, the industry will eventually hit a wall where further investment and noise reduction efforts yield diminishing returns. He welcomes the ongoing experiments, viewing them as a necessary test for his conjectures.
If Kalai is correct, the implications for physics are significant. He suggests that the failure to build these machines would force a reevaluation of certain exotic states of matter and fundamental principles. For now, he encourages the community to maintain a high level of scrutiny regarding experimental claims, emphasizing that scientific reality must take precedence over experimental enthusiasm.