For decades, tech enthusiasts have hoped that breakthroughs in quantum computing would allow us to do wonderful things, such as:

• “[disrupt the] financial, pharmaceutical, and security industries”

• “transform our machine learning and artificial intelligence capabilities”

• (“hugely reduce the time and cost of… calculations [that predict the properties of pharmaceutical drugs]”

One of the first steps to this bright future is the achievement of what’s known as quantum supremacy—the creation of a quantum computer capable of solving problems that a classic computer cannot.

But skeptics like Phillip Ball and mathematician Gil Kalai now argue that large scale quantum computing projects will always be hampered by irreducible noise in the system.

Kalai recently explained his argument in an interview with Quanta Magazine: “[the results of an experiment performed by Kalai and colleagues] shows that the noise level [in a quantum computer] cannot be reduced, because doing so will contradict an insight from the theory of computing about the power of primitive computational devices. Noisy quantum computers in the small and intermediate scale deliver primitive computational power. They are too primitive to reach “quantum supremacy” — and if quantum supremacy is not possible, then creating quantum error-correcting codes, which is harder, is also impossible.”

Will quantum supremacy be achieved by 2025, rather than proving elusive for years to come if not indefinitely?

The question resolves positively if quantum supremacy has been demonstrated by 2025. Precisely defining quantum supremacy is itself somewhat tricky. We will thus use a working definition that John Preskill, inventor of the term, makes public declarations to the effect that it has been definitively shown.