Welcome to the quantum science podcast.

Each episode we bring you stories about developments in science and mathematics.

I'm Susan Vallett.

In the first, researchers have shown that adding more qubits to a quantum computer can make it more resilient.

It's an essential step on the long road to practical applications.

That's next.

Quantum Magazine is an editorially independent online publication

supported by the Simons Foundation to enhance public understanding of science.

How do you construct a perfect machine out of imperfect parts?

That's the central challenge for researchers building quantum computers.

The trouble is that their elementary building blocks, called cubits, are exceedingly sensitive to disturbance from the outside world. Today's prototype quantum computers are too

error-prone to do anything useful. In the 1990s, researchers worked out the theoretical foundations

for a way to overcome these errors, called quantum error

correction. The key idea was to coax a cluster of physical cubits to work together as a single,

high-quality, logical cubit. The computer would then use many such logical cubits to perform

calculations. They'd make that perfect machine by transmuting

many faulty components into fewer reliable ones. Here's Michael Newman, an error correction researcher

at Google Quantum AI on quantum computers. They get exponentially better as they get bigger. And so

that's really the only path that we have,

that we know of, towards building a large-scale quantum computer. This computational alchemy has its limits. If the physical cubits are too failure-prone, error correction is counterproductive. In that case,

adding more physical cubits will make the logical cubits worse, not better.

But if the error rate goes below a specific threshold, the balance tips.

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