In 1994, Peter Shor, a mathematician then at Bell Labs in New Jersey, proved that a quantum computer would have the power to solve some problems exponentially faster than a classical machine. The question was: Could one be built? Skeptics argued that quantum states were too delicate — the environment would inevitably jumble the information in the quantum computer, making it not quantum at all.
A year later, Shor responded. Classical error-correcting schemes measured individual bits to check for errors, but that approach wouldn’t work for quantum bits, or “qubits,” since any measurement would destroy the quantum state, and hence the calculation. Shor figured out a way to detect whether an error had occurred without measuring the state of the qubit itself. Shor’s code marked the beginning of the field of quantum error correction.
The field has flourished. Most physicists see it as the only path to building a commandingly powerful quantum computer. “We won’t be able to scale up quantum computers to the degree that they can solve really hard problems without it,” said John Preskill, a physicist at the California Institute of Technology.
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