When people first hear about quantum computers, a common response is “where and when can I get one?” But that’s the wrong question, and not just because you’ll be disappointed with the answer. Quantum computers are often said to promise faster, bigger, more multi-layered computation—but they are not, and might never be, an upgrade of your laptop. They’re just not that sort of machine. So what are they, and why do we want them?
You could argue that your laptop is already a quantum computer, because the laws of quantum physics govern the ways that electricity passes through it. In part that’s just pointing out that, ultimately, quantum physics governs all the properties of materials at the atomic scale. What’s more, as the scale of electronics shrinks, strange quantum effects that don’t usually manifest in the
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