While some quantum technologies, like quantum computing, are still in the early stages of their enormous promise, others are so common that they’re almost mundane. The billions of transistors—tiny electrical switches—inside smartphones and other modern devices couldn’t have been built without understanding quantum mechanics.
Another example is lasers, which were predicted by quantum mechanics in the early 20th century, decades before the first one was built. Today, lasers are a quantum technology that’s become entirely commonplace—you can buy one on a keychain for less than the price of a meal.
‘One of the most impressive examples of quantum sensors is MRI machines,’ says Jose Lado, a physics professor at Aalto University. ‘We take them for granted, but they let you see inside the body with a precision that was unthinkable before. To me, they’re truly a science fiction achievement of quantum technology.’
Magnetic resonance imaging, or MRI for short, works by detecting radio waves given off by the nuclei of hydrogen atoms in a magnetic field. Lado explains that these waves can only have very specific frequencies. It’s as though each nucleus can only hum at a specific pitch based on how strong the magnetic field is around it.
Quantum mechanics is the reason that works—it’s the cornerstone of MRI. ‘If you’re able to map all those frequencies, then you can create a three-dimensional map inside the body. Quantum mechanics is what sets those frequencies,’ he says.
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