This Week's Science News

The Milky Way lost two arms, a fat Schrödinger cat, a new theory for the origin of life, and more

[Below follows a transcript with references for those who’d rather read]

A Fat Schrödinger Cat

Image: Yiwen Chu / ETH Zurich

Swiss researchers have made the fattest Schrödinger cat ever.  At least that’s how the headlines put it. They’re alluding to Erwin Schrödinger’s famous thought experiment from 1935  about a cat that’ both dead and alive at the same time. Except it’s a crystal, not a cat. And it’s in a superposition of two oscillation states, not dead and alive. But, well, at least they don’t need to worry about the litter box.

With his thought experiment, Schrödinger wanted to illustrate that quantum mechanics has bigger implications about reality than physicists back then acknowledged. They knew that quantum mechanics allows particles to be in two states at the same time—say left or right—which is called a superposition. They also know that these superpositions only exist until you make a measurement, and then they suddenly “collapse” to one definite outcome. But they thought that’s only the case for small particles. Schrödinger argued that if quantum mechanics is right, these superpositions don’t just exist for small things. You could amplify them so that they also exist for large things. Like, for example, cats. Until you measure them.

In Schrödinger’s experiment, a cat is in a box, together with a vial of poison, a trigger mechanism, and a radioactive atom. The nucleus of the atom has a fifty percent chance of decaying in a certain amount of time. If it decays, the trigger breaks the vial of poison, which kills the cat.

But the decay follows the laws of quantum physics. Before you measure it, the nucleus is both decayed and not decayed, and so, it seems that before one opens the box, the cat is both dead and alive. Schrödinger by the way, had a dog.

As you have undoubtedly noticed cats are usually either dead or alive and not both. But just why that is so, physicists still only partly understand. We do understand that tiny interactions with air molecules and even the cosmic microwave background radiation make it impossible to observe superpositions. But they don’t make them go away. Yet, somehow, a measurement does it. That we don’t know how this happens is what’s called the “measurement problem” of quantum mechanics.

That’s why physicists are trying to bring heavier and heavier objects into superpositions so see what happens. For this new paper they used the heaviest object so far. They did it with an oscillating crystal in a cavity coupled to a superconducting circuit. The circuit is a qubit and can be in two different states, depending on how the current flows. It also can be in a superposition of those two states. The researchers then showed that they could transfer the superposition of states from the qubit to the crystal, which was then in two types of oscillations at the same time.

The oscillating crystal is big – 16 micrograms. That’s about 100 quadrillion atoms. Now you might say 16 micrograms isn’t much for a cat and I’d agree, but it’s huge compared to the mass of an electron which is about 10 to the minus 21 micrograms.

It’s also a lot bigger than earlier quantum “cat” experiments. A previous one for example brought 100 million photons into a superposition, so this one’s much of an improvement. But yes, this is physics, where cows are spheres and cats are crystals.