You’ve got to feel bad for Shrödinger’s cat. This poor unnamed kitty existing in a state of quantum undeath just to satisfy the naval-gazing thought experiments of a bunch of nerds. For those of you lucky enough to not know what any of that means, here’s a quick and dirty explanation. “Shrödinger’s cat” is a thought experiment devised by Erwin Shrödinger that exemplifies quantum weirdness and the paradoxes that go along with it. According to quantum physics, particles can exist in a state called a superposition, wherein they occupy multiple different states at once until they are observed, and then lock in to one defined state. To illustrate the sort of reality hemorrhaging problems this could cause on a large scale, Erwin thought about killing a cat.
You put a cat into a sealed metal box and rig up an execution device with a switch. Flip the switch and the cat dies, don’t flip the switch and the cat lives. Simple and horrible enough. But what happens if you make it a quantum switch? In Shrödinger’s thought experiment the execution device is triggered when a radioactive atom decays. Radioactive atoms exist in a superposition until observed, meaning that whether or not they have decayed is only solidified when they are observed. While unobserved, the atom is both decayed and not decayed. So if the cat’s execution is triggered by radioactive decay, until someone opens the box and observes whether the cat is alive or dead, the classic interpretation of quantum mechanics states that the cat is both alive and dead at the same time. Opening the box causes a “quantum jump” that, until now was thought to be completely random and independent of continuity.
This thought experiment is about a lot more than killing cats. It illustrates the problem with large scale systems that are built around quantum principals, such as quantum computers. But according to a recent paper published in Nature, Yale physicists Michel Devoret and Zlatko Minev have figured out how to save Shrödinger’s cat, solving many of the problems associated with building fully functional quantum computers and overturning decades of established knowledge of how quantum physics operates.
A quantum jump is the sudden change of energy states in any subatomic particle or artificial atom containing quantum information—known as a qubit. These quantum jumps in the qubits of quantum computers end up manifesting as calculation errors. Or dead cats. But if you could build an early warning system for quantum jumps, you would be able to get into the system and save the cat from immanent death. The new experiment devised by of Yale University is essentially an early warning system.
The system works by using microwaves to “stir” a radioactive atom, as it is being observed, which results in quantum jumps. The signal of these quantum jumps is then amplified and monitored in real time. The researchers found that there is a specific signal—a drop off in detection photons emitted by the atom—that will give advance warning of a quantum jump.
According to Zlatko Minev:
“Quantum jumps of an atom are somewhat analogous to the eruption of a volcano. They are completely unpredictable in the long term. Nonetheless, with the correct monitoring we can with certainty detect an advance warning of an imminent disaster and act on it before it has occurred.”
Not only that, but they found that with this early warning system, the quantum jump could be reversed. Meaning that, in the thought experiment that has now gone completely off the rails, you could resurrect the cat. I guess. I’m just glad it’s not a real cat. The big deal here is that this suggests that quantum jumps are not completely random or completely independent.
Beyond saving a hypothetical cat, this means that one of the big and previously insurmountable challenges of quantum information technology has been solved. Hopefully this is enough, and no one will actually attempt the real thought experiment.