spaceSpace and Physics

Scientists Spring A Trap On Schrodinger's Cat By Predicting Quantum Jumps


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

jumping cat

Microscopic equivalents of Shrodinger's cat can be intercepted mid-jump between an interterminate state and either alive or dead state, something previously thought impossible. Credit: Kat Stockton

Herding cats is proverbially hard. Herding quantum cats, or controlling their leaps, was considered impossible. Yet having gained new insight into the phenomenon known as quantum jumps, one team of physicists have reversed these jumps, which they compare to rescuing Schrödinger's cat as it jumps to its doom.

Professor Michel Devoret and his colleagues were the ones to observe these so-called quantum jumps, an atomic transition that occurs when an outside observer causes a superposition to shift to one form or the other – a process thought to be discrete, random, and therefore impossible to predict. They created a superconducting artificial atom (an object that behaves electronically like a single atom) and irradiated it, sparking jumps in energy levels. In doing so, they found advance warning of when they would occur. This created the potential to give scientists control over a process previously thought uncontrollable, since they could react to the warnings.


In fact, Devoret describes in Nature reversing a jump mid-flight, which could allow for corrections of errors in quantum computing. A Yale media release compares their work to saving Schrödinger's cat when it is already part-way to death.

Although Erwin Schrödinger had a real feline companion named Milton, Schrödinger's cat usually refers to his thought experiment. In this scenario, a cat is placed in a sealed box with a lethal weapon, which will be triggered if a radioactive particle decays in a certain period of time. The particle in question has a 50/50 chance of doing this. According to Schrödinger's interpretation of quantum physics at the time, the cat would be neither alive nor dead until someone opened the box, but instead existing in what is called a superposition of live and dead waveforms.

The idea struck Schrödinger as ridiculous, and he used it to argue something must be wrong with our understanding of the quantum world. While most physicists today don't believe this is what would happen if anyone got ethical approval to try the experiment, it appears to work well as a description of what is occurring at the subatomic level. In the cat thought-experiment, the jump is when the cat goes from being both alive and dead to either alive or dead.

When the great physicist Niels Bohr proposed quantum jumps more than a century ago, he envisaged them as random. Despite Schrödinger's pushback against the idea, the existence of quantum leaps was accepted by most physicists even before they were eventually observed in 1986.


Devoret and his team's observations revealed a sudden absence of a specific type of photon immediately before the jump. Moreover, they showed each jump is continuous, rather than instantaneous, providing an opportunity to reverse them using a specifically designed energy pulse, something Devoret and his co-authors were able to do 83 percent of the time, far more than was possible without warning.


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