Two boxes, one cat: Schrödinger’s cat gets 21st-century upgrade

27 May 2016

It seems Schrödinger’s cat has gotten too big for its box, as Yale theoretical physicists have proposed ‘Schrödinger’s cat 2.0’, a quantum theory equation that suggests the cat could be in two places at once.

The theory surrounding Schrödinger’s cat is best-known, not just in the scientific community and philosophical communities, but in the wider world, too, as the theory that asks the question: if we don’t see something, does it exist?

Envisioned by Ireland-based physicist Erwin Schrödinger in 1935, Schrödinger’s cat quantum mechanics theory posits that a cat is placed in a sealed box with a radioactive substance that will be triggered if an atom of the radioactive substance decays.

If we are to go by Schrödinger’s theory, the cat can be either alive or dead, unless the box is opened, which will change its entire quantum state.

This rather simplified theory is still used today by science, whereby a wave-packet of light composed of hundreds of particles finds itself simultaneously in two distinctly different states, with each state corresponding to an ordinary form of light found abundantly in nature.

Now, however, a team of theoretical physicists from Yale University has developed a variant theory 20 years in the making that takes that same cat, but doubles down on the potential, mind-bending possibilities.

Two boxes, one cat

According to this new theory, there are now two boxes in which Schrödinger’s cat can be either alive or dead in both of these boxes at the same time, which adds quantum entanglement into the mix.

This entanglement allows a local observation to change the state of a distant object instantaneously, which, in this case, allows a cat state to be distributed in different spatial modes.

Double down cats

Schrödinger’s cat 2.0. Image via Michael S. Helfenbein/Yale University

To put ‘Schrödinger’s cat 2.0’ into practice, the researchers put together two 3D microwave cavities, as well as a monitoring port, all of which is connected by a superconducting, artificial atom.

While obviously no cat would be used in this experiment, the researchers’ ‘cat’ consisted of confined microwave light within the two cavities.

‘This cat is big and smart’

“This cat is big and smart. It doesn’t stay in one box because the quantum state is shared between the two cavities and cannot be described separately,” said Chen Wang, a postdoctoral associate at Yale and first author of a study in the journal Science, describing the research.

“One can also take an alternative view, where we have two small and simple Schrödinger’s cats, one in each box, that are entangled.”

So where does the potential benefit for quantum computing come in?

Well, one of the challenges facing current quantum computers is making them able to correct errors without disturbing any information at the blistering speed at which they can attempt to solve problems.

With Schrödinger’s cat 2.0, however, it turns out generating a cat in two boxes is considered the first step towards having “logical operation between two quantum bits in an error-correctible manner”, according to co-author Robert Schoelkopf.

Cat in a box image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic