Alive and dead and in two places at once: the mystery of Schrodinger’s cat

We all know the story of Schrodinger’s cat – the unlucky beast that spends its days both living and dead in a box until someone lets it out. Well, now it can get out, sort of. Scientists have shown that the cat can be alive and dead, and can also be in two boxes at once.

Schrodingers cat

Originally, the cat was the protagonist in a story used to explain the Copenhagen interpretation of quantum mechanics. He (or she) is sealed in a box along with a radioactive particle, which could decay at any time, and a vial of poison gas, which will break if the particle does decay. Schrodinger argues that until we open the box and find out if the cat is alive or dead, it is both, in what theoretical physicists like to call a “superposition of states”. In short, unobserved microscopic matter is in multiple states simultaneously until we take a measurement.

The scientists at Yale used an experiment not nearly as life threatening as this one to show that the cat can be split in two. They connected two aluminium boxes called microwave chambers by a sapphire chip and aluminium circuit, which acted as a switch which could be on or off. They introduced an electromagnetic wave oscillating in two opposite directions at once into the first box, connected the boxes, and then when the switch was turned off and the cavities were no longer connected, they counted the number of photons in each box. Sounds weird, but by showing that the total number of photons was always even, they showed that the boxes still acted as if they were connected.

It sounds small, and maybe even obvious, but this is new information and could be used for things like measuring the phase of light to improving quantum computers. In a quantum computer, numbers are stored as quantum bits, or qubits. Normal bits can store either a 0 or a 1, but a qubit can be in both of those states, and all states in between, at once. That makes quantum computers much faster than standard computers at lots of types of problems, particularly optimisation, as all possibilities can be calculated simultaneously and the results compared. But the qubits are more delicate – they could be affected by the outside environment and we can’t correct them without disturbing them. Conveniently, this is where the cat comes back in. If the qubits in the computer can be linked to other qubits, these could be used to correct the errors.

Quantum computers may be the only way to continue to improve the power of computers without compromising the size. So good luck Tiddles, we’re relying on you…


C. Want, Y. Y. Gao, P. Reinhold, R. W. Heeres, N. Ofek, K. Chou, C. Axline, M. Reagor, J. Blumoff, K. M. Sliwa, L. Frunzio, S. M. Girvin, L. Jiang, M. Mirrahimi, M. H. Devoret, R.J. Schoelkopf, Science Vol 352 p. 1087, 27th May 2016, A Schrodinger cat living in two boxes, (accessed 14/06/2016)

Emily Conover, Science News, 26th May 2016, Schrodingers cat now dead and alive in two boxes at once (accessed 14/06/2016)

Joshua Sokol, New Scientist, 4th June 2016, Schrodinger’s cat can survive being split in two

Julia Layton, How Stuff Works, 7th June 2016, Scientists prove Schrodinger’s cat can be in two places at once, (accessed 14/06/2016)


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