Physicists manage to 'breed' Schrodinger's cat in breakthrough that could help explain the quantum world

The cat in famous thought experiment can be alive and dead at the same time
Physicists amplified pairs of classical states of light to generate 'enlarged' cat
This could uncover the limit, if one exists, of the quantum world, they say

Published: 19:07 BST, 1 May 2017 | Updated: 08:41 BST, 2 May 2017

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Scientists have developed a way to 'breed' Schrodinger's hypothetical cat in a breakthrough experiment that could bridge the gap between the quantum and the visible - or classical - worlds.

The cat in the famous thought experiment can be alive and dead at the same time, in a quantum phenomenon known as superposition.

But, whether this effect translates to larger objects has long remained a mystery.

Physicists have now created a way to amplify pairs of classical states of light to generate 'enlarged' cats, in effort to uncover the limit (if there is one) of the quantum world.

The cat in the famous thought experiment can be alive and dead at the same time, in a quantum phenomenon known as superposition. But, whether this effect translates to larger, macroscopic objects has long remained a mystery. The paradox is illustrated above

SCHRODINGER'S CAT

Schrödinger's cat is a thought experiment created by Austrian physicist Erwin Schrödinger in 1935.

In the hypothetical experiment a cat is placed in a sealed box next to a radioactive sample, a Geiger counter, and a bottle of poison.

The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, releasing the poison and killing the cat, until the box is opened.

This means the cat is both dead and alive inside the box, a mixture of both states, until the box is opened.

'One of the fundamental questions of physics is the boundary between the quantum and classical worlds,' says CIFAR Quantum Information Science Fellow Alexander Lvovsky.

'Can quantum phenomena, provided ideal conditions, be observed in macroscopic objects?

'Theory gives no answer to this question – maybe there is no such boundary.

'What we need is a tool that will probe it.'

In the new experiment, the researchers 'bred' the physical analogue of the Schrodinger cat.

This, in this case, is the superposition of two coherent light waves, in which the fields of the electromagnetic waves point in opposite directions at once.

Based on an idea first proposed over a decade ago by researchers in Australia, the team bred these states to create optical 'cats' of higher amplitudes.

'In essence, we cause interference of two 'cats' on a beam splitter,' said Anastasia Pushkina, co-author and University of Calgary graduate student.

'This leads to an entangled state in the two output channels of that beam splitter.

'In one of these channels, a special detector is placed.

'In the event this detector shows a certain result, a 'cat' is born in the second output whose energy is more than twice that of the initial one.'

Doing this, the researchers converted a pair of negative squeezed 'cats' of amplitude 1.15 to a single positive 'cat' of amplitude 1.85.

Doing this, the researchers converted a pair of negative squeezed 'cats' of amplitude 1.15 to a single positive 'cat' of amplitude 1.85. Entangled particles are illustrated above

Over the course of the experiment, they generated several thousand of these enlarged cats.

According to the researchers the experiment has implications for future work in quantum communication, teleportation, and cryptography.

'It is important that the procedure can be repeated: new 'cats' can, in turn, be overlapped on a beam splitter, producing one with even higher energy, and so on,' says lead author Demid Sychev, a graduate student from the Russian Quantum Center and the Moscow State Pedagogical University.

'Thus, it is possible to push the boundaries of the quantum world step by step, and eventually to understand whether it has a limit.'