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One of the peculiar laws of quantum physics is that a particle can be in two different physical states at the same time - like how the Cheshire Cat could separate itself from its smile.

If, for example, a beam of neutrons is divided into two beams using a silicon crystal, it can be shown that the individual neutrons can travel simultaneously along both paths in what is known as a 'quantum superposition'.

And now scientists have measured this bizarre property, which means that they might be able to control the behaviour of neutrons in future

Scientists have observed for the first time a weird quantum phenomenon known as the 'Cheshire Cat' effect (illustration shown). The 'cat' in question was a subatomic neutron particle, and the ghostly 'grin' the particle's magnetic moment, which describes the strength of its coupling to an external magnetic field

The groundbreaking research was performed by an team at the Institut Laue-Langevin (ILL) in Grenoble, France.

Researchers from the Vienna University of Technology performed this separation of a particle from one of its properties.

The study published in Nature Communications showed that a neutron's 'magnetic moment' could be measured independently of the neutron itself.

The landmark observation demonstrated, for the first time, the weird quantum phenomenon known as the 'Cheshire Cat' effect.

The 'cat' in question was a subatomic neutron particle, and the ghostly 'grin' the particle's magnetic moment, which describes the strength of its coupling to an external magnetic field.

In the familiar 'macro' world, the one we see all around us, an object and its properties are always bound together and inseparable. 

It would be crazy to imagine a rotating ball, for instance, becoming separated from its spin.

Yet this is exactly what the international team of Austrian, French and US physicists managed to achieve.

Using an apparatus called an interferometer, they split a beam of neutrons and sent them along two paths, each with an opposite spin - the directional preference of their magnetic moment.

The experiment was set up in such a way that only neutrons with a spin parallel to their direction of motion - those travelling along an 'upper' path - were detected, a process known as 'post-selection'.

Subtle tweaking and measurements using a magnetic field led to the strange conclusion of the experiment.

While the physical particles themselves were observed flying along the upper path, the magnetic moment of the same particles could be detected emerging from the lower path. 

This is the Institut Laue-Langevin neutron source where the Quantum Cheshire Cat was created. Using an apparatus called an interferometer, the scientists split a beam of neutrons and sent them along two paths, each with an opposite spin - the directional preference of their magnetic moment

PhD student Tobias Denkmayr, from the Vienna University of Technology, said: 'By preparing the neutrons in a special initial state and then post-selecting them, we can achieve a situation in which both possible paths in the interferometer are important for the experiment.

'Along one of the paths, only an interaction with the particles themselves has an effect, but the other path is only sensitive to a magnetic spin coupling. 

'The system behaves as if the particles were spatially separated from their properties.'

The success of the experiment depended on making so-called 'weak measurements' that avoided the collapse of the quantum system.

Just as a spun coin comes up either heads or tails when caught, different quantum properties that exist at the same time in a 'superposition' are collapsed into a single state by the act of observation. 

'These weak measurements give you less information,' said Dr Hartmut Lemmel from the Institut Laue-Langevin. 

'As a result you need to do lots of observations to achieve any sort of certainty that you have seen what you think you have seen.'

Researchers from the Vienna University of Technology performed the first separation of a particle from one of its properties in the experiment. Pictured from left to right are Professor Yuji Hasegawa, Tobias Denkmayr, Dr Stephan Sponar, Dr Hartmut Lemmel, and Hermann Geppert

Whether the research has any practical potential remains unclear at present. 

One possible application could be high precision measurements of quantum systems that are often affected by disturbance.

Dr Stephan Sponar, another member of the Vienna University of Technology team, said: 'Consider a quantum system that has two properties: you want to measure the first one very precisely but the second makes the system prone to perturbation. 

'The two can be separated using a quantum Cheshire Cat, and possibly the perturbation can be minimised.'