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Light’s quantum weirdness works in SPACE

Scientists have taken a quantum physics experiment first devised in the late 1970s to new levels, sending light to space and back.

In the study, the researchers fired light particles, called photons, 3,500 kilometres (2,174 miles) into space, bouncing them off a satellite.

An analysis of how the photons returned to Earth confirmed that light acts as both a particle and a wave, even on a vast scale.

 

Scientists have taken a quantum physics experiment first devised in the late 1970s to new levels, sending light to space and back (stock image)

THE STUDY  

The researchers sent a pulse of laser light into a device called a beam splitter, paving two paths for the light to take.

One path is shorter and straight, while the other is a detour.

The light on the detour path then re-joins the light on the straight path, and both pulses head towards a satellite 3,500 kilometres away from Earth, with one lagging behind.

When the light reaches the satellite, it bounces back to Earth, where it encounters a device that can do one of two things – either nothing, or hold up the first pulse so the pair merge.

This decision is random, and corresponds to Wheeler’s delayed choice.

If the device does nothing, the path lengths remain unequal, but if it adds a delay to the first pulse, the path lengths become equal.

When the paths are unequal, the photons arrive together, allowing the researchers to tell which path they took.

In this case, they act like particles.

But when the paths are equal, it is impossible to tell which path each photon took.

In this way, light acts as a wave.

By repeating the experiment several times, the researchers were able to create an interference pattern characteristic. 

It has been known since the 1920s that light behaves as both a particle and a wave – a process called ‘wave-particle duality.’

And experiments devised in the 1970s by physicist, John Wheeler, showed that this was the case on Earth.

Wheeler’s experiment in 1978 was called the ‘delayed choice experiment’ and involved sending a beam of light into an apparatus, before changing the set-up to see if it changed from acting like a particle to a wave, as expected.

Since then, several experiments have tested this theory, but until now, the longest distance this has been tested on is about 87 miles (140 kilometres).

But researchers from the University of Padova have now set a new distance record of more than 3,500 kilometres (2,174 miles) for detection of this bizarre behaviour.

Speaking to Space.com, Dr Giuseppe Vallone, one of the researchers who worked on the study, said: ‘The law of quantum mechanics…should be valid for any distance, right.

‘But of course, if we don’t test it, we cannot be sure.’

The researchers sent a pulse of laser light into a device called a beam splitter, paving two paths for the light to take.

One path is shorter and straight, while the other is a detour.

The light on the detour path then re-joins the light on the straight path, and both pulses head towards a satellite 3,500 kilometres away from Earth, with one lagging behind.

When the light reaches the satellite, it bounces back to Earth, where it encounters a device that can do one of two things – either nothing, or hold up the first pulse so the pair merge.

This decision is random, and corresponds to Wheeler’s delayed choice.

If the device does nothing, the path lengths remain unequal, but if it adds a delay to the first pulse, the path lengths become equal.

The researchers sent a pulse of laser light into a device called a beam splitter (BS), paving two paths for the light to take. One path is shorter and straight, while the other is a detour. The light on the detour path then re-joins the light on the straight path, and both pulses head towards a satellite 3,500 kilometres away from Earth, with one lagging behind

The researchers sent a pulse of laser light into a device called a beam splitter (BS), paving two paths for the light to take. One path is shorter and straight, while the other is a detour. The light on the detour path then re-joins the light on the straight path, and both pulses head towards a satellite 3,500 kilometres away from Earth, with one lagging behind

When the paths are unequal, the photons arrive together, allowing the researchers to tell which path they took.

In this case, they act like particles.

But when the paths are equal, it is impossible to tell which path each photon took.

In this way, light acts as a wave.

By repeating the experiment several times, the researchers were able to create an interference pattern characteristic.

Speaking to New Scientist, Giulio Chiribella, a quantum physicist at the University of Oxford who was not involved in the study, said: ‘This experiment shows that, at least on a distance of approximately 3,500 kilometres, the predictions of quantum theory are still valid.

‘This result is likely to be the first of a series of experimental tests where the fundamental features of quantum mechanics will be probed at increasingly large scales.’ 

 

Read more at DailyMail.co.uk


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