Paintball demo targets mysteries of quantum physics for TV show

Physicist Dr Winfried Hensinger has been helping the BBC understand the complexities of quantum physics - by taking part in a spot of paintballing.

Dr Hensinger, a Reader in Quantum, Atomic and Optical Physics, took up the sporting challenge for a report on his groundbreaking research by BBC programme Inside Out.

The programme, to be broadcast next Monday (31st October at 7.30pm on BBC 1, South East only), will look at the work being done by Dr Hensinger and his team on the development of a large-scale quantum computer - one of the big science quests of modern times.

But to help the programme makers get to grips with the complex principles involved in quantum mechanics, and how these might be used to revolutionise everyday life, Dr Hensinger joined presenter Kaddy Lee Preston for a day of shooting paint at a target using paintball guns.

In quantum physics, scientists understand that some particles can exist in two places at the same time - but this understanding defies classical physics and scientific measurement. The paintball contest, which involved firing brightly coloured paint at a target with two slits, helped to demonstrate this idea.

Dr Hensinger says: "We were really demonstrating the famous double slit experiment, which describes one of the key features of quantum mechanics. When you fire electrons at a wall with two slits in it, they have to go through one of the two slits in order to hit the wall behind. But what we find from the pattern on the back wall is that the electrons actually go through both slits at once. It seems they can be in two places at the same time.

"So, when you sit in your car, you have a choice to drive forward or backwards. But in the world of quantum mechanics, you can drive forward and backwards at the same time.

"However, when we set up a device to look closely at the slits themselves to witness this, we then find that the electron 'chooses' and goes through one slit only. So as soon as we try to measure something in the quantum world (i.e. which path the electron has taken), we collapse the quantum state. The paintball demo was used to illustrate the double slit experiment, first to see what one would expect from classical physics and then what would happen if the quantum physics would apply (which it does in the case of atoms or electrons)."

The BBC team went on to film in Dr Hensinger's lab, where they looked at what a quantum computer might look like in the future. The first model would have to be very big indeed, but the ultimate ambition would be to create computers invisible to the naked eye yet capable of holding vast quantities of information that could be processed at unimaginable speed.

Dr Hensinger already uses rock guitar to teach students frequency analysis and sound harmonics - some of the fundamentals of physics.

He says: "I believe it is really important to show to the general public how fascinating quantum physics research really is and its tremendous implications for society. The programme did a tremendous job in making this complicated topic accessible to a wider audience."