Skip to main content

Quantum vampires

The title of this piece may sound like the latest Young Adult bestseller (and I reserve all rights, thank you very much) but I was thinking of something a little more down to earth... yet at the same time rather more exciting. Even though it has been out for a while, I get more emails about my book on quantum entanglement, The God Effect than almost any other. I think it is because the subject is mind-boggling even to physicists (the whole business really started when Einstein wrote a paper to the effect of 'this entanglement stuff is so weird, quantum theory must be wrong'... but it was Einstein who was proved to be in error), and because some of the applications are amazing, notably quantum teleportation, which produces an effect like a Star Trek transporter on the scale of quantum particles.

I just thought I'd give a taster for the subject by using a little extract from The God Effect where the scientists head for the sewers:

By 2004, [Anton] Zeilinger and his team had achieved teleportation over significantly greater distances – in fact across the river Danube. A year after their ground-breaking long range transmission of entangled photons across the Danube, the Austrian team was back in the sewers, this time achieving teleportation from one side of the river to the other. (Quantum entanglement experimenters seem to have a functional relationship with the sewage system rivaled only by utility workers and Buffy the Vampire Slayer.)

As always with teleportation there are two “channels”, one carrying the entangled particles, the other transmitting the conventional information that will be used to complete the teleportation process. Entangled photons were pumped along a fiber optic cable running through the sewer system under the Danube, while the conventional information was beamed by microwave for 600 meters across the river. This may not seem ground breaking, but as their paper in Nature commented they had “demonstrated quantum teleportation over a long distance and with high fidelity under real world conditions outside a laboratory”. 

This is a significant blow to those critics who have said that teleportation could only occur under highly controlled laboratory conditions. The team points out that it’s also possible that this technique could be used as an alternative approach to make quantum repeaters that would enable entanglement to be shared anywhere around the world, as teleporting an entangled particle transfers the particle’s state, including its entanglement.

As this demonstrates, even if there never can be “real” teleportation of physical objects, it doesn’t mean that this isn’t a development of great importance. Teleportation even its limited form will prove vitally useful in making quantum computers real. Quantum computers rely on qubits, where information is stored in the quantum state of a particle. This may be very powerful, but it is also difficult to transfer that quantum state safely from place to place within the computer – or even between two quantum computers.

Teleportation means that, provided a supply of entangled particles is available, something that is now relatively easy to achieve, a qubit can be teleported from one place to another using only a conventional link. So a satellite pumping out entangled photons to two locations could enable quantum computers in two locations to swap qubits over the Internet.

Comments

Popular posts from this blog

Why I hate opera

If I'm honest, the title of this post is an exaggeration to make a point. I don't really hate opera. There are a couple of operas - notably Monteverdi's Incoranazione di Poppea and Purcell's Dido & Aeneas - that I quite like. But what I do find truly sickening is the reverence with which opera is treated, as if it were some particularly great art form. Nowhere was this more obvious than in ITV's recent gut-wrenchingly awful series Pop Star to Opera Star , where the likes of Alan Tichmarsh treated the real opera singers as if they were fragile pieces on Antiques Roadshow, and the music as if it were a gift of the gods. In my opinion - and I know not everyone agrees - opera is: Mediocre music Melodramatic plots Amateurishly hammy acting A forced and unpleasant singing style Ridiculously over-supported by public funds I won't even bother to go into any detail on the plots and the acting - this is just self-evident. But the other aspects need some ex

Is 5x3 the same as 3x5?

The Internet has gone mildly bonkers over a child in America who was marked down in a test because when asked to work out 5x3 by repeated addition he/she used 5+5+5 instead of 3+3+3+3+3. Those who support the teacher say that 5x3 means 'five lots of 3' where the complainants say that 'times' is commutative (reversible) so the distinction is meaningless as 5x3 and 3x5 are indistinguishable. It's certainly true that not all mathematical operations are commutative. I think we are all comfortable that 5-3 is not the same as 3-5.  However. This not true of multiplication (of numbers). And so if there is to be any distinction, it has to be in the use of English to interpret the 'x' sign. Unfortunately, even here there is no logical way of coming up with a definitive answer. I suspect most primary school teachers would expands 'times' as 'lots of' as mentioned above. So we get 5 x 3 as '5 lots of 3'. Unfortunately that only wor

Which idiot came up with percentage-based gradient signs

Rant warning: the contents of this post could sound like something produced by UKIP. I wish to make it clear that I do not in any way support or endorse that political party. In fact it gives me the creeps. Once upon a time, the signs for a steep hill on British roads displayed the gradient in a simple, easy-to-understand form. If the hill went up, say, one yard for every three yards forward it said '1 in 3'. Then some bureaucrat came along and decided that it would be a good idea to state the slope as a percentage. So now the sign for (say) a 1 in 10 slope says 10% (I think). That 'I think' is because the percentage-based slope is so unnatural. There are two ways we conventionally measure slopes. Either on X/Y coordiates (as in 1 in 4) or using degrees - say at a 15° angle. We don't measure them in percentages. It's easy to visualize a 1 in 3 slope, or a 30 degree angle. Much less obvious what a 33.333 recurring percent slope is. And what's a 100% slope