10 billion bits of entanglement achieved in silicon

January 20, 2011, Oxford University

An illustration of a phosphorus nuclear spin entangled with its bound electron spin. Image: Stephanie Simmons.
(PhysOrg.com) -- Scientists from Oxford University have made a significant step towards an ultrafast quantum computer by successfully generating 10 billion bits of quantum entanglement in silicon for the first time – entanglement is the key ingredient that promises to make quantum computers far more powerful than conventional computing devices.

The researchers used high magnetic fields and low temperatures to produce entanglement between the electron and the nucleus of an atom of phosphorous embedded in a highly purified crystal. The electron and the nucleus behave as a tiny magnet, or 'spin', each of which can represent a bit of quantum information. Suitably controlled, these spins can interact with each other to be coaxed into an entangled state – the most basic state that cannot be mimicked by a conventional computer.

An international team from the UK, Japan, Canada and Germany, report their achievement in this week's Nature.

‘The key to generating entanglement was to first align all the spins by using high magnetic fields and low temperatures,’ said Stephanie Simmons of Oxford University’s Department of Materials, first author of the report. ‘Once this has been achieved, the spins can be made to interact with each other using carefully timed microwave and radiofrequency pulses in order to create the entanglement, and then prove that it has been made.’

The work has important implications for integration with existing technology as it uses dopant atoms in silicon, the foundation of the modern computer chip. The procedure was applied in parallel to a vast number of phosphorous atoms.

‘Creating 10 billion entangled pairs in silicon with high fidelity is an important step forward for us,’ said co-author Dr John Morton of Oxford University’s Department of Materials who led the team. ‘We now need to deal with the challenge of coupling these pairs together to build a scalable quantum computer in silicon.’

In recent years has been recognised as a key ingredient in building new technologies that harness quantum properties. Famously described by Einstein as “spooky action at distance” – when two objects are entangled it is impossible to describe one without also describing the other and the measurement of one object will reveal information about the other object even if they are separated by thousands of miles.

Creating true entanglement involves crossing the barrier between the ordinary uncertainty encountered in our everyday lives and the strange uncertainties of the quantum world. For example, flipping a coin there is a 50% chance that it comes up heads and 50% tails, but we would never imagine the coin could land with both heads and tails facing upwards simultaneously: a quantum object such as the electron spin can do just that.

Dr Morton said: ‘At high temperatures there is simply a 50/50 mixture of spins pointing in different directions but, under the right conditions, all the spins can be made to point in two opposing directions at the same time. Achieving this was critical to the generation of spin .’

Explore further: Quantum networks advance with entanglement of photons, solid-state qubits

More information: A report of the research entitled ‘Entanglement in a solid-state spin ensemble’ is published online in the journal Nature on 19 January 2011. doi:10.1038/nature09696

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1.6 / 5 (7) Jan 20, 2011
I don't know whether of not I'm totally of here but this isn't such big news is it? I mean it's not like they used qu-bits or anything.... And correct me if I'm wrong but the bits are individually entangled not to each other, right?
2.3 / 5 (3) Jan 20, 2011
what they did was essentially say we can create an ready state - a state where every bit is entagled to each other -- no very useful

Its kinda like saying i have 200 golf balls... and they are in a box(ion trap) and i can make them all have their brand name face up... and if I bump the box I can tilt them all to the left by the same degree...

So you can create a base state now pretty easily but to make it useful you need to then effect one bit at a time.--- much harder

-- but this step had to be done.
4 / 5 (5) Jan 20, 2011
The title of this article is a little misleading. It is not an entangled state of 10 million qubits, but an ensemble of 10 million electron spin-nuclear spin entanglement.

This is a very nice result anyway and to me it looks very much related to NMR quantum computing, but instead of being molecules in a liquid it is atoms in a Silicon crystal.

The original idea for precision doped atoms in Si was to individually adress/read-out single atoms and entangle pairs(or more) of atoms. This is an even harder task.

Nice work!
5 / 5 (1) Jan 20, 2011
@Technicalengeneering : This is a big deal.
Individual electrons are entangled with individual phosphorus nucleus, thus the electron-nucleus pair are qubits.
The next challenge for these guys is to get the electrons to interact with each other so that they can be used for computation.
1 / 5 (1) Jan 20, 2011
I wonder if you could use a given group of entangled particles to entangle other particles around them?
not rated yet Jan 21, 2011
cosmic rays will rain on this parade unless shielding is discovered. Even current equipment is subject to bit flips from cosmic rays.
not rated yet Feb 08, 2011
What would Scotty do...?

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