14 quantum bits: Physicists go beyond the limits of what is currently possible in quantum computation

April 1, 2011, University of Innsbruck

Up to 14 quantum bits were entangled in an ion trap.
(PhysOrg.com) -- Quantum physicists from the University of Innsbruck (Austria) have set another world record: They have achieved controlled entanglement of 14 quantum bits (qubits) and, thus, realized the largest quantum register that has ever been produced. With this experiment the scientists have not only come closer to the realization of a quantum computer but they also show surprising results for the quantum mechanical phenomenon of entanglement.

The term entanglement was introduced by the Austrian Nobel laureate Erwin Schrödinger in 1935, and it describes a quantum mechanical phenomenon that while it can clearly be demonstrated experimentally, is not understood completely. Entangled particles cannot be defined as single particles with defined states but rather as a whole system. By entangling single , a quantum computer will solve problems considerably faster than conventional computers. "It becomes even more difficult to understand entanglement when there are more than two particles involved," says Thomas Monz, junior scientist in the research group led by Rainer Blatt at the Institute for Experimental Physics at the University of Innsbruck. "And now our experiment with many particles provides us with new insights into this phenomenon," adds Blatt.

World record: 14 quantum bits

Since 2005 the research team of Rainer Blatt has held the record for the number of entangled quantum bits realized experimentally. To date, nobody else has been able to achieve controlled of eight particles, which represents one quantum byte. Now the Innsbruck scientists have almost doubled this record. They confined 14 calcium atoms in an ion trap, which, similar to a quantum computer, they then manipulated with laser light. The internal states of each atom formed single qubits and a quantum register of 14 qubits was produced. This register represents the core of a future quantum computer. In addition, the physicists of the University of Innsbruck have found out that the decay rate of the atoms is not linear, as usually expected, but is proportional to the square of the number of the qubits. When several particles are entangled, the sensitivity of the system increases significantly. "This process is known as superdecoherence and has rarely been observed in quantum processing," explains Thomas Monz. It is not only of importance for building quantum computers but also for the construction of precise atomic clocks or carrying out quantum simulations.

Increasing the number of entangled particles

By now the Innsbruck experimental physicists have succeeded in confining up to 64 particles in an ion trap. "We are not able to entangle this high number of ions yet," says Thomas Monz. “However, our current findings provide us with a better understanding about the behavior of many entangled particles." And this knowledge may soon enable them to entangle even more atoms.

Some weeks ago Rainer Blatt’s research group reported on another important finding in this context in the scientific journal Nature: They showed that ions might be entangled by electromagnetic coupling. This enables the scientists to link many little quantum registers efficiently on a micro chip. "All these findings are important steps to make quantum technologies suitable for practical information processing," Rainer Blatt is convinced.

The results of this work are published in the scientific journal Physical Review Letters.

Explore further: Quantum computer - tune in now: Atomic antennae transmit quantum information across microchip

More information: 14-Qubit Entanglement: Creation and Coherence. Thomas Monz, Philipp Schindler, Julio T. Barreiro, Michael Chwalla, Daniel Nigg, William A. Coish, Maximilian Harlander, Wolfgang Hänsel, Markus Hennrich, Rainer Blatt. Phys. Rev. Lett. 106, 130506 (2011) DOI:10.1103/PhysRevLett.106.130506

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2.3 / 5 (3) Apr 01, 2011
April Fools joke?
5 / 5 (1) Apr 01, 2011
I would like to know a new estimate as to when a practical quantum computer will become available?
5 / 5 (1) Apr 01, 2011
available to whom -- scientists or consumers -- it is thought that QC's will not be useful to the average consumer -- but they said that about regular computers as well

But right now QC's are built to handle specialized question much like Computers of the past. But having to super cool atoms may make this technology unreasonable to have at home.
5 / 5 (14) Apr 01, 2011
Maybe one day tech support will ask:
"Ok go to Start> Control Panel> System> Entanglement.
Does it show all your qubits are still entangled?"
5 / 5 (1) Apr 01, 2011
Having to be ever more careful to avoid "superdecoherence" does not scale. Linking separatly entangled components does not provide anything approaching expontential capacity.

I fully expect extremely useful QCs to be developed however I see no evidence to suggest QCs would ever be capable of fulfilling their origional promise.
not rated yet Apr 02, 2011

The idea would work something like conventional computer design, where we have various processors and devices, each specialized to a specific task.

A motherboard would be designed with several different types of quantum chips which are then queried as needed when the time arises.

And yes, quantum computers do have some potential practical applications both in business computing and in gaming. They certainly have potential practical applications in servers and cloud computing.

Even very specialized QC gives the potential to design certain types of searches, "switch", and "loop" statements and other control structures in machine logic whereby all possibilities are solved simultaneously, and only the correct one is given as a return...this would make web pages compile and load much faster, and it would make games and certain other algorithms run much, much faster and smoother.
not rated yet Apr 02, 2011
You should all understand that when scientists/engineers give criticisms or limitations of a technology those statements are made with respect to what is understood -at the time-.

So as QC's are understood right now, with the limited number of algorithms we have realized to give exponential speed ups, there's little to no practical value for consumers.

That does not mean things can't or won't change, but until things do change the current state remains as it is.

It would do all of you very well to -accurately- interpret the information you read, which means to understand implied and obvious contexts unless explicitly stated otherwise. For example if a physicists tells you explicitly that due to certain laws of nature energy can never be created from nothing, at any time, then you can interpret the statement to stand beyond today. But if someone tells you a new technology has 'the following limitations', it should be obvious that the future was not addressed.
not rated yet Apr 02, 2011
Not sure if you guys feel about linking outside of physorg, but I came across this from a submission on reddit and this user gave some interesting comments about the practical value of quantum computers as he understood them today;

not rated yet Apr 04, 2011
"the decay rate of the atoms is not linear, as usually expected, but is proportional to the square of the number of the qubits."
Does this make Quantum Computing far less feasible than hoped for?
not rated yet Apr 04, 2011

I am remined of the history of computing that i took in college. It started with the Babbage machine and continued to modern day. Modern computers have been in existance since pretty much the fifties but they did not make it into the home until the 80's and then it was not widespread with truely useful software until maybe 93-95.

Puters were built with the design in mind that they should be able to do claculations quickly., faster than man at least. But the primary goals of QC are a bit different... QC will hopefully model the quantum world better than any normal computer can because it will be fundamentally using more Quantum rules than a classical computer can simulate well.

It was hoped that many extremely had classical problem could be done on a QC with an exponential speed up but this now seems unlikely with new maths that have arisen in the field pointing to QC algorithms not being able to deliever the necessary power.

But as i said before we have PC why not PQC's
not rated yet Apr 05, 2011

Even very specialized QC gives the potential to design certain types of searches, "switch", and "loop" statements and other control structures in machine logic whereby all possibilities are solved simultaneously, and only the correct one is given as a return...this would make web pages compile and load much faster, and it would make games and certain other algorithms run much, much faster and smoother.

I very much doubt that. The main problem is that every time you check the answer, the coherence is lost and while you get the correct answer, you then have to spend time in reloading all the data into the qubits to do it again.

So memory bandwidth becomes a limiting issue for all but trivial problems.

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