New Quantum Record: 14 Entangled Bits

Tx-0 writes "Quantum physicists from the University of Innsbruck 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. 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."

Comments

"Superdecoherence"

[AdmiralXyz]

From TFA:

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 is somewhat troubling, isn't it? If the decay rate is quadratic in the number of qubits, and this turns out to be due to some fundamental physical law as opposed to limitations of the current technology, does that mean we can never have quantum computers with any significant amount of memory?

Re:"Superdecoherence"

[DWMorse]

does that mean we can never have quantum computers with any significant amount of memory?

16k ought to be enough for ANYbody.

Re:"Superdecoherence"

[greeneggs2000]

From TFA:

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 is somewhat troubling, isn't it? If the decay rate is quadratic in the number of qubits, and this turns out to be due to some fundamental physical law as opposed to limitations of the current technology, does that mean we can never have quantum computers with any significant amount of memory?

Not really. The researchers trapped and entangled 14 ions in a single ion trap. Quantum computers based on ion traps will have thousands of traps, with never more than one or two ions per trap. (Machines with hundreds of traps have been tested, ions moved between traps, etc.; see, e.g., [1]) It has been known since at least 1997 [2] that you can't have a scalable system with only a single ion trap (that would be true even were the decay rate quadratic in the number of ions per trap).

[1] Home, J. P. et al. Complete methods set for scalable ion trap quantum information
processing. Science 325, 1227–1230 (2009). arXiv:0907.1865 [quant-ph]
[2] Wineland, D.J. et al. Experimental issues in coherent quantum state manipulation
of trapped atomic ions. J. Res. Natl. Inst. Stand. Technol. 103, 259–328 (1998). arXiv:quant-ph/9710025

By the way, an arXiv link for this article is arXiv:1009.6126 [quant-ph].

Re:"Superdecoherence"

[SoftwareArtist]

Someone please correct me if I'm wrong, but my understanding is that computing power depends on the number of entangled bits. The promise of quantum computers is that they can solve in O(N) time certain problems that a conventional computer would need O(exp(N)) time to solve - but only if all N bits are entangled. If you're limited to 16 entangled bits, you can't solve problems any larger than N=16 without losing the linear scaling.

Re:Very cool

[Anonymous Coward]

So support life extension. Why so many geeks are against life extension but for all kinds of projects that will take centuries to pan out is beyond me. Why explore space if you can't explore time?

Re:14 quantum bits

[VortexCortex]

Hell yeah! In a few years, I will be able to play Super Mario on a quantum computer!

Yes, but then you'll have to deal with Bowser's Peach Paradox -- The game will start with the Princess being both captured and not captured, and you'll only find out which if you complete the game and observe the ending.

"I'm sorry Mario, but our Princess exists in a super position of both being in another castle, and awaiting your return safely at home."

Only after you observe the game's ending will you discover the game's plot:
You either attempted to save the Princess from the evil clutches of King Kupa,
or it's another case of Mario going mad and destroying an innocent kingdom for no good reason.

Of course the credits will either reveal that the game's events haven't taken place yet (it was all a dream (ala Mario 2), ), or that the story has all happened before, an infinite number of times, and the princes might have just been captured again!

Talk about replayability...
Insert Qubits to Contiue.

Re:14 quantum bits

[infurnus]

Only after you observe the game's ending will you discover the game's plot:
You either attempted to save the Princess from the evil clutches of King Kupa,
or it's another case of Mario going mad and destroying an innocent kingdom for no good reason.

So basically, the plot to Braid?

big deal

[Quiet_Desperation]

I can get more things entangled by just leaving a couple extension cords unattended for a few days.

Re:big deal

[jjohnson]

My wire-clothes-hanger closet computer is orders of magnitude more powerful than yours. I just need seed funding to commercialize it.

Expect 20 in 20 yrs, 25 in 100 yrs, 30 in 1000 yrs

[gweihir]

Seriously, the speed the number of entangled quantums is rising with, clearly points to exponential increase in complexity. This means we will likely never see quantum computers that can be used for any real problem size. Not that this has been clear for about a decade or so.

Re:Very cool

[cgenman]

Because life is not an int that can just be increased? "Life Extension" is largely a sham promoted by con artists?

It's not like most geeks are against medicine, living well, reducing unnecessary risks, etc. But to say that you're researching "Life Extension" is like saying that you're researching "engineering bigger things" or "making fast stuff." Sure, someone doing research biology into the breakdown of DNA over time can be said to be doing "life extension." But anyone who says that they're doing life extension is probably an Israeli microcorp that releases 6 months of press releases, then disappears leaving nothing behind but bewildered investors and a badly dated looking website.

First command!

[mfnickster]

The first command they'll run on the quantum computer:

cat schroedinger.txt | tee alive.txt dead.txt

Re:Yeah yeah, right...

[lennier]

...cut the chit-chat...does Linux run on it yet?

Yes and no.

Re:14 quantum bits

[c0lo]

Some physicists think that we will be able to distinguish a change of state eventually [...]. Some do not.

Meanwhile, there is a group of physicist are in a superposition of the state thinking that FTL is and is not possible... they pertain to the class of String Theorists.

Paradoxically, the nature of their thinking state is totally opposite to quantum mechanics: any attempt to get an answer from their part will NOT result in a collapsing of their thinking state into one of the defined choices, but rather in setting the mind of the asking person into an indeterminate and fuzzy state (i.e. the "decoherence of the observer" effect).

Furthermore, in deep contrast with the normal quantum entanglement (on which the super-decoherence was observed), the above mentioned sub-system of String Theorist are believed as becoming more stable as the number of scientists in the group increases - in other words, a successful conversion of a new scientist to the group (will require an O(0) effort - i.e. constant, even if non-negligible) is most likely to result in a supra-linear increase in the stability of the so called "group coherence" and their capacity to influence the outside world.

Notes of caution for the young and adventurous - a short term exposure of an external observer may result in an assessment of the "thinking state" as being "incoherent", even if a longer period of observation will most likely note that the discourse and argumentation show patterns that are stable and that strongly resembles rationality and method. The external observer is warmly advised to refrain from searching for the "method behind the madness" under the risk of a fate worst than "living in the basement of their Mum" - see the reference to the "observer decoherence" effect above.