Three tiny qubits, another big step toward quantum computing

Sep 29, 2010

(PhysOrg.com) -- The rules that govern the world of the very small, quantum mechanics, are known for being bizarre. One of the strangest tenets is something called quantum entanglement, in which two or more objects (such as particles of light, called photons) become inextricably linked, so that measuring certain properties of one object reveals information about the other(s), even if they are separated by thousands of miles. Einstein found the consequences of entanglement so unpalatable he famously dubbed it "spooky action at a distance."

Now a team led by Yale researchers has harnessed this counterintuitive aspect of quantum mechanics and achieved the entanglement of three solid-state , or , for the first time. Their accomplishment, described in the Sept. 30 issue of the , is a first step towards quantum error correction, a crucial aspect of future quantum computing.

"Entanglement between three objects has been demonstrated before with photons and charged particles," said Steven Girvin, the Eugene Higgins Professor of Physics & Applied Physics at Yale and an author of the paper. "But this is the first three-qubit, solid-state device that looks and feels like a conventional microprocessor."

The new result builds on the team's development last year of the world's first rudimentary solid-state quantum processor, which they demonstrated was capable of executing simple algorithms using two qubits.

The team, led by Robert Schoelkopf, the William A. Norton Professor of Applied Physics & Physics at Yale, used artificial "atoms"—actually made up of a billion aluminum atoms that behave as a single entity—as their qubits. These "atoms" can occupy two different energy states, akin to the "1" and "0" or "on" and "off" states of regular bits used in conventional computers. The strange laws of , however, allow for qubits to be placed in a "superposition" of these two states at the same time, resulting in far greater information storage and processing power.

In this new study, the team was able to achieve an entangled state by placing the three qubits in a superposition of two possibilities—all three were either in the 0 state or the 1 state. They were able to attain this entangled state 88 percent of the time.

With the particular the team achieved, they also demonstrated for the first time the encoding of quantum information from a single qubit into three qubits using a so-called repetition code. "This is the first step towards quantum error correction, which, as in a classical computer, uses the extra qubits to allow the computer to operate correctly even in the presence of occasional errors," Girvin said.

Such errors might include a cosmic ray hitting one of the qubits and switching it from a 0 to a 1 state, or vice versa. By replicating the qubits, the computer can confirm whether all three are in the same state (as expected) by checking each one against the others.

"Error correction is one of the holy grails in today," Schoelkopf said. "It takes at least three qubits to be able to start doing it, so this is an exciting step."

Explore further: Physicists discuss quantum pigeonhole principle

More information: Citation: DOI: 10.1038/nature09416

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Quantum_Conundrum
1.6 / 5 (7) Sep 29, 2010
Progress is progress, but my goodness...

It took an entire year to go from 2 qubits to 3 qubits?

At the rate of 1 qubit per year, it'll be 21 years before they have a machine with 3 quantum bytes.

At the rate of 50% per year, it'll still take over 5 years before they can make a machine with 24 qubits, or 3 quantum bytes.

Unless someone figures out a way to generalize their circuitry, this is going to take decades or centuries to have any real progress.
PhysicsLver21
3 / 5 (4) Sep 29, 2010
At the rate of 1 qubit per year, it'll be 21 years before they have a machine with 3 quantum bytes.
At the rate of 50% per year, it'll still take over 5 years before they can make a machine with 24 qubits, or 3 quantum bytes.
Unless someone figures out a way to generalize their circuitry, this is going to take decades or centuries to have any real progress.


What makes you think that there is only going to be a 50% increase every year in quantum bit manipulation, storage, ect..

At the rate of our knowledge and expansion of science I can see this increasing exponentially... maybe in 2 years we can make a machine with 8 qubits, maybe a year after that it only increases by 2... then perhaps the next couple years that increases exponentially?
Quantum Processing and computing just doesn't occur over night.. or in a matter of 10, 15 years... I don't see a feasible quantum computing coming about until the next 30 - 50 years maybe even longer but hey.. that is NOT that far off.
epsi00
2 / 5 (1) Sep 29, 2010
progress can sometimes be compared to a dam. water accumulate little by little and then the dam can no longer hold it...
malapropism
4.5 / 5 (2) Sep 29, 2010
It took an entire year to go from 2 qubits to 3 qubits?

But I think the point of the article is not so much that they increased the number of qubits by 50% but that they devised, created and demonstrated a workable error-correction scheme at the qubit level. That's actually a really important step forward.
Dr_Doe
3.3 / 5 (3) Sep 30, 2010
They'll find better/quicker means of manipulating qubits to the point where it may have taken a year to add a third one but now knowing what they do, it might only take 9 months to add another. Once they can build a small scale but workable Q-pc and use it to further there work then I believe they'll be able to double it with in a couple years which prior to that took 10... People seem to forget that we are constanly improving and what took us a year to do now will only get shorter as we learn and discover new techniques. Nano technology is gonna revolutionize our lifetime and I strongly believe it's gonna happen with-in 20 years.....I hope!
kevinrtrs
1 / 5 (4) Sep 30, 2010
People seem to forget that we are constantly improving and what took us a year to do now will only get shorter as we learn and discover new techniques.

So imagine what happens when you have all the knowledge imaginable: You could create the universe and everything in it in just six days!!!!
elbeasto
5 / 5 (1) Sep 30, 2010
"... qubits to be placed in a "superposition" of these two states at the same time"

"... superposition of two possibilities—all three were either in the 0 state or the 1 state"

Pretty sure that is a contradiction. Keyword in second statement is "either". A qubit in superposition IS both values until measured. Once measured it is no longer a superposition nor are the bits entangled. Speaking of which, anyone know how they are re-entangling the qubits after measurements?
Skeptic_Heretic
5 / 5 (2) Sep 30, 2010
People seem to forget that we are constantly improving and what took us a year to do now will only get shorter as we learn and discover new techniques.

So imagine what happens when you have all the knowledge imaginable: You could create the universe and everything in it in just six days!!!!

You'd have to exist first. Your flavor of Udayism is ridiculous, and a sign of a weak mind.
gwrede
2.3 / 5 (3) Sep 30, 2010
People seem to forget that we are constantly improving and what took us a year to do now will only get shorter as we learn and discover new techniques.
So imagine what happens when you have all the knowledge imaginable: You could create the universe and everything in it in just six days!!!!
You'd have to exist first. Your flavor of Udayism is ridiculous, and a sign of a weak mind.
Religion aside, you'd also need a good dose of energy. My first guess is, a nuclear power plant the size of the universe. :-)
Justsayin
1 / 5 (1) Oct 03, 2010
A 30-qubit quantum computer would equal the processing power of a conventional computer that could run at 10 teraflops (trillions of floating-point operations per second). http://computer.h...rintable
malapropism
not rated yet Oct 03, 2010
People seem to forget that we are constantly improving and what took us a year to do now will only get shorter as we learn and discover new techniques.

So imagine what happens when you have all the knowledge imaginable: You could create the universe and everything in it in just six days!!!!

Your religion-supporting suggestion is a non-sequitir because "all knowledge imaginable" equates to "infinite knowledge" - to acquire infinite knnowledge would require infinite time and therefore cannot yet have happened (the continued existence of the universe we live in precludes it a priori).

Why do you (apparently) believe what was written in the Hebrew bible by rather primitive tribespeople some 3,000 or 4,000 or so years ago?
ffrankblu
not rated yet Oct 05, 2010
If you live outside of time or can travel it like we would a street then it would be a possibility or as with string theory there are infinite universes then most likely beings have learned to traverse them so in my mind anything is possible.