Simulations Show Quantum Error Not As Bad As Believed

aarondubrow writes "Because quantum systems become unstable quickly, their error threshold is an important factor. How many bits can 'break' before the system stops working? An international team of researchers used the supercomputers at the Texas Advanced Computing Center to simulate the error threshold of a topological quantum system and found a much higher threshold than had previously been reported."

Comments

NSFW warning

[aBaldrich]

goatse troll

Quantum Errors

[rossdee]

I had a Quantum hard drive fail about 2 months after the warranty expired. Fortunately you could still READ the data on it, you just couldn't write to it.
This was in the days of SCSI hard drives and Amiga computers.

Quantity of errors

[Zibodiz]

I think this comment thread is a good simulation of 'quantum errors'. Once you start getting that many errors, the best thing is just to not bother reading further. So I guess, for comparison, they're saying that the test showed that the computer didn't have as many errors as this thread has spam, so maybe it wasn't so bad. Only one out of three bits was a 'goat'.

Actual Information on the Subject:

[Hartree]

This is about a rather specialized type of quantum computer. Or more realistically, a proposed idea for a quantum computer.

One of the problems for quantum computing is the fragility of the quantum states that could be used. Even a tiny disturbance can cause the thing to screw up in a manner called decohering. So, there has been a push to find possible quantum computing elements that are extremely well insulated from the outside world, or that will tolerate a lot of disturbance without decohering.

Certain quantum states of quasi-particles called anyons (no joke. That's what they are called) in 2 dimensions are thought to be extremely stable.

Recently, there have been observations of states similar to these in surfaces of materials called topological insulators. They haven't conclusively shown that the right sort of states (called nonabelian) exist yet.

But, even if these so called "topologically protected" quantum states of the right sort exist, you still need an algorithm for how to compute with them.

What the Texas Advanced Computing Center team did was simulate a proposed algorithm called topological color coding for a specific case. When they did this, they found that it can withstand 10% of the underlying quantum bits screwing up.

So, it's a simulation of a proposed set of rules for computing with a proposed (but not yet demonstrated) set of quantum bits, using special quantum particles (that are composed of more than one normal particles bound together) that have not yet been shown to exist.

Although this is a very interesting area, it's a simulation of a vaporware program to run on a vaporware computer that is based on vaporware physics.

So, to say the least it's a ways off. But for solid state physics geeks it's a very hot topic of research.

Obligatory non-goatse links with useful info:
http://en.wikipedia.org/wiki/Topological_quantum_computer

Original paper abstract: http://arxiv.org/abs/0910.0573 with links to full paper.

This work was done by the computational physics group at Texas A&M: http://comp-phys.tamu.edu/ among others.

Re:Probability

[formfeed]

the alternate approach could handle noise and used probabilities to make a mostly valid assumption.

It's called Wikipedia.

The error rate exists as a superposition of itself

[VortexCortex]

Both good and bad was the the error rate
of the simulated Quantum state:
A superposition the states did make
having properties hard not to misstate.

Thus, when the research groups did separate
to further test the quantum error rate
they each observed a quantum error state
that they could not, in fact, equate!

Indeed, the collapsed quantum state
resulted in results so disparate,
their virtual machines could not re-simulate
these quantum effects they could not contemplate.

As the scientists began to debate
over a single quantum error rate
Their tense and stressed emotional state
caused some of them to scorn and berate,
and sparked others to recriminate.

(I would dare to speculate
that they were even too irate
to relate or even cogitate
the average quantum error rate.)

I hope they can remunerate
the costs that we associate
with researching the quantum error state,
so their teams do not have to inflate
the local unemployment rate!

Alas, science has yet to negate,
(or even circumnavigate)
the risks that one begins to take
by observing a Quantum error rate.

Vacuum tube logic

[ResidentSourcerer]

Really bad old days:

The latest thing was the replacement of relays with vacuum tubes. While an individual tube is reasonably reliable -- better than a light bulb -- collect a bunch together and you always have one blowing out.

I heard that with one such school sized computer after WWII the basic flip-flop was a 7 vacuum tube circuit, wired so that ANY two of the tubes could fail and the device would still function.

Several flip-flops were in a drawer. Indicator lights on the drawer front showed status. Red light on drawer, open drawer. Each flip-flop board had indicator lights showing which tubes were good.

People would race though the corridors with shopping carts of tubes doing hot replacements while the machine was running. My recollection was that even so uptime was usually measured in minutes before some other thing would break.