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First Electronic Quantum Processor Created
ScienceDaily is reporting that the first rudimentary solid-state quantum processor has been created by a team led by Yale University researchers. "Working with a group of theoretical physicists led by Steven Girvin, the Eugene Higgins Professor of Physics & Applied Physics, the team manufactured two artificial atoms, or qubits ('quantum bits'). While each qubit is actually made up of a billion aluminum atoms, it acts like a single atom that can occupy two different energy states. These states are akin to the '1' and '0' or 'on' and 'off' states of regular bits employed by conventional computers. Because of the counterintuitive laws of quantum mechanics, however, scientists can effectively place qubits in a 'superposition' of multiple states at the same time, allowing for greater information storage and processing power."
You can find the lab site here with several papers freely available in pre-publication form on arxiv from the researchers. I'm trying to find the "basic algorithms" the article alludes to that these rudimentary processors can perform. I thought only a handful were applicable (Shor's algorithm) to quantum computing. Anyone know?
My work here is dung.
http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature08121.pdf
(For those with access to Nature through school or work...)
they did not manufacture "two artificial atoms, or qubits". They manufactured two clusters of atoms that acted as qubits.
A qubit is not actually a quantum particle. It is a unit of quantum information. Now, do you consider the qubit to be the system or the state?
Fish.
Ah, so then you agree that it wasn't a chicken egg? ie Chicken came first (from non-chicken egg), then laid chicken egg.
Neither: It was the Rooster who came first (it happens to every guy once in a while).
Authority questions you. Return the favor.
Riiiiight. What's a qubit?
640K qubits ought to be enough for anybody
-Billco, Fnarg.com
This idea was invented by Shampoo.
coding is life
Yes the first. The Dwave guys aren't building quantum computers. Their system lacks entanglement between the qubits, which is essential to running quantum algorithms. They have also been less than forthcoming about the coherence in their system.
Slashdot: where don knuth is an idiot because he cant grasp the awesome power of php
No, no, you've got it backwards.
A non-chicken laid a chicken egg (i.e. the egg's genes were those of a chicken), from which hatched a chicken.
The ScienceDaily article and the /. summary seem to be confused on the experimental setup. From the Nature article, "[e]ach qubit has a split Josephson junction...." The Josephson effect is an effect where two superconductors are separated by a very thin insulating layer. A "supercurrent" composed of paired correlated electrons (Cooper pairs) can tunnel across this barrier under certain circumstances. Cooper pairs act as bosons, just as atoms do in Bose-Einstein condensates, so they have long been a focus of research for quantum computing. In this experiment, the device was a "180nm Nb film was d.c.-magnetron sputtered on the epipolished surface of an R-plane corundum wafer," meaning that the superconductor they used was niobium, and the insulator was aluminum oxide, aka corundum. They built it out of these, in other words.
They go on to mention that the apparatus was cooled to 13 millikelvin using a helium dilution refrigerator. Now, niobium is superconductive to about 9 kelvin in the pure state (and about 23 kelvin in some alloys), so I would assume the extra effort to make it that cold has more to do with preserving the delicate electronic state of the qubits than with merely chilling the superconductors.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
I took a class on Quantum computing, and studied many specific QC algorithms, so I know a little bit about them. A lot of misunderstandings about them, so let me summarize.
Quantum Computers are not super-computers. On a bit-for-bit (or qubit-for-qubit) scale, they're not necessarily faster than regular computers, they just process info differently. Since information is stored in a quantum "superposition" of states, as opposed to a deterministic state like regular computers, the qubits exhibit quantum interference around other qubits. Typically, your bit starts in 50% '0' and 50% '1', and thus when you measure it, you get a 50% chance of it being one or the other (and then it assumes that state). But if you don't measure, and push it through quantum circuits allowing them to interact with other qubits, you get the quantum phases to interfere and cancel out. If you are damned smart (as I realized you have to be, to design QC algorithms), you can figure out creative ways to encode your problem into qubits, and use the interference to cancel out the information you don't want, and leave the information you do want.
For instance, some calculations will start with the 50/50 qubit above, and end with 99% '0' and 1% '1' at the end of the calculation, or vice versa, depending on the answer. Then you've got a 99% chance of getting the right answer. If you run the calculation twice, you have a 99.99% chance of measuring the correct answer.
However, the details of these circuits which perform quantum algorithms are extremely non-intuitive to most people, even those who study it. I found it to require an amazing degree of creativity, to figure out how to combine qubits to take advantage of quantum interference constructively. But what does this get us?
Well it turns out that quantum computers can run anything a classical computer can do, and such algorithms can be written identically if you really wanted to, but doing so gets the same results as the classical computer (i.e. same order of growth). But, the smart people who have been publishing papers about this for the past 20 years have been finding new ways to combine qubits, to take advantage of nature of certain problems (usually deep, pure-math concepts), to achieve better orders of growth than possible on a classical computer. For instance, factoring large numbers is difficult on classical computers, which is why RSA/PGP/GPG/PKI/SSL is secure. It's order of growth is e^( n^(1/3) ). It's not quite exponential, but it's still prohibitive. It turns out that Shor figured out how to get it to n^2 on a quantum computer (which is the same order of growth as decrypting with the private key on a classical computer!). Strangely, trying to guess someone's encryption key, normally O(n) on classical computers (where n is the number of possible keys encryption keys) it's only O(sqrt(n)) on QCs. Weird (but sqrt(n) is still usually too big).
There's a vast number of other problems for which efficient quantum algorithms have been found. Unfortunately, a lot of these problems aren't particularly useful in real life (besides to the curious pure-mathematician). A lot of them are better, but not phenomenal. Like verifying that two sparse matrices were mulitplied correctly has order of growth n^(7/3) on a classical computer, n^(5/3) on a quantum computer. You can find a pretty extensive list by googling "quantum algorithm zoo."
Unfortunately [for humanity], there is no evidence yet that quantum computers will solve NP-complete problems efficiently. Most likely, they won't. So don't get your hopes up about solving the traveling salesmen problem any time soon. But there is still a lot of cool stuff we can do with them. In fact, the theory is so far ahead of the technology, that we're anxiously waiting for breakthroughs like this, so we can start plugging problems through known algorithms.