珞珈山水BBS -- 单文区文章阅读

搜索

单文区文章阅读 [返回]
发信人: leader (kikizh), 信区: C.S 标题: 量子计算机－－－Scientists claim to have a breakthrough that will revolutionise computing 发信站: BBS 珞珈山水站 (Fri Feb 9 21:40:42 2007) Scientists claim to have a breakthrough that will revolutionise computing Peter Judge Thursday February 8, 2007 The Guardian A Canadian company with substantial venture capital backing claims to have b uilt a "quantum computer" that will ultimately solve problems beyond the pow er of conventional systems - and will demonstrate it over a live link next w eek. While most scientists believe a useful system is at least 20 years away, D-W ave (dwavesys.com), based in Burnaby, British Columbia, says it has a breakt hrough in a field that already promises revolution. The company says it expe cts to sell quantum computers next year that can solve knotty problems from protein structure to financial optimisation. Article continues The company has persuaded investors to put $20m (??10m) into its radical n ew take on quantum computing and promises to show a prototype next Tuesday i n its labs. A quantum computer can, in theory, be vastly more powerful than a convention al one because it uses quantum properties to carry out multiple calculations simultaneously. That's because quantum systems (such as various properties of electrons) simultaneously embody different "states". The best known simil e is that of Schr??dinger's cat, the thought experiment in which a cat in a box is both alive and dead - until someone opens the box. In a quantum computer, every quantum bit (or "qubit") is simultaneously both 0 and 1. Put two qubits together, and you have a system whose values are si multaneously every value from 0 to 3. A system with only 300 qubits is in 10 90 (one followed by 90 zeros) states simultaneously - more than the number o f atoms in the known universe. If (and it's a big "if") you can frame your c alculation in the correct way then rather than grinding through each individ ual step of the calculation (what is 2+2? Add 2 to 0, add 2 to 2, read the r esult) the quantum computer will move directly to the correct answer. What i s 2+2? The quantum state: 4. (Wikipedia's full, and very mathematical, descr iption is here). But quantum computers literally stop working if you look at them. If any int erference, even thermal noise, gets in from the outside world, quantum state s "collapse". The cat is alive or dead, the bits are 0 or 1, not both, and t he computer loses its magical multiplicity. So far, quantum computers have o nly been isolated long enough for a few thousand operations - too short to d o anything really useful. Some scientists, such as Michael Dyakonov of the U niversity of Montpellier in France, believe thermal noise makes quantum comp uting as impossible as perpetual motion. But D-Wave's "Orion" is designed to collapse: it uses a so-called "adiabatic " process, in which the quantum states evolve towards the answer. Noise actu ally helps this, according to D-Wave's founder, the scientist Geordie Rose. His Orion system is a 16-qubit chip, built with the metal niobium using conv entional lithography, and cooled to just above absolute zero. "The quantum states are like the notes of a chord," says Seth Lloyd, profess or of mechanical engineering at MIT, who helped develop adiabatic quantum co mputing (AQC) theory. "If you could hear quantum states, you would hear a co mplex chord, changing towards a single note, which is the answer." The trade-off is that an AQC solves only one problem. It takes any set of in puts and settles into the one state that solves that problem for those input s. Orion solves a theoretical magnetic field problem, called the two-dimensi onal Ising model, which would take exponential amounts of time on a normal c omputer. It can solve more useful problems, such as protein folding and fina ncial optimisation, after a conventional computer translates them into the I sing model. With 16 qubits, it won't do anything a conventional computer can't, but D-Wa ve hopes to add qubits quickly if the unproven technology works. "The jury i s out," says Lloyd. "It's a long shot, but they've gone about it in the best possible way: they've said 'Let's build it and see'." Others are less optimistic. "My gut instinct is that I doubt there is a majo r 'free lunch' here," says Professor Andrew Steane of Oxford University. "Th at means I doubt that this computing method is substantially easier to achie ve [in the present of noise and imperfection] than any other." · If you'd like to comment on any aspect of Technology Guardian, send your emails to tech@guardian.co.uk -- ※ 来源:·珞珈山水BBS站 http://bbs.whu.edu.cn·[FROM: 159.226.37.*]
[返回单文区目录]

单文区文章阅读 [返回]

发信人: leader (kikizh), 信区: C.S
标题: 量子计算机－－－Scientists claim to have a breakthrough that will revolutionise computing
发信站: BBS 珞珈山水站 (Fri Feb 9 21:40:42 2007)

Scientists claim to have a breakthrough that will revolutionise computing

Peter Judge

Thursday February 8, 2007

The Guardian

A Canadian company with substantial venture capital backing claims to have b
uilt a "quantum computer" that will ultimately solve problems beyond the pow
er of conventional systems - and will demonstrate it over a live link next w
eek.

While most scientists believe a useful system is at least 20 years away, D-W
ave (dwavesys.com), based in Burnaby, British Columbia, says it has a breakt
hrough in a field that already promises revolution. The company says it expe
cts to sell quantum computers next year that can solve knotty problems from
protein structure to financial optimisation.

Article continues

The company has persuaded investors to put $20m (??10m) into its radical n
ew take on quantum computing and promises to show a prototype next Tuesday i
n its labs.

A quantum computer can, in theory, be vastly more powerful than a convention
al one because it uses quantum properties to carry out multiple calculations
simultaneously. That's because quantum systems (such as various properties
of electrons) simultaneously embody different "states". The best known simil
e is that of Schr??dinger's cat, the thought experiment in which a cat in
a box is both alive and dead - until someone opens the box.

In a quantum computer, every quantum bit (or "qubit") is simultaneously both
0 and 1. Put two qubits together, and you have a system whose values are si
multaneously every value from 0 to 3. A system with only 300 qubits is in 10
90 (one followed by 90 zeros) states simultaneously - more than the number o
f atoms in the known universe. If (and it's a big "if") you can frame your c
alculation in the correct way then rather than grinding through each individ
ual step of the calculation (what is 2+2? Add 2 to 0, add 2 to 2, read the r
esult) the quantum computer will move directly to the correct answer. What i
s 2+2? The quantum state: 4. (Wikipedia's full, and very mathematical, descr
iption is here).

But quantum computers literally stop working if you look at them. If any int
erference, even thermal noise, gets in from the outside world, quantum state
s "collapse". The cat is alive or dead, the bits are 0 or 1, not both, and t
he computer loses its magical multiplicity. So far, quantum computers have o
nly been isolated long enough for a few thousand operations - too short to d
o anything really useful. Some scientists, such as Michael Dyakonov of the U
niversity of Montpellier in France, believe thermal noise makes quantum comp
uting as impossible as perpetual motion.

But D-Wave's "Orion" is designed to collapse: it uses a so-called "adiabatic
" process, in which the quantum states evolve towards the answer. Noise actu
ally helps this, according to D-Wave's founder, the scientist Geordie Rose.
His Orion system is a 16-qubit chip, built with the metal niobium using conv
entional lithography, and cooled to just above absolute zero.

"The quantum states are like the notes of a chord," says Seth Lloyd, profess
or of mechanical engineering at MIT, who helped develop adiabatic quantum co
mputing (AQC) theory. "If you could hear quantum states, you would hear a co
mplex chord, changing towards a single note, which is the answer."

The trade-off is that an AQC solves only one problem. It takes any set of in
puts and settles into the one state that solves that problem for those input
s. Orion solves a theoretical magnetic field problem, called the two-dimensi
onal Ising model, which would take exponential amounts of time on a normal c
omputer. It can solve more useful problems, such as protein folding and fina
ncial optimisation, after a conventional computer translates them into the I
sing model.

With 16 qubits, it won't do anything a conventional computer can't, but D-Wa
ve hopes to add qubits quickly if the unproven technology works. "The jury i
s out," says Lloyd. "It's a long shot, but they've gone about it in the best
possible way: they've said 'Let's build it and see'."

Others are less optimistic. "My gut instinct is that I doubt there is a majo
r 'free lunch' here," says Professor Andrew Steane of Oxford University. "Th
at means I doubt that this computing method is substantially easier to achie
ve [in the present of noise and imperfection] than any other."

· If you'd like to comment on any aspect of Technology Guardian, send your
emails to tech@guardian.co.uk

--

※ 来源:·珞珈山水BBS站

http://bbs.whu.edu.cn·[FROM: 159.226.37.*]

[返回单文区目录]