The logo of the Quantum Technology Lab spelt out with the laser beams used in the Boson Sampling device.
Image: Alisha Toft
A new type of machine could rival quantum computers in exceeding the power of classical computers, researchers say.
Quantum computers rely on the bizarre properties of atoms and the other construction blocks of the universe. The world is a fuzzy place at its very smallest levels — in this realm where quantum physics dominates, things can seemingly exist in two places at once or spin in opposite directions at the same time.
The new computers rely on "boson" particles, and resemble quantum computers, which differ from traditional computers in important ways. Normal computers represent data as ones and zeroes, binary digits known as bits that are expressed by flicking switch-like transistors on or off. Quantum computers, however, use quantum bits, or qubits (pronouced "cue-bits"), that can be on and off at the same time, a state known as "superposition."
This allows the machines to carry out two calculations simultaneously. Quantum physics permits such behavior because it allows for particles that can exist in two places at once or spin in opposite directions at the same time.
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In principle, quantum computers could solve certain problems much faster than can classical computers, because the quantum machines could run through every possible combination at once. A quantum computer with 300 qubits could run more calculations in an instant than there are atoms in the universe.
However, keeping qubits in superposition is challenging, and the problem grows more difficult as more qubits are involved. As such, building quantum computers that are more powerful than classical computers has proven very difficult.
Now, though, two independent teams of scientists have built a novel kind of device known as a boson-sampling computer. Described as a bridge between classical and quantum computers, these machines also make use of the bizarre nature of quantum physics. Although boson-sampling computers theoretically offer less power than quantum computers are capable of producing, the machines should still, in principle, out-perform classical computers in certain problems.
In addition, a boson-sampling computer does not require qubits. As such, "it's technologically far simpler to create than building a full-scale quantum computer," said researcher Matthew Broome, a quantum physicist at the University of Queensland in Australia.
Boson-sampling computers are actually a specialized kind of quantum computer (which is known more formally as a universal quantum computer).
"The main difference between boson-sampling computers and universal quantum computers is that boson-sampling quantum computers can't solve a universal set of problems like universal quantum computers can," Broome said. "But they are still conjectured to be able to solve problems that would be massively intractable for classical computers. Boson sampling computers are an intermediate model of a quantum computer."
Boson-sampling computers are not based on qubits, but on particles called bosons. "In our case, we use photons," said researcher Ian Walmsley, a quantum physicist at the University of Oxford in England. Photons are the packets of energy that make up light, and are one type of boson.
Broome and Walmsley were in separate groups that each devised a boson-sampling computer, based off concepts first described by theoretical computer scientist Scott Aaronson at MIT. The computers involve multiple devices that can each generate single photons. The photons are inserted into a network where they can interact with one another. They emerge from outputs equipped with sensors to analyze the particles.
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15 Comments
Add CommentDamn, what an exciting time is coming to computing and I am so old that I am not going to see it.
Reply | Report Abuse | Link to thisIMO, if, in principle, these concepts are not foolish tripe, then they are not adequately explained here to distinguish them from nonsense.
Reply | Report Abuse | Link to this"Quantum computers, however, use quantum bits, or qubits..., that can be on and off at the same time, a state known as "superposition."
"This allows the machines to carry out two calculations simultaneously. Quantum physics permits such behavior because it allows for particles that can exist in two places at once or spin in opposite directions at the same time."
How can the probabilistically indeterminate particle/wave states or location/velocity of particles allow the simultaneously positive and negative answers to any question? Wouldn't solution to a particle location derived question collapse the waveform disallowing further computations based on particle motion? Does superposition really allow particles to spin in opposing directions simultaneously? what does all this tripe really mean, if anything?
"Since boson-sampling computing is in its infancy, it remains uncertain whether these computers can solve problems beyond boson sampling."
So, if I understand correctly, the problem solved by a boson sampling machine is... boson sampling? Wow - what an achievement for quantum computing! I wonder if it can simulate a Windows computer?
:-) ... superposition reminds me of the time when man could not visually detect very fast things... i.e.: dealing cards from the bottom of the deck ... Once we have the tools we will surely witness Quantum Speed / Time...
Reply | Report Abuse | Link to thisSuperposition is not tripe.
Reply | Report Abuse | Link to thisQuantum particles have many possible states as their wave functions describe. Until they are observed, e.g., by measuring them, quantum particles' many states are still probable and must be treated as if they coexist.
For example, electrons have two spin states that are equally probable. As electrons pass through a magnetic field, their trajectories reflect their spin state: half fly in one direction ("left"), half fly in the other ("right"). It is impossible to predict which direction each electron will go because each direction is equally probable.
If either set of electrons goes through a second magnetic field, they still split into two streams: half go left, half go right. Without superposition, the "left" electrons would go left through both magnetic fields. The "right" electrons would always go right.
In other words, both states coexist until an observation is made. After that measurement, both states still coexist.
As for the boson-sampling comment, the question is whether or not this new method has wider applications. Nobody knows yet, but they want to find out.
It's called research.
I did not say superposition is tripe - I quoted the more complete statement: "This allows the machines to carry out two calculations simultaneously" - I think that it is tripe.
Reply | Report Abuse | Link to thisThis article does not serve to support research by stating, for example, "A new type of machine could rival quantum computers in exceeding the power of classical computers, researchers say." I see no evidence or even suggestion of that here except is it is believed that quantum computers can perform multiple calculations simultaneously using superposition.
Electronic circuits become faster & cheaper by being made smaller. Eventually, electronic circuits will be so small that they cannot control the path of electrons. Some new technology that allows even smaller circuits will allow continuation of increasing circuit densities - the rest is, IMO, hyperbole.
Well, it's always good to see other opinions.
Reply | Report Abuse | Link to thisBack in the early 80's Sciam did a great article on the fuzzy logic required for quantum computing. I do think that once a true qbit is put to work you can do many calculations at once and remember there is an infinite number of possibilities between 0 and 1 if you are not stuck in integer land.
Reply | Report Abuse | Link to thisBut the concepts of fuzzy logic served me well on a project that involved talking to multiple OS systems at the same time, by creating some fuzzy algorithms I was able to identify the responding host and make the next move. This was before network architecture was firmly established and some was IBM mainframe, DEC 9600 Clusters running VMS and WS running DOS with a lot of overhead to start with.
I was so glad to be able to use the ideal of states within states and see it work as advertised. Jtdwyer, we may soon be using the aggregated spin of a Bose-Einstein condensate to keep the qbit in a state of superposition and again until directly observed the state is stable. The trick is to observe without observing and much work has been done on that concept. What it will also give us if it works as advertised is instant communication with space craft that are too far away to control at light speed but not at entangled speed.
I would just keep my eyes open and MIT is notorious for delivering great science that barely sees the day of light. Ask Angela Belcher how it worked out for her in 2006. So far only DARPA has jumped on her miracle in a shell. See http://web.mit.edu/newsoffice/2006/sciam-belcher.html also an update, but not the original work which was earth shatteringly simple http://www.scientificamerican.com/article.cfm?id=angela-belcher-building-t
That's a really great implementation of fuzzy logic, David. I found fuzzy logic to be extrememly helpful with database integration when it's applied to computational linguistics for approximate string matching.
Reply | Report Abuse | Link to thisAs for the Bose-Einstein condensate (BEC) device, that will likely be just a proof-of-concept. One of my profs in grad school did some pioneering work on the BEC. He found that its properties are useful in ways that you mention, but it's also an extremely delicate state of matter, which maintains stability at sub-microKelvin temperatures.
It will be very interesting to see, though, what can be learned by means of entangled matter for communication. Empirical evidence indicates that Bell states are both space- and time-independent, which could make for instantaneous quantum communication on relativistic scales.
Cool, huh?
Yes most cool.
Reply | Report Abuse | Link to thisI wonder what is going to come with the announcement that water doped graphite shows superconducting properties at room temperature. I have also seen some very novel attempts at not observing while observing quantum states. It is starting to make physics as tense driven as Latin, but it makes the ideal of using entanglement feasible in the relative world. I think we are very close to some meshing of the two disciplines finally.
I also think that what we have learned about controlling matter to the atomic level with lasers opens doors that we haven't made it down the hall to see yet. Who will turn in their grave Albert of Neils? Maybe they will both applaud at the same time but in different space. Well they were so entangled, we will hear it at the same time anyway.
Thanks to scientists for Quantum Computer.
Reply | Report Abuse | Link to thisYes,
Only Photon can do this function. The mass of a photon is 1.659x10^-54 gm, accordingly, energy = 9.309779x10^-22 ev. Photons coagulated and makes matter. Number of photons changes means properties changes thus matter changes. 10^6 photons able to form Planck Constant with effect of angular quantum number (l). An electron has 9 orbits; outer orbit emits 1000 photons at excited state. In a system, it proves the Eigen value of electron as,
E (nx, ny, nz) = 1000 [nx^2 + ny^2 + nz^2] x energy of a photon / 2x (root of 3/2) x l^2 = 0.1140 Kev, where, l = angular quantum number = 10^-10 m. We know, Eigen value of electron = 0.1128 Kev (for Ground state), when, nx=ny=nz= 1 = quantum number. Similarly we get the energy of other state by changing nx=2, ny=nz= 1, or 3, then E = 0.2280 Kev (for First excited state), Eigen value gives 0.2256 Kev. For quantum number 9, E = 0.3420 Kev (Just before the generating state), Eigen value gives 0.3384 Kev and for 12, E = 0.4560 Kev (Generating state), Eigen value gives = 0.4512 Kev.
All facts written in my book Complete Unified Theory (page-424, 1998)
The complete Unified Theory is single theory and applicable all from particles to the universe.
Nirmalendu Das
Dated: 30-12-2012.
The tragedy is that entanglement cannot be expected or controlled everywhere
Reply | Report Abuse | Link to thisThere is NO WAY that I'll buy a book you've written.
Reply | Report Abuse | Link to thisI prefer concise, accessible language, proper grammar, and complete thoughts.
Since when does a photon have a rest mass?
Reply | Report Abuse | Link to thisThank God that several other people have already said unflattering things about nirmalgopa's comment! It is hard to believe that someone would have the patience to type all that, and the totally unrealistic expectation that someone else would understand it. It could really make someone feel inadequate! Many years ago (in real, Earth time), there was a letter published in Science entitled "Ably Elucidated Precepts," in which the author promised to refrain from "glottologically superfluous utterances." A noble goal!
Reply | Report Abuse | Link to thisAdiabatic quantum computing (available now) is expected to set the stage for a universal gate model quantum computer (available in 10 to 15 years).
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