Quantum computers could revolutionize the way we tackle problems that stump even the best classical computers.
Single atom transistor recently introduced has been seen as a tool that could lead the way to building a quantum computer. For general introduction how quantum computer work, read A tale of two qubits: how quantum computers work article.
D-Wave Announces Commercially Available Quantum Computer article tells that computing company D-Wave has announced that they’re selling a quantum computing system commercially, which they’re calling the D-Wave One. D-Wave system comes equipped with a 128-qubit processor that’s designed to perform discrete optimization operations. The processor uses quantum annealing to perform these operations.
D-Wave is advertisting a number of different applications for its quantum computing system, primarily in the field of artificial intelligence. According to the company, its system can handle virtually any AI application that can be translated to a Markov random field.
Learning to program the D-Wave One blog article tells that the processor in the D-Wave One – codenamed Rainier – is designed to perform a single mathematical operation called discrete optimization. It is a special purpose processor. When writing applications the D-Wave One is used only for the steps in your task that involve solving optimization problems. All the other parts of your code still run on your conventional systems of choice. Rainier solves optimization problems using quantum annealing (QA), which is a class of problem solving approaches that use quantum effects to help get better solutions, faster. Learning to program the D-Wave One is the first in a series of blog posts describing the algorithms we have run on D-Wave quantum computers, and how to use these to build interesting applications.
But is this the start of the quantum computers era? Maybe not. D-Wave Announces Commercially Available Quantum Computer article comments tell a story that this computer might not be the quantum computer you might be waiting for. It seem that the name “quantum computer” is a bit misleading for this product. There are serious controversies around the working and “quantumness” of the machine. D-Wave has been heavily criticized by some scientists in the quantum computing field. First sale for quantum computing article tells that uncertainty persists around how the impressive black monolith known as D-Wave One actually works. Computer scientists have long questioned whether D-Wave’s systems truly exploit quantum physics on their products.
Slashdot article D-Wave Announces Commercially Available Quantum Computer comments tell that this has the same central problem as before. D-Wave’s computers haven’t demonstrated that their commercial bits are entangled. There’s no way to really distinguish what they are doing from essentially classical simulated annealing. Recommended reading that is skeptical of D-Wave’s claims is much of what Scott Aaronson has wrote about them. See for example http://www.scottaaronson.com/blog/?p=639, http://www.scottaaronson.com/blog/?p=198 although interestingly after he visited D-Wave’s labs in person his views changed slightly and became slightly more sympathetic to them http://www.scottaaronson.com/blog/?p=954.
So it is hard to say if the “128 qubits” part is snake oil or for real. If the 128 “qubits” aren’t entangled at all, which means it is useless for any of the quantum algorithms that one generally thinks of. It seem that this device simply has 128 separate “qubits” that are queried individually, and is, essentially an augmented classical computer that gains a few minor advantages in some very specific algorithms (i.e. the quantum annealing algorithm) due to this qubit querying, but is otherwise indistinguishable from a really expensive classical computer for any other purpose. This has the same central problem as before: D-Wave’s computers haven’t demonstrated that their commercial bits are entangled.
Rather than constantly adding more qubits and issuing more hard-to-evaluate announcements, while leaving the scientific characterization of its devices in a state of limbo, why doesn’t D-Wave just focus all its efforts on demonstrating entanglement, or otherwise getting stronger evidence for a quantum role in the apparent speedup? There’s a reason why academic quantum computing groups focus on pushing down decoherence and demonstrating entanglement in 2, 3, or 4 qubits: because that way, at least you know that the qubits are qubits! Suppose D-Wave were marketing a classical, special-purpose, $10-million computer designed to perform simulated annealing, for 90-bit Ising spin glass problems with a certain fixed topology, somewhat better than an off-the-shelf computing cluster. Would there be even 5% of the public interest that there is now?
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Tomi Engdahl says:
Scientists Build First Working Quantum Network
http://www.pcmag.com/article2/0,2817,2402931,00.asp
Scientists at the Quantum Dynamics division of the Max Planck Institute of Quantum Optics (MPQ) in Garching, Germany announced Wednesday that they have built the very first, elementary quantum network comprised of a pair of entangled atoms that transmit information to each other via single photons.
That and a couple of bucks will get you a cup of coffee, plus anything from a perfectly secure data exchange system to the massive scaling via distributed processing of the already mind-bogglingly powerful, if theoretical, potential of a standalone quantum computer.
These are indeed heady days for the pioneers of quantum computing, with each news cycle seemingly bringing forth a major breakthrough in a subatomic frontier that appears poised to revolutionize how our calculating machines deliver us everything from satellite mapping to LOLcats.
“This approach to quantum networking is particularly promising because it provides a clear perspective for scalability,” Rempe told the journal. His colleague and leader of the experiment, Dr. Stephan Ritter, added, “We were able to prove that the quantum states can be transferred much better than possible with any classical network.”
The team was able to fix their atoms in optical cavities, basically a couple of highly reflective mirrors a short distance from each other, by means of fine-tuned laser beams.
Photons entering the cavity bounce around the mirrors “several thousand times,” which actually enhances the atom-photon interaction and enables the network node atoms to absorb the photon-based data packets “coherently and with high efficiency,” according to the scientists.
Quantum networking is the practical application of experimental quantum cryptography, like the “blind quantum computing” demonstration by another team of researchers at the University of Vienna’s Center for Quantum Science and Technology earlier this year, which involved transmitting an algorithm to acomputer, running it, and receiving it back without the computer’s operator being able to snoop on those operations.
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Tomi Engdahl says:
Weird! Quantum Entanglement Can Reach into the Past
https://developers.google.com/speed/articles/spdy-for-mobile
Spooky quantum entanglement just got spookier.
Entanglement is a weird statewhere two particles remain intimately connected, even when separated over vast distances, like two die that must always show the same numbers when rolled.
For the first time, scientists have entangled particles after they’ve been measured and may no longer even exist.
“Whether these two particles are entangled or separable has been decided after they have been measured,”
Essentially, the scientists showed that future actions may influence past events, at least when it comes to the messy, mind-bending world of quantum physics.
In the quantum world, things behave differently than they do in the real, macroscopic world we can see and touch around us.
Tomi Engdahl says:
Is the Age of Silicon Computing Coming to an End? Physicist Michio Kaku Says “Yes”
http://www.dailygalaxy.com/my_weblog/2012/05/is-the-age-of-silicon-coming-to-an-end-physicist-michio-kaku-says-yes.html
Traditional computing, with its ever more microscopic circuitry etched in silicon, will soon reach a final barrier: Moore’s law, which dictates that the amount of computing power you can squeeze into the same space will double every 18 months, is on course to run smack into a silicon wall due to overheating, caused by electrical charges running through ever more tightly packed circuits.
“In about ten years or so, we will see the collapse of Moore’s Law. In fact, already, already we see a slowing down of Moore’s Law,” says world-renowned physicist, Michio Kaku. “Computer power simply cannot maintain its rapid exponential rise using standard silicon technology.”
Despite Intel’s recent advances with tri-gate processors, Kaku argues in a video interview with Big Think, that the company has merely delayed the inevitable: the law’s collapse due to heat and leakage issues.
“So there is an ultimate limit set by the laws of thermal dynamics and set by the laws of quantum mechanics as to how much computing power you can do with silicon,” says Kaku, noting “That’s the reason why the age of silicon will eventually come to a close,” and arguing that Moore’s Law could “flatten out completely” by 2022.”
Kaku see several alternatives to the demise of Moores Law: protein computers, DNA computers, optical computers, quantum computers and molecular computers.
“If I were to put money on the table I would say that in the next ten years as Moore’s Law slows down, we will tweak it. We will tweak it with three-dimensional chips, maybe optical chips, tweak it with known technology pushing the limits, squeezing what we can. Sooner or later even three-dimensional chips, even parallel processing, will be exhausted and we’ll have to go to the post-silicon era,” says Kaku.
Kaku concludes that when Moore’s Law finally collapses by the end of the next decade, we’ll “simply tweak it a bit with chip-like computers in three dimensions. We may have to go to molecular computers and perhaps late in the 21st century quantum computers.”
We’ll place our bets on quantum computing.
To leapfrog the silicon wall, we have to figure out how to manipulate the brain-bending rules of the quantum realm – an Alice in Wonderland world of subatomic particles that can be in two places at once. Where a classical computer obeys the well understood laws of classical physics, a quantum computer is a device that harnesses physical phenomenon unique to quantum mechanics (especially quantum interference) to realize a fundamentally new mode of information processing.
The fundamental unit of information in quantum computing (called a quantum bit or qubit), is not binary but rather more quaternary in nature, which differs radically from the laws of classical physics.A qubit can exist not only in a state corresponding to the logical state 0 or 1 as in a classical bit, but also in states corresponding to a blend or superposition of these classical states.
In other words, a qubit can exist as a zero, a one, or simultaneously as both 0 and 1, with a numerical coefficient representing the probability for each state.
Tomi Engdahl says:
Franken-Physics: Atoms Split in Two & Put Back Together
http://www.livescience.com/20926-quantum-physics-atoms-split.html
Physicists have just upped their ante: Not only have they split atoms but, even trickier, they’ve put them back together.
Their secret? Quantum physics.
A team of scientists was able to “split” an atom into its two possible spin states, up and down, and measure the difference between them even after the atom resumed the properties of a single state.
The research wasn’t just playtime for quantum physicists: It could be a steppingstone toward the development of a quantum computer
In the classic double-slit experiment, atoms are fired at a wall with two breaks in it, and they pass through to the other side, where they hit a detector, creating the kind of interference pattern expected from a wave. If atoms behaved the way we intuitively expect particles to behave, they should emerge out of one slit or the other, with no interference pattern. As more and more atoms passed through the slits, there should be a cluster of them around the two points behind the slits.
Since this is quantum mechanics, that’s not what happens.
Instead, there’s an interference pattern that shows peaks and valleys. The atoms behave like light waves. The atom is in two places at once.
But if you try to see the atom in one or both places, it “collapses” into one, as the act of observing it determines its fate; hence, the interference pattern disappears.
In the experiment at Bonn, the researchers fired two lasers in sequence at a single atom of cesium, moving it to the left or right. The lasers allowed the researchers to control the movement of the atom precisely
Each atom has a spin state, which is either up or down. By moving the atom in two directions at once (using both lasers), the scientists were able to make it “split.”
It was in two states at once — up and down.
It’s not possible to see both states at once. If one were to try to measure the state of the atom, it would “collapse” into a single state.
Since atoms — and other quantum particles — behave like waves, they have phases, just as waves do.
n addition to measuring that phase difference, the researchers also saw “delocalization” — the double path through space the atom takes — at a greater distance than ever before, on the scale of micrometers as opposed to nanometers.
It’s this dual nature, called a superposed state, of atoms that would make quantum computers so powerful. The bits (known as “qubits”) could be in more than one state at once, allowing for calculations that would take ordinary computers an extremely long time. It also means that quantum computers could be useful for simulating other quantum systems.
Tomi Engdahl says:
Quantum Microphone
http://www.edn.com/electronics-blogs/anablog/4375473/Quantum-Microphone
Physicists from Chalmers University of Technology in Sweden, led by Per Delsing, have demonstrated a new kind of detector for sound at the level of quietness of quantum mechanics.
This ushers in a new class of quantum hybrid circuits that mix acoustic elements with electrical ones
The “quantum microphone” is based on a single electron transistor, that is, a transistor where the current passes one electron at a time. The acoustic waves studied by the research team propagate over the surface of a crystalline microchip, and resemble the ripples formed on a pond when a pebble is thrown into it.
The wavelength of the sound is a mere 3 micrometers, but the detector is even smaller, and capable of rapidly sensing the acoustic waves as they pass by
The detector is sensitive to waves with peak heights of a few percent of a proton diameter, levels so quiet that sound can be governed by quantum law rather than classical mechanics, much in the same way as light.
“The experiment is done on classical acoustic waves, but it shows that we have everything in place to begin studies of proper quantum-acoustics, and nobody has attempted that before”, says Martin Gustafsson, PhD student and first author of the article.
Tomi Engdahl says:
IBM Scientists “Waltz” Closer to Using Spintronics in Computing
http://www-03.ibm.com/press/us/en/pressrelease/38566.wss
- IBM Research is the first to synchronize electron spins and image the formation of a persistent spin helix.
- Spintronics could enable a new class of magnetic-based semiconductor transistors resulting in more energy efficient electronic devices.
The Spintronics Waltz
A previously unknown aspect of physics, the scientists observed how electron spins move tens of micrometers in a semiconductor with their orientations synchronously rotating along the path similar to a couple dancing the waltz, the famous Viennese ballroom dance where couples rotate.
IBM scientists imaged the synchronous ‘waltz’ of the electron spins by using a time-resolved scanning microscope technique. The synchronization of the electron spin rotation made it possible to observe the spins travel for more than 10 micrometers or one-hundredth of a millimeter, increasing the possibility to use the spin for processing logical operations, both fast and energy-efficiently.
Tomi Engdahl says:
D-Wave goes public with 81-qubit protein modeling
All together now: ‘It’s quantum, innit?’
http://www.theregister.co.uk/2012/08/22/d_wave_claims_working_protein_solution_on_quantum_computer/
D-Wave – whose claims to have a working quantum computer have been met with skepticism and major contracts in equal measure – has published a paper in Nature in which it demonstrates the application of quantum annealing to protein folding analysis.
Protein folding is a difficult problem in the classical world, because of the vast number of possible solutions. As D-Wave’s authors put it in their paper (online in full here): “Finding low-energy threedimensional structures is an intractable problem even in the simplest model, the Hydrophobic-Polar (HP) model.”
http://www.nature.com/srep/2012/120813/srep00571/full/srep00571.html
D-Wave’s paper claims to demonstrate the first application of quantum principles to solving protein folding. It’s only been performed on a small scale – using 81 qubits – and is intended as a benchmark.
Moreover, the authors state that the scale of the problem they’ve demonstrated would still be solvable using a classical computer.
“This study provides a proof-of-principle that optimization of biophysical problems such as protein folding can be studied using quantum mechanical devices,” the authors write.
Tomi Engdahl says:
Boffins receive quantum key from moving plane
Alice and Bob play catch
http://www.theregister.co.uk/2012/09/17/qkd_from_moving_airplane/
A group of German researchers has taken a step closer to achieving quantum key distribution with satellites, receiving quantum keys transmitted by a moving airplane.
The experiment is described in this paper (PDF) presented to the QCrypt conference in Singapore last week.
Led by Sebastian Nauerth at the Ludwig Maximilian University of Munich, the researchers achieved a stable connection over 20 Km for ten minutes, and in that time achieved a key rate of 145 bits/s. While that’s far too slow for a data channel, this only refers to the rate at which the keys are transmitted.
Tomi Engdahl says:
Australian researchers create world’s first working quantum bit
Another step taken towards the development of ultra-powerful computers
http://www.cio.com.au/article/436933/australian_researchers_create_world_first_working_quantum_bit/#closeme
Researchers at the University of New South Wales have created the world’s first working quantum bit based on a single atom in silicon, which they claim will lead to the development of ultra-powerful computers in the future.
In a paper published in scientific journal Nature, the research team described how it was able to both read and write information using the spin, or magnetic orientation, of an electron bound to a single phosphorous atom embedded in a silicon chip.
This enabled them to form a quantum bit or “qubit”, the basic unit of data for quantum computers, which promise to solve complex problems “that are currently impossible on even the world’s largest supercomputers,” according to team leader Dr Andrea Morello.
“These include data-intensive problems, such as cracking modern encryption codes, searching databases and modelling biological molecules and drugs.”
Tomi Engdahl says:
“Your co-workers who keep using Schrödinger’s cat metaphor may need to find a new one. New Scientist reports that “by making constant but weak measurements of a quantum system, physicists have managed to probe a delicate quantum state without destroying it”
Source: http://science.slashdot.org/story/12/10/04/010223/quantum-measurements-leave-schrdingers-cat-alive
Tomi Engdahl says:
Quantum computer boffin ‘had to sit down’ on getting Nobel Prize call
Deserved glory, trouserfuls of cash for French/US pair
http://www.theregister.co.uk/2012/10/09/nobel_physics_prize_2012/
The Nobel Prize for physics has gone to French and US boffins for their work quantum manipulation.
Serge Haroche of Collège de France and David Wineland at the National Institute of Standards and Technology in the University of Colorado will share the prize and the £744,000 winnings that go with it for work on single photons and ions.
The Nobel committee said that the pair won for “ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems”.
The scientists’ work has helped build laser-cooled atomic clocks and is a building block for the current research in quantum computing.
“Their work demonstrates very fundamental behaviour of quantum systems under complete control, and underpins quantum technologies relevant to quantum computing and atomic clocks.”
Tomi Engdahl says:
What are quantum computers good for?
Forget cracking crypto, think modelling reality itself to help build a better one
http://www.theregister.co.uk/2012/11/17/how_to_build_and_use_a_quantum_computer/
The problem with trying to explain quantum computing to the public is that you end up either simplifying the story so far as to make it wrong, or running down so many metaphorical rabbit-burrows that you end up wrong.
So The Register is going to try and invert the usual approach, and try to describe quantum computing at a more materialistic level: how do you build one, and when it’s built, how do you use it? Hopefully, a concrete framework will make it easier to understand quantum computing along the way.
And we promise not to reiterate the story of Schroedinger ‘s cat. Not even once.
Tomi Engdahl says:
Researchers achieve mathematical breakthrough that could lead to actual teleportation
http://www2.electronicproducts.com/Researchers_achieve_mathematical_breakthrough_that_could_lead_to_actual_teleportation-article-fajb_math_quantum_physics_jan2013-html.aspx
Protocol sets rules for effective transport of quantum information instantaneously
For the last decade, theoretical physicists have been working to prove that the intense connections between particles as established in the quantum law of “entanglement” could be used as a more effective way to teleport quantum bits of information.
Recently, researchers from Cambridge University published a mathematical solution in which they worked out how entanglement could be “recycled” to increase the efficiency of these connections, and demonstrating a new protocol that could open the door to several potential applications.
You see, entanglement involves two particles (e.g. electrons, protons, etc.) that are intrinsically bound together and retain synchronization whether they’re next to one another or on opposite sides of the globe. Using this connection, quantum bits of information can be relayed instantaneously using traditional forms of communication.
Under this theory, two teleportation protocols were developed: one that could send scrambled information that required correction by the receiver, or a bit more recently, “port-based” teleportation that doesn’t require the correcting of information by the receiver, but rather a ridiculous amount of entanglement, so much so that each object sent would destroy the entangled state.
Tomi Engdahl says:
Quantum computer one step closer after ‘true’ quantum calculation
Baby steps
http://www.theregister.co.uk/2013/02/25/quantum_calculation_phase_estimation/
An international group of physicists has had an important “first” acknowledged by the journal Nature Photonics: they built the first complete single-qubit system to implement a key algorithm in quantum computing.
While prior experiments have demonstrated that the quantum states produced in a phase estimation could be read out, what the Nature: Photonics publication recognises is that this experiment runs the whole process: input, processing, and output.
As the researchers write in their paper: “all demonstrations to date have required already knowing the answer to construct the algorithm.”
Tomi Engdahl says:
Quantum Cryptography Secures the Electrical Grid
http://www.designnews.com/author.asp?section_id=1386&doc_id=261288&cid=NL_Newsletters+-+DN+Daily
the intricacy of renewable energy requires sophisticated methods of grid operation for both energy management and security applications.
To safeguard the grid’s management system, scientists hope to employ the latest encrypted data security measure — quantum cryptography.
A team of researchers at the Los Alamos National Laboratory has successfully demonstrated the use of the new technology to safeguard data transmission.
The new technology is based on a recently developed Quantum Cryptography transmitter that supports the advance security measure at a low latency of 120 ms for every 125 km distances. The researchers hope to help energy providers detect any unwanted tampering to the grid’s energy supply, especially with the added complexity of renewable energy management. The team is now in search of funding for a next-gen transmitter designed for mass production.
Tomi Engdahl says:
Spooky action at a distance is faster than light
Chinese boffins put the clock on information transfer between entangled particles
http://www.theregister.co.uk/2013/04/08/chinese_entanglement_transfer_experiment/
As Einstein put it, it’s impossible for anything – even information – to move faster than the speed of light. Yet the lower bound of that impossibility, the minimum speed at which entanglement can’t possibly be transmitting information between two particles, appears to be around four orders of magnitude higher than c, the speed of light in a vacuum.
So: since we know that entanglement exists (it’s been observed and is the basis of so-called “quantum teleportation”), it’s perfectly reasonable to ask at what rate the information transfer is violating general relativity?
According to this paper at Arxiv, once Earth’s inertial frame of reference is taken into account, the lower bound of the speed of “spooky action” is 1.38 x 104 the speed of light in a vacuum.
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Tomi Engdahl says:
D-Wave wins the quantum-classical horse race, kind of
For the right problem, quantum computing wins
http://www.theregister.co.uk/2013/05/15/d_wave_quantum_computer_test/
It’s official, it seems: the D-Wave isn’t a “real” quantum computer, but it does handle some classes of problems a lot faster than a classical desktop computer.
That’s the result of the first attempt to benchmark the company’s adibiatic quantum computer, but it comes with caveats.
The company says its D-Wave Two offers a “512-qubit processor chip … housed inside a cryogenics system within a 10 square meter shielded room.”
The company doesn’t claim to have a fully quantum computer, but instead to have designed and manufactured “processors required to use quantum effects to compute”.
In a paper to be presented to the ACM conference in Italy on May 15 and published in the New York Times, McGeoch tests the adibiatic quantum computation technique called quantum annealing against various solvers running on desktop computers.
McGeoch compared these two approaches to three software solvers: IBM’s CPLEX, the open-source METSlib tabu search solver, and the Akmaxsat solver.
However, the test result – particularly the QUBO test – are being taken as evidence that something quantum-like is happening in the D-Wave, since it converged on the solution almost instantly compared to the classical computer. So it seems that with the right problem – in particular, a problem that maps well onto the quantum hardware – entanglement and superposition are happening.
For D-Wave, the challenge will be to “generalise” its hardware so as not to be confined only to esoteric problems.
Tomi Engdahl says:
Google Buys a Quantum Computer
http://bits.blogs.nytimes.com/2013/05/16/google-buys-a-quantum-computer/
Google and NASA are forming a laboratory to study artificial intelligence by means of computers that use the unusual properties of quantum physics. Their quantum computer, which performs complex calculations thousands of times faster than existing supercomputers, is expected to be in active use in the third quarter of this year.
The Quantum Artificial Intelligence Lab, as the entity is called, will focus on machine learning, which is the way computers take note of patterns of information to improve their outputs. Personalized Internet search and predictions of traffic congestion based on GPS data are examples of machine learning. The field is particularly important for things like facial or voice recognition, biological behavior, or the management of very large and complex systems.
Google said it had already devised machine-learning algorithms that work inside the quantum computer, which is made by D-Wave Systems of Burnaby, British Columbia. One could quickly recognize information, saving power on mobile devices, while another was successful at sorting out bad or mislabeled data. The most effective methods for using quantum computation, Google said, involved combining the advanced machines with its clouds of traditional computers.
“The tougher, more complex ones had better performance,” said Colin Williams, D-Wave’s director of business development. “For most problems, it was 11,000 times faster, but in the more difficult 50 percent, it was 33,000 times faster. In the top 25 percent, it was 50,000 times faster.”
The machine Google and NASA will use makes use of the interactions of 512 quantum bits, or qubits, to determine optimization. They plan to upgrade the machine to 2,048 qubits when this becomes available, probably within the next year or two.
Google did not say how it might deploy a quantum computer into its existing global network of computer-intensive data centers, which are among the world’s largest. D-Wave, however, intends eventually for its quantum machine to hook into cloud computing systems, doing the exceptionally hard problems that can then be finished off by regular servers.
Tomi Engdahl says:
Launching the Quantum Artificial Intelligence Lab
http://googleresearch.blogspot.fi/2013/05/launching-quantum-artificial.html
We believe quantum computing may help solve some of the most challenging computer science problems, particularly in machine learning. Machine learning is all about building better models of the world to make more accurate predictions. If we want to cure diseases, we need better models of how they develop. If we want to create effective environmental policies, we need better models of what’s happening to our climate. And if we want to build a more useful search engine, we need to better understand spoken questions and what’s on the web so you get the best answer.
So today we’re launching the Quantum Artificial Intelligence Lab. NASA’s Ames Research Center will host the lab, which will house a quantum computer from D-Wave Systems, and the USRA (Universities Space Research Association) will invite researchers from around the world to share time on it. Our goal: to study how quantum computing might advance machine learning.
Machine learning is highly difficult. It’s what mathematicians call an “NP-hard” problem. That’s because building a good model is really a creative act.
Classical computers aren’t well suited to these types of creative problems. Solving such problems can be imagined as trying to find the lowest point on a surface covered in hills and valleys.
That’s where quantum computing comes in. It lets you cheat a little, giving you some chance to “tunnel” through a ridge to see if there’s a lower valley hidden beyond it. This gives you a much better shot at finding the true lowest point — the optimal solution.
We’ve already developed some quantum machine learning algorithms. One produces very compact, efficient recognizers — very useful when you’re short on power, as on a mobile device.
Tomi Engdahl says:
Nasa buys into ‘quantum’ computer
http://www.bbc.co.uk/news/science-environment-22554494
A $15m computer that uses “quantum physics” effects to boost its speed is to be installed at a Nasa facility.
It will be shared by Google, Nasa, and other scientists, providing access to a machine said to be up to 3,600 times faster than conventional computers.
Unlike standard machines, the D-Wave Two processor appears to make use of an effect called quantum tunnelling.
This allows it to reach solutions to certain types of mathematical problems in fractions of a second.
Effectively, it can try all possible solutions at the same time and then select the best.
Google wants to use the facility at Nasa’s Ames Research Center in California to find out how quantum computing might advance techniques of machine learning and artificial intelligence, including voice recognition.
Canadian company D-Wave Systems, which makes the machine, has drawn scepticism over the years from quantum computing experts around the world.
Until research outlined earlier this year, some even suggested its machines showed no evidence of using specifically quantum effects.
But physicists have repeatedly found that the problem with a gate-based approach is keeping the quantum bits, or qubits (the basic units of quantum information), in their quantum state.
“You get drop out… decoherence, where the qubits lapse into being simple 1s and 0s instead of the entangled quantum states you need. Errors creep in,”
Instead, D-Wave Systems has been focused on building machines that exploit a technique called quantum annealing – a way of distilling the optimal mathematical solutions from all the possibilities.
Annealing is made possible by an effect in physics known as quantum tunnelling, which can endow each qubit with an awareness of every other one.
“The gate model… is the single worst thing that ever happened to quantum computing”, Geordie Rose, chief technology officer for D-Wave, told BBC Radio 4′s Material World programme.
Dr Rose’s approach entails a completely different way of posing your question, and it only works for certain questions.
Tomi Engdahl says:
Physicists Create Quantum Link Between Photons That Don’t Exist At the Same Time
http://science.slashdot.org/story/13/05/22/2343208/physicists-create-quantum-link-between-photons-that-dont-exist-at-the-same-time
“Physicists have long known that quantum mechanics allows for a subtle connection between quantum particles called entanglement, in which measuring one particle can instantly set the otherwise uncertain condition, or ‘state,’ of another particle—even if it’s light years away. Now, experimenters in Israel have shown that they can entangle two photons that don’t even exist at the same time.”
Tomi Engdahl says:
Physicists Create Quantum Link Between Photons That Don’t Exist at the Same Time
http://news.sciencemag.org/sciencenow/2013/05/physicists-create-quantum-link-b.html?ref=hp
Now they’re just messing with us. Physicists have long known that quantum mechanics allows for a subtle connection between quantum particles called entanglement, in which measuring one particle can instantly set the otherwise uncertain condition, or “state,” of another particle—even if it’s light years away. Now, experimenters in Israel have shown that they can entangle two photons that don’t even exist at the same time.
Entanglement is a kind of order that lurks within the uncertainty of quantum theory.
Entanglement can come in if you have two photons. Each can be put into the uncertain vertical-and-horizontal state. However, the photons can be entangled so that their polarizations are correlated even while they remain undetermined.
For example, if you measure the first photon and find it horizontally polarized, you’ll know that the other photon has instantaneously collapsed into the vertical state and vice versa—no matter how far away it is. Because the collapse happens instantly, Albert Einstein dubbed the effect “spooky action at a distance.”
In recent years, physicists have played with the timing in the scheme.
And even though photons 1 and 4 never coexist, the measurements show that their polarizations still end up entangled.
So what’s the advance good for? Physicists hope to create quantum networks in which protocols like entanglement swapping are used to create quantum links among distant users and transmit uncrackable (but slower than light) secret communications.
Tomi Engdahl says:
First Observation of Spin Hall Effect in a Quantum Gas Is Step Toward ‘Atomtronics’
http://www.scienceworldreport.com/articles/7389/20130607/first-observation-spin-hall-effect-quantum-gas-step-toward-atomtronics.htm
A new phenomenon discovered in ultracold atoms of a Bose-Einstein condensate (BEC) could offer new insight into the quantum mechanical world and be a step toward applications in “atomtronics”—the use of ultracold atoms as circuit components. Researchers at the National Institute of Standards and Technology (NIST) have reported the first observation of the “spin Hall effect” in a cloud of ultracold atoms.
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Tomi says:
D-Wave Large-Scale Quantum Chip Validated, Says USC Team
http://hardware.slashdot.org/story/13/06/28/2237243/d-wave-large-scale-quantum-chip-validated-says-usc-team
“A team of scientists says it has verified that quantum effects are indeed at work in the D-Wave processor, the first commercial quantum optimization computer processor. The team demonstrated that the D-Wave processor behaves in a manner that indicates that quantum mechanics has a functional role in the way it works.”
Tomi says:
Large-scale quantum chip validated
http://scienceblog.com/64278/large-scale-quantum-chip-validated/
A team of scientists at USC has verified that quantum effects are indeed at play in the first commercial quantum optimization processor.
The team demonstrated that the D-Wave processor housed at the USC-Lockheed Martin Quantum Computing Center behaves in a manner that indicates that quantum mechanics has a functional role in the way it works. The demonstration involved a small subset of the chip’s 128 qubits.
In other words, the device appears to be operating as a quantum processor — something that scientists had hoped for but have needed extensive testing to verify.
The quantum processor was purchased from Canadian manufacturer D-Wave nearly two years ago
“Using a specific test problem involving eight qubits, we have verified that the D-Wave processor performs optimization calculations [that is, finds lowest-energy solutions] using a procedure that is consistent with quantum annealing and is inconsistent with the predictions of classical annealing,” said Daniel Lidar, scientific director of the Quantum Computing Center and one of the researchers on the team. Lidar holds joint appointments at USC Viterbi and the USC Dornsife College of Letters, Arts and Sciences.
See more at: http://news.usc.edu/#!/article/52818/large-scale-quantum-chip-validated/
Tomi Engdahl says:
Boffins confirm quantum crypto can keep a secret
Hack-defeating QKD protocol validated in two sets of tests
http://www.theregister.co.uk/2013/09/02/your_secrets_are_safe_with_quanta_after_all/
Over recent years, the gap between theoretical security of quantum crytography and practical implementation has provided plenty of fun for super-geniuses the world over.
Yes, quantum cryptography is supposed to be unbreakable.
However, practical implementations of quantum cryptography left various possible attack vectors. To close these attacks (described in more detail below), the quantum crypto community proposed a new protocol, MDI-QKD (measurement device independent quantum key distribution), and now, two research groups working independently have verified that MDI-QKD gets a long way towards a provably-secure quantum crypto scheme.
Since Charlie never reports polarisation values, all a third party (Eve) would be able to determine is whether Alice and Bob are synchronised. Eve can’t tell from observing Charlie what the secret negotiated between Alice and Bob is.
The Canadian experiment took the MDI-QKD proposal on a field test – not using it to generate random keys, but to determine whether the measurement scheme would work over realistic distances. Charlie was kept on campus, while Alice and Bob were 6 km and 12 km away, respectively.
In the US-China test, Alice, Bob and Charlie were confined to the lab (albeit using a 50 km fibre on a reel): their test was demonstrating that MDI-QKD allows truly random keys to be generated. Not only that, but the test showed that realistic key generation rates of 25 kbit secure keys can be generated using the technique.
In both cases, the answer was “yes”. So while companies making commercial QKD kit had already started responding to the earlier attacks, there is now a protocol available for future designs.
Tomi Engdahl says:
Quantum Computers Check Each Other’s Work
http://tech.slashdot.org/story/13/09/30/1933201/quantum-computers-check-each-others-work
“Quantum computers can solve problems far too complex for normal computers, at least in theory. That’s why research teams around the globe have strived to build them for decades. But this extraordinary power raises a troubling question: How will we know whether a quantum computer’s results are true if there is no way to check them?”
Tomi Engdahl says:
Quantum Computers Check Each Other’s Work
http://news.sciencemag.org/physics/2013/09/quantum-computers-check-each-other%E2%80%99s-work
Quantum computers can solve problems far too complex for normal computers, at least in theory. That’s why research teams around the globe have strived to build them for decades. But this extraordinary power raises a troubling question: How will we know whether a quantum computer’s results are true if there is no way to check them? The answer, scientists now reveal, is that a simple quantum computer—whose results humans can verify—can in turn check the results of other dramatically more powerful quantum machines.
Because each qubit can embody so many different states, quantum computers could compute certain classes of problems dramatically faster than regular computers by running through every combination of possibilities at once. For instance, a quantum computer with 300 qubits could perform more calculations in an instant than there are atoms in the universe.
Currently, all quantum computers involve only a few qubits “and thus can be easily verified by a classical computer, or on a piece of paper,” says quantum physicist Philip Walther of the University of Vienna. But their capabilities could outstrip conventional computers “in the not-so-far future,” he warns, which raises the verification problem.
Scientists have suggested a few ways out of this conundrum that would involve computers with large numbers of qubits or two entangled quantum computers. But these still lie outside the reach of present technology.
The existence of undetectable errors will depend on the particular quantum computer and the computation it carries out. Still, the more traps users build into the tasks, the better they can ensure the quantum computer they test is computing accurately. “The test is designed in such a way that the quantum computer cannot distinguish the trap from its normal tasks,” Walther says
Tomi Engdahl says:
Quantum Computer Passes Math Test, But Doesn’t Answer the Big Question
http://www.wired.com/wiredscience/2013/10/quantum-computer-ramsey/
Is the world’s first commercial quantum computer the real deal or not? No one is quite sure.
The most recent experiment adding fodder to this debate used the quantum computer made by the Canadian company D-Wave Systems to determine hard-to-calculate solutions in a mathematical field known as Ramsey theory. Despite the machine’s success, many scientists are still skeptical of this quantum computer’s legitimacy.
“At the moment, it’s not clear to my eyes that D-Wave device is what we would call a quantum computer,” said computer scientist Wim van Dam from the University of California, Santa Barbara, who was not involved in the recent work.
Quantum computers harness the weird quirks of the subatomic world to run algorithms at extremely quick speeds and solve problems that stymie our current electronic devices. That’s because classical computers rely on transistors that hold memory in the form of zeros and ones. A quantum computer, by contrast, uses subatomic particles (called qubits) that can be a one, a zero, or a simultaneous superposition of these two states.
Since the early 2000s, researchers have been able to build rudimentary quantum computers but it wasn’t until 2011 that D-Wave announced a commercial product with a 128-qubit processor. If it were truly a quantum computer, it would be leaps and bounds ahead of any other product, but the company’s statements have been met with raised eyebrows from the computer science community. Still, D-Wave sold its first products to companies such as Lockheed Martin while their second-generation device was bought up by Google and NASA.
The latest experiment used the D-Wave machine to find solutions to optimization problems in what is known as Ramsey theory, after British mathematician Frank Ramsey.
D-Wave’s device was able to implement an algorithm to calculate Ramsey numbers for different configurations, though none that weren’t already known from previous work.
While noting that the D-Wave experiment’s calculations were correct, the authors of a commentary piece in the same issue wrote that “many more tests would be needed to conclude that the logical elements are functioning as qubits and that the device is a real quantum computer.”
Graeme Smith and John Smolin from IBM’s Watson Research Center, the authors of the commentary, question just how coherent the qubits of D-Wave’s computer are. Coherence refers to how long the particles are able to remain in a state of superposition (where they are both zero and one simultaneously), which is notoriously tricky to maintain. Even small amounts of noise can cause the qubits’ quantum mechanical wavefunction to collapse, turning them into classical objects that don’t work like a true quantum computer.
But the algorithms used to calculate these Ramsey numbers “don’t need as much coherence as a full-blown quantum computer,” said physicist Frank Gaitan of the University of Maryland, who worked on the D-Wave experiment.
Gaitan adds that D-Wave’s machine is not necessarily a universal quantum computer, which could run any algorithm given to it. Instead, it is designed to be particularly good at solving optimization problems, such as those in Ramsey theory, and the evidence from his research shows that the device “uses some kind of quantum effect that solves some kind of problems.”
Even then, there is still some question as to whether D-Wave’s system is truly a quantum computer.
Tomi Engdahl says:
Google’s Quantum Computer in Limbo After Government Shutdown
http://www.wired.com/wiredenterprise/2013/10/dwave-nasa/
When Google and NASA announced plans to boot up an honest-to-goodness quantum computer at NASA’s Ames Research Center, it seemed like the beginning of something very big.
Researchers from around the world would get their chance to kick the tires of a D-Wave Two — an entirely new type of computer built by a Canadian company that claims it has harnessed the computing power of quantum physics. Lockheed Martin was already running a D-Wave system operated out of the University of Southern California, but the Google-funded Ames Quantum Artificial Intelligence Lab was to be the company’s second customer.
“We’re excited to get started,” wrote Google Engineering Director Hartmut Neven in a blog post back in May, after the search giant purchased the machine. And last month, a NASA Ames spokeswoman told us that engineers expected to have the system up and running by October.
But then came the government shutdown, which has shuttered everything from Yosemite National Park to, yes, the NASA Ames Research Center.
As it turns out, Google just barely dodged a bullet. The NASA team booted up their D-Wave Two just days before the federal government shutdown would have put a complete stop to the project. But with NASA and Ames almost completely shut down, it’s not exactly clear what’s happening with the machine.
Because the D-Wave has to be finely calibrated — it operates at near-zero Kelvin — it would be extremely costly to shut the thing down and then restart it when the government comes back to life. So the machine is now operational, but it’s in a kind of limbo, at least as far as NASA is concerned. “All the people from NASA who are supposed to be testing the computer now are standing down and it’s just sitting there, wasting electricity,” says Lee Stone, the Ames union president who was one of the few people at NASA who could speak to us during the shutdown.
Radosavljevic-Szilagyi says that scientists are still figuring out what the machine can actually do. “It’s still early days with the quantum computer,”
The big question is just how long D-Wave’s supercooled processor can remain in what scientists call a state of superposition.
“At the moment, it’s not clear to my eyes that D-Wave device is what we would call a quantum computer,”
Tomi Engdahl says:
First Experimental Evidence That Time Is an Emergent Quantum Phenomenon
http://science.slashdot.org/story/13/10/23/129220/first-experimental-evidence-that-time-is-an-emergent-quantum-phenomenon
“One of the great challenges in physics is to unite the theories of quantum mechanics and general relativity. But all attempts to do this all run into the famous ‘problem of time’ — the resulting equations describe a static universe in which nothing ever happens. In 1983, theoreticians showed how this could be solved if time is an emergent phenomenon based on entanglement, the phenomenon in which two quantum particles share the same existence”
“Now quantum physicists have performed the first experimental test of this idea by measuring the evolution of a pair of entangled photons in two different ways.”
Tomi says:
World record for quantum memory smashed
A quantum leap
http://www.theinquirer.net/inquirer/news/2307486/world-record-for-quantum-memory-smashed
SCIENTISTS HAVE MADE a quantum leap in the search for ultra-fast computing.
Boffins at Simon Fraser University managed to keep information in a quantum memory state for 39 minutes, smashing a hypothetical world record.
Previous attempts yielded results of under 30 seconds at room temperature and just under three minutes in cryogenic conditions.
The global race to harness the power of qubits has high stakes – the ability to create computers capable of calculating many times faster. Qubits are able to exist simultaneously in a superimposed state of ’0′ and ’1′.
This experiment involved a new type of silicon that could, scientists believe, be the secret of creating long term memory in quantum systems.
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Tomi Engdahl says:
A Link Between Wormholes and Quantum Entanglement
http://news.sciencemag.org/physics/2013/12/link-between-wormholes-and-quantum-entanglement
This advance is so meta. Theoretical physicists have forged a connection between the concept of entanglement—itself a mysterious quantum mechanical connection between two widely separated particles—and that of a wormhole—a hypothetical connection between black holes that serves as a shortcut through space. The insight could help physicists reconcile quantum mechanics and Einstein’s general theory of relativity, perhaps the grandest goal in theoretical physics. But some experts argue that the connection is merely a mathematical analogy.
Entanglement links quantum particles so that fiddling with one can instantly affect another. According to the bizarre quantum laws that govern the subatomic realm, a tiny particle can be in two opposite conditions or states at once.
Wormholes, on the other hand, are a prediction of Albert Einstein’s general theory of relativity, which describes how massive objects warp space and time, or spacetime, to create the effects we call gravity.
At first glance, entanglement and wormholes both seem to offer a way around Einstein’s dictum that nothing can travel faster than light. But in both cases, that hope is dashed. Entanglement cannot be used to send signals faster than light because one cannot control the output of the measurement on the first atom and thus willfully set the state of the distant one. Similarly, one can’t zip through a wormhole because it’s impossible to escape the black hole on the other end.
Sonner also finds that the entangled particles in the 3D world are connected by a wormhole in the 4D world, as he also reported online on 20 November in Physical Review Letters.
Tomi Engdahl says:
Graphene Flakes May Spin Gold Into Quantum Computing
http://www.eetimes.com/document.asp?doc_id=1320494&
According to new research published at the Massachusetts Institute of Technology (MIT) last week, graphene can host quantum electronic states at its edge due to a spin selectivity of which researchers were previously unaware.
The two-dimensional carbon material can be used in this new way allowing for the discovering of unexpected properties and use cases. Published in the journal Nature, the study shows that graphene also offers, under certain extreme conditions, additional benefits including exotic uses such as quantum computing.
This could ultimately lead to the creation of quantum computers, according to one researcher, although the extreme conditions required would make it necessarily a highly specialized machine for high-priority computational tasks such as national laboratories.
Tomi Engdahl says:
NSA dreams of quantum computer that can break encryption
Spy agency is apparently not close to a quantum breakthrough, but it’s trying.
http://arstechnica.com/information-technology/2014/01/nsa-dreams-of-quantum-computer-that-can-break-encryption/
The National Security Agency is conducting what it calls “basic research” to determine whether it’s possible to build a quantum computer that would be useful for breaking encryption.
The news isn’t surprising—it would be surprising if the NSA wasn’t researching quantum computing given the measures it’s taken to undermine encryption standards used to protect Internet communications. The NSA’s quantum work was described in documents leaked by Edward Snowden and published today in the Washington Post. A three-page NSA document describes a project to conduct “basic research in quantum physics and architecture/engineering studies to determine if, and how, a cryptologically useful quantum computer can be built.”
This is part of a $79.7 million research program called “Penetrating Hard Targets.” A project goal for fiscal 2013 was to “Demonstrate dynamical decoupling and complete quantum control on two semiconductor qubits,” the basic building block of a large-scale quantum computer. The NSA description of the program says the agency will “[c]ontinue research of quantum communications technology to support the development of novel Quantum Key Distribution (QKD) attacks and assess the security of new QKD system designs.”
Tomi Engdahl says:
Boffins say D-Wave machine could be a classic*
*Classical computer, that is
http://www.theregister.co.uk/2014/02/04/boffins_say_dwave_machine_could_be_a_classic/
First, the world thought that D-Wave hadn’t built a quantum computer; then, it thought there was a quantum computer in the box; next, there was disappointment that the D-Wave machine didn’t speed things up (but might still be quantum); and now, it starts to look like it’s not quantum after all.
Their conclusion is that their classical model achieves “as good or better correlation with the D-Wave machine’s input-output behaviour than simulated quantum annealing does”.
Tomi Engdahl says:
He Said She Said – How Blogs are Changing the Scientific Discourse
http://wavewatching.net/2014/02/09/he-said-she-said-how-blogs-are-changing-the-scientific-discourse
The debate about D-Wave’s “quantumness” shows no signs of abating, hitting a new high note
Tomi Engdahl says:
Mysterious Quantum ‘Dropletons’ Form Inside Semiconductors Shot With Lasers
http://www.wired.com/wiredscience/2014/02/quantum-droplets-dropleton-lasers-semiconductors/
By shooting a semiconductor with ultra-fast laser pulses, scientists have discovered a new quasiparticle that behaves like a drop of liquid. They describe it as a quantum droplet, and named it “dropleton.”
These things were not predicted under any theory and surprised scientists when they appeared unexpectedly in extremely low temperature semiconductor experiments. They have properties unlike anything seen before.
After checking with some mathematical models, they realized they had discovered something completely new. In the exciton, the electrons and holes were forming something like hydrogen atoms.
The finding doesn’t have any immediate applications — “I don’t think somebody’s going to build a device based on a quantum droplet,” said Cundiff
Tomi Engdahl says:
Single chip photon source brings quantum comms closer
Turning research labs into devices
http://www.theregister.co.uk/2014/04/02/single_chip_photon_source_brings_quantum_comms_closer/
Down at the “basic research” level, there’s a lot the labs can accomplish with quantum mechanics: entanglement, information teleportation, simple quantum computations and more. Now, an international collaboration believes it’s brought exploitation of quantum effects closer to a commercial development.
The researchers have created what they hope lays out the “yellow brick road” they need to follow to create a single integrated source of single photons – ultimately at high enough output rates to permit quantum communications in the megahertz range.
Their work combines a source of single photons, lithium niobate waveguides, low-loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro-optic switches.
A high-quality source of single photons that can be entangled for information teleportation “is a hot application of what this sort of system is projected to be used for,” he said. In computing systems, “we would expect this sort of technology would form a core unit to produce qubits in a quantum computer. A series of these devices would product a series of qubits, which is a key challenge of optical quantum computing.”
Tomi Engdahl says:
Boffins make noise about D-Wave chip: it seems quantum
Thermal ‘knob’ turns up the heat
http://www.theregister.co.uk/2014/04/03/boffins_make_noise_about_dwave_chip_it_seems_quantum/
Researchers from University College, London, and the University of Southern California, have weighed into the ongoing “is it quantum?” D-Wave debate with an interesting approach, testing the device under a variety of noise conditions.
The D-Wave chip is chilled to 20 millikelvin to prevent thermal noise from overwhelming the quantum effects the company says are the basis of its computations.
“You can have global quantum behaviour without a quantum speedup, but you can’t have a quantum speedup without global quantum behaviour,” Aaronson said, also noting that observing quantum-like behaviour in special instances doesn’t predict the scaling behaviour of the D-Wave device.
Tomi Engdahl says:
Error-Free Quantum Computing Made Possible in New Experiment
http://spectrum.ieee.org/tech-talk/computing/hardware/errorfree-quantum-computing-made-possible-in-new-experiment
For quantum computing to ever fulfill its promise, it will have to deal with errors. That’s been a real problem until now, because although scientists have come up with error correction codes, the quantum machines available couldn’t make use of them. But researchers report today that they’ve created a small quantum computing array that for the first time performs with enough accuracy to allow for error correction—paving the way toward practical machines that could outperform ordinary computers.
Martinis and his colleagues used superconducting quantum circuits that are just one of several possible designs for quantum computing systems. The qubits themselves are Josephson junctions—two layers of superconductor separated by a thin insulating layer.
By creating an arrangement of five qubits in a line, the researchers showed they could perform the logic operations at the heart of modern computing with an accuracy of 99.92 percent for a quantum logic gate involving one qubit and 99.4 percent for a quantum logic gate involving two qubits. The quantum computing arrangement, based on an approach known as “surface code” architecture, has an accuracy requirement of just 99 percent as opposed to a much more stringent 99.99 percent needed by many other quantum computing architectures.
Tomi Engdahl says:
Introduction To Quantum Computing
http://semiengineering.com/introduction-to-quantum-computing/
First in a series: Why quantum computing is different from quantum effects, and the challenges of getting these computers working on a grand scale.
Quantum computing has attracted a lot of attention lately. Recent revelations about the extent of the U.S. National Security Agency’s data collection programs, along with several large-scale corporate data breaches, have called attention to the need for secure communications. Quantum computing has potentially far-reaching implications for data security, both reducing the effectiveness of conventional encryption techniques and offering alternative methods that are theoretically unbreakable.
Meanwhile, D-Wave Systems claims to be offering the first commercially available quantum computing system. Arguments are raging about whether the results D-Wave has achieved are actually “quantum” in nature and, if they are, how to measure the performance of such a system.
Tomi Engdahl says:
D-Wave wooing universities down under
Next wave will be software, quantum computing outfit tells El Reg
http://www.theregister.co.uk/2014/02/17/dwave_wooing_universities_down_under/
While controversy continues over the nature of its machines, quantum computing company D-Wave is wearing out the shoe-leather talking to academic users – and The Register.
In Australia to present to universities and the HPC community at large about D-Wave, the company’s director of business development and strategic partnerships
“We’re looking for application expertise in optimisation problems,”
That’s quite a long way from the pop-culture view of quantum computing, that pitches it as the perfect all-purpose encryption cracker.
With a few thousand variables, it’s a problem that defies complete solution with classical computing, but D-Wave says the TSP is in the class of optimisation problems it’s addressing. “We would expect that within a few generations, we’ll be able to solve the travelling salesman problem very quickly,” Williams told The Register.
“Heuristics can get distracted into exploring the same part of a problem again and again,” he continued. “With a quantum solution, you can look at different approaches – ‘show me all possible solutions’, or ‘give me a count of the possible solutions’.”
Which raises the question of how D-Wave’s computers actually function. The hard work, Williams said, is in the programming: to run on the D-Wave quantum annealing device, the user problem has to be expressed as a formula describing the problem’s energy state.
“The aim is to minimise the energy function,” he said. The D-Wave chip starts at a low-energy state (which is why it’s cryogenically cooled – Williams said today’s 10 milli-Kelvin temperatures will seem relatively warm in the future), and a transverse magnetic field is applied which, in theory, gives the qubits an equally-weighted superposition of ones and zeroes.
The act of computing occurs when two things happen simultaneously: the transverse magnetic field is removed, while at the same time, a second field that expressed the problem is increased. This is when the “annealing” in “quantum annealing” takes place – the problem is annealed onto the qubits.
D-Wave is acutely aware that it has to make programming the machines accessible in languages that people actually use, like C, C++, Python and Matlab.
Tomi Engdahl says:
Flipping the switch
Physicists design quantum triggers that can be activated by a photon
http://news.harvard.edu/gazette/story/2014/04/flipping-the-switch/
Harvard researchers have succeeded in creating quantum switches that can be turned on and off using a single photon, a technological achievement that could pave the way for creating highly secure quantum networks.
Built from single atoms, the first-of-their-kind switches could one day be networked via fiber-optic cables to form the backbone of a “quantum Internet” that allows for perfectly secure communications
“From a technical standpoint, it’s a remarkable accomplishment,” Lukin said of the advance. “Conceptually, the idea is very simple: Push the conventional light switch to its ultimate limit.”
Though fabricated in a way similar to how traditional computer chips are made, the integrated circuits built by Thompson and Tiecke don’t run on electricity, but on light.
The chips use nanophotonic technology — essentially the ability to create “wiring” that can channel and control the pathway of light — to build optical circuits that can then be connected to fiber optic cables.
Tomi Engdahl says:
Introduction To Quantum Computing
http://semiengineering.com/introduction-to-quantum-computing/
First in a series: Why quantum computing is different from quantum effects, and the challenges of getting these computers working on a grand scale.
Tomi Engdahl says:
Quantum Random Number Generator Created Using A Smartphone Camera
https://medium.com/the-physics-arxiv-blog/602f88552b64
Physicists have exploited the laws of quantum mechanics to generate random numbers on a Nokia N9 smartphone, a breakthrough that could have major implications for information security