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"Still, a practical reversible computer has yet to be built using this or other approaches."

Since quantum computers of any kind have to be reversible due to the very nature of QM, every realization of quantum computation is a reversible computer.

This includes the controversial D-Wave machine as well IBM's QC chip that you can play with online.

But nothing report here is particularly new. It has been known for quite some time now that breaking encryption takes a lot of qubits, whereas quantum chemistry can be accelerated with relative modest qubits amounts, assuming they can implement universal QC gate model operations.

This could be a real game changer if it manages to change some minds. We need nuclear tech to cope with the nuclear waste, and this can be done in an inherently safe and responsible way that turns the waste into energy.

I very much hope this example in doing this on the small scale, as with these diamond batteries, will translate into support for bigger inherently safe designs that allow to transmute nuclear waste into lesser problems.

Maybe the tap water got somehow tainted with hallucinogens?

It not like that there are some strange little tit bits that'll support the simulation thesis, but overall it doesn't add up at all.

http://wavewatching.net/2012/0...

... but the degree of entanglement.

Why do we keep trying to tame a potential run-away chain reaction if there are perfectly good alternatives?

Indeed. Love the guy, and there are other seriously high flying theorists who entertain the idea, but the notion that a classical computer could simulate reality is nevertheless rather far fetched.

At any rate, there is no value in the notion, unless you can derive some theory from it, that'll allow for an experimental test.

Heres an experimental test; we all stop doing anything entertaining. If we make our 'ratings' drop we'll get cancelled and then we'll know.

Indeed. Love the guy, and there are other seriously high flying theorists who entertain the idea, but the notion that a classical computer could simulate reality is nevertheless rather far fetched.

At any rate, there is no value in the notion, unless you can derive some theory from it, that'll allow for an experimental test.

Pretty good picture of the process.

One thing to add though, in addition to quantum tunneling true quantum annealing should also be able to tap into another resource: Entanglement. If qubits are entangled they are described by the same wavefunction, i.e. they are essentially a non-localized smeared out unity, and will experience the valleys in more than one place. Entanglement is very short lived on the D-Wave machine, and very sensitive to temperature increase.

The fact that the chip's performance is extremely dependant on the temperature indicates that it plays a crucial role, despite having at best very short lived uncontrolled entanglement on the chip.

(It also means that HTSC technology will not do, this approach to quantum computing has to be very close to absolute zero).

There's a world of difference between a classical system like you describe and quantum annealing.

At any rate, entanglement on the chip has been demonstrated, and outside experts comparing different models to characterize the chip, also came to the conclusion that it indeed performs quantum annealing.

At this point this question can be regarded as settled.

The only open, remaining question is how useful quantum annealing will be in practice.

As to Feynman, his original proposal of a quantum simulator is much closer to adiabatic quantum computing, i.e. D-Wave, then the gate model that took hold after Deutsch's seminal paper.

Google ran the same test on the previous chip, before they committed to buying the machine. This test is for the new ~1K qubit chip.

Other than that, coding for this machine is certainly not straightforward, and it is more an experimental device at this time. Certainly not something that'll give you a price performance advantage over conventional hardware, but as they keep doubling their qubit density every 15 months this may change in the not too distant future.

There are some similarities but the story has long moved past that.

D-Wave has published about chip architecture for quite some time now. You must be frequenting the wrong science sites.

Google for instance is following their overall approach but throw in hardware error correction. The latter has to be implemented via software on the D-Wave chip, which in essence is nothing more than a bunch of coupled josephson junctions (I heinously oversimplify of course, but there are now dozens of publication like this since D-Wave left the stealth mode).

D-Wave has published about chip architecture for quite some time now. You must be frequenting the wrong science sites.

Google for instance is following their overall approach but throw in hardware error correction. The latter has to be implemented via software on the D-Wave chip, which in essence is nothing more than a bunch of coupled josephson junctions (I heinously oversimplify of course, but there are now dozens of publication like this since D-Wave left the stealth mode).

It also confirms that D-Wave's machine uses quantum effects to speed up computation, but this point was never in dispute.

Boy, are you wrong on that count.

As to the term quantum computer. It computes with qubits, it's not universal, but in that it resembles some of the analog computers of yore.

The most interesting inherently safe reactor design can also use nuclear waste as fuel and transmute it into less harmful radionuclides.

CANDU is a very smart reactor design, not only because it can use natural, unenriched uranium, but also because this gives it inherent security features (natural uranium ore really doesn't like to entertain a fission reaction, so the reaction shuts down quickly when things start to go awry).

Nobody like to have a nuclear power plant in their backyard, but if I had the choice I'd always opt for CANDU over any other reactor (unless it's was an experimental spallation reactor, can't beat the safety of those).

Canada has a lot of very innovative start-ups such as D-Wave and General Fusion, the former received some federal venture capital, but with regards to fusion Canada turned out the lights long ago. There isn't even anybody designated anymore at the federal level for that file.

Pathetic given that Canada used to be a pioneer in nuclear technology as evideneced by the CANDU reactor design.

Canada has a lot of very innovative start-ups such as D-Wave and General Fusion, the former received some federal venture capital, but with regards to fusion Canada turned out the lights long ago. There isn't even anybody designated anymore at the federal level for that file.

Pathetic given that Canada used to be a pioneer in nuclear technology as evideneced by the CANDU reactor design.

It's really not all crackpotty. After all you can drive the reaction with a particle accelerator to create a non-critical reactor design, a design so flexible it can handle all sorts of nuclear fuel while also allowing for the transmutation of nuclear waste.

From my point of view the latter is much more environmentally sound than to bury the crap.

Your priors need updating.

After all you can buy a machine now that solves numerical problems with qubits (no transistors involved).

The quantum speed-up evidence is still shaky, but this is not nothing, and the speed-up conjecture for the gate model is as ironclad as physics can make it, nor is there any reason to think it cannot be built. It's just much harder to scale up than quantum annealing.

True, the heuristic for quantum chemistry like DFT are pretty good but that only takes you so far. Statistical physics with the particle model is much easier but then you miss all the emergent phenomena of collective quantum dynamics like superconductivity.

That's why I am excited about quantum computing. Recent research from the ETHZ group of Mathias Troyer have shown that quantum chemistry will already greatly benefit from even modest quantum computing resources (unlike Shor's algorithm which is pretty useless unless you are with the NSA).

True, the heuristic for quantum chemistry like DFT are pretty good but that only takes you so far. Statistical physics with the particle model is much easier but then you miss all the emergent phenomena of collective quantum dynamics like superconductivity.

That's why I am excited about quantum computing. Recent research from the ETHZ group of Mathias Troyer have shown that quantum chemistry will already greatly benefit from even modest quantum computing resources (unlike Shor's algorithm which is pretty useless unless you are with the NSA).

A better source for entangled photon pairs will come in handy for Quantum Cryptography, but Quantum Computing requires many entangled qubits.

There is no indication how these resonators could produce more than pair-wise entanglement, after all this is very different from the Josephson junction loops that D-Wave and the future Google chip are build on. These allow an arbitrary coupling via the magnetic flux (only restricted by the chip's geometry).

Regrettably, this just yet another poorly written pop-science article not informed by any actual knowledge of quantum information science. If I had a cent for each of them I'd be rich by now.

By I much prefer inherently safe reactor designs.

You are barking up the wrong tree.

Of course there is no conspiracy and I very much appreciate that Jeff Bezos invests into General Fusion.

What I find problematic is that ITER crowds out other fusion research due to its cost overuns. For instance there are now only 1 1 1/2 positions allocated to the Shiva star device (a machine GF could put to good use for plasma compression experiments). This is just enough money to prevent a mothballing of the machine, but not enough to actually get some research done.

This is not conspiracy but just how the world works. As ITER absorbs more money the overall public budget doesn't grow, and government is too inflexible to allow for private partnership (especially with, god forbid, a Canadian company).

Other interesting and scientifically sound approaches are limping along on pitiful drips of venture money e.g. General Fusion.

And while some public money goes into Polywell research, it's produced on a dime when compared to ITER.

Don't mean to knock the work that's done to advance the Tokamak design, but it shouldn't be the only game in town.

Yes, but you can distinguish quantum annealing behavior from regular thermal annealing. And when you compare the D-Wave device to simulations of both it conforms much closer to the former.

Also the extreme temperature sensitivity is more indicative of actual quantum annealing.

The machine is not faster than conventional machines at this point.

But Troyer et. al. actually confirmed that the D-Wave machine is performing quantum annealing as advertised.

In order to perform on the same level they used a highly optimized solver, not off-the-shelf optimizer software that the D-Wave machine outperforms handily.

The machine is not faster than conventional machines at this point.

But Troyer et. al. actually confirmed that the D-Wave machine is performing quantum annealing as advertised.

In order to perform on the same level they used a highly optimized solver, not off-the-shelf optimizer software that the D-Wave machine outperforms handily.

Originally I meant to bet with Matthias Troyer if the D-Wave machine was truly a quantum annealer. At the time Matthias wrote me:

""Actually, we can't bet anymore since I know the results that we're going to publish and we'll say yes to quantum :-). We should have done the bet a year ago."

So we decided to bet if the current crop of D-Wave machines can already beat conventional computing.

Obviously I lost that bet, but not by much.

It will be interesting to see how the next chip generation will fare, there is still lots of room for higher qubit integration. In comparison to conventional CMOS the D-Wave chip structures are huge.

Conventional chip design doesn't have lots of room at the bottom any more. D-Wave on the other hand still has plenty of room at the bottom.

That's why I will continue to bet on them.

" In THEORY you can delete bits, but in practice you actually can't ."

If I give you a bunch of RAM SIMs there's no way you can tell me what was written on them.

At any rate, fully reversible computing means the ability to completely reverse arbitrarily complex algos, being able to reconstruct a couple of previous bit states isn't cutting it.

And yes, you actually can delete bits, the entropy heat signature this produces is theoretically well understood, and Landauer's principle has recently been experimentally confirmed.
 

... when I took the EdX's CS191x Quantum Mechanics and Quantum Computation course.

This is actually a requirement for such a simulator as all unitary QM transformations are reversible.

It's kind of ironic that Google released this project given that they are at the same time heavily betting on D-Wave with a radically different approach to QM than the Gate based model.

The D-Wave founder Geordie Rose is know for disparaging the Quantum Gate based model as completely impractical, and in turn other QC researchers have been very critical of his approach to the matter. Spawning a contentious controversy almost as old as the Canadian start-up itself.

This is actually a requirement for such a simulator as all unitary QM transformations are reversible.

It's kind of ironic that Google released this project given that they are at the same time heavily betting on D-Wave with a radically different approach to QM than the Gate based model.

The D-Wave founder Geordie Rose is know for disparaging the Quantum Gate based model as completely impractical, and in turn other QC researchers have been very critical of his approach to the matter. Spawning a contentious controversy almost as old as the Canadian start-up itself.

The process has major advantages. It uses an inherently safe reactor design and is net energy positive.

Don't understand why there is only on place on earth where this is seriously investigated and scaled up.

This is the first direct evidence for gravity waves, but another very clever indirect one earned a Nobel Price in 1993.

... and yet again overlooking the fact that such simulation machines would certainly be more like quantum computers.

Plato's Cave - The n-th sequel. Like most sequels pretty lame really.

If you care about the environment you should want the mountain of nuclear waste reduced. And treating it with a particle accelerator, using a so called spallation reaction, you can do exactly this, while running the whole thing as an inherently save reactor with net energy gain.

The technology is proven and an industrial scale prototype is about to be build in Belgium.

"It is really hard to make large systems show quantum effects."

Well, I guess it depends on your meaning of "hard" and "quantum effect". Too me the Meisner effect is certainly quantum mechanical in nature, and easy to demonstrate with macroscopic superconductors.

The Josephson effect is another poster boy for a macroscopic quantum phenomenon.

So there is little doubt about the quantum nature of D-Wave's Josephson junction circuitry. But you are entirely correct that decoherence is what needs to be prevented by isolating the system. One thing to note though: A quantum annealer is less sensitive to this than a gate based quantum computer.

On one hand decoherence, i.e. the uncontrolled entanglement with the environment, is something you want to minimize, while on the other hand you want the coupled qubits on the chip to be entangled. Arguing that there is no entanglement between the qubits while at the same time suffering bad decoherence, implies that D-Wave really would have done a remarkably bad job of insulating their system.

Given how close to absolute zero this machine operates, and the sensitivity of the performance to the slightest temp increase, I don't see a reason to reconsider my stance.

D-Wave has Josephson junction qubits on their chip and couple them. Yet, somehow they are supposed to end up with a machine that is a classical annealer? Although the behavior of the box is exactly what you'd expect from a quantum annealer?

Seems rather far fetched.

I wished before anybody was writing about D-Wave they'd watch this video form the last Q+ hang-out where the Troyer et. al. research into the characteristics of the D-Wave machine was presented.

When it comes to uploading consciousness the fundamental question is if a classical computer can fully simulate a brain, or if we have some inherent physical resources not captured by the Turing model.

You cannot upload consciousness, it is a physical property of reality not an abstraction. We can experience abstractions, abstractions cannot experience us.

When it comes to uploading consciousness the fundamental question is if a classical computer can fully simulate a brain, or if we have some inherent physical resources not captured by the Turing model.

The Google Quantum AI lab puts this news into perspective and I put my positive spin on it here.

Having talked with one of the co-authors of the paper, he actually came away impressed at how far D-Wave has come in ten years. Although not yet far enough that I'd win my bet with him, that the D-Wave two could beat classical computing across the board.

So in short, yes, the BBC's reporting on quantum computing is atrocious. Not the first time either.

The Google Quantum AI lab puts this news into perspective and I put my positive spin on it here.

Having talked with one of the co-authors of the paper, he actually came away impressed at how far D-Wave has come in ten years. Although not yet far enough that I'd win my bet with him, that the D-Wave two could beat classical computing across the board.

So in short, yes, the BBC's reporting on quantum computing is atrocious. Not the first time either.

The quantum computing fear is really nothing new.

It makes the current encryption scheme more valuable but there are post-quantum schemes as well as quantum cryptography as alternatives.

D-Wave scaled up superconducting foundry output for their quantum chip, see no reason to not leverage this for conventional superconducting chips.

But quantum decoherence is, i.e. how the wave nature is actually suppressed in our macroscopic world.

QM offers up the Ehrenfest theorem to explain how we get there, but this theorem is not completely consistent. So gaining an experimental leg up on this process, that the Copenhagen Interpretation just swept under the rug as 'Quantum State Collapse', is what makes experiments with ever larger quantum systems so interesting.

What most people don't realize is that nuclear waste can be treated to render it harmless more quickly. And it can be done with a sub-critical reactor design.

I don't understand how you can call yourself an environmentalist and not be in favor of this technology.

One of the earlier papers that supported their claim of actual quantum annealing is linked and discussed at this blog post.

D-Wave's publication list is too long at this point in order to give a synopsis here, but there are many blogs that follow this story, so it really isn't that hard to get a more up-to-date picture.