What are the real-world benefits of quantum computers and how do they work?

[ISamson]

Hello,

I have found out that in the future we might have quantum computers, which will be more powerful than today's computers. Instead of trying every option available to the computer, quantum computers will be able to try many different possible solutions at the same time. What would be some of the daily-life, scientific and social advantages of such technology?
I was just wondering...
Thanks.

 

[phinds]

Hello,

I have found out that in the future we might have quantum computers,

The people who have already developed quantum computers would be surprized to hear that it is still in the future.

What would be some of the daily-life, scientific and social advantages of such technology?

Have you done any research on this? What have you found ?

 

[f95toli]

Have a look at the website for IBM's Quantum Experience, there you will find quite a lot of information about applications.

 

[russ_watters]

The people who have already developed quantum computers would be surprized to hear that it is still in the future.

Sorry, but such people do not exist; quantum computing is still in the theoretical/experimental stage of development, speculating on how they *might* work. There are no functional general purpose "quantum computers".

 

[phinds]

Sorry, but such people do not exist; quantum computing is still in the theoretical/experimental stage of development, speculating on how they *might* work. There are no functional general purpose "quantum computers".

Huh. I was sure that there had been a couple developed that we not yet in any way practical but were true quantum computers (very small number of qubits) and one that is bigger but arguably not necessarily a true quantum computer. I'm remembering that incorrectly?

 

[russ_watters]

Huh. I was sure that there had been a couple developed that we not yet in any way practical but were true quantum computers (very small number of qubits) and one that is bigger but arguably not necessarily a true quantum computer. I'm remembering that incorrectly?

There is a company selling what they claim are quantum computers, but there are a great many academics who believe the product to be fraudulent or perhaps a "that isn't what that word means".
https://en.m.wikipedia.org/wiki/D-Wave_Systems

I haven't done much research on this, so I'm a bit unclear on why it would be so difficult to tell. Right now people are looking at its underwhelming performance, but I don't see why they can't just crack it open and look at the hardware. That might be a subject worthy of its own thread.

Otherwise, that IBM project is a research project and they are not claiming it to be a general purpose quantum computer.

 

[phinds]

There is a company selling what they claim are quantum computers, but there are a great many academics who believe the product to be fraudulent or perhaps a "that isn't what that word means".
https://en.m.wikipedia.org/wiki/D-Wave_Systems

Yes, that's the one that I was thinking of that there has been subject to considerable controversy.

Otherwise, that IBM project is a research project and they are not claiming it to be a general purpose quantum computer.

OK, I guess I read too much into it. Thanks.

 

[f95toli]

There is a company selling what they claim are quantum computers, but there are a great many academics who believe the product to be fraudulent or perhaps a "that isn't what that word means".
https://en.m.wikipedia.org/wiki/D-Wave_Systems

No, there is disagreement about just how "quantum " the D-wave computer is; but I don't think anyone is claiming that it is fraudulent. The computers DO work (I know people who use them in their research) and there is certainly some quantum effects involved (entanglement of neighboring qubits). However, it is not clear whether the parameters they use (T1, T2 times for the qubits, strength of coupling, topology etc) are good enough to actually give you an exponential speedup compared to a "classical" annealer operating using only thermal effects.
Note that the D-Wave computer is not a general purpose QC; but D-Wave has never claimed that it is. It is a quantum annealer which -if it works- would be be very good at solving a large class of important optimization problems; especially if they are able to scale if up a bit further.

I haven't done much research on this, so I'm a bit unclear on why it would be so difficult to tell. Right now people are looking at its underwhelming performance, but I don't see why they can't just crack it open and look at the hardware. That might be a subject worthy of its own thread.

See above. Showing that something is actually a QC is a very hard problem; the only way that is known to work is to get it to do something exponentially faster than a classical computer but even that is problematic. D-Wave has already demonstrated speedup for a couple (perhaps more) optimization problems but in both cases someone was then able to come up with a new classical algorithm that could be run in polynomial time on an ordinary computer.
Note that no one doubts that the basic building blocks of their circuit is "quantum" (they are just flux qubits).

Otherwise, that IBM project is a research project and they are not claiming it to be a general purpose quantum computer.

The IBM computer IS a general purpose QC (it supports all gate operations and can -at least in theory- be used for all known algorithms); it is just too small to do anything of practical importance.

 

[phinds]

The IBM computer IS a general purpose QC (it supports all gate operations and can -at least in theory- be used for all known algorithms); it is just too small to do anything of practical importance.

Yes, that's what I was referring to originally.

 

[f95toli]

This News&Views regarding a recent PRL article is relevant to the discussion about the D-Wave computer above

https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.119.110502

 

[stoomart]

Note that the D-Wave computer is not a general purpose QC; but D-Wave has never claimed that it is. It is a quantum annealer which -if it works- would be be very good at solving a large class of important optimization problems; especially if they are able to scale if up a bit further.

My understanding is these chips work as an ASIC attached to a classical computer system, which is used for solving NP-complete problems. The applications for QC in my field (cybersecurity) is breaking cryptography (something the NSA is said to have invested in), and machine learning, which has made huge improvements in user/system/process behavior analytics.

 

[stoomart]

This News&Views regarding a recent PRL article is relevant to the discussion about the D-Wave computer above

https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.119.110502

Non-paywalled link - https://arxiv.org/abs/1703.03871

 

[FactChecker]

There are two different quantum computer development directions that seem the most advanced. IBM is working on a processor that can do logic like Shor's algorithm to factor large integers. They have been able to put a couple of dozen qubits on the chip, so it is a long way from being a practical general purpose computer. D-wave has developed a quantum annealing computer that has a thousand qubits. The nature of quantum annealing makes it a poor choice for problems that require exact solutions based on logic like that required for Shor's algorithm. But it can still be very powerful for problems that fit it well. Google claims to show performance on a type of problem that is millions of times better than any traditional computer. Neither approach is ready for general purpose computing, but the potential is there.

PS. Judging the capabilities of a quantum computer by its number of qubits can be tricky. Although two dozen qubits in an IBM chip may seem small, if it can find a 1-step solution of a problem with 2²⁴ ≈ 17 million possible combinations, that is nothing to sneeze at.

 

[StoneTemplePython]

Although two dozen qubits in an IBM chip may seem small, if it can find a 1-step solution of a problem with 2²⁴ ≈ 17 million possible combinations, that is nothing to sneeze at.

I'm not sure what you mean but this. The general view that I've read is for solving NP Complete or Hard-er problems, you get a quadratic speed-up in a quantum computer, not exponential. This neatly mirrors the shift from a 1 norm in classical probability to the 2 norm.

If instead of solving, you just aim for "good", and you are using local search to drive down a cost function for an intractable problem (quite common, e.g. in deep learning), your search process may look like simulated annealing -- and it appears quantum annealing could have a big speedup over that.

Here's a decent read on the matter:

http://news.mit.edu/2015/3q-scott-aaronson-google-quantum-computing-paper-1211

(I've also read Aaronson's book though it underperformed my expectations.)

 

[FactChecker]

If instead of solving, you just aim for "good", and you are using local search to drive down a cost function for an intractable problem (quite common, e.g. in deep learning), your search process may look like simulated annealing -- and it appears quantum annealing could have a big speedup over that.

I agree. This is the type of problem for which quantum annealing could have a tremendous advantage. Also if there is some advantage to randomly selecting one of several near-optimal solutions (for instance, to keep an enemy guessing), then quantum annealing could do that.

 

[gleem]

I came across this article while looking for AI advances. Quantum computer apparently are move formidable than just the speed of their processing. That being having the ability to breach security of all current computer systems. Can anybody elaborate on this capability.

Edit: Is it the speed of the processing by which they can de-encrypt files?

 

[Mark44]

I haven't done much research on this, so I'm a bit unclear on why it would be so difficult to tell.

Such a machine would be and not be a quantum computer, simultaneously.

 

[Greg Bernhardt]

Interesting development

Physicists Made an Unprecedented 53 Qubit Quantum Simulator
https://motherboard.vice.com/en_us/article/7xwz7b/53-qubit-quantum-simulator-computer

 

[stoomart]

I came across this article while looking for AI advances. Quantum computer apparently are move formidable than just the speed of their processing. That being having the ability to breach security of all current computer systems. Can anybody elaborate on this capability.

Edit: Is it the speed of the processing by which they can de-encrypt files?

There is the potential to break common encryption schemes in use today, but not all schemes are susceptible to this attack. See https://en.wikipedia.org/wiki/Quantum_computing#Potential

 

[andrei3000]

Hi,...can someone explain to me how a quantum computer will work?it based on Copenhagen Interpretation and for the moment we don't know if the cat is dead or alive at the same time.We can live in a MWI Universe as far as we know...so the Super position maybe don't exist...

 

[andrei3000]

Nothing?no answer from nobody?is a lot of "fuss" on this topic...but I think is all somehow a thing that no one really understands...Is based on particle Superpositions...but was not yet proved as 100% real for our reallity...Are now 3 theories about our Universe:Copenhagen Interpretation(only here the QC will work),Many-Worlds Interpretation and Pilot-Wave Interpretation...In which one of them are we??and maybe is not even one of the 3 as we know...so??

 

[cosmik debris]

Nothing?no answer from nobody?is a lot of "fuss" on this topic...but I think is all somehow a thing that no one really understands...Is based on particle Superpositions...but was not yet proved as 100% real for our reallity...Are now 3 theories about our Universe:Copenhagen Interpretation(only here the QC will work),Many-Worlds Interpretation and Pilot-Wave Interpretation...In which one of them are we??and maybe is not even one of the 3 as we know...so??

I think you are asking too much of people. I think you are asking people to teach you about Quantum computing which requires an understanding of Quantum Mechanics. No one is going to be able to do that in a few posts on here. You are best to study and then ask specific questions about details you do not understand.

Cheers

 

[andrei3000]

I don't want to be teached,I just want to know how Super Position will work on Quantum Computer if we can't actually prove Copenhagen Interpretation is 100& accurate,not even Einstein aproved this theory...

 

[cosmik debris]

I don't want to be teached,I just want to know how Super Position will work on Quantum Computer if we can't actually prove Copenhagen Interpretation is 100& accurate,not even Einstein aproved this theory...

It's an interpretation, there is no proof. This is what I mean, you have many misconceptions and you need to study first.

Cheers.

 

[f95toli]

I don't want to be teached,I just want to know how Super Position will work on Quantum Computer if we can't actually prove Copenhagen Interpretation is 100& accurate,not even Einstein aproved this theory...

Interpretations have nothing to do with what actually physically HAPPENS; the predictions of the theory and the actual math is the same in ALL interpretations. Hence, it does not matter which interpretation you prefer when designing a quantum computer.

Also, note that quantum computers DO work; there are many research groups around the world that have had prototypes up and running for many years; the fact that these are too small to do anything useful does not change the fact that they demonstrate that the basic principle works just fine.

BTW, there is no interpretation that says that "superposition does not exist" for the simple reason that superposition of states has been an integral part of all modern physics for a very long time (close to a 100 years), is extremely well established and is also part part of "everyday science" such as basic chemistry.

 

[Jaccer]

Interpretations have nothing to do with what actually physically HAPPENS; the predictions of the theory and the actual math is the same in ALL interpretations. Hence, it does not matter which interpretation you prefer when designing a quantum computer.

Also, note that quantum computers DO work; there are many research groups around the world that have had prototypes up and running for many years; the fact that these are too small to do anything useful does not change the fact that they demonstrate that the basic principle works just fine.

BTW, there is no interpretation that says that "superposition does not exist" for the simple reason that superposition of states has been an integral part of all modern physics for a very long time (close to a 100 years), is extremely well established and is also part part of "everyday science" such as basic chemistry.

Yeah , the predictions of theory and actual mathematics are the same in all interpretations.

 

[Evo]

This forum (Computing and technology) is for actual hardware and software questions, so the thread is moved.

 

[jeremyfiennes]

Is there an actually functioning quantum computer that to a definite question like "What is two plus two" can give a definite answer like "Four, fullstop"?

 

[gleem]

Is there an actually functioning quantum computer that to a definite question like "What is two plus two" can give a definite answer like "Four, fullstop"?

Check out this website
https://quantumexperience.ng.bluemix.net/qx/experience

 

[jeremyfiennes]

I did, but it didn't answer my question. I want to know whether there is an actual physical functioning machine, like the classical one I am writing this on.

 

[gleem]

Yes IBM will let you use one.

Welcome to the IBM Q Experience!
Explore the world of quantum computing! Check out our User Guides and interactive Demos to learn more about quantum principles. Or, dive right into create and run algorithms on real quantum computing hardware, using the Quantum Composer and QISKit software developer kit.

My emphasis.

 

[gleem]

I also appears that IBM has or is about to bring a 16 Qubit computer on line for their Q Experience program.

 

[f95toli]

I also appears that IBM has or is about to bring a 16 Qubit computer on line for their Q Experience program.

The 16-qubit machine has been online for a while. There is now a 20-qubit processor online (which not everyone can access) and the 50-qubit machine is -we are told- in the pipeline (assuming is passes all tests)
This page summarized (in real-time) the status of all the IBM hardware that can currently be accessed via the cloud
https://quantumexperience.ng.bluemix.net/qx/devices

Note also that it is expected that both Google and Rigetti Computing will at some point start offering cloud access to their machines.Btw, since this is probably not apparent to everyone: compare the T1 and T2 times of the 20 qubit machine and the 5 qubit machine; the coherence times of the former are better which is very interesting. They are making progress extremely quickly...

 

[Elemental]

As mentioned, several corporations, including mine, have quantum computers actually in use on practical problems, but I've not seen dramatic success stories to date. I was fortunate to get an in-depth briefing on this technology a couple of years ago.

The idea is that each qubit is in a quantum superposition of logic 0 and logic 1, so each run of an algorithm, involving multiple steps with multiple qubits, yields a solution which is also a superposition of many possible solutions. Presto: parallel processing! Nevertheless, the actual output of each run is only a single number, due to the "projection postulate" (ala von Neumann). So in order to achieve "parallel processing", the same algorithm has to be run many many times, and the ensemble of outputs fall into a statistical distribution per the Born rule. The statistical result can then be viewed as the desired answer.

The biggest obstacle is isolating the qubits from the environment so that they display quantum rather than classical behavior. This is approached using super-cooling, super-conducting, or other techniques. The success metric is the "coherence time", which is the average duration before the pure the quantum state decays due to environmental interaction. Limiting factors include the number of qubits which can be so isolated simultaneously, and the numbers of channels through which each qubit can be logically connected with other qubits without destroying quantum coherence.

What I find interesting is that quantum computers appear to be a practical application of quantum theory, without which they would not work as advertised. This is similar to Navstar GPS which requires relativity, even though some of the engineers didn't believe in it during development.