Submitted by **giuliomagnifico** t3_zuxy0d
in **technology**

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**eggybread70**
t1_j1lzt18 wrote

"But can it run Crysis?" jokes aside, can anyone give this noob an idea of the practical applications of this architecture? What kind of algorithms lend itself to it, what kind of solutions will it excel at?

{Edit} changed "Far Cry" to "Crysis" to get the meme right...

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**nagareteku**
t1_j1m6fas wrote

Simulations and cryptography mainly. It might have potential to reduce time complexity of algorithms from exponential to quasi exponential or even polynomial time (n-bit encryption).

Computations that may take longer than the age of the universe to perform on classical computers can now be approximately computed on quantum computers on a practical time scale of mere months or years.

Quantum computers are however very similar to Field Programmable Gate Arrays. They are specifically designed for one fixed algorithm at a time, but perform extremely well at it.

This means that it will likely be unable to run Far Cry or Crysis, just like how bitcoin miners cant crack your passwords, nor Deep Crack can stream and record 4K video.

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**shadowalker125**
t1_j1m7r5w wrote

>Quantum computers are however very similar to Field Programmable Gate

Arrays. They are specifically designed for one fixed algorithm at a

time, but perform extremely well at it.

Wouldn't that make it more like an ASIC rather than an FPGA? Or can they be changed?

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**nagareteku**
t1_j1mfh79 wrote

Variables such as temperature of qubits, voltage and time of laser pulses can be changed. The arrangements of specific quantum gates can be varied as well. Unlike an ASIC, quantum computers can be reconfigured from time to time to fit the required algorithm.

For now, quantum computers are far from general-purpose, and even then it will be redelegated into a discrete "QPU" card similar to your GPU for quantum-related computing purposes.

Affordable room temperature and pressure superconductors will need to be mainstream before that happens.

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**squidmanwillie**
t1_j1opptr wrote

Did they ever solve the EC issues with quantum?

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**[deleted]**
t1_j1mw80o wrote

[deleted]

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**troyboltonislife**
t1_j1n1pa7 wrote

will this be used for machine learning at all? can these computers do the linear algebra used in machine learning?

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**nagareteku**
t1_j1nf075 wrote

Nobody knows what would happen in the future, but I would guess that in very niche use cases such as the Travelling Salesman problem (TSP). For classical computers the most commonly used is the Held-Karp algorithm that solves the TSP in just O(n^(2)2^(n)) compared to the naive (n!). The best quantum exact algorithm is Ambaninis algorithm at O(1.728^(n)) found in 2019.

Quantum chips can be used to accelerate machine learning for pathfinding AI that may face the TSP, such as for location app servers and self driving cars.

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**noideaman**
t1_j1ngjvs wrote

Notice, you didn’t reduce complexity to polynomial switching to quantum. We still don’t know if NP-Complete problems can be solved in polynomial time on a quantum computer. If I recall, the top theoreticians think no.

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**nicuramar**
t1_j1nv1yn wrote

Yeah, BQP (the problem class solved by quantum computers) is generally believed to be disjunct from NPC.

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**_Asparagus_**
t1_j1nkwct wrote

Ambanini's algorithm will almost certainly never be used practically. It relies on Grover search to achieve its speedup, which has been basically shown to not be practical in the foreseeable future (see here for example. Held-Karp isn't used in practice either, since the exponential complexity is detrimental very quickly, and instead heuristics are used (this usually for example what popular software like Gurobi does). So extremely unlikely that TSP will be something quantum will help us with

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**troyboltonislife**
t1_j1nlb5y wrote

is held karp an approximation or does it solve it fully?

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**_Asparagus_**
t1_j1njvo6 wrote

No, it won't. ML applications of anything quantum are extremely limited, especially in this regime of qubit numbers.

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**troyboltonislife**
t1_j1nllvd wrote

I guess I am not fully understanding of what calculations these computers are good for? I guess I thought they would be able to do something like linear algebra (multiplying many numbers together quickly) but it sounds like no

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**nicuramar**
t1_j1nv8jm wrote

The are good for solving problems in a class called BQP. There is a list here: https://cstheory.stackexchange.com/questions/31139/problems-in-bqp-but-conjectured-to-be-outside-p

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**professorDissociate**
t1_j1n60ey wrote

I feel like AI will eventually be something that really takes off thanks to QPUs.

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**craigularperson**
t1_j1ncqps wrote

Okay, now explain it to me like I am five?

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**nagareteku**
t1_j1ngso4 wrote

Quantum chips will solve some math problems faster than normal computers. It is unlikely these chips will be used to run computer games.

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**BronzeHeart92**
t1_j1ptn6m wrote

One can only imagine tho what sorts of games these would have in future...

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**Gekokapowco**
t1_j1ngg4m wrote

Is it like a really fast CPU? Exceedingly fast at doing a single, potentially complex task? Vs a GPU which can do a lot of simple tasks at once?

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**km89**
t1_j1ohf92 wrote

Sort of, but not really.

It could be faster than classical computers at a specific task, yes.

But it's not just churning through the same steps a classical computer would, faster than a classical computer would. It's something entirely different, which is why the biggest benefit is likely going to be the simulation of systems we can't currently simulate.

So it's not like a really fast CPU, the way a car is a faster vehicle than a horse. It's more like a petting zoo versus a conservation zoo. Some of the same things are present in both, but they really have almost entirely different purposes.

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**Extension_Bat_4945**
t1_j1nrzrc wrote

What I do wonder tho is, how will all these investment return itself? I can’t imagine a good business case for now…

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**danielravennest**
t1_j1qusz1 wrote

Quantum computers have the potential to solve certain kinds of problems faster than regular computers. IBM is a computer company, so they are investing in quantum computer research. Sometimes research doesn't pay off, but you never make progress unless you try.

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**Extension_Bat_4945**
t1_j1rgsml wrote

I get that, but normally companies mostly invest in technology/research that will profit in the future. And I’m sceptical quantum computing can return the investment, as I don’t see a business model yet and the investment has been huge.

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**maqp2**
t1_j1tlzza wrote

One extremely useful purpose is protein folding which is what IBM (that the article is about) is also doing: https://protein-folding-demo.mybluemix.net/

the tl;dr is it will result in much faster faster medicine/vaccine development.

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**nicuramar**
t1_j1nuwen wrote

> Simulations and cryptography mainly. It might have potential to reduce time complexity of algorithms from exponential to quasi exponential or even polynomial time (n-bit encryption).

Yeah, so cryptanalysis, not cryptography (encryption, decryption, signing, verifying) so much. Cryptanalysis is however still completely infeasible on today's quantum computers.

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**[deleted]**
t1_j1nvy20 wrote

[deleted]

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**workerMcWorkin**
t1_j1orozx wrote

Does this mean that quantum computers could handle redundant loads in massive proportions?

I’m thinking replacing servers and such.

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**pm_me_wet_kittehs**
t1_j1qfjt9 wrote

pretty much anything that current tech can do efficiently, is not a problem a quantum computer can, and vice versa.

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**Goliath--CZ**
t1_j1nuj32 wrote

So you're saying that there might one day be a quantum computer that can only run crisis extremely well?

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**CreamofTazz**
t1_j1m59n4 wrote

So far quantum computers are only really good at solving complex math equations faster than digital computers

Mind you a lot of encryptions are just really complex math equations that your computer is given the answer to. Because QCs use superpositions of qubits (meaning they're in a complex state of 2 or more variables) they're able to hold significantly more information per qubit than a bit (which is just a single state of 0 or 1).

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**nagareteku**
t1_j1mhvgd wrote

Qubits do not store any more information than bits, it is just that the representation of n qubits requires 2^(n) bits because there are 2^(n) different combinations that n qubits can take.

Qubits "store" just as much information as bits, the primary difference is that qubits have a probability of being observed at both states at once. Consider a 2-level state qubit with state |0> ground and |1> excited. A quantum state can be a normalised linear combination of |0> and |1>. It does not consist of every single state similar to how a pair of spinning D20s does not store all 400 possible combinations.

When observed, the qubit collapses to either |0> or |1> with their respective probabilities depending on the observable. Repeated measurements will only show the same result, as predicted by the Born Rule due to wavefunction collapse. This means that while each qubit holds a superposition of both |0> and |1>, when measured, it will produce a fixed result of length 1 bit.

Such a system produces only probabilistic results, and not definite results from the classical computers we are used to. Quantum computing will make a lot of brute-force algorithms scale better, but it wont replace classical computers, nor provide a universal speedup or extreme amounts of storage. Furthermore, the larger the number of qubits, the harder it is to ensure that all qubits are properly isolated from each other.

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**nicuramar**
t1_j1nvke3 wrote

> Qubits do not store any more information than bits

How don't they, though, when each qubit requires a complex number (with modulus 1) to describe? Even if this information isn't directly available to measurement.

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**Shorts_Man**
t1_j1oekjw wrote

Are quantum processors only good for one calculation since all the qubits are collapsed afterwards?

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**sirbruce**
t1_j1mx8i3 wrote

> it wont replace classical computers, nor provide a universal speedup or extreme amounts of storage.

That's a very bold and definitive statement about future technology. In truth no one can really know what quantum computing might enable in the future.

Also, for someone making definitive statements,

> due to wavefunction collapse

is an odd choice of phrase given that wavefunction collapse is ill-defined and not even proven to actually exist.

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**skittlesmcgee33**
t1_j1n8rvb wrote

What I’m most excited for is simulations of quantum systems - particularly in biotech. Today we can only really model the simplest of molecules accurately. There’s just too many degrees of freedom we can’t accurately predict within a quantum system.

And in biology form = function. Know how it’s structured, and you can know how it’ll behave. Will be huge for new treatments.

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**n351320447**
t1_j1mdqai wrote

Cracking bitcoin

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**nagareteku**
t1_j1mjlky wrote

Maybe the US government already has the capability to crack SHA256 hashing and AES encryption using quantum computing accelerators. This could be old declassified technology.

If ₿ had been cracked there are far more significant vulnerabilities that would be uncovered. A malicious actor would keep the technology secret while gaining remote access to banks and numerous computing devices.

I believe that while quantum computers have not yet been used to mine or steal bitcoins, it is an eventuality and a large pot of gold for malicious uses of quantum computing.

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**StinkiePhish**
t1_j1n9bhj wrote

It will crack elliptic curve cryptography before hashing or symmetric encryption (AES). For bitcoin, that means the secp256k1 curve.

It's estimated that 2,330 qubits *with error correction* are needed to crack secp256k1. This IBM computer does not have error correction so we're not near half way there.

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**KAMSPioneer**
t1_j1noanj wrote

Totally. Just to be clear for the thread, a useful quantum computer will break ECC way, *way* before AES or SHA2.

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**pm_me_wet_kittehs**
t1_j1qg1oa wrote

for symmetric algorithms, a quantum computer would turn 256 bits of security into the equivalent of "Only" 128 bits. Double the key length amd any advantage just goes up in smoke. quantum won't help in a practical manner for AES

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**maqp2**
t1_j1tmb9l wrote

Also, SHA256 does lossy compression, and obtaining preimages larger than 256 bits can not be done at all, QC or not.

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**nicuramar**
t1_j1nvptv wrote

> Maybe the US government already has the capability to crack SHA256 hashing and AES encryption using quantum computing accelerators. This could be old declassified technology.

That's extremely unlikely to be the case. Especially since quantum computers don't provide any useful speedup for those applications.

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**lunartree**
t1_j1mdyez wrote

Breaking encryption.

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**RubberPny**
t1_j1m6m33 wrote

IIRC they are super useful for financial number crunching and forecasting.

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**N3UROTOXINsRevenge**
t1_j1nptvx wrote

How the hell says fry cry? It’s either doom or crysis.

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**eggybread70**
t1_j1nrqem wrote

Oops. I fucked up. You're right, it should be Crysis.

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**eggybread70**
t1_j1mhp30 wrote

Thanks, nerd bros.

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**Alucard256**
t1_j1mjei6 wrote

The most simple answer I can come up with is this: "classical computers" (as they are now known) work with 0's and 1's only, which can be thought of as "yes" and "no" *only*. Which in turn makes them great at anything with definite in inputs and leads to everything computers can do today. The problem is, it makes them very bad at anything that needs to deal with "maybe" and "probably" at all.

Quantum computers in contrast, work exclusively with "maybe" and "probably". Which means things like "true AI" (like C-3PO) will be possible. Weather forecasting will get *MUCH* better. Machines won't be limited to doing "exactly what you said"... they will be able to "do what you meant". Anything having to do with "probability" instead of "certainty" (which is currently nearly impossible to work with) will suddenly be as easy as using Excel to record item prices and produce an average.

In addition to all of that, quantum computes work with much more information at a time. Again, keeping it very simple: classical computers work with individual bits to make a byte which represents (roughly) a single letter or number; quantum computers can work with entire *concepts* at a time.

All of this is also why "what kind of solutions will it excel at?" is a really hard question. It's like trying to come up with answers about what the internet will be good for... in 1910 or so.

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**Treczoks**
t1_j1mzvci wrote

Primarily just quantum benchmarks and academic uses. Those toys are still years from being even remotely useful for real-world, practical calculations.

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**dutch_meatbag**
t1_j1nmoyc wrote

That was a blast from 2004.

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**Sk8nk**
t1_j1mtqtw wrote

Creating holographic wormholes.

Physicists Create a Holographic Wormhole Using a Quantum Computer

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