Talk:Quantum computing/Archive 2

This youtube video discusses a paper by google employees,^[1] which claims or demonstrates the computational advantage of D-Wave's quantum annealing concept, and I don't yet see it being discussed in the article. JMK (talk) 19:40, 3 September 2017 (UTC)

who will fix it?Juror1 (talk) 17:53, 30 November 2017 (UTC)

It seems like this article would benefit from explaining how quantum computers work physically. I assume they manipulate individual atoms, but how?

It seems to me that nobody really knows how it (sort of) works. It seems the researchers in the lab are playing with atomic scale phenomena that they don't fully understand. Since these researchers were trained to believe in quantum theory as the undisputed truth they preach their religion as fact. In the end they create mechanisms that can do some sort of awkward computing and they call these mechanisms "Quantum Computers". — Preceding unsigned comment added by 31.168.26.225 (talk) 15:39, 15 June 2016 (UTC)

Comment so that archiving will work. (Answer already in article.) — Arthur Rubin (talk) 12:28, 31 May 2015 (UTC)

and where is the critique section of this article? — Preceding unsigned comment added by 75.163.218.83 (talk) 05:12, 4 September 2015 (UTC)

i second that nomination , do you know that so called supercomputers are idle most of time. having more states doesnt not equate to efficiency, and superpostion collapse implies even less output. less states. Juror1 (talk) 17:59, 30 November 2017 (UTC)

Agreed. In the overview we find the statement: "Quantum computers share theoretical similarities with non-deterministic and probabilistic computers." Wow. Do you seriously suppose that the normal Wikipedia reader has any clue about determinism or probabilistic systems? Why even write something like that at the top of an article. Anyone who already knows about determinism, etc., also (probably) has some knowledge about Quantum Systems. The author of that statement could not do any better at pushing casual readers away from this topic. If anything, we need to draw more people into Computer Science in general, and bleeding-edge research in specific. Bloviation like the statement I referenced does much more harm than good by immediately throwing out arcane, industry-specific terminology. It literally turns readers off. I'm a computer scientist / engineer by education and trade, and it turned me off Big Time. Come on people. Write something that actual people can read and comprehend. Use your words. And not the 3-dollar ones, either. Plain English will do just fine.

There's an old-saying about being able to explain something in simple terms ... If you can't, you probably don't understand the subject yourself. Cheers. — Preceding unsigned comment added by 98.194.39.86 (talk) 03:44, 25 October 2016 (UTC)

The first two sentences read:

Quantum computing studies computational systems (quantum computers) that make direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from binary digital electronic computers based on transistors.

I changed to:

Quantum computing is computing using quantum-mechanical phenomena, such as superposition and entanglement. Quantum computers are devices that perform quantum computing. They are different from binary digital electronic computers based on transistors.

This was reversed with the motivation that the previous version "reads better". Here is my motivation for why my version is better:

It is shorter. It is divided into more sentences. (It is a well established fact that shorter sentences are easier to read.) It says what the article is about. The previous version assumes, but does not say, that QC is a subject area. It says that QC is a phenomenon and not the study of this phenomenon. Isn't it decided that the phenomenon itself is more important than the study of it? Removing to perform operations on data makes it shorter, which is good. The first sentence should never use a word that is so difficult that it needs to be explained in the same sentence. (Because the first sentence should be as short as possible.) I think computing is OK. If it is too difficult for the reader, then reading the article about computing first is necessary to understand this article. --Ettrig (talk) 11:42, 13 December 2017 (UTC)

https://www.dwavesys.com/d-wave-two-system
Isn't this a real Quantum Computer ? With 2000 Qubits !!!! It seems to me like they and NASA once and for all have solved the necessary superconducting problem, through vacuum. No particles is no temperature - and the superconducting problem solved - !???
Although expensive, large companies can afford them - and make more money perhaps ? Boeing720 (talk) 00:31, 19 December 2017 (UTC)

The D-Wave device is not a universal quantum computer, see D-Wave Systems#Controversy. Luca (talk) 09:16, 19 December 2017 (UTC)

I'd like to join the chorus asking for a bit more content pitched to the educated layman. In particular, one point that brought me here in an unsuccessful search for an explanation doesn't seem to be found.

I second the call for a worked-through 3-qubit problem if that's feasible. That might help me visualize how, when the superposition collapses, you know that you are observing the solution to the problem you were running on the quantum computer. That seems to be saying that there is only one possible position, which doesn't track with the idea of superposition. Grossly simplified, if the problem you are trying to solve is 2+2, how do you manipulate the qubits to collapse the probabilities down to 100% for 4? MvH took a stab at this in #14 on the talk page, but it was too general to make much sense to a layman.210.178.60.82 (talk) 12:41, 19 January 2018 (UTC)

The initial addition on Quantum Supremacy (16:54, 5 July 2017 by user Schlafly) provided a definition of the term, and seemed to add additional information to the base subject matter of quantum computing. On 13:29, 12 December 2017, user 185.78.8.131 edited the section and added material relating to assertion of controversy about the concept of Quantum Supremacy, and apparently to quantum mechanics in general.

First, controversy is fine and I feel it should be placed into it's own section rather than being post-pended to an existing one. However, it may better placed in the article on quantum mechanics where it may receive a greater level of review.

Second, the sentence starting with "Those such as Roger Schlafly," caught my attention. Wondering to whom "those" referred, I checked the three references given, and found them to all point to a blog authored by Schlafly. To me, this seems to run afoul of original-research and or NPOV and or reliable sources.

So I've flagged this section with POV-section. — Preceding unsigned comment added by Debrown (talk • contribs) 17:27, 1 February 2018 (UTC)

non fundamental mimicking of the shared noise attractor which may include a percentage of constant values (some percentage of the time the attractor is activated, so we have pseudorandom data within a range of values, and some percentage of the time the machine runs, a constant value is appearing according to the entaglement angles chart, but a randomizer selects among a. the pseudorandom data of the attractor and b. the constant value - a. and b. have standard percentages of activations, but they appear randomly via a randomizer - we have to run the program many times in order we average the results.)

This isn't an actual quantum computer but a Pseudoquantum one.

It's useful for some problems. — Preceding unsigned comment added by 2A02:2149:8430:F500:24AD:8759:82E7:D432 (talk) 16:23, 9 February 2018 (UTC)

and how to find the correct constant number and the correct attractor (at the beginning you can start with known problems and use it for educational reasons, then you can upgrade the system) — Preceding unsigned comment added by 2A02:2149:8430:F500:24AD:8759:82E7:D432 (talk) 16:31, 9 February 2018 (UTC)

in some problems random (false/erroneous)solution testing is helpful

in bigger problems it doesn't work well — Preceding unsigned comment added by 2A02:2149:8430:F500:24AD:8759:82E7:D432 (talk) 16:38, 9 February 2018 (UTC)

Analogue systems add more noise... but it's better than nothing. analogue logic gates allow interference phenomena to occur. You run it many times and all percentages of voltage per order of digit must be described by their lower order of significance digits (and some information is lost + we have noise) — Preceding unsigned comment added by 2A02:2149:8888:3A00:A10A:46B7:5026:A29A (talk) 00:30, 17 February 2018 (UTC)

we don't have 0 and 1 but values from 0% to 100% and when we have less than 100% the digit has to become zero and the lower ranked digits should express now with absolute zeros and ones the number

the initial percentaged analogue digits should communicate with analogue logic gates and a random generator which is activated sometimes, and an other random generator shuffles the percentages of entagled configuration vs pure noise

• sometimes we have 40% entaglement and 60% noise, we shuffle though the modes of operation with another randomizer
• the entaglement can be the same number, the opposite number, or any known standard logic operation

With the recent surge of interest in quantum computing, an increasing number of readers come to this article to learn what quantum computing is. But this article isn't as good as it could be, and I think it can be significantly improved. Maybe we can discuss some concrete proposals to improve the article? If we have reasonable consensus on some proposals, someone can go ahead and make changes. My suggestions are

1. Merge the long Timeline section with the article Timeline of quantum computing and remove it from this article.
2. More ambitiously, restructure the sections after the lede to clearly answer the questions a reader may have. I think the answer to many of these questions are already in the article, but some of them are hard to find. Some questions a reader may have:
   1. "What is a quantum computer?" (explain what it is)
   2. "Why do we want to build a quantum computer?" (describe applications and motivation for building one, examples of problems that can be solved exponentially faster on a quantum computer, etc.)
   3. "How are quantum computers made?" (discuss physical implementations, such as ion traps, etc., and the challenges in building a quantum computer)
   4. "Who is building quantum computers?" (Companies, universities, etc., perhaps with some examples. This could be part of the previous section, with examples of who is using which technology. E.g., Company X and Prof. Y at University Z are building quantum computers from ion traps.)
   5. "Where can I learn more?" (a short, curated further reading list with some guidance would be great; e.g., we should distinguish between popular science articles for the lay person, detailed overview articles for more interested readers, textbooks for undergraduates and grad students, etc.)
3. We could follow the model of having a high-level encyclopedic overview in this article, and a more detailed explanation of what quantum computing is in another article, as done by quantum mechanics and introduction to quantum mechanics, and general relativity and introduction to general relativity (both of which are featured articles!).

That's all I can think of for now, but I'm sure others probably have concrete proposals to improve this article as well. Let's discuss them! — Robin (talk) 18:09, 20 May 2018 (UTC)

"The calculation usually ends with a measurement, collapsing the system of qubits into one of the {\displaystyle 2^{n}} 2^{n} eigenstates, where each qubit is zero or one, decomposing into a classical state.'

This is way too complicated for me, and I'm not exactly new to algorithms.

Please tell how quantum computing works in laymen's terms. Like: "For example, if quantum computers had enough bits you could encode the Travelling Salesmen problem for 5 cities like this, and after such and such trick, and measuring the qubit 1 to 5, by simply ordering the probabilities you'd have the perfect route."

Joepnl (talk) 00:10, 13 June 2018 (UTC)

I find it odd that Yuri Manin is listed as the first person to propose the idea of quantum computation. The reference given is a 1980 book on (classical) computability which makes a brief mention (only in its preface!) of the possibility of using quantum effects for computation. Nowhere in the body of that book is quantum computing discussed. The idea of using quantum effects for computation was already articulated in Feynman's 1959 talk There's Plenty of Room at the Bottom:

Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics. So, as we go down and fiddle around with the atoms down there, we are working with different laws, and we can expect to do different things. We can manufacture in different ways. We can use, not just circuits, but some system involving the quantized energy levels, or the interactions of quantized spins, etc.

The current timeline is dubious and needs to be fixed. Feynman's 1959 talk is the earliest reference I know of (and is cited in the Britannica article on quantum computing), but there may be others. Would anyone care to comment/suggest other possible early references on using quantum effects in computing devices? Stablenode (talk) 17:01, 21 April 2018 (UTC)

Following up, an English translation of Manin's entire discussion of quantum computation in his 1980 book is given in Manin's own 1999 paper Classical computing, quantum computing, and Shor's factoring algorithm. It is literally 3 paragraphs long.

The following text is a contribution to the prehistory of quantum computing. It is the translation from Russian of the last three paragraphs of the Introduction to [Ma2] (1980). For this reference I am grateful to A. Kitaev [Ki]. “ Perhaps, for better understanding of this phenomenon [DNA replication], we need a mathematical theory of quantum automata. Such a theory would provide us with mathematical models of deterministic processes with quite unusual properties. One reason for this is that the quantum state space has far greater capacity than the classical one: for a classical system with N states, its quantum version allowing superposition accommodates c^N states. When we join two classical systems, their number of states N1 and N2 are multiplied, and in the quantum case we get exponential growth c^(N1*N2). These crude estimates show that the quantum behavior of the system might be much more complex than its classical simulation. In particular, since there is no unique decomposition of a quantum system into its constituent parts, a state of the quantum automaton can be considered in many ways as a state of various virtual classical automata. Cf. the following instructive comment at the end of the article [Po]: ‘The quantum–mechanical computation of one molecule of methane requires 10^42 grid points. Assuming that at each point we have to perform only 10 elementary operations, and that the computation is performed at the extremely low temperature T = 3.10^−3 K, we would still have to use all the energy produced on Earth during the last century.’ The first difficulty we must overcome is the choice of the correct balance between the mathematical and the physical principles. The quantum automaton has to be an abstract one: its mathematical model must appeal only to the general principles of quantum physics, without prescribing a physical implementation. Then the model of evolution is the unitary rotation in a finite dimensional Hilbert space, and the decomposition of the system into its virtual parts corresponds to the tensor product decomposition of the state space. Somewhere in this picture we must accommodate interaction, which is described by density matrices and probabilities.”

Peter Shor in his 2000 arXiv article (Introduction to Quantum Algorithms) has a very clear summary of where Manin's contribution lies; it certainly cannot be said that he was the first to suggest the idea of quantum computing:

In 1982, Feynman [19] argued that simulating quantum mechanics inherently required an exponential amount of overhead, so that it must take enormous amounts of computer time no matter how clever you are. This realization was come to independently, and somewhat earlier, in 1980, in the Soviet Union by Yuri Manin [30]. It is not true that all quantum mechanical systems are difficult to simulate; some of them have exact solutions and others have very clever computational shortcuts, but it does appear to be true when simulating a generic quantum mechanics system. Another thing Feynman suggested in this paper was the use of quantum computers to get around this. That is, a computer based on fundamentally quantum mechanical phenomena might be used to simulate quantum mechanics much more efficiently. In much the same spirit, you could think of a wind tunnel as a “turbulence computer”. Benioff [5] had already showed how quantum mechanical processes could be used as the basis of a classical Turing machine. Feynman [20] refined these ideas in a later paper.

I propose the timeline be changed to reflect Feynamn's earlier observations in the 1950s and make it clear that Manin's short observation in 1980 was articulating a motivation for pursuing this approach to computing. To claim that Manin spawned the field is ridiculous. Stablenode (talk) 19:57, 22 April 2018 (UTC)

in my opinion the 1959 talk by Feynman has at best a very tenuous link to the field: there is no hint of exploiting quantum effects for computation in the talk, in the quoted section computing is not mentioned at all (it is earlier, but there only the potential of miniaturization is discussed, not quantum effects). So I think it's not correct to write that Feynman "states the possibility of using quantum effects for computation". Maybe one could say he implies it, but the reference to "different laws" that apply at the quantum level could just as well imply (as mentioned before in the talk) that they pose novel problems Compared to later contributions like those of Wiesner or Holevo that are very explicit about using QM for information processing and Feynman's 1982 talk, I find it a stretch to include "Plenty of Room" as having started this field. --Qcomp (talk) 18:02, 30 August 2018 (UTC)

As I have understood it, a Qubit state cannot be directly read. But this can be solved (I only have vague ideas of how), but even then errors may occur. The studied particle behaves according to a certain probability, which not always is correct. Nevertheless an error corrected Qubit can be obtained (somehow), and would then equal a logic Qubit. If I'm not all wrong here, the logic Qubit is very desirable, and could possibly be given a headline high up (?).
IBM predicted in May 2018 that Quantum Computing will be mainstream in five years according to this short video (press "play"). Are we inline with the progress of Quantum Computers from a society aspect ? Binary technology can still be used for decades ahead, in stand alone (embedded) system - but what about internet, as Quantum Computers comes for real. Let's say a 300 logic qubit machine, what would its impact on internet be ? Boeing720 (talk) 09:40, 25 December 2018 (UTC)

We start with some discussion about binary number, that 2^3 = 8. Then say that they are complex numbers, with the probability being the modulus. OK, but so what? Then a leap into vagueness.

It reads like it has been written by someone that read a quantum paper without understanding it, and picked out a few key words.

This is the nature of the topic. There is only either journalistic fluff or heavy research papers. There is thhe book by Neilsen which I may try to wade through if I have time, but like all this stuff it enjoys heavy mathematical treatment of simple ideas. (As an analogy, one does not need to start with partial differential equations in order to develop the idea that Apples fall off trees.)

So what is required for this article is someone that actually understands the topic, yet can write clearly. Sadly, I doubt if that person exists. Tuntable (talk) 02:13, 17 September 2018 (UTC)

I tend to agree. Boeing720 (talk) 09:42, 25 December 2018 (UTC)

Hello! I'd like to propose a few improvements to this Wikipedia article. But first, a disclosure, which is also displayed in the connected contributor template above: I am submitting this request on behalf of Intel via Interfuse Communications, and as part of my work at Beutler Ink. Given my conflict of interest, I'm seeking volunteer editors to review and implement the proposed content appropriately, and I will not edit the article directly. This request is related to another one I submitted here for the Timeline of quantum computing article, which has been answered already. I propose updating this article with the following claims to the "Timeline" section:

• Intel confirms development of a 17-qubit superconducting test chip.^[1]
• QuTech successfully tests silicon-based 2-spin-qubit processor.^[2]
• Intel begins testing silicon-based spin-qubit processor, manufactured in the company's D1D Fab in Oregon.^[3]
• Intel confirms development of a 49-qubit superconducting test chip, called "Tangle Lake".^[4]

Additional sourcing is available for each of these claims, but these were the sources preferred by the reviewing editor of the related edit request.

@Qcomp: Since you assisted with the other request, I'm curious if you're willing to review this one as well and update the article appropriately.

Thanks again for your consideration. Inkian Jason (talk) 19:44, 5 September 2018 (UTC)

Thanks for your suggestions and contribution. I have a problem with this whole section of the article. Given that the main article is Timeline of Quantum Computing this here should be, in my opinion, a very restricted subset of that more detailed timeline. It does start out that way but then quickly becomes a potpourri of big, small, and marginal advances full of marketing-speak; I think, the list should only contain a few items per "branch" (different implementations, algorithms, complexity results) that represent such big steps that the interested layperson can appreciate them clearly as progress. WHat's the opinion of other authors of this article? without a better idea what's the consensus here I'm reluctant to add to a list that I'd much rather shorten first. --Qcomp (talk) 13:39, 11 September 2018 (UTC)

Not an author, but I think that the general Wikipedia approach pushes towards keeping things simple. The major advancements in the field of quantum computing should be enough to provide information to the reader, and "minor" ones can be kept in the timeline. #!/bin/DokReggar -talk 14:06, 11 September 2018 (UTC)

@Qcomp and DokReggar: Thank you both for replying. I see what you mean regarding redundancy between this article's "Timeline" section and the Timeline of quantum computing article. The reason I'm attempting to add details about Intel's work is because the company is currently not mentioned at all, yet "IBM" appears in the article's prose approximately 30 times. I am not sure what the criteria are for inclusion, but my goal was to make this article more equitable. Are there ways to address this imbalance? Inkian Jason (talk) 21:33, 11 September 2018 (UTC)

I agree that the timeline is unbalanced; in my opinion, what we should have is maybe one entry saying that beginning in 2012, major technology companies such as IBM, Google, and Intel made significant investments in the construction of quantum computers based on superconducting qubits and announced in rapid succession the availability of devices with several tens of qubits. Maybe it would also make sense to add to the timeline here only with one year delay, picking the few most relevant contributions out of the more extensive main Timeline-article. However, I think a renovation of the section has to be discussed further (and I don't have time right now to attempt it). For the time being, I think it's appropriate to include the announcements on the spin-qubit processor, because it's (to my knowledge) the first contribution of a major commercial actor to this implementation. As a test balloon for a more sparse way of reporting the timeline here, I'd propose an entry:

In late 2017 and early 2018 IBM^[1], Intel^[2], and Google^[3] each reported testing quantum processors containing 50, 49, and 72 qubits, respectively, all realized using superconducting circuits. These circuits are approaching the range in which simulating their quantum dynamics is expected to become prohibitive on classical computers, although it has been argued that further improvements in error rates are needed to put classical simulation out of reach.^[4]

let me know what you think. --Qcomp (talk) 10:41, 12 September 2018 (UTC)

Seems good and terse enough for me. Thanks for your work! #!/bin/DokReggar -talk 13:19, 12 September 2018 (UTC)

@Qcomp: Thanks for proposing specific wording for a summary. I certainly understand your preference to summarize where appropriate. Do you mind clarifying what exactly is being trimmed in favor of the suggested wording? Thanks in advance. Inkian Jason (talk) 20:40, 12 September 2018 (UTC)

sure; I'm proposing to replace the "November 2017" (IBM), March 2018 (Google), and your proposed January 2018 (49 qubit chip) entries by the one given above. I would argue that these three announcement have some significance due to the approach to the supposed "no-longer-simulable" threshold, though there is of course no hard threshold and in quoting only the number of qubits and not the achieved qubit lifetimes and gate fidelities (especially compared to the smaller devices before: do we see scalability in that the fidelities stay constant even though the system gets bigger?), it's not clear how big a step they really represent. In a few years time, neither the small difference in number nor in time of announcement will seem important, that's why I think a single entry is appropriate.
If the change does not meet with resistance I would then (slowly) try to concentrate the timeline here to a few major scientific and technological advances. E.g., I do not see the point of pure business announcements like the one of April 2018 in this timeline, but it would be etter if we could develop some set of criteria here what should be included in the timeline. --Qcomp (talk) 21:54, 12 September 2018 (UTC)

@Qcomp: OK, thanks for clarifying. Your summary seems appropriate. Inkian Jason (talk) 22:44, 12 September 2018 (UTC)

I see the summary was added with this edit. Thanks again for your help. Inkian Jason (talk) 15:18, 17 September 2018 (UTC)

I'm a bit late to this discussion, but I agree that this section is just far too cluttered for this article. Given that we already have a timeline of quantum computing, I'm in favor of drastically cutting this section down to a paragraph or two. --Robin (talk) 05:18, 28 January 2019 (UTC)

Does this mean "in EVERY superposition of up to {\displaystyle 2^{n}} 2^{n} different states simultaneously"? If not, surely "an arbitrary superposition" is exactly ONE superposition state, and being on one state "simultaneously" does not seem meaningful. JohnjPerth (talk) 00:42, 28 January 2019 (UTC)johnjPerth

I think the word 'simultaneously' is a bit redundant and confusing. I think a 'superposition' is intrinsically being partly in many states simultaneously.

118.209.183.247 (talk) 07:37, 12 March 2019 (UTC)

In Further Reading, I added... *Lloyd, Seth (2006) Programming The Universe, Alfred A. Knopf. 2601:580:106:5243:34B1:52ED:44D3:4115 (talk) 12:08, 11 May 2019 (UTC)

The Lede section says: "nor have commercially useful algorithms been published for today's small, noisy quantum computers."

How small? Like 2 qubits? 16? Is that how "size" is measured? This is the critical paragraph that explains if we are talking dreams or reality. More should be said on that — explicitly. See also MOS:LEDE.
--2602:306:CFCE:1EE0:81AE:F280:6717:4833 (talk) 16:05, 8 September 2019 (UTC)JustAsking

The Basic paragraph mentioned a keyword eigenstate(s). Please give inline citation on that because that paragraph is supposed to be read by as a "Basic", by a person who probably never learnt quantuam mechanics. --Kittyhawk2 (talk) 07:56, 26 September 2019 (UTC)

Reuters has an article on disagreements about the Google claims: https://www.kitco.com/news/2019-10-23/Google-claims-quantum-supremacy-others-say-hold-on-a-qubit.html Kdammers (talk) 03:31, 27 October 2019 (UTC)

https://en.wikipedia.org/wiki/Quantum_computing#Timeline will be a never-ending list that will take up most of the page. Some of the most important information have already been repeated throughout this article. Do you have objections? Vtomole (talk) 16:01, 20 November 2019 (UTC)

I agree: there should be a (regular text) section about the development of quantum computing since the 1980s, but not a newsticker as it is now (except for the time until 1996 - but even there items like QKD and quantum teleportation do not belong. And having already Timeline of quantum computing is enough - there's no need to have two lists without clearly defined and distinct criteria on what belongs on which --Qcomp (talk) 18:44, 20 November 2019 (UTC)

No objections. I personally dislike the "thousand small paragraphs" style. Maybe decide what is truly essential and keep that in 3-4 paragraphs and move the rest into Timeline of quantum computing, if it isn't already there. BernardoSulzbach (talk) 17:15, 23 November 2019 (UTC)

Hi all, I've created a new account largely to fix up this mess of an article. Please see my user page for information about me.

I've done a fairly thorough rewrite of the introduction and the (now renamed) Basic Concepts section. I will try to find time over the next few weeks to rewrite most of the rest of the article. To be clear, the article as it was written was full of fairly egregious misconceptions. It is clear that no expert has helped out for a long time. I'm fairly knowledgeable about the subject and decided that I'm going to do it if no one else is going to.

I am not an experienced editor of Wikipedia, so I would appreciate it if anyone better connected than me can put me in touch with an experienced editor. I would gladly work with that person to make this article a worthy exemplar of Wikipedia as a whole. As it stands, I think the article is an embarrassment to the quantum computing community. We should never have allowed the article to persist like this for so long.

I regularly use Wikipedia for research as well as personal reasons, and I don't donate as often as I should. Let this effort stand as my contribution to the Wikipedia project.

Yuval Rishu Sanders (talk) 11:01, 27 September 2019 (UTC)

Thank you for your work, it is good to have experts editing technical articles. I watch this page but have never contributed to it other than reverting vandalism. A small tip for editing: as you can see here, [[voltage]]s (voltages) produces the same as [[Voltage|voltages]] (voltages) yet is simpler and cleaner. BernardoSulzbach (talk) 14:12, 27 September 2019 (UTC)

Very nice that you want to clean the article! Please can you comment on my last edit, in particular why Google removed this artice and materials to it?ZBalling (talk) 21:03, 27 September 2019 (UTC)

Just getting onto this now. The Google article was never intended to be publicised, and was leaked to the media via NASA only by mistake. It wouldn't be appropriate for me to comment further. I appreciate the other comments on how to edit Wikipedia properly, and I'm glad that experienced editors can be checking to make sure I do a good job. Yuval Rishu Sanders (talk) 08:03, 7 October 2019 (UTC)

I've finished up the next stage of this rewrite, which is to replace the confusing and incorrect pair of sections on quantum operations with a more reasonable introduction to quantum logic gates. I am aware that the current presentation could be too technical and I would appreciate any non-expert comments and criticisms.

In the next stage of this project, I hope to write something about the basic idea of how we implement quantum operations. To give away the punchline, I tend to explain this in terms of Schroedinger's equation and pulse shaping. That section is a bit harder to write because very few authors think to say how quantum computers are suppose to work at a purely abstract level. Those discussions are usually focussed on one possible implementation or another, which is a shame because the underlying principle isn't hardware-specific. Yuval Rishu Sanders (talk) 10:07, 7 October 2019 (UTC)

I've reviewed your edit and improved on some minor points. As suggestions, I recommend checking out MOS:WE and MOS:NOTE. As I said in my previous comment, you should try to simplify links when you can, as in . BernardoSulzbach (talk) 14:28, 7 October 2019 (UTC)

Thanks. Apologies for links, I’ve been using the rich text editor. I’m still learning the wiki markup language, whatever it’s called. I’ll take a closer look at your suggested links. Again, thanks for the help. Yuval Rishu Sanders (talk) 23:03, 24 October 2019 (UTC)

"I’ve been using the rich text editor." I honestly thought it would generate better markup. Ultimately, as long as the text is correct, verifiable and good to read, the technical details will get resolved in the long-term. Thank you for your work. BernardoSulzbach (talk) 14:26, 25 October 2019 (UTC)

I've made some edits in the hopes of improving the style. I'm sure it's not yet up to snuff, but I think I've dealt with some of the major concerns. It would be good to get a few people involved with this project, and I'll start asking around. Yuval Rishu Sanders (talk) 05:10, 4 January 2020 (UTC)

MOS:INTRO says that opening paragraphs should avoid "difficult to understand terminology" and that "the average Wikipedia visit is a few minutes." I expect that this article is visited by many non-scientists looking for a very high level explanation and an overview of what's currently possible. Such readers will not get very far past references to Turing Machines and Lambda Calculus. How can the introduction to such a technical concept be rewritten for readers with only introductory (or no) relevant background? I suggest moving the contents of the Basic concepts section to the opening paragraphs, and demoting the more technical definitions and historical content to lower in the intro, or elsewhere in the article. Do editors agree? Bosons (talk) 16:55, 4 January 2020 (UTC)

If I understand this correctly, it is proof there there is in fact a category of problems only solvable and testable by quantum machines, that a standard computer would not be able to solve regardless of time or complexity available^[1][2]. David Duetsch's 1985 paper [page 5] states "The fact that classical physics and the classical universal Turing machine do not obey the Church-Turing principle in the strong physical form (1.2) is one motivation for seeking a truly quantum model"^[3]

"Any computational problem that can be solved by a classical computer can also, in principle, be solved by a quantum computer. Conversely, quantum computers obey the Church–Turing thesis; that is, any computational problem that can be solved by a quantum computer can also be solved by a classical computer. While this means that quantum computers provide no additional advantages over classical computers in terms of computability, they do in theory enable the design of algorithms for certain problems that have significantly lower time complexities than known classical algorithms. Notably, quantum computers are believed to be able to quickly solve certain problems that no classical computer could solve in any feasible amount of time—a feat known as "quantum supremacy." The study of the computational complexity of problems with respect to quantum computers is known as quantum complexity theory."

--KyleBrochu (talk) 21:10, 30 June 2020 (UTC)

Hmm, the 1985 paper may conflict with what is stated on the page, but it also may not. The introduction states:

"Computing machines resembling the universal quantum computer could, in principle, be built and would have many remarkable properties not reproducible by any Turing machine. These do not include the computation of non-recursive functions, but they do include‘quantum parallelism’, a method by which certain probabilistic tasks can be per-formed faster by a universal quantum computer than by any classical restriction of it."

I'm not sure that this is a refutation. He doesn't claim that there are undecidable problems that a quantum computer can solve or claim that quantum computers do not satisfy the standard definition of the Church-Turing Thesis (what he calls the "conventional, non-physical view" of the thesis). Rather at first glance what he appears to do is define a new stronger, "physical version of the Church- Turing principle" (he explicitly states "I propose to reinterpret Turing’s 'functions which would naturally be regarded as computable'"), which is: "Every finitely realizable physical system can be perfectly simulated by a universal model computing machine operating by finite means". He then says that classical computers do not satisfy this stronger principle but conjectures that quantum computers do. I'm not sure now how exactly to judge this and will have to look more into this paper.

The reference provided in the section on computability (Nielsen pg. 126), however, is more straightforward. It states:

"Quantum computers also obey the Church-Turing thesis. That is, quantum computers can compute the same class of functions as is computable by a Turing machine. The difference between quantum computers and Turing machines turns out to lie in the efficiency with which the computation may be performed".

This appears to corroborate the claim made on this page. Online it is actually fairly difficult to find an answer to this problem as research overwhelmingly deals with complexity and very little with computability. Lots of online forums agree with this page, but those are obviously not reliable sources and it is certainly possible that they are agreeing with Wikipedia precisely because they based their answer on what they read on Wikipedia.

And on the other two articles you provided, they do not conflict with the page. They state that there are problems that a quantum computer can solve that classical computers cannot feasibly solve, i.e. it takes too much time; they do not state that a quantum computer can solve a problem a classical one cannot. Look at the important qualification in the title of the first article: "Finally, a Problem That Only Quantum Computers Will Ever Be Able to Solve". The title includes "ever be able to solve" because the article then goes on describe how the researchers "prove, with a certain caveat, that quantum computers could handle the problem efficiently while traditional computers would bog down forever trying to solve it." In other words, they are merely saying the researchers have identified a problem that would take a classical computer infeasibly long to solve. That's why the article then goes on to talk about the complexity classes BQP and PH—because they're talking about time complexity, not computability. The second article you provide similarly discusses the separation of BQP and PH (it asks in the introduction: "Can polynomial-time quantum algorithms be simulated by classical algorithms in the polynomial-time hierarchy?"); it is not speaking to computability.

--Jaydavidmartin (talk) 23:56, 13 October 2020 (UTC)

its interesting how quantum computing is getting so nuch more attention and discussion than neuromorphic computing even though neuromorphic computing technology is closer to bieng available to the public. — Preceding unsigned comment added by RJJ4y7 (talk • contribs) 14:50, 29 November 2020 (UTC)

Hi,

About the reference supporting the claim that quantum computers can solve any problem which can be solved by classical computers, actually talks about 'hybrid' computers, which allow classical computers as a special case.

Yes, if you make a definition of quantum computer that includes classical computers as a special case this claim becomes true.

That is like saying "Petrol cars can have the same carbon efficiency as electric cars" by having a reference to Hybrid cars, point being you can turn off the engine!

Can someone support the sentence with a better reference? Current news about China's recent quantum computer says it calculates *one* array of numbers only (to a better accuracy and speed than a classical computer can).

Createangelos (talk) 10:44, 7 December 2020 (UTC)

Apologies, I interpreted the statement as being about abstract classical and quantum computers, not quantum computers in the practical, real-world sense. Would phrasing like "In terms of abstract computing models, any computational problem solvable by a classical computer is also solvable by a quantum computer." help? This is roughly the phrasing used further down the page in the "Computability theory" section. Fawly (talk) — Preceding undated comment added 12:10, 7 December 2020 (UTC)

Thanks for saving my blushes and only privately notifying me that I clicked the wrong reference! I like your distinction between abstract vs classical. The Nielsen reference does seem to elide quantum computing with reversible computing a bit, but I have not fully read it yet.Createangelos (talk) 16:52, 7 December 2020 (UTC)

Is this considered RS? https://gadgets.ndtv.com/laptops/news/quantum-computer-china-supremacy-google-sycamore-billion-trillion-times-faster-supercomputer-2334255 If it is, maybe we should include the claim. Charles Juvon (talk) 21:41, 5 December 2020 (UTC)

This article just came out in Science: https://science.sciencemag.org/content/early/2020/12/02/science.abe8770 Charles Juvon (talk) 02:48, 6 December 2020 (UTC)

Discussion of this might better belong in quantum supremacy; as far as I can tell, this new device isn't a universal quantum computer, it's more like a machine for demonstrating quantum supremacy. Fawly (talk) 03:33, 6 December 2020 (UTC)

I agree. Charles Juvon (talk) 19:38, 6 December 2020 (UTC)

Regardless of whether it should primarily be in quantum supremacy, it should at least be mentioned here, since people running across articles on it are most likely to come here to check it out. Kdammers (talk) 16:29, 15 December 2020 (UTC)

Hello, I was wondering if it would be a good idea to add in a portion that is related to how quantum computers are implemented in the real world. The main thing I was left curious about after reading was how qubits are present within the quantum computer and how it is actually made. This can also be expanded to have a direct comparison between a quantum computer to the current computers we have now. — Preceding unsigned comment added by EddyLuceddy (talk • contribs) 02:03, 4 April 2021 (UTC)

The introduction says that digital quantum computers use quantum logic gates. I believe that quantum computers are analog "when you are not looking", and digital "when you are looking". Or, alternatively and maybe more accurate, measurement of a qubit register causes its quantum state to collapse such that it is lined up with the basis vectors (the basis vectors labels the outcomes, "0", "1", "10", "11", "100", "101", et.c.). Between two measurements however, the qubits may assume any value and does not have to line up to the basis vectors. This is the computer-equivalent to the old debate of whetever a particle is a wave (analog) or a particle (discrete). See Quantum logic gate#Measurement for a description of this. -- Omnissiahs hierophant (talk) 22:11, 29 October 2020 (UTC)

If I may chime in, it is somewhat ridiculous to use the adjective digital there as it implies the existence of analog quantum computers and both are ill-defined. I would count all quantum computers as digital, as only digital measurements could ever be made... because of the whole "quantum" bit; not to beat a dead horse, but that is literally what quantum means. Footlessmouse (talk) 22:15, 29 October 2020 (UTC)

Haha yes :) You have a point there! It is impossible to look while you are not looking. Maybe what I was thinking was that the calculations are using real numbers (technically complex) for when we are between measurements. There is nothing that stops the angles and probability amplitudes from being irrational numbers according to quantum physics afaik. Are computer scientists going to repeat the old derpy particle/wave debate or are we just going to move ahead already lol -- Omnissiahs hierophant (talk) 22:22, 29 October 2020 (UTC)

I don't know about CS, but physicists have 100% given up on the philosophy, lol. I personally never understood the whole ordeal, obviously it's neither while both are semi-suitable approximations under appropriate conditions. As far as the article is concerned, however, I believe it is a simple mistake by an eager editor that didn't quite know enough to realize that's not an appropriate description. It is easily remedied. Footlessmouse (talk) 22:38, 29 October 2020 (UTC)

John Preskill said himself that the environment is not the only problem with QCs because the Bloch sphere is continuous. Nothing in the article mentions this. Amplitudes can be positive, negative, complex, vector or spinor. The Born rule is metaphysical fluff and cannot be derived. One of the main skepticisms, from those like Nobel Robert Laughlin, is that these machines are just analog computers in their quantum evolution. Probabilities imply a theory about measurement, which has yet to be resolved. Matt C. 98.3.44.47 (talk) 20:06, 21 April 2021 (UTC)

• multicharacter: allowing a large number of characters in a multicharacter numeral system (not allowing only two [binary] or ten [decimal] characters, but way more)

• monodigit: a monodigital computer which uses only one digit (but this digit might represent many characters)

• qu/quantum: exhibiting superposition or allowing superposition (not enforcing it in all cases but when needed; usually it's needed)

These computers supposedly solve the problem of quantum coherence between different qu-digits, but it's hard for a single digit to be versatile enough to express many characters, with high fidelity and not distorted.

Nowadays multicharacter monoqudigits work better as simulations, but they are slow (not a true quantum computer).

I searched Google Scholar, but it doesn't have any information about this topic. What is a "monoqudigit?" Jarble (talk) 14:47, 31 May 2021 (UTC)

i tried writing a comparison between quantum and classical/neuromorphic computers but wasent able to find any good sources about this.

any ideas? RJJ4y7 (talk) 18:35, 4 August 2021 (UTC)

One aspect of Quantum Computers that I think should be stressed is that they have a very different memory architecture than traditional computers. The article does talk about quantum computers' memory architecture, but I think it should talk a little bit about how it differs from traditional memory architecture. For instance, quantum computers don't have RAM. What do you guys think? CessnaMan1989 (talk) 04:06, 1 November 2021 (UTC)

What do you mean with "memory architecture"? A grid of transmons is a kind of "memory layout" (even requires a routing plane), and ion trap computers have arrays of ions, addressable by shining lasers on them. This article does not mention that, afaik? You would need to go to the specific technology page for that, and maybe you find it mentioned in the cited references · · · Omnissiahs hierophant (talk) 12:05, 1 November 2021 (UTC)

By "memory architecture", I mean the kinds of components used and those components' positions/locations in the computer to store data. Some of the cited references certainly do make the comparisons and contrasts that I'm talking about, but they still aren't mentioned clearly in the article, which is why I'm thinking of adding a few sentences just to clarify. CessnaMan1989 (talk) 19:56, 1 November 2021 (UTC)

This article was the subject of a Wiki Education Foundation-supported course assignment, between 22 January 2020 and 14 May 2020. Further details are available on the course page. Peer reviewers: Wintersfire.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 07:35, 17 January 2022 (UTC)

This article was the subject of a Wiki Education Foundation-supported course assignment, between 30 March 2020 and 5 June 2020. Further details are available on the course page. Student editor(s): Williamdolsen.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 07:35, 17 January 2022 (UTC)

I think the lead sentence(s) can be improved. I added to refs (Mike and Ike, and Hidary). I tried to amalgamate them into the intro, but @Fawly reverted my changes. Let's figure this out! :) Mike and Ike says: "Quantum computation and quantum information is the study of the information processing tasks that can be accomplished using quantum mechanical systems."

Hidary says: "A quantum computer is a device that leverages specific properties described by quantum mechanics to perform computation"

Maybe we should consult one or two more refs? Thanks! Lwoodyiii (talk) 16:28, 27 July 2022 (UTC)

What is your objection to the present lead? I agree with the revert, because I think that neither the reference to "atomic scale" nor the one to "mathematical modeling" are helpful here. I'm mostly ok with the lead; I'm not sure why we write "collective" superposition and entanglement are enough. If one wants to add more keywords of what makes quantum computers work it should be "coherence" or "noncontextuality", but especially the latter is too technical for the lead, imho.

Mermin writes in the introductory section 1.1 What is a quantum computer? of his text book "Quantum Computer Science" that a quantum computer is a computer "whose operation exploits certain very special transformations of its internal state [...] that are allowed by the laws of quantum mechanics." --Qcomp (talk) 17:26, 27 July 2022 (UTC)

I have a couple of "objections" I guess :) One is using the word "computation" and then "perform calculations". They are essentially the same and I prefer computation much more to calculations. I also don't know why we need the word "collective". Lastly, I don't think we need to say that devices that perform quantum computations are known as quantum computers. This is addressed in the physical implementation section (third paragraph). Thank you for the Mermin quote!

Here's a suggestion that addresses some of the complaints mentioned in this discussion. I think it's important to still keep in the "quantum computers" line, since the third sentence of the lead references quantum computers: it makes sense to define it first. I'm also happy with combinations of the current lead with this version below.

Quantum computing is a type of computation whose operations can harness phenomena of quantum mechanics, such as superposition, interference, and entanglement. Devices that perform quantum computations are known as quantum computers. Fawly (talk) 21:41, 27 July 2022 (UTC)

No complaints here, just want to work collaboratively. :) I can get behind your lead sentence you wrote out! Thanks! — Preceding unsigned comment added by Lwoodyiii (talk • contribs) 22:39, 27 July 2022 (UTC)

made the edit! :) Fawly (talk) 17:33, 28 July 2022 (UTC)

Awesome! Thanks @Fawly! :) Lwoodyiii (talk) 22:10, 28 July 2022 (UTC)

Can someone make the introduction simpler, easier to understand for someone like myself who knows very little about this topic? The intro seems to assume that everyone reading would be aware of the specific terminology. I am a strong advocate for knowledge being presented plainly, at least on a site like Wikipedia where laymen come to obtain knowledge about various things, many of which they do not have a mastery in. Noel Malik (talk) 20:48, 21 January 2023 (UTC)

I'll work on it. Part of the problem is that it needs to summarize the body, and the body has a lot of technical content. Could you tag the worst parts with relevant tags like {{technical inline}} so I know what to prioritize?      — Freoh 21:00, 21 January 2023 (UTC)

I did so. Thank you Noel Malik (talk) 19:25, 22 January 2023 (UTC)

Noel Malik, I'll continue working on the other lead paragraphs, but I tried to make the first paragraph a bit more accessible. Do you feel like it's an improvement? I think that it's a difficult concept to summarize in an accessible way, so if you know of other educational resources that you feel explain it better, I'd like to know.      — Freoh 15:34, 24 January 2023 (UTC)

Much better. As for resources perhaps you can check these out:

Noel Malik (talk) 18:55, 24 January 2023 (UTC)

I overhauled the third paragraph and removed your last {{technical inline}} tags. I'll keep working on this article, but let me know if there's anything in particular that you think I should prioritize.      — Freoh 23:30, 24 January 2023 (UTC)

Large multi-mono-atomic groupings cannot maintain cohesion for long. An old idea is to replace each atom with a vial (cartridge), so now each vial plays the role of a single atom, then we entangle the vials among each other. The problem is that particles inside a vial may entangle with other ones of the same vial (so now the vial doesn't act as a single atom), in order to avoid that we use few atoms on each vial [seems clever but it isn't for other reasons/small mistakes become important] and we cool each vial to make it almost a condensate [seems clever but it isn't for other reasons/each person should have a quantum computers, so superconductivity at room temperature is the only solution, not extreme temperatures]. Some reverberative NON-MEASURED laser radiation (the laser should allow different quantum states of oscillation that will be not revealed to us) will increase cohesion inside the mini vats. Sounds great but until now the result is randomness. Crucial details are under development. Akio (Akio) 00:28, 13 May (UTC)

A classical computer analogue, uses a noise generator to introduce noise when needed and entangled quantum rotation statistics. Then we run trillions of times the wavefunctional collapse in order we average the result (most tasks though do not require large averagings, so even a billion or a million might work for simple tasks). That quantum analugue is 10^7 times slower than an ideal quantum computer, but it works, also we don't have large arrayed quantum entangletrons (computer). Human averaging algorithms might not be perfect, but a good noise generator is way better than the natural noise if we add some mistakes of measurement of a future actual large entangletron (quantum computer). Yoritomo (Yoritomo) 04:01, 15 May (UTC)

Each digit should be partially connected (at variable rates that change for each task) with all other digits (at a unique percentage to each other digit), but also to separate non-interconnected randomness (at variable rates that change for each task, at a unique percentage to each other digit). This is called "tensor computing". That works fine for many tasks, you might not get the absolute answer but you will get close after a trillion trials. If you want the absolute answer (well to get even closer, because even getting the absolute answer is something probabilistic), you then should allow partial variable dynamics take action, a combinatorics method of "communicating vessels" (well partially communicating at different rates for each digit and partially introducing variable separate-noise rates to each digit). These combinatoric communicating vessels use as their grain an algorithmic module that acts as the smallest particle. An actual quantum computer uses as a grain-module an infinitely small module and we cannot, but we can get very close and minimize our grain-module enough to perform each task with a classical super computer. Nowadays a classical pseudo-entangletron is better than an entangletron (quantum computer) simply because we can already build a very complex one! Ieyasu (Ieyasu) 04:32, 15 May (UTC)

your first digit is totally random, all other digits are probabilistically separately random (not of the same random series) with some statistical probability of indruducing the initial random digit— Preceding unsigned comment added by 2A02:587:4103:2300:C8D5:96C1:1BF2:71A7 (talk)

This section was copied to the Quantum Mind page on 1 Feb 2018 by user: wcrea6:

Quantum computing is computing using quantum-mechanical phenomena, such as superposition and entanglement.^[1] A quantum computer is a device that performs quantum computing. They are different from binary digital electronic computers based on transistors. Whereas common digital computing requires that the data be encoded into binary digits (bits), each of which is always in one of two definite states (0 or 1), quantum computation uses quantum bits, which can be in superpositions of states. One of the greatest challenges is controlling or removing quantum decoherence. This usually means isolating the system from its environment as interactions with the external world cause the system to decohere. Currently, some quantum computers require their qubits to be cooled to 20 millikelvins in order to prevent significant decoherence.^[2] As a result, time consuming tasks may render some quantum algorithms inoperable, as maintaining the state of qubits for a long enough duration will eventually corrupt the superpositions.^[3]

1. use a classical computer
2. design a noise generator biasing algorithm

   (For example white noise is unbiased. Usually here we don't want that pattern. Also a channeling connectome is required in order many layers of results, evolve in a system. We run many times the program per second and we use sieving formulas for the finds.)

3. mimic a quantum computer approach for that single problem

make page: quantomime: Classical system which mimics a quantum one.

They lead to the exact same article, but the Quantum Computing language links seem to supersede the Quantum Computer one. So there are about 30 links language links missing from the Quantum Computing article. Justcheckingin (talk) 05:22, 1 April 2023 (UTC)

I see the issue that you are talking about, but I am not very familiar with Wikidata, so I am not sure about the best course of action. It seems that other languages of Wikipedia have separate articles for the two, like pt:Computação quântica and pt:Computador quântico, so I do not know whether it would be best to merge d:Q17995793 and d:Q176555 or just to add the missing language links to d:Q17995793. It might be worth asking at the help desk or teahouse (or maybe asking at the Wikidata project site instead).  — Freoh 11:11, 2 April 2023 (UTC)

If I understand the wikidata guide page wikidata:Wikidata:Sitelinks to redirects correctly, the solution is to make sitelinks to redirect pages and tag them with a badge “intentional redirect”. I wonder if there is a tool to do this since otherwise it involves a lot of manual labour. Jähmefyysikko (talk) 15:51, 2 April 2023 (UTC)

I made a query here: wikidata:Wikidata:Project chat#Quantum computing and quantum computer Jähmefyysikko (talk) 16:47, 2 April 2023 (UTC)

Received a reply: It should indeed be done by adding sitelinks to redirects, but unfortunately there is no tool. Also, I noticed that in some wikis, there are no redirects to their Quantum computing/computer page. In this case it is not possible to make a sitelink directly, but it would require a creation of a new redirect page to that wiki. Jähmefyysikko (talk) 11:59, 3 April 2023 (UTC)

Jähmefyysikko, if I understand correctly, the best solution here would be to ensure that every language of Wikipedia that has a quantum computer page also has a quantum computing page (and vice versa), creating a new redirect for languages that have one but not the other. I do not speak most of these languages, so I do not feel comfortable making dozens of redirect pages with titles that I do not understand. Do you think that it would be appropriate to add Wikidata entries pointing directly to the existing pages? For example, adding an entry to d:Q17995793 linking to als:Quantencomputer? Then, we could leave it to people who speak those languages to create the quantum computing redirects and update the Wikidata entry to the (more precise) sitelink to redirect.  — Freoh 11:58, 6 April 2023 (UTC)

I agree that we should not make new redirects to foreign wikis. Also, it is not possible to link d:Q17995793 to als:Quantencomputer, since that page is already linked to d:Q176555.

I did link some wikis (in european languages with which I am not very unconfortable with) to existing redirects, but beyond that I do not think there is much we can do from here. It is up to those wikis to create the pages and add sitelinks if they wish to. Jähmefyysikko (talk) 13:42, 6 April 2023 (UTC)

Given that Quantum Computing is far from producing useful results (aside from deliberately far-fetched demos), why is the material on Skepticism buried so deep under engineering? I would think that most of the readers aren't as interested in the mathematical formalisms as in whether QC is living up to the hype. Igor Markov 00:39, 26 June 2023 (UTC)

Thanks Igor Markov for your recent additions to the article! I agree that we should make these limitations more prominent, but I think that we should avoid a dedicated top-level criticism section.^[1] I have just added an introductory paragraph to § Engineering that gives some better context, and I think that we could include more balance throughout the article. For example, as soon as we introduce quantum search, we could mention that the quadratic speedup is unlikely to be useful anytime soon. I will try to trim the mathematical formalisms in § Quantum information processing, but I think that it would be better to mention algorithmic problems in § Algorithms and engineering challenges in § Engineering rather than having a separate uselessness section.  — Freoh 22:48, 26 June 2023 (UTC)

@Freoh, this makes sense, except that it's more work :) If you can make such changes, all the power to you.

- Igor Markov 23:10, 26 June 2023 (UTC)

The lead on this article is too long. To be more readable to a wider audience, it should be shorter.

I caution anyone against putting a simple "lead too long" template on the article (Template:Lead too long), because it will show the message at the top of the article to all readers, whether or not they have the ability or desire to change the article. However, here on the talk page this message may be more signal and less noise. 96.227.223.203 (talk) 02:28, 31 August 2023 (UTC)

I have corrected the wrongful use of the word "exponentially" in a couple of places where it was simply meant as an equivalent to "a lot". I am aware of this trend where "exponentially" has become a buzzword. But.. The word "exponential" is a well defined mathematical term (see article Exponential growth). Seeing expressions such as "expeonentially faster" etc in cheap tv-movies is one thing that one may shake one's head at and shrug. But, not least for reasons of clarity, I don't think this kind of buzzwording should occur in a technical Wikipedia article.

- RP Nielsen (talk) 13:02, 2 November 2023 (UTC)

I support your change as an improvement. But "exponentially" does have a legit common meaning as "a very lot" in addition to it's mathematical meaning. Sincerely, North8000 (talk) 14:26, 2 November 2023 (UTC)

I reverted the change, because the use of "exponential" there was not "wrongful" or equivalent to "a lot". The whole point of the best know quantum algorithms is that they provide an exponential speedup over the bets known (and, as conjectured, the best possible) classical algorithms. Here "exponential speedup" means that as a function of input size (in bits) the best classical algororithms take an exponentially growing number of steps, while the best quantum algorithms only need a polynomial number of steps. Shor's algorithm is the best know example, but there are many more, see Quantum Algorithm Zoo.--Qcomp (talk) 00:11, 3 November 2023 (UTC)

Well in that case perhaps that needs to be clarified, because the way it is presently articulated is confusing and misleading (as one is prone to think that "exponential" is used in the popular, 'urban' sense mentioned before), so I would say that at the very least those parts of the article need to be re-articulated, and special expressions or special use tof, need to be clarified. - The whole point of encyclopedic articles is to explain the topic to non-experts; in other words that one don't have to already be an expert who knows all the inside esoteric phrases, to be able to read the article.

- RP Nielsen (talk) 13:06, 3 November 2023 (UTC)

Its a pity that language has been so contaminated that we can no longer use well-defined terminology, but it's unfortunately true that "exponential" is often used in an almost meaningless way nowadays. I've added a footnote to the first use of "exponentially faster", to indicate that (and in which way) here we mean indeed "exponentially faster":

Here and in the following „exponentially faster” has a precise complexity theoretical meaning regarding the potential quantum speedup enabled by quantum computers. Namely, that for certain problems the worst-case time complexity (number of elementary steps needed to solve the problem) of the quantum algorithm scales superpolynomially better than the best known classical algorithm. It thus implies the conjecture that the set of problems efficiently solvable on a quantum computer (BQP) is strictly larger than the set of problems efficiently solvable on a classical computer (BPP). See, for example, Nielsen and Chuang, Quantum Computation and Quantum Information, chapter on quantum computational complexity or Scott Aaronson. "How Much Structure Is Needed for Huge Quantum Speedups?". Edited transcript of a rapporteur talk delivered at the 28th Solvay Physics Conference in Brussels on May 21, 2022. arXiv:2209.06930.

Qcomp (talk) 14:46, 3 November 2023 (UTC)

Thank you. Though I wonder if the point could not have been made in a much simpler and clearer way, by a formulation along the lines of how you expressed it in your previous reply, when you said:

Here "exponential speedup" means that as a function of input size (in bits) the best classical algororithms take an exponentially growing* number of steps, while the best quantum algorithms only need a polynomial number of steps.

*(and - as a sugestion- possibly with "exponentially growing" linking to the exponential growth article, just to make sure everyone is on board)

Apart from being simpler and much more digestible, this formulation also shows directly where it is the link to exponential growth enters the picture. - Of course it doesn't give you the opportunity to flex the muscle of how much you know about it, but on the upside it's easy and straight foreward for anyone to see what it means.

- RP Nielsen (talk) 07:10, 4 November 2023 (UTC)

I am glad that @Qcomp caught this issue quickly, but @RP Nielsen was not that far off in that the wording didn't make sense to non-experts. I added a parenthetical remark to point out that "exponentially faster" is with respect to input size scaling. Qq8 (talk) 10:31, 5 November 2023 (UTC)

Thanks again. But I'm afraid the parenthesis doesn't really clarify much about the legitimacy of the expression. And @Qcomp's footnote remains an unnecessarily extensive half-a-page of what, to the non-expert, appear to be more or less inconprehensible giberish. And I apologize in case if this my assessment might hit a sore nerve, but..

Keep in mind that IT'S A FOOTNOTE, the whole, and sole, point of which was to avoid confusion with the popular catchphrase. - It doesn't have to go in depth with complexity theory, or account for implications (all that is better done the article itself rather than in the footnote). - It's ONLY purpose was to clarify that the expression "exponentially faster" is an inside term, and (in a reasonably conceivable way) explain to the non-expert(!) what is meant by it, so as to avoid confusion with the popular catchphrase.

@Qcomp already did that excellently in his earlier reply to me, and so my suggestion was that THAT wording be used IN STEAD of the, as I said, unnecessarily extensive, and rather esoteric, half-a-page of insider giberish (I apologize again).

Thus, I suggest, for example, the following wording in stead:

Here and in the following „exponentially faster” has a precise complexity theoretical meaning. Namely, that as a function of input size (in bits) the best classical algororithms take an exponentially growing number of steps, while the best quantum algorithms only increase by a polynomial number of steps.

So I suggest this, or a similarly clear and to-the-point wording, to replace the footnote, althought I will abstain from making that edit myself, from fear of offening some if I did. So I'll leave that up to you guys. But that is how I would suggest the footnote be worded, in stead of what it is at present. But I leave it up to you guys to do that edit, if and in case you decide that what I have argued here makes any sense. RP Nielsen (talk) 19:19, 5 November 2023 (UTC)

On rereading the footnote I agree that it was unnecessary lengthy and detailed (an attempt to support that there's indeed an exponential speedup, and to be as precise as possible what speedup is claimed - I don't accept the qualification as "gibberish", though, especially since all technical terms were properly linked ;-), and I agree that most of that would rather belong in the complexity section or the quantum speedup article and I removed it from the footnote. --Qcomp (talk) 22:03, 5 November 2023 (UTC)

Just a sidebar...it's quite common and legit for there to be a common meaning of a term which is different than it's technical meaning. The latter does not make the former illegitimate. North8000 (talk) 14:27, 5 November 2023 (UTC)

Even with the footnote, I still disagree with the expression "exponentially faster". I think it also is not neutral due to how ambiguous it is. By ambiguous, I mean that from a reader's perspective, I would have thought you are claiming that there is an exponential speedup for ALL problems. For some problems however, this is definitely not the case. Erdabravest (talk) 00:39, 6 March 2024 (UTC)

Hey everyone,

Would it be helpful to place more emphasis on why one would use quantum computing from the get go rather than starting from a hardware perspective?

The current beginning talks about the use of quantum computing in terms of quantum devices being operated but I would argue that the entire existence of quantum computing though is due to using quantum mechanics to better solve scalability problems that classical algorithms cannot manage.

From what I understand , if I were a reader, I would also risk "putting the word quantum in front of everything." Would it be fair to say this?

I am not sure if people agree with me on this. Thoughts? Erdabravest (talk) 00:56, 6 March 2024 (UTC)

@Aislo8858 has added content about a corporation with plans to do work on quantum computing. In my opinion these plans are "news" not "knowledge" and don't belong in an encyclopedia. Johnjbarton (talk) 15:34, 18 October 2024 (UTC)

This article was the subject of a Wiki Education Foundation-supported course assignment, between 19 August 2024 and 7 December 2024. Further details are available on the course page. Student editor(s): Worma123, Mvallego (article contribs). Peer reviewers: Orahmel.

— Assignment last updated by Orahmel (talk) 19:44, 27 November 2024 (UTC)

A new section on Open Problems was added, but it has two major problems. First it is based on a single reference from Dec. 2024 (this month) written by a single author with no significant publication record on the topic. Second the items in this list are so briefly discussed that only someone already knowledgable on the topic would know what was said.

I think the concept of an "Open Problems" section is reasonable, but it should be backed by reliable references from within the field of study and the content should give enough background for a reader to understand how the problem is related to quantum computing. Johnjbarton (talk) 04:04, 6 December 2024 (UTC)

A third major problem is that the text that was added here was cut and pasted from a copyrighted source. If information from this source is ultimately judged worthy enough by local editors to be added to this article, it should only be done so using properly paraphrased text making use of an editor's own words. Regards,  Spintendo  08:18, 6 December 2024 (UTC)

Why is there a picture of a green laser from French wikipedia labeled as a quantum crypto layout? The image is literally shiny but doesn't have anything to do with quantum crypto, unless it is an implied joke on smoke and mirrors.

Grover's algorithm does little or nothing to speed up vs brute force when you include circuit implementation the fact that queries must be sequential, and error correction overhead. The British version of NSA published a paper "On the practical cost of Grover for AES key recovery", Sarah D. and Peter C., UK National Cyber Security Centre, March 22, 2024 https://csrc.nist.gov/csrc/media/Events/2024/fifth-pqc-standardization-conference/documents/papers/on-practical-cost-of-grover.pdf that concludes the practical security impact of Grover on plausible quantum hardware is limited, even for AES-128. Chadnibal (talk) 13:59, 13 February 2025 (UTC)

I agree about the image and removed it. The interesting Grover algorithm paper should wait until it has either lot of citations or is discussed in a review paper. Johnjbarton (talk) 16:57, 13 February 2025 (UTC)

Cool, I chuckled happily when I saw the laser was gone.

I'm planning to quote that GCHQ paper in a talk I'm giving in April, was having qualms myself, more now you mention it, are they really a reputable source or do they have spooky motivations? It pulled me in because it seems so clear and consistent. I'm already putting a disclaimer on my footnote for the recent MITRE paper that doesn't give sources and seems to have several mistakes. Chadnibal (talk) 15:15, 28 February 2025 (UTC)

Someone could make the case for the Grover paper. Generally we don't cite conference papers due to the high rates of non-notable results and low review criteria. On the plus side, it may be the that UK Centre has a tall reputation and the conference has higher than normal standards, IDK. Johnjbarton (talk) 18:06, 28 February 2025 (UTC)

I deleted two paragraphs of "Potential applications" as not encyclopedic. These are just reports of investments or industrial puffery. Johnjbarton (talk) 23:50, 16 April 2025 (UTC)