I'm actually searching two types of documents (could be the same):

1) A synthesis about all the main gap/problems that make the physical realisation of a quantum computer actually infeasible.

2) Something more polemical that criticizes the point of view "quantum computers arrive soon! They will break the actual instantiation of RSA", and consider that there is no good reason to think there will be a quantum computer functional for cryptanalysis during this century.

I'm not sure of the existence of 2), but I met so many physicists who are skeptical about the optimistic projection (4000 qubits in one decade). Maybe people here have heard about a such document?


You can look up work by Gil Kalai, who is a longstanding and outspoken critic of quantum computing (his most recent essay: Kalai, 2019). He often bases his view on assumptions that I entirely disagree with, but its a refreshing reminder that certain ideas are taken for granted in the industry, namely that NISQ computers will yield practical applications. Kalai's analyses and views aren't necessarily mainstream.

I don't know of any comprehensive papers that address (2) but some example analyses looks into how quantum computers might impact Bitcoin and find that any impact is unlikely (Aggarwal, 2017, Tessler).

With respect to cryptography, NIST is currently sponsoring the development of post-quantum cryptography standards that would possibly be secure against quantum attacks even if a large quantum computer were made available in the near term. Google has even begun implementing a variation of one of these protocols (HRSS) for key exchange. However, claims that a protocol is "post-quantum" should generally be taken with a grain of salt since its entirely unknown whether a method to break these protocols (classical or quantum) exists.

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  • $\begingroup$ In fact, the initiative of NIST looks really strange to me, because I can not understand how to etablish a standard, if we have no idea of the real power of these fictional computers : we can not compare tradeoff security-efficiency... ; The paper of Kalai is exactly what I search. But do you know another paper that has the same conclusion but with a physicist point of view (i.e more focus on physical qubit that on logical qubit)? $\endgroup$ – Ievgeni Sep 4 '19 at 7:50
  • $\begingroup$ I found this discussion that seems perfectly fit : scirate.com/arxiv/1903.10760#1336 $\endgroup$ – Ievgeni Sep 4 '19 at 9:48
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    $\begingroup$ I have found enough mistakes in Dyakonov's work that I tend to ignore his arguments. Specifically in the paper you linked, he's conflated experimental degrees of freedom with mathematical ones, to conclude something along the lines of "300-qubit QC has more degrees of freedom than particles in the universe, making control impossible." But algorithms (no amplitude encoding!) often get away with something like poly or polylog number of parameters with respect to number of qubits. $\endgroup$ – forky40 Sep 5 '19 at 15:35
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    $\begingroup$ This post by Scott Aaronson is relevant, and may also help you find more skeptics: scottaaronson.com/blog/?p=1211 $\endgroup$ – forky40 Sep 5 '19 at 15:36
  • $\begingroup$ Thank you, I read some part of the discussion, and even it's a little bit old, it seems to me (but I don't have huge knowledge about this topic) still actual.. $\endgroup$ – Ievgeni Sep 6 '19 at 14:25

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