There are currently 98 questions tagged . These largely fall into five categories:

  • quantum key distribution, which is the only topic mentioned in the tag wiki
  • post-quantum cryptography
  • quantum cryptanalysis
  • unforgeable quantum tokens
  • questions that are not even clear on what ‘quantum cryptography’ means, like What is Quantum Cryptography?

The overlap between these categories is essentially nil. The prior discussion of quantum tag reform came to no conclusions about .

What purpose does the ‘quantum cryptography’ tag serve that is not better served by more specific tags?


2 Answers 2


The term ‘quantum cryptography’ is consistently confusing. The only topic the tag covers according to the tag wiki is quantum key distribution; quantum money might be in scope but is a bit of a different beast and seems to have only three questions about it; and quantum cryptanalysis and post-quantum cryptography are explicitly out of scope, so all questions about those topics which are tagged are wrongly categorized. It would be clearer if we had a tag. We should:

  1. Rename to .
  2. Replace it by where appropriate.
  3. Replace it by where appropriate.
  4. Maybe add a new tag for the three questions about that (Can quantum money exist?, Are there any applications of Quantum Computation to Cryptography? (besides Cryptanalysis), and Cryptocurrency for quantum computers that is physically impossible to double-spend?).

The tag is useful

because key-distribution and money-system don't cover all the theoretical applications of Quantum cryptography: Quantum e-voting... Because quantum key-distribution and quantum money are closely related (in term of techniques), and it seems not relevant to separate them in term of tags.

and we should keep it as is.

  • $\begingroup$ @Ievgeni Which questions do we have about ‘quantum e-voting’ and why would they not be better served by a quantum-voting tag? (What is quantum e-voting, and is there any serious cryptographic literature on the subject? arxiv.org/abs/1810.05083 suggests the answer may be no.) $\endgroup$ Nov 18, 2019 at 14:48
  • $\begingroup$ Actually there is no questions on quantum e-voting that justify to create a specific tag for that. But because this topic exists (even, it's not well considered), it's not absurd to imagine questions about quantum e-voting (or other applications). A generic tag is interesting to cover many specific applications that we don't have in mind actually. $\endgroup$
    – Ievgeni
    Nov 18, 2019 at 14:56
  • $\begingroup$ Would it be inadequately served by the combination of the existing quantum-computing and voting tags? $\endgroup$ Nov 18, 2019 at 15:06
  • $\begingroup$ For this specific purpose, maybe yes, but how could be sure that any "cryptographic application" of "Quantum technologies" (which are not just Quantum-computing) will be covered? $\endgroup$
    – Ievgeni
    Nov 18, 2019 at 15:14
  • $\begingroup$ Maybe we should have evidence of that before using a tag for a term that is consistently vague and confusing? $\endgroup$ Nov 18, 2019 at 15:24
  • $\begingroup$ Maybe "quantum communication" would be more general than quantum-k-d, and would be less confusing that quantum-cryptography. $\endgroup$
    – Ievgeni
    Nov 18, 2019 at 15:28
  • $\begingroup$ But is it helpful to introduce new broader tags for questions we don't even have? Tags are here for categorization—what categorization purpose would that serve? How does it help to narrow down a search, and how does it help to watch specific subjects of interest? $\endgroup$ Nov 18, 2019 at 15:29
  • $\begingroup$ I understand your point of view, and I don't have any close answer. But separate quantum money, quantum k-d and quantum e-voting doesn't seem "the best option" to me. I wuold suggest to create a tag "quantum communication" according to the technologies used and not the application $\endgroup$
    – Ievgeni
    Nov 18, 2019 at 15:34

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