Assuming only that the density matrix of the universe evolves in a way that preserves a trace of 1 and preserves the absence of negative eigenvalues, is there a proof that all subsystems of the universe (partial traces over parts of the universe) must evolve according to a completely positive, tr...
Many papers assert that Hamiltonian simulation is BQP-complete
(e.g., arxiv.org/abs/1501.01715 and arxiv.org/abs/1610.06546).
It is easy to see that Hamiltonian simulation is BQP-hard because any quantum algorithm can be reduced to Hamiltonian simulation, but how is Hamiltonian simulation in BQP...
@Blue Hmm... I think, instead of talking about the universe, it should talk about a closed system. As for the tags, I'd question the relevance of quantum-decoherence and density-matrixfor that question. As for relevance to this site, that's something that needs to be decided by the community and not a mod in my opinion. A tag they could use is quantum-channel. Although this leads to questions about the possibility of the cptp-maps tag being a synonym...
Or well, whether it should just be replaced on that question
I am a computer science student and currently search in for resources from where I can learn about quantum computer, its model and it's working principle and it's gates and some simple algorithms.
On other stack exchanges, I can edit my comments (albeit for a limited period of time). Why can't we do it here? I find it even more important here than in other SEs because I use a lot of LaTeX and too often it's not obvious at first whether or not the LaTeX will "compile" properly (no missing b...
Frankly I'm tired of people editing my questions (and even titles) in ways that introduce new errors or even worse errors. In one case the user simply just moved the last part of the sentence to the beginning. The user was probably not ill-intentioned,but it made the question make less sense, and...
@Blue If you go to the What should a tag wiki excerpt contain?, you'll find that, although it's better than nothing, a generic definition isn't quite what we want in a tag excerpt. We want something that's specific to 'how does this apply to this SE' and 'how do we use this tag on this SE', so, while Wiki's a good basis to start things from, it often needs a little more to make it really good and relevant.
However, you're also copying stuff without attribution, which is... Not such a great idea, I'm afraid. It's great that you're trying to get all the excerpts up! Just, relax - there's no rush, so it's worth spending a bit more time to get it done really well, as opposed to "that's that job done, I can move on now"
