The quantum computing tag is relevant for computing that uses quantum states such as superposition and/or entanglement to locate low energy states as solutions to complex problems (rather than laboriously enumerating and checking solutions as would be done with non-quantum traditional computing). Also consider posting your question to the dedicated quantum computing stack exchange.
Questions tagged [quantum-computer]
919 questions
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Why is Google's quantum supremacy experiment impressive?
In the Nature paper published by Google, they say,
To demonstrate quantum supremacy, we compare our quantum processor against state-of-the-art classical computers in the task of sampling the output of a pseudo-random quantum circuit. Random…
Bridgeburners
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What can the D-Wave quantum computer do?
The media are reporting the commercially sold 128-bit quantum computer from D-Wave
http://news.google.com/news?ned=us&hl=us&q=d-wave+quantum&cf=all&scoring=n
which of course sounds amazing. The gadget is described as something capable of doing…
Luboš Motl
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Canonical examples of quantum channels
I have a conjecture about quantum channels. On which examples should I test it before I try to prove it, ask it on StackExchange, or write a paper about it?
(Note: This is meant to be a reference question. But whenever I have a conjecture, I do…
Norbert Schuch
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What is the use of a Universal-NOT gate?
The universal-NOT gate in quantum computing is an operation which maps every point on the Bloch sphere to its antipodal point (see Buzek et al, Phys. Rev. A 60, R2626–R2629). In general, a single qubit quantum state, $|\phi\rangle = \alpha |0\rangle…
Joe Fitzsimons
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Examples of number theory showing up in physics
Are there any interesting examples of number theory showing up unexpectedly in physics?
This probably sounds like rather strange question, or rather like one of the trivial to ask but often unhelpful questions like "give some examples of topic A…
Joe Fitzsimons
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Can quantum entanglement travel faster than the speed of light?
Recently I was watching a video on quantum computing where the narrators describe that quantum entanglement information travels faster than light!
Is it really possible for anything to move faster than light? Or are the narrators just wrong?
Vineet Menon
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Basic questions in Majorana fermions
Why any fermion can be written as a combination of two Majorana fermions? Is there any physical meaning in it? Why Majorana fermion can be used for topological quantum computation?
Timothy
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Why not implement quantum circuits on classical computers?
I have somehow lost sight of the big picture in my study of quantum computing. I understand that we still don't know if quantum computers are more powerful than classical ones, in the sense of computational complexity. But I'm wondering:
Since…
theQman
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What is "code" in "toric code"?
When I first heard people talking about using Kitaev's toric code to do topological quantum computation, I was thinking how many lines does the toric code have. Then I was told that
the "code" really represents quantum states. Later, I understood…
Xiao-Gang Wen
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If the ground states of interacting QFTs are so complicated, how did Nature find them?
My question was inspired by trying to understand the paper Quantum Algorithms for Quantum Field Theories, by Jordan, Lee, and Preskill. The main result of that paper is that scattering experiments in one of the simplest-possible interacting quantum…
Scott Aaronson
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direct sum of anyons?
In the topological phase of a fractional quantum Hall fluid, the excitations of the ground state (quasiparticles) are anyons, at least conjecturally.
There is then supposed to be a braided fusion category whose irreducible objects are in 1-1…
André
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Does quantum computing rely on particular interpretations of quantum mechanics?
It is my understanding that quantum computing relies on quantum superposition and entanglement to work--qbits must exist in all states simultaneously before giving a particular result when observed.
Would this mean that quantum computing is…
qcquestion
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Could quantum computers break any cipher?
I've been told that physicists and computer scientists are working on computers that could use quantum physics to increase significantly computation capabilities and break any cipher so cryptography becomes meaningless.
Is it true?
Ephasme
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Why doesn't the no-cloning theorem make lasers impossible?
As I understand lasers, you start off with a few photons that are in an identical state, and other photons that are created later tend to have the same quantum numbers due to Einstein-Bose statistics. Isn't each photon that "joins" the group of…
yippy_yay
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Quantum and classical physics are reversible, yet quantum gates have to be reversible, whereas classical gates need not. Why?
I've read in many books and articles that because Schrödinger's equation is reversible, quantum gates have to be reversible. OK. But, classical physics is reversible, yet classical gates in classical computers are not all reversible ! So the…
Anarchasis
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