A computation model which relies on quantum-mechanic phenomena, such as entanglement and superposition. This generalizes the probabilistic model of computation.
Questions tagged [quantum-computing]
271 questions
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How to define quantum Turing machines?
In quantum computation, what is the equivalent model of a Turing machine?
It is quite clear to me how quantum circuits can be constructed out of quantum gates, but how can we define a quantum Turing machine (QTM) that can actually benefit from…
Ran G.
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Why did Google not use an NP problem for their quantum supremacy experiment?
Reading discussions of the recent quantum supremacy experiment by Google I noticed that a lot of time and effort (in the experiment itself, but also in the excellent blog posts by Scott Aaronson and others explaining the results) is spent on…
Vincent
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Why and how is a quantum computer faster than a regular computer?
I'm currently reading a book (and a lot of wikipedia) about quantum physics and I've yet to understand how a quantum computer can be faster than the computers we have today.
How can a quantum computer solve a problem in sub-exponential time that a…
Tom
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Would the P vs. NP problem become trivial as a result of the development of universal quantum computers?
If someone were to build a universal quantum computer, would that have any implications on the problem of P vs. NP?
Barte
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What is the difference between quantum TM and nondetermistic TM?
I was going through the discussion on the question How to define quantum Turing machines? and I feel that quantum TM and nondetermistic TM are one and the same. The answers to the other question do not touch on that. Are these two models one and the…
bongubj
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Quantum lambda calculus
Classically, there are 3 popular ways to think about computation: Turing machine, circuits, and lambda-calculus (I use this as a catch all for most functional views). All 3 have been fruitful ways to think about different types of problems, and…
Artem Kaznatcheev
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Can Quantum Computing solve Problems not even a Turing Machine can solve?
In his book "The Fabric of Reality", Penguin Books 1998, p. 218, David Deutsch says that the first quantum computer (built 1989 in the office of Charles Bennet, IBM Reasearch) "became the first machine ever to perform non-trivial computations that…
ggreiter
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Quantum Computing and Turing Machines: Are Turing Machines still an Accurate Measure?
In class last week, my professor commented and said that Turing machines are used as a standard measure/model of what is computable and are a helpful basis of discussion for that subject. She also said that all variants of Turing machines are proven…
alvonellos
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Universality of the Toffoli gate
Regarding the quantum Toffoli gate:
is it classicaly universal, and if so, why?
is it quantumly universal, and why?
Ran G.
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Could quantum computing eventually be used to make modern day hashing trivial to break?
Simply put, if one were to build a quantum computing device with the power of, say, 20 qubits, could such a computer be used to make any kind of modern hashing algorithm useless?
Would it even be possible to harness the power of quantum computing…
hakusaro
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Is Quantum Computer analog?
We used to have analog computers several decades ago. Modern days computers are Digital. What about Quantum computers? Is it analog or digital? I am asking this since qubit can be many things at the same time.
gpuguy
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What specifically makes quantum computers useful?
I know that quantum computers are able to process a superposition of all possible states with a single pass through the logic.
That seems to be what people point to as being what makes quantum computers special or useful.
However after you have…
Alan Wolfe
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Why is a quantum computer not capable of solving more problems than a classical computer?
On the Wikipedia page for quantum algorithm I read that
[a]ll problems which can be solved on a quantum computer can be solved on a classical computer. In particular, problems which are undecidable using classical computers remain undecidable using…
user2609980
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Will the future quantum computers use the binary, ternary or quaternary numeral system?
Our current computers use bits, so they use the binary numeral system. But I heard that the future quantum computers will use qubits instead of simple bits.
Since in the word "qubit" there is the word "bi" I first thought that this meant that…
Core-Crash
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Quantum Computing - Relationship between Hamiltonian and Unitary model
When developing algorithms in quantum computing, I've noticed that there are two primary models in which this is done. Some algorithms - such as for the Hamiltonian NAND tree problem (Farhi, Goldstone, Guttman) - work by designing a Hamiltonian and…
user340082710
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