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1500 questions
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1 answer
What is the difference between relaxation, dephasing, and decoherence?
Many sources seem to loosely use the terms "relaxation", "dephasing", and "decoherence" interchangeably, while others seem to treat certain of them as special cases of another terms, but I can't find any statements that explictly distinguish…
tparker
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2 answers
Number of Qubits Required for Simulation of Caffeine and Penicillin Molecules
I recently read this report from BCG, which stated:
For scientists trying to design a compound that will attach itself to,
and modify, a target disease pathway, the critical first step is to
determine the electronic structure of the molecule.…
Greenstick
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13
votes
2 answers
How to calculate the distance of stabilizer code?
How to calculate the distance of the stabilizer code [[n,k,d]]? It's better if you can make a 3-qubit example. And what's the relationship between d and Pauli group?
Zeo
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1 answer
General parametrisation of an arbitrary $2 \times 2$ unitary matrix
From Nielsen & Chuang's Quantum Computation and Quantum Information (QCQI):
Since $U$ is unitary, the rows and columns of $U$ are orthonormal, form which it follows that there exist real numbers $\alpha$, $\beta$, $\gamma$ and $\delta$ such that $$…
Tech Solver
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Approximating unitary matrices
I currently have 2 unitary matrices that I want to approximate to a good precision with the fewer quantum gates possible.
In my case the two matrices are:
The square root of NOT gate (up to a global phase)
$$G = \frac{-1}{\sqrt{2}}\begin{pmatrix} i…
Adrien Suau
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13
votes
2 answers
Quantum Supremacy: How do we know that a better classical algorithm doesn't exist?
According to the Wikipedia (Which quotes this paper https://arxiv.org/abs/1203.5813 by Preskill) the definition of Quantum Supremacy is
Quantum supremacy or quantum advantage is the potential ability of
quantum computing devices to solve problems…
P. C. Spaniel
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13
votes
3 answers
Are correlations stronger than those allowed by quantum mechanics possible?
We know how a quantum correlation setup can help us with a better probability of winning games like the CHSH. But what is the upper bound that physics can allow? Is it the quantum correlation setup? Or can we exceed them in general sense to get much…
Siddhant Singh
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13
votes
2 answers
Where do we put error correction code in quantum circuit?
First of all : I am a beginner in quantum computing.
I would like to have a resource (or an answer if it is not complicated) explaining where we put the error correction codes in a quantum circuit.
Indeed, I know we have different possible errors…
Marco Fellous-Asiani
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Can we speed up the Grover's Algorithm by running parallel processes?
In classical computing, we can run the key search (for example AES) by running parallel computing nodes as many as possible.
It is clear that we can run many Grover's algorithms, too.
My question is; it possible to have a speed up using more than…
kelalaka
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5 answers
Advances on imperfect quantum copying
It is known by the no-cloning theorem that constructing a machine that is able to clone an arbitrary quantum state is impossible. However, if the copying is assumed not to be perfect, then universal quantum cloning machines can be generated, being…
Josu Etxezarreta Martinez
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13
votes
3 answers
Which programming language is suitable for a beginner?
I understand there are a lot of programming languages (e.g. Q#, Qiskit, etc.)
Which one is suitable for someone that just started learning programming and doesn't know anything about quantum mechanics?
Daniel Mana
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13
votes
1 answer
Significance of Clifford operations from quantum error correction perspective
In the literature on QECC, Clifford gates occupy an elevated status.
Consider the following examples which attest to this:
When you study stabilizer codes, you separately study how to perform encoded Clifford gates (even if these aren't applicable…
Tanmay Singal
- 170
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13
votes
1 answer
How are magic states defined in the context of quantum computation?
Quoting from this blog post by Earl T. Campbell:
Magic states are a special ingredient, or resource, that allows quantum computers to run faster than traditional computers.
One interesting example that is mentioned in that blog post is that, in…
glS
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13
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2 answers
Is the "Quantum Volume" a fair metric for future, elaborate, high value quantum computations?
A metric called the "quantum volume" has been proposed to somehow compare the utility of different quantum computing hardware. Roughly speaking, it measures their worth by the square of the maximum depth of quantum computations it permits but limits…
user1039
13
votes
1 answer
Does the quantum coherence in the FMO complex have any significance to quantum computing (on a biological substrate)?
The quantum effects of the FMO complex (photosynthetic light harvesting complex found in green sulfur bacteria) have been well studied as well as the quantum effects in other photosynthetic systems. One of the most common hypotheses for explaining…
TanMath
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