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1500 questions
10
votes
2 answers
Why did D-Wave choose the Chimera graph the way they did?
D-Wave makes use of a $(n,k=4)$-Chimera structured graph in their computers. Meaning a $n\times n$ grid of unit cells, with each unit cell consisting of a complete bipartite graph on $2k=8$ nodes ($4$ for each side), also called $K_{4,4}$.
Why did…
nippon
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10
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What quantum gates admit a basis-independent interpretation of their action?
The SWAP gate swaps the state of the two qubits so that in the computational basis $|01\rangle \rightarrow |10 \rangle$ with a matrix representation given by:
\begin{bmatrix}
1 & 0 & 0 & 0 \\
0 & 0 & 1 & 0 \\
0 & 1 & 0 & 0 \\
0 & 0 & 0 & 1…
user97154
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10
votes
1 answer
Proof of an Holevo information inequality for a classical-classical-quantum channel
Suppose I have a classical-classical-quantum channel $W : \mathcal{X}\times\mathcal{Y} \rightarrow \mathcal{D}(\mathcal{H})$, where $\mathcal{X},\mathcal{Y}$ are finite sets and $\mathcal{D}(\mathcal{H})$ is the set of density matrices on finite…
Stephen Diadamo
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10
votes
1 answer
What is the set of generators for the qutrit Clifford group?
According to this article, any Clifford gate, acting on $n$ qubits, can be generated by Hadamard, CNOT, and S gates.
What are the set of generators for qutrit Cliffords?
BlackHat18
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10
votes
2 answers
Is Qiskit more popular than cirq? Why?
It seems like most people are using Qiskit, what's the difference?
nighthawk30
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10
votes
1 answer
Are there connections between long-range entanglement and topological quantum computation?
Long-range entanglement is characterized by topological order (some kinds of global entanglement properties), and the "modern" definition of topological order is the ground state of the system cannot be prepared by a constant-depth circuit from a…
Yupan Liu
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10
votes
2 answers
Shortest sequence of universal quantum gates that correspond to a given unitary
Question: Given a unitary matrix acting on $n$ qubits, can we find the shortest sequence of Clifford + T gates that correspond to that unitary?
For background on the question, two important references:
Fast and efficient exact synthesis of single…
user120404
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10
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1 answer
What is the status of quantum computing compared with other (photonic) quantum technologies?
There is a number of emerging quantum technologies, among which we find the category of photon-based quantum technologies, including quantum key distribution or quantum random number generators.
The question is: what is the short-term viability of…
agaitaarino
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10
votes
1 answer
How to keep track of entanglements when emulating quantum computation?
I am trying to build a quantum computation library as my university project. I am still learning all the aspects of the Quantum Computing field. I know there are efficient libraries already for quantum emulation. I just want to make my own, which…
Midhun XDA
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2 answers
In Grover's Algorithm, why does the optimal number of iterations involve a floor?
On page 157 of Kaye, Laflamme and Mosca they write that in Grover's algorithm we need to apply Grover's iterate a total of:
$$\Big\lfloor \frac{\pi}{4} \sqrt{N}\Big\rfloor$$
(They actually wrote $\Big\lfloor \frac{\pi}{4}…
Quantum spaghettification
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Quantum Chemistry and Quantum Computing
Predicting the energy of molecules to high accuracy during the course of a chemical reaction, which in turn allows us to predict reaction rates, equilibrium geometries, transition states among others is a Quantum Chemical problem.
Quantum Computing…
user3483902
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2 answers
What is the difference between a qubit and a quantum state?
In general, a qubit is mathematically represented as a quantum state of the form $\lvert \psi\rangle = \alpha \lvert 0\rangle + \beta \lvert 1\rangle$, using the basis $\{ \lvert 0\rangle, \lvert 1\rangle \}$. It seems to me that a qubit is just a…
user72
10
votes
1 answer
What happens if two separately entangled qubits are passed through a C-NOT gate?
Suppose I transform a state as follows:
I start with the state $\lvert 0\rangle \otimes \lvert0\rangle \otimes \lvert0\rangle \otimes \lvert 0 \rangle$.
I entangle the 1st and 2nd qubits (with an H gate and C-NOT).
I then then entangle the 3rd and…
Midhun XDA
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10
votes
2 answers
Is BQP only about time? Is this meaningful?
The complexity class BQP (bounded-error quantum polynomial time) seems to be defined only considering the time factor. Is this always meaningful? Do algorithms exist where computational time scales polynomially with the input size but other…
Daniel Tordera
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10
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Does the symmetric logarithmic derivative operator have a geometric interpretation?
In the context of Bures metric and quantum Fisher information, an important object is the symmetric logarithmic derivative (SLD). This is usually introduced as a way to express the derivative of a parametrised state as a superoperator acting on the…
glS
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