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6
votes
1 answer
How to get subspace of quantum circuit?
How can I get a subspace of a quantum circuit? More precisely, I'm dealing with quantum circuit with data qubits ('q') and ancilla qubits ('anc'), such as $(q_0,q_1,...,q_n,anc_0,..anc_m)$.
After some quantum operations, I'd like to get a unitary…
Jin
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6
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1 answer
How close or far apart are the distributions generated by two Haar random states?
Consider two $n$ qubit Haar-random quantum states $|\psi\rangle$ and $|\phi\rangle$. Let $D_{|\psi\rangle}$ and $D_{|\phi\rangle}$ be the two probability distributions (over $n$-bit strings) obtained by measuring $|\psi\rangle$ and $|\phi\rangle$…
BlackHat18
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6
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In Nielsen and Chuang, how can $\frac{1}{2(e-1)}$ result from $\frac12\int_{e-1}^{2^{t-1}-1}dl\frac{1}{l^2}$?
From Nielsen and Chuang's book: $\textit{Quantum computation and quantum information}$, how can (5.34) equal (5.33)? I.e.
$$\dfrac{1}{2} \int_{e-1}^{2^{t-1}-1} dl \dfrac{1}{l^2} = \dfrac{1}{2(e-1)}.$$
narip
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6
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In QAOA why do we need $m \log(m)$ repetitions to get at least $F_{p}(\beta , \gamma) - 1$ with probability of $1 - 1/m$?
In the original QAOA paper from Farhi
https://arxiv.org/pdf/1411.4028.pdf,
it is stated in chapter 2 last paragraph (page 6) that: when measuring $F_{p}(\beta , \gamma)$ we get an outcome of at least $F_{p}(\beta , \gamma) - 1$ with probability of…
Hannah
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6
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1 answer
How to generate all stabilizer states numerically?
I would like to obtain a list of all stabilizer states in the given dimension (not necessarily qubit systems). What is an efficient way of generating this list numerically?
Ver
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6
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1 answer
What is the probability of finding the second qubit as $0$ in the state $|\psi\rangle=\frac1{\sqrt2}|00\rangle+\frac12|10\rangle-\frac12|11\rangle $?
Assuming two qubits start in the state:
$|\psi\rangle = \frac{1}{\sqrt 2}|00\rangle + \frac{1}{2}|10\rangle- \frac{1}{2}|11\rangle $
What is the probability of measuring the second qubit as 0? And what is the new state of the system after measuring…
Lizzo
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6
votes
2 answers
How does the CX gate work?
I have a silly question as I am an absolute beginner! So as described in Qiskit:
It performs the NOT operation (equivalent to applying an X gate) on the second qubit only when the first qubit is $|1\rangle$ and otherwise leaves it unchanged.
in…
Delaram Nematollahi
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6
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3 answers
Simulator-dependent implementations in Q#
I have a Q# operation:
operation init_and(a: Qubit, b: Qubit, target: Qubit) : Unit is Adj {
// Uncomment this when using Toffoli simulator.
// CCNOT(a, b, target);
// Uncomment this when doing resource estimates.
…
Craig Gidney
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6
votes
1 answer
Quantum Fourier Transform for general cyclic groups
The QFT on the group $\mathbb{Z}_N$ is given by
\begin{equation}
QFT\,|k\rangle =\frac{1}{\sqrt{N}} \sum_{j=0}^{N-1} e^{2\pi i\,jk/N}|j\rangle\,.
\end{equation}
The usual circuit implements the QFT with $N=2^n$ on $n$ qubits. Does anyone know how to…
pomello gaudente
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6
votes
1 answer
Difference between Bell's inequality and CHSH
In this section of the Scholarpedia article on Bell's theorem, the first paragraph comments that Bell's original inequality is not ideal for experimental verification because it requires perfect anti-correlation of the variables, and for that reason…
Pedro
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6
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2 answers
How many shots should one take to get a reliable estimate in a quantum program?
When testing my quantum programs, I wonder how many shots I must take to get a specific accuracy.
Are there any papers that you can recommend that analyze this?
Hannah
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6
votes
1 answer
Hardware wise, how does D-Wave achieve quantum annealing?
Quantum computers have shown a new way to compute old problems. D-Wave has a quantum annealer, and Wikipedia describes the D-Wave quantum computer and its use of quantum annealing properties. Hardware wise, how does D-Wave achieve quantum…
user3483902
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6
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1 answer
Can I partially collapse the wavefunction in Qiskit?
I'm trying to do something similar to this question, where I want to partially measure the system before getting the output. In particular, say I have 4 qubits. I want to measure two of them, and then get the state vector associated with the other…
Germ
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6
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2 answers
What is a maximal number factored by Shor's algorithm so far?
With reference to a similar question here, I would like to know what is the maximal number which has been factored with Shor's algorithm so far on actual quantum hardware.
The reason I am asking a similar question as the link is that this question…
Martin Vesely
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6
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3 answers
How can I obtain transformation matrix of a quantum circuit in the Qiskit?
I need to draw a quantum circuit in Clifford+T library and obtain automatically its transformation matrix. Is there any feature on Qiskit in this case?
Moein sarvaghad
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