# Questions tagged [quantum-gate]

For questions regarding usage, performance, implementation, application or theory related to quantum gates.

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### Can we initialize two arrays in two different qubits in a 2-qubit quantum circuit in IBMq?

Can we initialize two different arrays in two different qubits in a 2 qubit quantum circuit? I tried in IBMq but it showing error. So don't understand. from qiskit import QuantumRegister, ...
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### Understanding notation regarding phase oracle continued

Since I am not able to comment on my post, I had to register an account and start a new post. Maybe my old post can be deleted, which is found : here I am new to quantum computing. I cannot get my ...
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### How to use more than 3 classical registers in a single quantum circuit in Qiskit without getting error: not enough memory slots?

I'm trying to run a quantum circuit on qasm simulator which has more than 3 classical registers. It gives error when I try to execute it. The circuit looks ...
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### How can the result of 1 million transformations on a qubit be verified to be correct?

I tried to do almost a million transformations on a qubit. I made a three qubit circuit with equal superposition of |0> and |1> (using Hadamard gate) and on the first qubit (qubit 0), added one ...
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### Building Unitaries in TSP Quantum Phase Estimation Qiskit?

In the paper [https://arxiv.org/pdf/1805.10928.pdf] 2 published by IBM, they use Quantum Phase Estimation to solve the TSP problem. I don't understand the reason why they can decompose the diagonal ...
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### General Shape of the Hamiltonian for a Desired Unitary

Suppose that, the unitary(the gate) that we want to have is 8*8 matrix. Now I want to write the most general shape of the Hamiltonian for my unitary and I want to prove that the unitary can be ...
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### Which book(s) us(es) the CNOT representation $e^{i\frac{\pi}{4}\left(I-Z\right)\otimes\left(I-X\right)}$?

I am looking for a book that uses the following representation of a CNOT , that so far I have only seen on Wikipedia. Because I'd like to properly cite the source, I am looking for a book that uses it:...
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### Find unitary $U$ that transforms state $|\phi \rangle$ to state $|\phi' \rangle$ knowing those states differ only by relative phase

Given: $|\phi \rangle = \sum_n c_n |a_n \rangle$ $|\phi' \rangle = \sum_n c'_n |a_n \rangle$ such that $\forall n: c_n = c'_n \lor c_n = -c'_n$, where $|a_n \rangle$ is a canonical basis, and ...
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### How to use the csv dataset file imported as a dataframe in QSVM Qiskit code

I am trying to run QSVM qiskit code with my custom dataset which I am loading as a pandas dataframe. When I execute the part below with my own dataset in the place of breast_cancer, it gives error &...
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### Quantum Haar Wavelet Transform

I am working on understanding the quantum haar wavelet transform and trying to understand how it actually do the dimension reduction mathematically. A lot of people suggested me to read this paper : ...
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### Why are the angle coding of the samples cascaded and only use so few qubits

I want to ask about the angle coding. Is the angle coding that Abbas said really like this? There are two samples and four features. Why does she only use two qubits? Instead of four. And the sample ...
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### How do you build the modified Toffoli gate using only local unitary and CNOT operations?

How do you build a circuit for a modified Toffoli gate using only local unitary operations and CNOT operations? The two-qubit unitary operation is given by: $\text{diag}\{1, 1, 1, e^{i\phi}\}$.
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### Is there a simple quantum gate that shows off the power of Quantum interference?

I'm trying to build a deep understanding of where the power of quantum computing comes from when compared to probabilistic computing. A naive observation might be that probabilistic computing would be ...
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### After a photon passes through the phase shifter, does it gain the geometric phase or dynamical phase?

In Quantum Mechanics, the phase can be divided into geometric phase and dynamical phase. In mach-zehnder interferometer, after the photon passes through the phase shifter, what kind of phase does it ...
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### Folded MPS state with Mid-circuit measurement

Among some documents I found to make a MPS state on quantum circuit, I can make it with stepped arrangement of unitary operators. ...
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I read this paper which states that we can establish relation between quantum gates and their polynomials. I used this to find the polynomial corresponding to $R_z$ gate and found it $4\theta x/\pi$ ...