# Questions tagged [quantum-gate]

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

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### How to simulate a $CNOT$ only using a single qubit?

I am looking to do a $CNOT$ on itself, i.e., if the qubit is in $|0\rangle$ it stays in $|0\rangle$ and if it is in $|1\rangle$ it becomes $|0\rangle$. We are allowed to use $H$, $X$, $Z$, and $CNOT$ ...
1 vote
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### Qiskit library.gaussian() does not accept parametric expression

I'm trying to build a gaussian pulse in qiskit where I keep the amplitude as a parameter but for the followig code ...
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### What are necessary and sufficient conditions for the output of a parametrized unitary $U(\theta)$ to be smooth?

Let us consider a unitary $U$ parameterised by $\theta \in \mathbb{R}$, i.e, $U(\theta)$. What are the necessary and sufficient conditions for the output states of this unitary to be smooth? One ...
42 views

### Visualizing Y-gate operation to achieve quantum state

In the below snippet how qc.y(1) helps to achieve the quantum state $i|10\rangle$ ? ...
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### How do qubits interact to form logic gates?

How do qubits interact to form, say, CNOT gates? There are very few comprehensive explanations of how quantum computing works. They all use obscure metaphors that don’t make sense (like Schrödinger’s ...
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1 vote
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### Obtaining the unitary matrix of a gate in analytic form in qiskit

Is there any way to obtain the unitary matrix of single way in analytic form? In numerical form, I could use a workaround like this (i.e. for an X Gate): ...
197 views

### What are the transversal gates of the $[[5,1,3]]$ code?

What are the transversal gates of the perfect 5-qubit code ( [[5,1,3]] code) ? Since this is a stabilizer code we have transversal Pauli gates. Are there any others? I am primarily interested in ...
1 vote
41 views

### Amplitude amplification in Grover algorithm

In "Quantum Computation and Quantum Information", they talk about Grover search. One part of the Grover search is Amplitude amplification: But i think the red line is not true. Because i do ...
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### 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 \$...