Questions tagged [hadamard]
Single qubit Hadamard gate transforms standard basis states (zero and one states) to their superpositions (plus and minus states)
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What is the |+⟩ and |-⟩ state?
In the Gates Glossary of IBM Quantum Experience it states
H gate
The H or Hadamard gate rotates the states |0⟩ and |1⟩
to |+⟩ and |−⟩, respectively. It is useful for making superpositions. ...
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Why is implementation of controlled Hadamard on IBM Q so complex?
With reference to question how to implement CCH gate I easily realized that CH gate can be implemented with $\mathrm{Ry}$ gates and $\mathrm{CNOT}$ followingly:
Note $\theta = \frac{\pi}{4}$ for ...
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Why is a Hadamard gate unitary?
The Hadamard gate is a unitary gate, but how does the matrix times its own conjugate transpose actually result in the $I$ matrix? I am currently looking at it as a scalar, 0.707..., multiplied by the ...
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Why do multi-bit hadamards expands to what they do?
I'm a Computer Scientist undergrad student studying for an exam in Quantum computing. In all of the algorithms I have been studying (Deutsch–Jozsa, Simons, Shors, Grovers) I constantly see multi-qubit ...
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Is quantum superposition state a truth or an assumption?
Please, be patient with my question
I already read that there is a heuristic that makes superposition a fact of reality. In addition, this superposition, when observed, it has a state of 0 or 1. ...
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What is the matrix representation for $n$-qubit gates?
Let's say I have more than one qbits $|0\rangle|1\rangle$ and I want to perform a $H$ on both of them. I know the matrix representation for the Hadamard on a single qbit is
$$\frac{1}{\sqrt{2}}\begin{...
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How do I prove that the Hadamard satisfies $H\equiv e^{i\pi H/2}$?
How can I demonstrate on the exponential part equality of the Hadamard matrix:
$$H=\frac{X+Z}{\sqrt2}\equiv\exp\left(i\frac{\pi}{2}\frac{X+Z}{\sqrt2}\right).$$
In general, how can I demonstrate on:
$\...
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Could the Hadamard gate have been constructed differently with similar characteristics?
Say we had a Hadamard-like gate with the -1 in the first entry instead of the last. Let's call it $H^1$.
$$H = \begin{bmatrix}1&1\\1&-1\end{bmatrix}$$
$$H^1 = \begin{bmatrix}-1&1\\1&...
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Can everything in QM be described with degrees instead of matrices and vectors?
I found this explanation.
"The Hadamard gate can also be expressed as a 90º rotation around the Y-axis, followed by a 180º rotation around the X-axis. So $H=XY^{1/2}H = X Y^{1/2}H=XY^{1/2}$."
Can ...
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Analysis of the second Hadamard in the Detusch-Josza Algorithm
Consider the Deutsch-Josza, algorithm, which first initializes the state $|0 \rangle^{\otimes n} | 1 \rangle$, creates a superposition using the the Hadamard gate and the $U_f$ to get into the state: $...
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Prove by induction $H^{\otimes n} \left| 0 \right>^{\otimes n} = \frac{1}{\sqrt{2^n}} \sum_{i=0}^{2^n -1} \left| i \right>$
Let H be the Hadamard operator.
$$ H = (\left| 0 \right> \left< 0 \right| + \left| 0 \right> \left< 1 \right| + \left| 1 \right> \left< 0 \right| -\left| 1 \right> \left< 1 \...
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How do 2 Hadamard gates act on a single qubit?
When I perform $2$ Hadamard $H$ gates on a single qubit, why is the probability of getting $0$ as the outcome 100%? Why is it not 50% 0 and 50% 1
instead?
Why is the second $H$ gate not putting the ...
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How to understand a phase operation between 2 Hadamard gates?
I would like to understand this image, of a "payload preparation" gate. A single H gate will create a superposition, while the phase will rotate 45 degrees. What does the second H gate do in this ...
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Finding a global phase that transform the Hadamard gate to an element of $SU(2)$ and propose an evoultion operator which implents the operation
I was looking back over an old assignment and I came across a question I wasn't quite sure how to do the problem statement is as follows:
The Hadamard rotation is an element of the group $U(2)$.
(i)...
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Projecting $\lvert ++ \rangle$ on Bell Basis
I understand that, projecting $\lvert 00\rangle$ on the Bell states would produce $\lvert\Phi^+\rangle$. Because,
$$
CNOT(H\lvert0\rangle \otimes \lvert0\rangle) = \frac{1}{\sqrt{2}}(\lvert00\rangle +...
