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# Questions tagged [hadamard-matrices]

In mathematics, a Hadamard matrix, named after the French mathematician Jacques Hadamard, is a square matrix whose entries are either $+1$ or $−1$ and whose rows are mutually orthogonal.

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### Apply the Hadamard transform to different state vectors

I am in the process of understanding a proof. First, the following is said there: $$H\begin{pmatrix}1\\0\\\vdots\\0\end{pmatrix}=\frac{1}{\sqrt{N}}\begin{pmatrix}1\\1\\1\\1\end{pmatrix}$$ This is ...
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### Hadamard transforms seen as rotations in higher dimensions

The Hadamard transform – i.e. the multiplication of a vector $x \in \mathbb{R}^{N}$ (with $N = 2^n$) by the Hadamard matrix $H_n$ – yields another vector $k = H_n x$ in $\mathbb{R}^{N}$. ...
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### Determinant of a Hadamard Matrix as a function of n?

A Hadamard matrix $H$ is a matrix with entries $\pm1$ and orthogonal columns. Given that the matrix is nxn, I got that the determinant is $2^n\times4$. However, this is clearly not correct since the ...
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### Inductive proof of $D_N=-H_n\cdot R_N \cdot H_n$ (Grover Iterator)

I am currently working on an inductive proof $D_N=-H_n\cdot R_N \cdot H_n$ (H is the Hadamard matrix for n Bits), the induction assumption (base case) and the induction condition have been done by me,...
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### Constructing Symmetric Hadamard Matrices

I'm trying to understand the exact degrees of freedom involved in constructing Hadamard matrices with elements in $\{1, -1\}$, and if possible, reduce them in such a way that they can be ...
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### Is there any proof that there doesn't exist a Hadamard matrix of size $6 \times 6$?

A matrix $H \in {\pm 1}^n$ is Hadamard matrix if $HH^T=nI_n$, where $I$ is $n\times n$ identity matrix. Hadamard's conjecture said that there exists Hadamard matrix of order 1,2 or $4n$, for every ...
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### Matrices with nearly balanced matches and mismatches between columns

I am interested in binary matrices with a near balanced number of matched and mismatched entries between columns. For example, a Hadamard matrix has a perfect balance between matched and mismatched ...
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### Fast calculation of the Hadamard transform of a 4X4 matrix

I'm reading a book envolves Hadamard transformations, and in one of the examples they are trying to reconstruct Y from RX+Z where all are 4X4 matrixes. R is given by: R= 1/4 * \begin{array}{l}5&3&...
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### Is there any proof that there doesn't exist a circulant Hadamard matrix of size $8 \times 8$?

Is there any proof that there doesn't exist an $8 \times 8$ circulant Hadamard matrix? A matrix $H \in \{\pm 1\}^{n \times n}$ is Hadamard if $H H^T = n I$, where $I$ is the $n \times n$ identity ...
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### Suggestions regarding Hadamard Matrices

I am a grade 12 student, and for this semester, I am interested in doing a math research paper instead of a science one. I've looked up the internet regarding the different topics I can tackle on, but ...
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### How many unit vectors can be “close to mutually opposite” in a high dimensional space?

This is actually a follow-up of this previous question: How many vectors can be "close to mutual orthogonal like 80 degrees" in a high dimensional space? To be specific: "almost opposite" ...
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### Using Hadamard's maximal determinant what are the the radii $R$, $r$ for an ellipsoid given a linear program?

Let $Ax \leq b$ be the $m$ inequalities of a linear program in $n$ variables and all entries of $A,b$ be from -1, 0,1. What values of $r, R$ can be supplied to the Ellipsoid algorithm so that when it ...
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### Is There a Unitary Transformation Which Maps Non-Orthogonal Vectors into 'Uniform' Vectors?

I would like to find a unitary matrix $U$ which maps normalised vectors $\mathbf{v}^{(i)}$ from the set: \mathcal{V} = \Bigg\{ \begin{pmatrix} 1 \\ 0\\ 0 \\ \vdots \end{pmatrix}, \...
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### Legendre symbol for constructing Hadamard matrix

If we have to construct Hadamard matrix of order n, and n is power of 2, we can use Kronecker mutiplication of matrices. I have heard, that in case of arbitrary n (divisible by 4, of course) we can ...
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### How to get the value of Hadamard matrix given its column and row index?

Please refer to https://en.wikipedia.org/wiki/Hadamard_matrix for the Sylvester's construction of Hadamard matrix. Given a Hadamard matrix $H\in R^{n\times n}$, then how to get the value of $H_{ij}$ ...
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### Prove $\det (A)\le \left(\max_{i,j}|A_{ij}|\right)^n n^{n/2}$

Prove $\det (A)\le \left(\max_{i,j}|A_{ij}|\right)^n n^{n/2}$ How do I prove this as an extension of the Hadamard Inequality? This expression is given as a corollary of the Hadamrd inequality in ...
A (±1)-matrix is a matrix whose entries are 1 and −1. An $n \times n$ (±1)-matrix is called an Hadamard matrix if the rows are orthogonal. Equivalently, An $n \times n$ (±1)-matrix $H$ is Hadamard ⇔ \$...