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In Qiskit, no state vector after measure and reset

You can use save_statevector from Qiskit Aer as follows ...
Egretta.Thula's user avatar
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Measuring one qubit in an entangled pair in another basis?

Yes, and no! If you have some basis change unitary $U$ for a single qubit, then the person holding the first qubit can perform that unitary on their qubit, using the mathematical description $U\otimes ...
DaftWullie's user avatar
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Finding the "dual" basis of an overcomplete basis for Quantum State Tomography

A general procedure to find the dual of any given frame $\{v_k\}_k$ is to compute the frame operator $S$, and then the (canonical) dual frame elements as $\tilde v_k\equiv S^{-1} v_k$. The dual frame ...
glS's user avatar
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What is the difference between classical-quantum and completely classical states?

Your expressions give a pretty clear distinction: in the classical-quantum state, the eigenbases $\left|y_x\right>$ can be different for different states $x$ of the classical register $A$, and in ...
Vladimir Lysikov's user avatar
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Matrices size of n-qubit controlled gates and n+2 states qubit?

By definition, qubit is a quantum system which has two basis states. If more states are allowed, this is called a qudit. It is true that 2 qubits can be seen as one system with 4 basis states $\left|...
Vladimir Lysikov's user avatar
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How to show that the GHZ state is absolutely maximally entangled?

I assume that you talk about the standard case of a $3$-qubit GHZ state (the generalized versions of $n$-qubit GHZ states are not absolutely maximally entangled): $$ |GHZ\rangle = \frac{1}{\sqrt{2}} \...
Ohad's user avatar
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How does this measurement in the Hadamard basis look like?

Answer refined based on updated question Your updated question boils down to something like “if we take a Hadamard transform of a superposition of two basis states and measure, why is our string ...
Mark Spinelli's user avatar
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Is possible to write a separable state as a finite or countable infinite sum of product states?

Yes, you can always write an integral of separable states as a (finite) convex combination of product states, owing to the fact that the set of separable states is compact. A quick way to see this is ...
John Watrous's user avatar
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Which single-qubit mixed states work for magic state distillation?

I've not kept sufficiently up to date with the most recent literature, however, here are some partial results: Along certain axes of the Bloch sphere, the divide between the octahedron and the ...
DaftWullie's user avatar
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How to properly understand Born's rule as written in the Feynman Lectures?

$\newcommand{\complexes}{\mathbb{C}}$I'm trying to make sense of Born's rule involving a single qubit. Probably, I'm mixing apples and oranges here, but I can't tell where or why. In "The ...
hft's user avatar
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How to properly understand Born's rule as written in the Feynman Lectures?

The $\phi_1$ and $\phi_2$ are not just "numbers" but "wavefunctions". For the two-slit experiment, they depend on a position, $x$, so the "functions" look like $\phi_1(x)$...
user1271772's user avatar
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quantum generalisation of random variables

If I understand your question, the way a classical random variable $X$ with support $\left[2^n\right]=\left\{0,\cdots,2^n-1\right\}$ is represented in quantum information is via a diagonal density ...
Tristan Nemoz's user avatar
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How to combine measurement of each term in Hamiltonian $H = aH_1 + bH_2$ to get final results?

Community Wiki It seems like you wish to perform a "Local Hamiltonian Simulation" where your Hamiltonian $H$ is the sum of two separate terms: $$H=aH_1+bH_2.$$ That is, you wish to ...
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Is the full quantum circuit always in a pure state?

Yes. If you prepare a state, say $|0\rangle ^{\otimes n}$ (or any pure state in general) and only perform quantum gates (which are unitary operations) and qubits are perfectly isolated (there are no ...
FDGod's user avatar
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Phase shift on qiskit quantum teleportation simulation

Qiskit uses little-endian bit ordering (see this answer for details). It seems that you didn't take that into consideration in some places in your code. For example, to tensor product ...
Egretta.Thula's user avatar
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How to know what eigenvalue corresponds to measurements of individual qubits in a multiqubit system?

If you consider the state $$\Omega_- = \frac{1}{\sqrt{2}}(|00\rangle + |11\rangle).\tag{1}$$ you will find that there is NO violation. Let me show this. Note that the approach I will use for solving ...
Alex's user avatar
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How to know what eigenvalue corresponds to measurements of individual qubits in a multiqubit system?

From your current description, it seems that you have found each eigenvector $\{|v_1\rangle,...,|v_4\rangle\}$ and its associated eigenvalue $\lambda_1,...,\lambda_4$. These eigenvalues represent the ...
Kilian's user avatar
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