New answers tagged quantum-state
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In Qiskit, no state vector after measure and reset
You can use save_statevector from Qiskit Aer as follows
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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 ...
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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♦
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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 ...
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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|...
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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}} \...
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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 ...
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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 ...
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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 ...
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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 ...
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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)$...
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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 ...
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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.$$
That is, you wish to ...
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Is the full quantum circuit always in a pure state?
Yes. If you prepare a state, say $|0\rangle ^{\otimes n}$ (or any pure state in general) and only perform quantum gates (which are unitary operations) and qubits are perfectly isolated (there are no ...
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Phase shift on qiskit quantum teleportation simulation
Qiskit uses little-endian bit ordering (see this answer for details). It seems that you didn't take that into consideration in some places in your code.
For example, to tensor product ...
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How to know what eigenvalue corresponds to measurements of individual qubits in a multiqubit system?
If you consider the state
$$\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 ...
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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 ...
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