# Questions tagged [entanglement]

For questions about the principle and application of quantum entanglement. It is a physical phenomenon which occurs when pairs or groups of particles are generated, interact, or share spatial proximity in ways such that the quantum state of each particle cannot be described independently of the state of the other(s), even when the particles are separated by a large distance—instead, a quantum state must be described for the system as a whole. (Wikipedia)

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### Why after breaking the entanglement does the phase disk in the second qbit not match the result?

I am new in IBM composer quantum and I have a doubt. I have the next circuit After reinitializing q0 and reading it. (breaking entanglement) The phase disk for qubit q1 says that 100% is 0, but the ...
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### General Proof of the Statement that You Need $1$ Ebit and $2$ Bits to Teleport $1$ Qubit?

I understand from the standard teleportation protocol that 1 ebit is used up in teleporting 1 qubit and thus, cannot be used again -- and thus, we need 1 fresh ebit of shared entanglement between ...
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### In a state $\alpha \vert HL \rangle + \beta \vert VR \rangle$ can a particle be measured in the $\{|L\rangle,|R\rangle\}$ basis?

Given a pair of entangled particles: $\alpha \vert HL \rangle + \beta \vert VR \rangle$ where: $\alpha^2 + \beta^2=1$ $H$ and $V$ are orthonormal vectors. $L$ and $R$ are orthogonal vectors (but not ...
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### How to check if a statevector is made of product of EPR pairs in Qiskit?

I have a statevector of 10 qubits. I want to check if the qubits 0,1 and 2,3 are EPR pairs/Bell pairs. The other qubits (4,5,6,7,8,9) have been measured. There are four possible 2-qubit states that ...
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### A doubt regarding Mach-Zehnder Interferometer functioning

I am tying to understand the working of Mach-Zehnder Interferometer in the physical sense (how it behaves and why it does so etc.). The source I am referring to is this: (https://www.cs.princeton.edu/...
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### Why can two atoms can be entangled?

As a qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the spin of the electron in ...
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### Are there separable states $\rho$ with separable pure decompositions requiring $\operatorname{rank}(\rho)^2$ components?

In What separable $\rho$ only admit separable pure decompositions with more than $\mathrm{rank}(\rho)$ terms?, examples were given of separable states $\rho$ with separable decompositions requiring ...
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