# 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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### Understanding a single qubit Pauli gadget in a quantum circuit [closed]

I'm trying to understand a Pauli gadget defined as $P = e^{-iαX} X^s$ in terms of ZX calculus since that is more intuitive to me. My limited knowledge of quantum computing and the maths involved ...
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### Is quantum computation effectiveness dependent on EPR non-locality?

Suppose 100 qubits are used to perform a quantum algorithm. According to the EPR view, each of these 100 qubits already have pre-determined states before we start the computation, which are just ...
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### How do I multiply a Bell state with a measurement operator?

A textbook that I am currently reading says the following: Alice and Bob share an entangled pair of qubits in the Bell state $(|00\rangle+|11\rangle)/\sqrt{2}$ . Alice performs a two outcome ...
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### Does tensor product of mixed states produce a product, correlated, or entangled state? [closed]

I am trying to understand the difference between correlated and entangled states; from what I gather, a correlated state is to a product state what a mixed state is to a pure state — the former is a ...
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### Is there a generalized quantum teleportation for n-qubit entangled states? [duplicate]

Quantum teleportation for single qubit is a fairly simple algorithm to follow. Even its extensions into the transportation of $n$ qubits is fairly simple: repeat the process $n$ times (or run $n$ ...
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### Symmetries of maximally bi-partite pure entangled states

My question focuses on bi-partite pure systems, but I am also interested in answers focusing on 2-qubit systems (this is actually the case I'm mostly interested in). While being written in a different ...
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### Truncation techniques in the proof of Area Law

I am currently understanding on the proof of Area Law in paper "Rigorous RG algorithms and area laws for low energy eigenstates in 1D" (https://arxiv.org/abs/1602.08828). In terms of the ...
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### When performing a projective measurement on a subsystem X entangled with another system Y, can the evolution of Y be unitary?

I am interested in the evolution of a subsystem Y entangled with another subsystem X. X and Y are initially in a pure product state. They undergo some global joint evolution E (not necessarily unitary)...
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### Is entanglement distillation possible between states of different fidelities?

I am looking for an algorithm that allows me to perform distillation from a pair of W-states of different fidelities. All the algorithms I found so far are focused on distilling identical states, ...
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### What are hamiltonians in the context of quantum computing

Sorry if this question is a bit too generic or basic, but my background lies only in mathematics and computer science. I am currently writing my thesis on the topic of simulating quantum computing ...
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### What is the Generalized Quantum Stein's Lemma and why is it important?

I'm sensing a lot of buzz about potential re-proofs of the Generalized Quantum Stein's Lemma - a generalization of the quantum counterpart to the classical Stein's Lemma, which is of some importance ...
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### The rationale for the payoff function of the CHSH game

The payoff of the CHSH game is the characteristic function $\mathbf 1(x\cdot y=(a+b \mod 2))$. What is the rationale for picking this particular payoff function? Is it a consequence of the CHSH ...
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### Transformation between the canonical basis and the degraded Bell basis

I would like to know if the following results of mine made are correct. My goal is to express the canonical basis $\{ |00\rangle , |01\rangle , |10\rangle , |11\rangle \}$ using a degraded Bell ...
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### How can I move a C.NOT over a circuit

I am doing some Quantum Computing Exercises and I am curious on how you go from left to right in this picture... I see not only how the c-not moves but also a new bond between X gates in second and ...
1 vote
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### Super-dense coding by adding quantum correlations between classical bits

Consider the following non-local game between Alice, Bob (who are spatially separated but share a maximally entangled state) and a referee: Referee samples two question bits "$x,y$" and ...
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### Are transversal entangling gates possible for stabilizer codes other than CSS?

It is well known that CSS codes can have lots of transversal entangling gates. For example, $CNOT$ is exactly transversal on 2 blocks of any $[[n,1,d]]$ CSS code. And https://arxiv.org/abs/1304....
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### Prove that convex combinations of product states admit a hidden variable model

Define product states as simple tensors $\rho_1 \otimes \rho_2$ and separable states to be (trace) norm limits of convex combinations of product states. We say that a state $\rho$ admits a hidden ...
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### Uniqueness, absolutely maximally entangled states, and the 3 qutrit code

There is a well known $[[3,1,2]]_3$ qutrit stabilizer code with stabilizer generators $XXX$ and $ZZZ$. This code is related to a $[[4,0,3]]_3$ qutrit stabilizer state with stabilizer ...
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### In e91 protocol, if one of the bases combination was not chosen, what should be done to avoid division by zero?

In e91 protocol, if one of the bases combination was not chosen, what should be done in this case to avoid division by zero? One solution that comes to mind is setting the whole value to zero, but is ...
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### What is the F12 rule for the Game of Life

This is more of a help call to find a specific rule set for the game of life. I'm currently reading the "Entanglement in the Quantum Game of Life", however they refere to the classical F12 ...
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### In quantum teleportation, why does measuring entanglement not destroy the whole state?

In quantum teleportation, we have three qubits. Sender, receiver and ancillary. First, we entangle the ancillary and target qubit. Next, we entangle ancillary and sender qubits. Now, the whole system ...
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