Questions tagged [quantum-discord]
For questions about the quantum discord, a form of nonclassicality due to the possibly non-accessible nature of the quantum mutual information.
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What are examples where the quantum discord is achieved by a non-projective POVM?
Consider the (asymmetric) quantum discord, defined as (borrowing notation from Eq. 4.13c of Zurek's review):
$$\mathcal D(\mathcal S:\mathcal A) = I(\mathcal S:\mathcal A) - \chi(\rho_{\mathcal A}),$$
...
glS♦
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Can't understand how $D_{A,B} + D_{A,C} \ge E_{A,B}+E_{A,C}$ is proved used the subadditivity of entropy
I am reading Monogamy properties of quantum and classical correlations. Eq.10 states that $$D_{A,B} + D_{A,C} \ge E_{A,B}+E_{A,C},$$ where $D_{i,j}$ is the quantum discord, and $E_{A,B}$ is the ...
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How to calculate Quantum Discord for two qubit system using Qutip?
Quantum discord of a bipartite system can be determined as:
$${D_A}({\rho _{AB}}) = I({\rho _{AB}}) - {J_A}({\rho _{AB}}),$$
The subscript of $A$ denotes that the measurement has been performed on the ...
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Local operation to change the maximally mixed 2 qubit state to $\frac{1}{2}(|01\rangle \langle01|+|10\rangle \langle10|)$?
A paper I read talked about local interactions on only a single subsystem, leaving the state of that subsystem invariant, and the observation of this requiring the whole state.
Here is the paper
Now ...
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Can separable states have quantum mutual information larger than one?
Consider bipartite (qubit) systems. The classical mutual information between a pair of binary
registers,
$$I(X:Y)\equiv H(X)+H(Y)-H(X,Y),$$
is always lesser than $1$ (and non-negative). On the other ...
glS♦
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What does a quantum mutual information larger than its classical upper bound represent?
Let $\rho$ be a bipartite state. Its quantum mutual information is defined as
$$\newcommand{\tr}{\operatorname{tr}}I(\rho) = S(\tr_B(\rho)) + S(\tr_A(\rho)) - S(\rho),$$
where $S(\sigma)$ is the von ...
glS♦
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Quantum discord of a tripartite system A:BC
I know that the quantum discord of a bipartite system can be determined as:
$${D_A}({\rho _{AB}}) = I({\rho _{AB}}) - {J_A}({\rho _{AB}}),$$
The subscript of $A$ denotes that the measurement has been ...
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Why is the quantum discord of $\rho$ zero iff $\rho=\sum_j p_j \pi_j\otimes \rho_j$ for mutually orthogonal projections $\pi_j$?
In (Wiseman 2012), the author mentions (equation (4), page 6), that a state $\rho$ has zero quantum discord (more precisely, zero Alice-discord) if and only if it can be written in the form
$$\rho = \...
glS♦
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Does computing the quantum mutual information $I(\rho^{AB})$ require full tomographic information of $\rho^{AB}$?
In the discussions about quantum correlations, particularly beyond entanglement (discord, dissonance e.t.c), one can often meet two definitions of mutual information of a quantum system $\rho^{AB}$:
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