Questions tagged [quantum-discord]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
2 votes
0 answers
27 views

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 ...
user avatar
  • 1,123
3 votes
0 answers
47 views

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 ...
user avatar
  • 18.7k
2 votes
0 answers
209 views

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 ...
user avatar
  • 18.7k
3 votes
1 answer
112 views

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 ...
user avatar
  • 255
2 votes
1 answer
78 views

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 = \...
user avatar
  • 18.7k
4 votes
1 answer
350 views

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 $\rho^{AB}$: ...
user avatar
  • 143