Skip to main content

Questions tagged [entanglement-breaking-channels]

a class of stochastic maps, or channels, whose action (when tensored with the identity) on an entangled state always yields a separable state.

Filter by
Sorted by
Tagged with
1 vote
1 answer
60 views

Is there a notion of approximate entanglement breaking (EB) channels?

Is there a notion of approximate entanglement breaking (EB) channels? Say, e.g. the output is always close to a separable state. If so, do the nice properties of the EB channels, such as additive ...
Shadumu's user avatar
  • 321
8 votes
3 answers
645 views

What channels preserve the purity of all pure inputs?

Consider channels $\Phi$ such that $\Phi(|\psi\rangle\!\langle\psi|)$ is pure for all $|\psi\rangle$. Is there a simple way to characterise channels with this property? Let's suppose $\Phi$ acts ...
glS's user avatar
  • 25.6k
3 votes
0 answers
77 views

How to write the joint action of a CP map that acts on a single qubit of a bipartite state?

The question Say I have a completely-positive (CP) map $\mathcal{A}_{ij}$ defined in terms of two projectors $\Pi_i = |i\rangle \langle i |$ and $\Pi_j = |j\rangle \langle j |$ that acts on a density ...
RobMuNu's user avatar
  • 31
3 votes
1 answer
900 views

How can one check if a given quantum channel is unitary?

A unitary channel is a channel $\mathcal{U}$ of the following form: $\mathcal{U}(\rho) = U\rho U^{\dagger}$. A mixed unitary channel is a channel $\mathcal{U}_m$ of the form: $\mathcal{U}_m(\rho) = \...
Hari krishnan S V's user avatar
1 vote
1 answer
183 views

Are entanglement breaking channels of any use?

As the name suggests, an entanglement breaking channel $\Phi$ is such that $(Id \otimes \Phi)[\rho]$ is always separable, even when $\rho$ is entangled. Won't such channels be useless, as they destroy ...
Zubin's user avatar
  • 253
1 vote
0 answers
96 views

A way to check if entanglement is increased or decreased

I was wondering if there is a way to check if the amount of entanglement is increased or decreased after a quantum operation without calculating the actual value. That is, it does not concern with the ...
KEN's user avatar
  • 19
2 votes
3 answers
445 views

Why are entanglement breaking channels, defined as $\Phi(\rho)=\sum_a \operatorname{Tr}(\mu(a)\rho)\sigma_a$, entanglement breaking?

Define an entanglement breaking channel $\Phi$ as a channel (CPTP map) of the form $$\Phi(\rho) = \sum_a \operatorname{Tr}(\mu(a)\rho) \sigma_a\tag A$$ for some POVM $\{\mu(a)\}_a$ and states $\...
glS's user avatar
  • 25.6k
5 votes
0 answers
171 views

Coherent Information and Entanglement Breaking channels

The book by John Watrous, "The Theory of Quantum Information" is an exciting read for anyone wanting to research quantum information theory. The following question presumes some background ...
K Gautam Shenoy's user avatar