• Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.


New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback


(propose a free ad)

Site Statistics

204 submissions , 162 unreviewed
5,030 questions , 2,184 unanswered
5,344 answers , 22,705 comments
1,470 users with positive rep
816 active unimported users
More ...

  Physical examples and implementations of covariant/symmetric quantum operations

+ 0 like - 0 dislike

In quantum information theory a covariant quantum operation $\Phi:\mathcal{B}(\mathcal{H}_1)\rightarrow \mathcal{B}(\mathcal{H}_2$) is an operation that is invariant under a group action that characterizes the symmetry of the input and output system. In other words, given unitary representations $U_1$ and $U_2$ of $G$ such a map satisfies: 
\begin{equation}U(2)(g)^{\dagger}\Phi(U_1(g)\rho U_1(g)^{\dagger})U_2(g)=\rho\end{equation}
for all $\rho\in \mathcal{B}( \mathcal{H}_{1})$ and for all $g\in G$.

One could construct such a map for example by using the dynamical evolution of a system and ensuring that the Hamiltonian H commutes with the unitary matrices $U_1(g)$ and $U_2(g)$: $[U_1(g),H]=[U_2(g),H]=0$. However, how often do such covariant quantum operations appear physically? What would be some non-trivial real physical examples?  

asked Sep 18, 2015 in Theoretical Physics by omicroncz (0 points) [ no revision ]

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
Please complete the anti-spam verification

user contributions licensed under cc by-sa 3.0 with attribution required

Your rights