Does anyone know anything about quantum information theory?(adsbygoogle = window.adsbygoogle || []).push({});

I am reading a text about transmitting quantum states, represented by density matrices, through channels. Here the depolarising channel is defined as the map:

X: -> (1-p)X + pτ Tr[X]

which with probability (1-p) maps the state onto itself and probability p maps it onto the maximally entangled state τ.

Now my question is: Why did the writers choose to insert Tr[X] = 1 (X is density matrix). Why is that important to have? From what I see, it could just as well be omitted. Come to think of it, I am not sure about the role that the trace of the density matrix plays in the process of transmitting signals and measuring. Could anyone clarify?

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Quantum Information

Loading...

Similar Threads - Quantum Information | Date |
---|---|

A Defining Krauss operators with normal distribution | Jan 22, 2018 |

A General quantum measurements | Jan 18, 2018 |

A Von Neumann Entropy of a joint state | Jan 17, 2018 |

**Physics Forums - The Fusion of Science and Community**