Partial trace

Solution

Past exam of the mathematics course of the University of Cambridge / 2002 / iii / Paper 33 / 3 / Solution

Past exam of the mathematics course of the University of Cambridge / 2002 / iii / Paper 33 / 4 / Solution

Past exam of the mathematics course of the University of Cambridge / 2004 / iii / Paper 53 / 3 / 1 / Solution

Past exam of the mathematics course of the University of Cambridge / 2004 / iii / Paper 53 / 3 / 2 / Solution

Past exam of the mathematics course of the University of Cambridge / 2004 / iii / Paper 53 / 3 / 3 / Solution

Past exam of the mathematics course of the University of Cambridge / 2004 / iii / Paper 54 / 2 / Solution

Past exam of the mathematics course of the University of Cambridge / 2004 / iii / Paper 54 / 4 / Solution

Past exam of the mathematics course of the University of Cambridge / 2005 / iii / Paper 37 / 1 / a / Solution

Past exam of the mathematics course of the University of Cambridge / 2005 / iii / Paper 37 / 1 / b / Solution

Past exam of the mathematics course of the University of Cambridge / 2005 / iii / Paper 37 / 3 / b / Solution

Past exam of the mathematics course of the University of Cambridge / 2005 / iii / Paper 37 / 4 / b / Solution

Past exam of the mathematics course of the University of Cambridge / 2006 / iii / Paper 33 / 5 / a / 2 / Solution

{wiki=Density_matrix}

A finite-dimensional density operator is Hermitian, positive semidefinite, and has trace one. In dimension $N$ it has $N^2-1$ real parameters. Schrödinger evolution is
$$
\rho_S(t)=U(t)\rho_HU(t)^\dagger
$$
when $\rho_H$ denotes the time-independent Heisenberg-picture state.


Density operator

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 Incoming links: Density operator