Minimally Entangled Typical Quantum States at Finite Temperature

We introduce a class of states, called minimally entangled typical thermal states, designed to resemble a typical state of a quantum system at finite temperature with a bias towards classical (minimally entangled) properties. These states reveal in an intuitive way properties such as short-range order which may often be hidden. A finite-$T$ density matrix renormalization group algorithm is presented which is only modestly slower than the $T=0$ density matrix renormalization group.