  It is assumed that in a measurement the system under study interacts with a
macroscopic measuring apparatus, in such a way that the density matrix of the
measured system evolves according to the Lindblad equation. Under an assumption
of non-decreasing von Neumann entropy, conditions on the operators appearing in
this equation are given that are necessary and sufficient for the late-time
limit of the density matrix to take the form appropriate for a measurement.
Where these conditions are satisfied, the Lindblad equation can be solved
explicitly. The probabilities appearing in the late-time limit of this general
solution are found to agree with the Born rule, and are independent of the
details of the operators in the Lindblad equation.
