Fig. 1.
A cargo particle is transported cooperatively by N molecular motors along a filament. The motors are firmly attached to the cargo but unbind from and rebind to the filament. Each state of the system, denoted by |n 〉, is characterized by the number n of bound motors that pull on the cargo particle. The latter number can vary between n = N (on the left) and n = 0 (on the right). In state |n 〉, the cargo particle has velocity vn, a motor unbinds from the filament with rate εn, and an additional motor binds to the filament with rate πn.