Principle (Observables). States for which the value of an observable can becharacterized by a well-defined number are the states that are eigenvectors forthe corresponding self-adjoint operator. The value of the observable in such astate will be a real number, the eigenvalue of the operator.

Axiom (Dynamics). There is a distinguished quantum observable, the Hamil-tonian H. Time evolution of states |ψ(t)〉 ∈ H is given by the Schr ̈odingerequationi~ ddt |ψ(t)〉 = H|ψ(t)〉 (1.1)

Axiom (Quantum observables). The observables of a quantum mechanical sys-tem are given by self-adjoint linear operators on H.

function sequenceSubscriber(observer) { // synchronously deliver 1, 2, and 3, then complete observer.next(1); observer.next(2); observer.next(3); observer.complete();  // unsubscribe function doesn't need to do anything in this // because values are delivered synchronously return {unsubscribe() {}};} // Create a new Observable that will deliver the above sequenceconst sequence = new Observable(sequenceSubscriber); 

As a publisher, you create an Observable instance that defines a subscriber function