In quantum mechanics a state space is similar, however in the state space two vectors which are scalar multiples of each other represent the same state. Furthermore, the character of values in the quantum state differ from the classical values: in the quantum case the values can only be measured statistically (by repetition over many examples) and thus do not have well defined values at every instant of time.
In quantum mechanics, a state space is similar; two vectors that are scalar multiples of each other represent the same state. Moreover, the characteristics of quantum states contrast with classical ones: in the quantum domain, measurements can only be statistically determined (through repeated trials) and thus do not have precise values at any specific moment.