In the lecture titled Entanglement and Complexity: Gravity and Quantum Mechanics, Professor Leonard Susskind implies (at time 17:49) that the complexity of a quantum state impacts how 'complicated' it is to 'navigate your way through the Hilbert space to find that state'.
I've heard this and similar sentiments a few times. Why is it true? How are Hilbert spaces 'navigated through' and why does seeking a more 'complex' [*] state make this navigation more 'difficult' [**]?
[*] meaning more entangled?
[**] difficult in what sense? Time consuming?