"The theory of quanta can be likened to medicine that cures the disease but kills the patient."
Hendrick Kramers

"I think I can safely say that nobody understands quantum mechanics."
Richard Feynman

"The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth."
(and)
"Anyone who is not shocked by quantum theory has not understood it."
Niels Bohr, 1885-1962

"I don't like it, and I'm sorry I had anything to do with it."
Erwin Schrodinger, 1887-1961

"If [quantum theory] is correct, it signifies the end of physics as a science."
Albert Einstein