quantum leap vs step back

quantum leap

noun
  • The discontinuous change of the state of an electron in an atom or molecule from one energy level to another. 

  • A large, massive, significant change. 

  • An abrupt, extreme change. 

step back

verb
  • Used other than figuratively or idiomatically: see step, back. 

  • To stop what one is doing and evaluate the current situation. 

  • To prevent oneself from becoming emotionally involved in a certain situation. 

  • to depart driving the train following the train they arrived into the station driving, so as to decrease service turnaround time. 

noun
  • A reversion to a former state or situation. 

How often have the words quantum leap and step back occurred in a corpus of books? (source: Google Ngram Viewer )