- #1

nomadreid

Gold Member

- 1,352

- 120

## Main Question or Discussion Point

In an explanation to distinguish the Heisenberg Uncertainty Principle from the Observer Effect, on p. 89 of "Quantum Computation and Quantum Information", Nielsen and Chuang start by writing:

"The correct interpretation of the uncertainty principle is that if we prepare a large number of quantum systems in identical states....."

However, according to the no-cloning theorem, we cannot perfectly copy an arbitrarily chosen unknown quantum state. So, do the authors mean "...if we were able to prepare (although in reality we cannot) a large number...." or "....if it happened that there were a large number of quantum systems in identical states and we knew that without measurement (which would collapse the states)...." Seems almost metaphysical to me, but maybe I am misinterpreting what Nielsen and Chuang meant, or maybe I am misinterpreting the no-cloning theorem, or maybe I am misapplying.

Any help would be appreciated.

"The correct interpretation of the uncertainty principle is that if we prepare a large number of quantum systems in identical states....."

However, according to the no-cloning theorem, we cannot perfectly copy an arbitrarily chosen unknown quantum state. So, do the authors mean "...if we were able to prepare (although in reality we cannot) a large number...." or "....if it happened that there were a large number of quantum systems in identical states and we knew that without measurement (which would collapse the states)...." Seems almost metaphysical to me, but maybe I am misinterpreting what Nielsen and Chuang meant, or maybe I am misinterpreting the no-cloning theorem, or maybe I am misapplying.

Any help would be appreciated.