Q:

Quantum vs number

Let us suppose one has a sentence : I want to find number of digits in the number. Do one allowed to change first occurrence of the word number to the word quantum? So that the new sentence would be : I want to find quantum of digits in the number. I am interested to find the answer because I am writing a program which will be able to find prime number with the specified number of digits and it seems for me to be really graceless to say number of digits in the number.

A:

As stangdon mentions, the general-use definition of the noun "quantum" is no longer common:

quantum (plural: quanta) :  1) quantity, amount  2) portion, part

Much more common is the use of "quantum" as an adjective, either to refer to advanced physics, or to make something sound really "cool" and "science-y" -- for example, a company called "Quantum Data Storage", which is actually just a traditional data repository that has nothing to do with quantum mechanics or quantum computing. 
So as others have said, I would not use "quantum" (or "quanta") for anything other than actual physics.

A:

"Quantum" is a technical term in physics to refer to the smallest possible unit of energy. "Quantum physics" refers to the theory that there is such a thing as a "smallest possible unit of energy", as opposed to "classical physics" which assumed that you could always divide any amount of energy, that if I can push with 10 units of force, then if I pushed half that hard it would be 5 units of force, etc, and there is no "smallest possible amount". Just like atomic theory says that there is a smallest amount of some substance you can have, and that if you tried to divide it in half, you wouldn't have that substance any more. Like if you divided one atom of sodium, what you have is not two smaller pieces of sodium, but something else.
My dictionary says that "quantum" can mean a quantity or amount, but I don't recall ever hearing the word used to mean that. Maybe that's a usage from some other technical field, or maybe it's just obsolete.

