# Role of entanglement in general purpose quantum computing

• I
I've been doing a course on Quantum Computing and I haven't managed to figure out so far how entanglement would be a useful resource on a general purpose quantum computer.

By general purpose quantum computer I mean some theoretical device that could possibly replace current classical computers in the future (if at all likely).

So my question probably boils down to how important a role would entanglement play in the substitution of current classical computers by quantum computers in the future?

## Answers and Replies

FactChecker
Gold Member
Entanglement is what gives quantum computers their enormous potential. Without that, they would be a LOT more trouble than they are worth. The quantum computer can find the solution of a problem with many conditions and constraints in one step. (I really should say "phase" instead of "step" because finding the solution actually takes a few steps ... but ignore that for now.) Suppose you need to find the unique combination of 100 binary inputs that will give a desired result. Entanglement would conceivably allow the solution to be found in one (or a small number) step by a quantum computer with 100 entangled qubits. If there is no shortcut algorithm, a traditional computer might need to start testing all 2100 ≈ 1029 combinations one at a time till it found the solution. Even the fastest traditional computer would need billions of years to solve it.

That is the enormous potential of the quantum computer. The problems with getting them to work and solve something are also enormous.

Last edited:
Strilanc