What's a quantum computer (DRAFT)

26/06/2026

A quantum computer is a device that leverages the principles of quantum mechanics to execute algorithms.

Despite popular belief, a quantum computer is not inherently more capable than a classical one from a strict computability perspective1. Any problem solvable by a quantum computer can theoretically be solved by a classical one.

The true differentiator lies in the type of problems each can solve efficiently, aka computational complexity2.

It is believed that there is a class of problems that can be solved efficiently (in polynomial time) on quantum computers, but not on classical ones. This complexity class is formally known as BQP3.

Footnotes

  1. Computability is defined as the ability to solve a problem via a procedure. Thus, any problem solvable by a quantum computer can also be solved by a classical one. ↩

  2. A quantum computer can solve efficiently problems that are in BQP (Bounded-error quantum polynomial time). The classical equivalent is P. ↩

  3. We know that BQP is a superset of P, it’s still unknown if it is a strict superset. ↩

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