The fundamentals, without the hype.
WHAT A CLASSICAL BIT IS
A value that is either zero or one.
WHAT A QUANTUM BIT IS
A system that can be in a combination of both states until measured.
WHAT SUPERPOSITION MEANS
Holding a weighted combination of states simultaneously.
WHAT ENTANGLEMENT MEANS
Two or more qubits whose states are correlated, such that measuring one determines the other.
WHAT MEASUREMENT DOES
Collapses the combination to a definite value, destroying the superposition.
WHY THAT MATTERS
You cannot simply read out all the possibilities. The result is one outcome, probabilistically.
WHAT THAT MEANS FOR ALGORITHMS
They must be constructed so that wrong answers cancel and right answers reinforce.
WHAT THAT IS CALLED
Interference, and it is the actual source of advantage.
WHAT QUANTUM COMPUTERS ARE NOT
Faster classical computers Useful for every problem A replacement for existing computing
WHAT THEY ARE
Machines that may solve specific classes of problem faster than any classical method.
WHAT TO BE SCEPTICAL OF
Claims of general speedups Products claiming quantum capability without describing the problem
