1. Meet the bit

Everything digital (this page, your photos, your games) is made of bits. A bit is the world's simplest thing: a switch that is either OFF (0) or ON (1).

Billions of these switches flipping very fast = your phone.

A bit is just 0 or 1. That's it.

2. Meet the qubit

A quantum bit (a qubit) is a switch built from something tiny, like an electron or a photon. And tiny things can do the spinning-coin trick.

So a qubit can be 0, be 1, or be a blend of both at once. Not broken. Not undecided. Genuinely both-ish.

A qubit can be 0, 1, or a blend of both.

3. Why blends are powerful

One qubit holds a blend of 2 possibilities. Two qubits: 4 possibilities at once. Three: 8. Every qubit you add DOUBLES it.

Just 50 qubits can hold more combinations at once than a big supercomputer can comfortably list one by one. That's the source of all the hype.

Double 2 three hundred times and you pass the number of atoms in the visible universe. 300 qubits could (in principle) hold a blend that big.

4. The catch

Here's the honest part: when you READ a qubit, the blend snaps and you get just 0 or 1: one plain answer, like a regular bit.

The art of quantum computing is choreographing the blend so that, when it snaps, the answer you get is very likely the RIGHT one. More on that in the next course.

Reading a qubit gives one answer: the trick is making it the right one.

5. Recap

Bit: 0 or 1, like a light switch.

Qubit: 0, 1, or a blend: like a spinning coin.

Each extra qubit doubles what the machine can juggle at once. But reading gives one answer, so quantum computers need clever choreography. Quiz time!