# How a Quantum Computer Works

By Aaron Feigenbaum

Topic: Computing, AI & Electronics

[Open the interactive Jig](https://ask.jig.com/j/6dHEQ4ChcukF)

## Guide

### 1. A computer colder than space

This golden "chandelier" is the inside of a real kind of quantum computer\. It hangs in a fridge that chills a tiny chip at the bottom\. Watch the outer case fade away, then follow along to see how it thinks\.

Drag anywhere to turn the scene\.

### 2. Bits: always 0 or 1

Your laptop counts with bits: tiny switches that are either 0 or 1\. Picture each one as an arrow that can only point straight up for 0 or straight down for 1\. The bars show which answer you would read\.

### 3. Qubits: a blend of both

A qubit is a quantum bit\. Until we look, it can be in a superposition: a real blend of 0 and 1, like an arrow tipped part of the way\. The tilt sets the chance of reading each answer\.

Measuring always gives a plain 0 or 1\. The blend only decides how likely each one is\.

### 4. Why it must be so cold

Qubits are fragile\. The faintest heat can knock their blend out of shape\. So each golden plate is colder than the one above it, down to the chip at the very bottom\.

The coldest plate sits near 0\.015 degrees above absolute zero, the coldest anything can ever get\. Deep space is about 2\.7 degrees\.

### 5. Steering with microwaves

A program becomes tiny bursts of microwaves, each lasting a few billionths of a second\. They travel down these thin cables to the chip and nudge each qubit to a new tilt\. The chip is smaller than a coin\.

### 6. Entangled: linked answers

Qubits can also be entangled, which means linked\. Each one alone gives a random answer, yet the two answers always match\. Press Measure to see it\.

### 7. Interference: the right answer grows

A quantum program works a bit like waves on a pond\. Waves that line up grow and waves that clash cancel out\. A clever program makes wrong answers cancel, so the right one shows up most often\.

It does not simply try every answer at once: the cancelling is the trick\.

### 8. What they are good for

Quantum computers will not replace your laptop\. They are built for special jobs, like working out how molecules and new materials behave\. Today's best chips hold around a hundred qubits, and engineers are teaching them to fix their own mistakes\.

Google's Willow chip, shown in 2024, has 105 qubits\.