Qubits are made up of controlled particles and the means of control (e.g. devices that trap particles and switch them from one state to another). There are 4 established qubit candidates: ion traps, quantum dots, semiconductor impurities, and superconducting circuits.
Original reproduction: <a href="https://en.wikipedia.org/wiki/User:Jbw2" class="extiw" title="en:User:Jbw2">Jbw2</a>, SVG version: <a href="//commons.wikimedia.org/wiki/User:WhiteTimberwolf" title="User:WhiteTimberwolf">WhiteTimberwolf</a>
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adapted from <i>Nanocomputers and Swarm Intelligence</i> (page 157) ISTE, Waldner, JB (2007), <a href="//commons.wikimedia.org/wiki/Special:BookSources/2746215160" title="Special:BookSources/2746215160">ISBN 2746215160</a>. Reproduced with author's authorization