Single photons can now be prepared in a quantum-mechanical superposition of colours, giving rise to a new qubit that could be useful in quantum-information processing. Stéphane Clemmen of Cornell University in the US and colleagues combined single photons in a single stream with photons from two strong laser pumps in a cryogenically cooled 100 m-long optical fibre, bumping their energy up and down and thus placing them in a superposition of two colours.