CHIP-BASED quantum computers are a step nearer thanks to two groups of physicists who have created quantum entanglement in solid materials for the first time.
Entanglement is the peculiar link between two quantum particles which means that anything that happens to one also affects the other. One team led by physicist Alfred Forchel of the University of Würzburg in Germany placed a single “quantum dot” – a fragment of semiconductor that acts like an artificial atom – into a small cavity within another semiconductor. By tuning the size of the cavity, Forchel and colleagues were able to entangle the quantum dot with a single photon.
A second team, led by physicist Tomoyuki Yoshie of the California Institute of Technology in Pasadena, produced a similar phenomenon within a tiny cavity designed to “trap” a photon. Holding the photon and the quantum dot together produced the entanglement.
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The teams’ work, reported in Nature (vol 432, p 197 and p 200), is significant because the fragile nature of entanglement makes it hard to control, particularly within a solid, where nearby atoms and fields can destroy it.
The experiments may have practical spin-offs and may provide a convenient way to build quantum computers out of semiconductor chips rather than out of individual ions and atoms, which are hard to store and manipulate.
