The notoriously counterintuitive features of quantum mechanics make it hard to design experiments to study the quantum fundamentals and to develop quantum computing and quantum cryptography. So a team of researchers has developed an algorithm for combining the building blocks of quantum optics experiments, such as beam splitters and mirrors, to achieve a particular goal, such as a certain photonic quantum state. The experimental arrangements generated so far are ones the researchers say they were unlikely to have thought of themselves, and some work in ways that are hard to understand.
Experiments in quantum optics, whether for fundamental or practical ends, tend to use a rather limited set of components to manipulate the quantum states of photons. Beam splitters can send laser light along two different paths with certain probabilities and generate so-called superposition states in which photons seem to take two paths at once. Nonlinear crystals generate pairs of quantum-connected (entangled) photons, and the usual mirrors and lenses guide laser beams.
The algorithm designed by Anton Zeilinger of the University of Vienna and his co-workers, called Melvin, takes elements like these and shuffles them to find an experimental arrangement that will produce specified quantum properties in the photon beams. For example, many experiments require entanglement, where two photons have some property, such as polarization or angular momentum, that is correlated—measuring the value for one photon tells you the value for the other. Researchers might also want to manipulate single photons.
To read more, click here.