Photons tune in and shape up Aug 3, 2011 8 comments Physicists
in the US have created a device that can emit single photons of
the right shape and colour for use in quantum information. The
advance is another step in the development of practical quantum-
computing and quantum-cryptography systems. Quantum computing
exploits the peculiar laws of quantum physics to process certain
calculations much faster than any of today's computers, whereas
quantum cryptography uses those laws to prevent eavesdropping on
secure communications. Both rely on the transmission of quantum
information, and one of the best media for transmitting quantum
information is single photons. However, photons also come with
some practical difficulties. Transferring quantum information
over long distances requires telecommunications optical fibres,
which work most efficiently at infrared wavelengths. Storing
quantum information involves devices called quantum memories,
which prefer photons at visible or near-visible wavelengths and
with a cer