Quantum Switch that Responds to Single Photons Developed
Some day we may see quantum computers capable of running parallel algorithms unlike anything a modern computer can perform. Before that though, we may see the deployment of quantum networks, analogous to the Internet but with vastly superior security, thanks to quantum mechanics. Researchers at Harvard University have recently designed a switch that could be used in such networks, and can be toggled on and off with single photons.
In quantum mechanics, particles can be put into special states that are very sensitive to any kind of interference, and will even change when measured. This property can be exploited to secure communications, as the act of eavesdropping would interfere with the particles and alert the communicating parties. Building quantum networks though is also quite difficult because of this sensitivity, and so they are limited to just tens of kilometers. This new switch however could enable quantum cryptography over thousands of kilometers. The switch is essentially a miniaturized version of macroscopic switches built in labs, consisting of a single atom between two mirrors. Using lasers and microwaves, the atom is put into a quantum mechanical state, which can allow light to pass through it. Striking the atom with another photon can destroy that state though, and prevent light from passing through it, creating the switching effect.
While labs will build three or four of the large versions to create a simple network, the Harvard design could allow for ten thousand of these switches to be built into chips, like integrated circuits. The researchers doubt this switch will be used to build quantum computers, but believe we could see it in prototype quantum networks in just a decade.