Researchers have developed an all-optical, fiber-based switch, opening the doors for building an ultra-fast quantum internet.

The switch could be used toward achieving two goals of the information technology world: a quantum internet, where encrypted information would be completely secure, and networking superfast quantum computers, researchers at the Northwestern University said.

According to the researchers, the switch would enable a common transport mechanism, such as the ubiquitous fiber-optic infrastructure, to be shared among many users of quantum information. Such a system could route a quantum bit, such as a photon, to its final destination just like an e-mail is routed across the internet today.

The researchers first produced pairs of entangled photons using another device called an Entangled Photon Source. The researchers used pairs of polarization-entangled photons emitted into standard telecom-grade fiber. One photon of the pair was transmitted through the all-optical switch. Using single-photon detectors, the researchers found that the quantum state of the pair of photons was not disturbed; the encoded entanglement information was intact.

The researchers said they can route quantum bits, or entangled particles of light, at very high speeds along a shared network of fiber-optic cable without losing the entanglement information embedded in the quantum bits.

My goal is to make quantum communication devices very practical, says Prem Kumar, director of Northwestern's Center for Photonic Communication and Computing. We work in fiber optics so that as quantum communication matures it can easily be integrated into the existing telecommunication infrastructure.

Quantum communication can achieve things that are not possible with classical communication, Kumar says. What makes a quantum bit, or qubit, so attractive is it can be both one and zero simultaneously as well as being one or zero. Additionally, two or more qubits at different locations can be entangled - a mysterious connection that is not possible with ordinary bits.