First step towards a quantum Internet

Gate using qubit made of entangled photon pairs could lead to 'automatically secure' networks

A US scientist has made a building block that could lead to a totally secure 'quantum Internet', according to a report in MIT Technology Review (TR).

Prem Kumar, professor of electrical engineering and computer science at Northwestern University, has created a quantum 'controlled NOT' logic gate within an optical fibre.

In classic binary logic, using the basic unit of a bit, a NOT gate outputs the opposite of the input: a 0 for a 1, or vice versa. Quantum computing uses qubits that can be in both states at once.

Kumar's team creates qubits from pairs of photons that are 'entangled', meaning that their changes in the physical state of one, such as a shift of polarisation, is mirrored in the other – which can be 100 kilometres further down an optical fibre.

A quantum gate could perform in an optical network the signal-boosting role that a repeater does in an electronic one, TR reports.

Professor Seth Lloyd, a quantum-computing researcher at MIT, told the magazine that this was an import step towards creating a quantum Internet in which communication would be 'automatically secure'.