# Light-based quantum circuit does basic maths

Summary: Researchers from the University of Queensland have taken a significant step in the quest to build a quantum computer, creating a light-based quantum circuit capable of basic calculations and moving quantum computing closer to a becoming a reality.

**Researchers from the University of Queensland have taken a significant step in the quest to build a quantum computer, creating a light-based quantum circuit capable of basic calculations and moving quantum computing closer to a becoming a reality.**

Theoretically, quantum computers leave even today's most powerful conventional supercomputers in the dust. It has also been long known that hypothetical large scale quantum computers could find the prime roots of large composite numbers, allowing them to "crack" modern data encryption.

This additional computing power is a result of the quantum bits, or "qubits", upon which quantum computing is based. Qubits are special bits that use the quantum properties of subatomic particles to make calculations. Quantum computers take advantage of a special quantum property called "superposition", allowing one quantum computer bit to act as many.

"One qubit can be in two possible states, two qubits can be in four, three qubits in eight, and so on," explained Professor Andrew White from the University of Queensland, who works on the project. Thus in a quantum computer every additional quantum bit will double computing power.

The Queensland research forms part of an Australia-wide collaboration called the Centre for Quantum Computer Technology (CQCT), whose "nodes" at several of Australia's largest universities are researching various aspects of quantum computing.

The quantum circuit pioneered by the Queensland researchers involves using a laser to send "entangled" photons through a linear optical circuit, White explained. Using this technology the group was able to create a circuit involving four qubits, which allowed them to calculate the prime roots of fifteen, three and five -- such calculations will eventually be used to crack common data encryption keys.

The Queensland research group acknowledged that the theorised code cracking ability of quantum computers may be why Australian quantum computer research is in part funded by a US government defence intelligence agency, the Defense Advanced Research Projects Agency (DARPA).

White speculated on the future implication of using quantum computers for encryption cracking: "If you're using the current technology for sending information, and you want your information to be private 30 years from now, I would be very worried by this," he said.

Quantum computers are largely an experimental technology, whose full potential may not come to fruition for 20 years or more. But White remains optimistic, "we have found no reason, in principal, why they won't work."

Kick off your day with ZDNet's daily email newsletter. It's the freshest tech news and opinion, served hot. Get it.