Manipulating Light on a Chip for Quantum Technologies

Via Physorg.com -

A team of physicists and engineers at Bristol University has demonstrated exquisite control of single particles of light — photons — on a silicon chip to make a major advance towards long-sought-after quantum technologies, including super-powerful quantum computers and ultra-precise measurements.

The Bristol Centre for Quantum Photonics has demonstrated precise control of four photons using a microscopic metal electrode lithographically patterned onto a silicon chip.

The photons propagate in silica waveguides — much like in optical fibres — patterned on a silicon chip, and are manipulated with the electrode, resulting in a high-performance miniaturized device.

“We have been able to generate and manipulate entangled states of photons on a silicon chip” said PhD student, Jonathan Matthews, who together with Alberto Politi performed the experiments. “These entangled states are responsible for famously ‘weird’ behaviour arising in quantum mechanics, but are also at the heart of powerful quantum technologies.”

“This precise manipulation is a very exciting development for fundamental science as well as for future quantum technologies.” said Prof Jeremy O’Brien, Director of the Centre for Quantum Photonics, who led the research.

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The team coupled photons into and out of the chip, fabricated at CIP Technologies, using optical fibres. Application of a voltage across the metal electrode changed the temperature of the silica waveguide directly beneath it, thereby changing the path that the photons travelled. By measuring the output of the device they confirmed high-performance manipulation of photons in the chip.

The researchers proved that one of the strangest phenomena of the quantum world, namely “quantum entanglement”, was achieved on-chip with up to four photons. Quantum entanglement of two particles means that the state of either of the particles is not defined, but only their collective state, and results in an instantaneous linking of the particles.

This on-chip entanglement has important applications in quantum metrology and the team demonstrated an ultra-precise measurement in this way.

“As well as quantum computing and quantum metrology, on-chip photonic quantum circuits could have important applications in quantum communication, since they can be easily integrated with optical fibres to send photons between remote locations,” said Alberto Politi.

“The really exciting thing about this result is that it will enable the development of reconfigurable and adaptive quantum circuits for photons. This opens up all kinds of possibilities,” said Prof O’Brien.