February 5, 2014

Big Leap Forward for Integrated Quantum Computer

Tiffany Trader
Nature Photonics quantum chip Feb 2014 300x

An international team of researchers led by Dr. Mark Thompson from the University of Bristol have for the first time successfully generated and manipulated single photons on a silicon chip – putting them substantially closer to realizing their goal of building a quantum computer. The technique involved shrinking the key components so they could be integrated onto a silicon microchip, according to the announcement.

Featured on the cover of Nature Photonics, the breakthrough solves the on-chip integration problem that had blocked the further development of large-scale quantum technologies. Previous efforts used external light sources to generate the photons, while the new chip integrates components that can generate photons inside the chip.

“Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step toward fully integrated quantum technologies,” the researchers write. The chip was fabricated by Toshiba using conventional manufacturing techniques, which bodes well for future production.

Quantum computing has long been considered the holy grail of technology. Computers built on quantum principles are expected to be orders of magnitude faster than the best-in-class conventional number crunchers. Although much of the work is still theoretical, the area has experienced rapid progress over the last decade with organizations like D-Wave, the University of Bristol and a few other sites claiming to have developed quantum processing abilities.

“We were surprised by how well the integrated sources performed together,” notes Joshua Silverstone, lead author of the paper. “They produced high-quality identical photons in a reproducible way, confirming that we could one day manufacture a silicon chip with hundreds of similar sources on it, all working together. This could eventually lead to an optical quantum computer capable of performing enormously complex calculations.”

Group leader Mark Thompson explains the process in more detail. “Single-photon detectors, sources and circuits have all been developed separately in silicon but putting them all together and integrating them on a chip is a huge challenge,” he says. “Our device is the most functionally complex photonic quantum circuit to date, and was fabricated by Toshiba using exactly the same manufacturing techniques used to make conventional electronic devices. We can generate and manipulate quantum entanglement all within a single mm-sized micro-chip.”

The international collaboration includes researchers from Toshiba Corporation, Stanford University, University of Glasgow and TU Delft. The next step is getting the other necessary components onto the chip, and then demonstrating the feasibility of large-scale photon-based quantum devices.

“Our group has been making steady progress towards a functioning quantum computer over the last five years,” Thompson remarks. “We hope to have within the next couple of years, photon-based devices complex enough to rival modern computing hardware for highly-specialized tasks.”

Interestingly, the research group maintains that an engineering-oriented approach is what enabled it “to make leaps and bounds in a field previously dominated by scientists.” To this end, the University of Bristol has proposed a new engineering specialty to turn out quantum engineers who are intimate with the fundamentals of quantum mechanics and can apply this knowledge to real world problems.

Bristol has established a Centre for Doctoral Training in Quantum Engineering for this purpose. The center will train a new generation of engineers, scientists and entrepreneurs to lead the quantum technology revolution. Using a multi-discipliarny approach, the program aims to bridge the gaps between physics, engineering, mathematics and computer science, while working in tandem with biologists and chemists and maintaining strong industry relationships.