April 18, 2016

First quantum computing data bus nears

RMIT University researchers have trialled a quantum processor capable of routing quantum information from different locations in a critical breakthrough for quantum computing.

The work opens a pathway towards the "quantum data bus", a vital component of future quantum technologies.

The research team from the Quantum Photonics Laboratory at RMIT in Melbourne, Australia, the Institute for Photonics and Nanotechnologies of the CNR in Italy and the South University of Science and Technology of China, have demonstrated for the first time the perfect state transfer of an entangled quantum bit (qubit) on an integrated photonic device.

Quantum information is encoded in single particles of light (photons). The perfect state transfer is applied to one photon of an entangled pair, relocating it to a distant location while preserving the delicate quantum information and entanglement. CREDIT RMIT University

Illustration of a one-dimensional perfect state transfer lattice connecting two quantum processors

Experimental data from the characterization and performance of perfect state transfer waveguide array.

Nature Communications - Experimental Perfect State Transfer of an Entangled Photonic Qubit



Quantum Photonics Laboratory Director Dr Alberto Peruzzo said after more than a decade of global research in the specialised area, the RMIT results were highly anticipated.

"The perfect state transfer has emerged as a promising technique for data routing in large-scale quantum computers," Peruzzo said.

"The last 10 years has seen a wealth of theoretical proposals but until now it has never been experimentally realised.

"Our device uses highly optimised quantum tunnelling to relocate qubits between distant sites.

"It's a breakthrough that has the potential to open up quantum computing in the near future."

The difference between standard computing and quantum computing is comparable to solving problems over an eternity compared to a short time.

"Quantum computers promise to solve vital tasks that are currently unmanageable on today's standard computers and the need to delve deeper in this area has motivated a worldwide scientific and engineering effort to develop quantum technologies," Peruzzo said.

"It could make the critical difference for discovering new drugs, developing a perfectly secure quantum Internet and even improving facial recognition.''

Peruzzo said a key requirement for any information technology, along with processors and memories, is the ability to relocate data between locations.

Full scale quantum computers will contain millions, if not billions, of quantum bits (qubits) all interconnected, to achieve computational power undreamed of today.

While today's microprocessors use data buses that route single bits of information, transferring quantum information is a far greater challenge due to the intrinsic fragility of quantum states.

"Great progress has been made in the past decade, increasing the power and complexity of quantum processors," Peruzzo said.

Robert Chapman, an RMIT PhD student working on the experiment, said the protocol they developed could be implemented in large scale quantum computing architectures, where interconnection between qubits will be essential.

"We experimentally relocate qubits, encoded in single particles of light, between distant locations," Chapman said.

"During the protocol, the fragile quantum state is maintained and, critically, entanglement is preserved, which is key for quantum computing."

Nature Communications Abstract

The transfer of data is a fundamental task in information systems. Microprocessors contain dedicated data buses that transmit bits across different locations and implement sophisticated routing protocols. Transferring quantum information with high fidelity is a challenging task, due to the intrinsic fragility of quantum states. Here we report on the implementation of the perfect state transfer protocol applied to a photonic qubit entangled with another qubit at a different location. On a single device we perform three routing procedures on entangled states, preserving the encoded quantum state with an average fidelity of 97.1%, measuring in the coincidence basis. Our protocol extends the regular perfect state transfer by maintaining quantum information encoded in the polarization state of the photonic qubit. Our results demonstrate the key principle of perfect state transfer, opening a route towards data transfer for quantum computing systems.

3 pages of supplemental information (pdf)

SOURCES - Eurekalert, RMIT, Nature Communications

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