December 11, 2018

Author: Carley Rosengreen

Creating an optical quantum computer with the potential to enhance computing power to engineer new drugs and optimise energy saving methods has taken a major step closer thanks to a Griffith University-led project.  

Associate Professor Mirko Lobino, an Australian Research Council Future Fellow from Griffith’s Centre for Quantum Dynamics and Queensland Micro and Nanotechnolohy Centre, led this research recently published in Science Advances.  

Prof Lobino worked in collaboration with the Australian National University and the University of New South Wales under the ARC Centre of Excellence for Quantum Computation and Communication Technology to investigate an optical microchip that has most of the basic functionality required for creating future quantum computers. 

Dr Francesco Lenzini from the University of Munster, who is the lead author of the paper, said it was the first optical microchip to generate, manipulate and detect a particular state of light called squeezed vacuum, which is an essential resource for a certain protocol of quantum computation.  

“This experiment is the first to integrate three of the basic steps needed for an optical quantum computer, which are the generation of quantum states of light, their manipulation in a fast and reconfigurable way, and their detection,” Dr Lenzini said.  

Prof Elanor Huntington from ANU said: “what we have demonstrated with this device is an important technological step towards making an optical quantum computer”. 

Prof Lobino said there were “already working towards the next generation of photonic microchips that will be more complex and have better performance, to take another step closer to a practical quantum computer”. 

“Aside from being able to engineer new drugs and materials, and improve energy-saving methods, optical quantum computing will enable ultra-fast database searches and help solve difficult mathematical problems in many different fields,” he said. 

The microchip, which is 1.5cm wide, 5cm long and 0.5mm thick, has components inside that’s interact with light in different ways. These components are connected by tiny channels called waveguides that guide the light around the microchip, in a similar way that wires connect different parts of an electric circuit.

The first part generates a type of quantum light called a squeezed vacuum. There are two squeezed state generators on the chip, which are connected to the two inputs of a device known as a reconfigurable directional coupler, which can entangle the two squeezed states, with a controllable amount of entanglement.  

To measure the entanglement generated in the microchip, both outputs of the directional coupler are guided to separate measurement components, known as homodyne detectors. The homodyne detectors allow measurement of the quantum light that prove entanglement.  

Prof Lobino said the next step for the microchip needed to create future quantum computers was to develop ways to integrate of single photon detectors and other quantum state engineering functionality.