OPTIQ

About

As we place more demands on computers and what we need them to do, quantum computing is the next frontier for faster and more powerful computers.

In order to realise the full benefits of quantum computing, quality hardware for quantum networking is needed, where different types of quantum computers (QC) and devices are interfaced together to enable the exchange of quantum information.

Furthermore, as different types of quantum computers are demonstrated, each with their own inherent strengths and weaknesses, interfacing different types of quantum computers together means they compensate for the errors caused by the other, thus moving towards fault‑free quantum computing.

Silicon is the main material for building electronic devices, but it can also be used for building optical circuits (networks of light channels), or a combination of both.

Almost all internet traffic is sent down silica glass optical fibre, but light signals disappear after ~100 km of fibre. The internet only works because of a device called the erbium doped fibre amplifier (EDFA). By a quirk of nature, erbium emits light very well at exactly the wavelength needed to go down optical fibre. In the EDFA, a length of fibre contains a small amount of erbium which is excited by a laser. Weak signal photons cause the excited erbium to spontaneously emit identical photons, which cascaded down the fibre to emit an identical, but much more powerful light signal. Implantation is the main technology used in microchip fabrication to introduce these erbium impurities into silicon electronic devices.

The current most powerful quantum computers are based on superconducting quantum bits (qubits). One of the main issues that limit all types of quantum computers is correcting errors; superconducting qubits are typically linked to surrounding qubits, which limits the type of error correcting codes that can be used. Erbium implanted silicon can emit light at the special wavelength that needs to be sent down optical fibre and optical circuits. At the University of Salford, researchers have shown for the first time that superconducting circuits can be linked to erbium implanted silicon.

Based on this demonstration, the team have designed a device that converts quantum information in superconducting circuits into telecoms wavelength optical photons. These photons can be sent into a photonic network that allows arbitrarily positioned superconducting qubits to be linked, which allows much more efficient error correcting codes to be used.

The technology is at an early stage, and the university are currently exploring the facilities to build the silicon waveguide part of the device.