A new milestone in reliably processing quantum computing information

Researchers at the Institute for Quantum Computing (IQC) at the University of Waterloo have achieved a significant breakthrough in controlling individual qubits composed of barium using laser light

This groundbreaking method is the most reliable and robust technique currently available for manipulating qubits, marking a pivotal advancement in pursuing functional quantum computers.

The waveguide breakthrough

This new method involves the utilisation of a small glass waveguide to separate laser beams and precisely focus them with a separation of four microns, approximately four-hundredths of the width of a single human hair.

The precision and simultaneous control of each focused laser beam on its target qubit can be controlled in parallel, which is unmatched by previous research. Unlike previous methods to create agile controls over individual ions, the fibre-based modulators do not affect each other.

The most flexible ion qubit control system

“This means we can talk to any ion without affecting its neighbours while retaining the capability to control each ion to the maximum possible extent. This is the most flexible ion qubit control system with this high precision that we know of anywhere, in academia and industry,” said Dr. K. Rajibul Islam, a professor at IQC and Waterloo’s Department of Physics and Astronomy.

The scientists directed their attention towards barium ions, which are gaining prominence within the trapped ion quantum computation domain. Barium ions possess advantageous energy states that can be the basis for a qubit’s zero and one states.

Furthermore, they can be manipulated using visible green light, unlike other atom types that necessitate higher energy ultraviolet light for similar manipulation. This distinction enables the researchers to leverage commercially accessible optical technologies that are not feasible for ultraviolet wavelengths.

Telescope-like optics: Achieving narrow laser beam spacing

The research team developed a waveguide chip to split a single laser beam into 16 distinct light channels. Subsequently, these channels are routed into individual modulators based on optical fibres. These modulators offer independent and agile control over various aspects of each laser beam, including its intensity, frequency, and phase.

To achieve the desired close spacing, the laser beams are concentrated through optical lenses that function like a telescope. The researchers ensured that each laser beam’s focus was precise and controlled by using accurate camera sensors for measurement.

The promising future

The new waveguide approach showcases a straightforward and highly accurate means of control, holding significant potential for manipulating ions to encode and process quantum data.

It also presents a promising avenue for its application in quantum simulation and computing, opening up exciting possibilities for the field.