Researchers develop new techniques for controlling individual qubits using lasers

Researchers at the University of Waterloo's Institute for Quantum Computing (IQC) have developed a new technique that uses lasers to control individual qubits made from the chemical element barium. The breakthrough is a key step toward realizing the capabilities of quantum computers.

The new technique uses thin glass waveguides to segment and focus laser beams with unprecedented precision. Each focused laser beam can be adjusted independently, making it possible to reliably manipulate individual qubits. Previous methods could not achieve this level of control.

One of the main advantages of the new technology is its ability to limit crosstalk, which is interference between adjacent ions. The researchers were able to reduce the crosstalk to just 0.01 percent of its relative strength, making it one of the best in the quantum world. This means that the laser beam can target specific ions without affecting its neighbors.

The researchers focused on the barium ion, which has the right energy state to be used as the zero and one energy levels of qubits. Unlike other atom types, barium ions can be manipulated using visible green light rather than higher energy ultraviolet light. This allows researchers to take advantage of commercially available optical techniques that were previously unavailable at ultraviolet wavelengths.

The team developed a waveguide circuit that divides a single laser beam into 16 different light channels. Each channel is then sent to its own fibre-based modulator, which individually controls the intensity, frequency and phase of each laser beam. A series of optical lenses are then used to focus the laser beam to a narrow gap.

The researchers monitored each laser beam with precise camera sensors, confirming their precise focusing and control. This highly accurate and flexible control system sets a new standard in academia and industry.

The ultimate goal of this research is to build barium ion quantum processors, because ions are the same natural qubits that do not need to be manufactured. The focus now is on finding ways to effectively control these ions.

Source: Laser Network