Laser Precision Qubit Control: Leap to Reliable Qubit Information Processing

Using laser light, researchers have developed a precise way to control individual barium qubits, advancing the prospects of quantum computing.

A new optical system designed to focus and control individual atoms.

Researchers have pioneered the use of laser light to control qubits made of barium more powerfully than any other method currently known. Reliably controlling qubits is an important step in realizing the efficient computers of the future.

Developed in At the University of Waterloo‘s Institute for Quantum Computing (IQC), this new method uses a small glass waveguide to separate the laser beams and focus them four microns apart, about four hundredths of the width of one human hair. The precision and extent to which a laser beam focused on its target qubit can be controlled coherently is unmatched by previous research.

Accuracy and Avoidance of Crosstalk

“Our design reduces the amount of crosstalk – the amount of light that falls on neighboring ions – to a small size of 0.01 percent, which is among the best in the quantum community,” said Dr. K. Rajibul Islam, IQC professor with the Waterloo Department of Physics and Astronomy. “Unlike previous methods of creating old controls over individual ions, fiber-based modules are unaffected.

“This means we can talk to any ion without affecting its neighbors while also maintaining the ability to control each ion to the extent possible. This is the most flexible and high-precision ion qubit system we know of anywhere, both in academia and industry. “

The green laser light is the right energy to control the energy of the barium ions. Credit: University of Waterloo

Barium Ions: The New Favorite of Quantum Computing

Barium ions were targeted by scientists, as they are becoming increasingly popular in the field of ion quantum computation. Barium ions have suitable energy fields that can be used as a zero and one level qubit and can be used with visible green light, unlike the high ultraviolet light required for others. atom similar conversion types. This allows researchers to use commercially available optical technology that is not available at ultraviolet wavelengths.

Waveguide Chip and its potential

The researchers created a waveguide chip that splits a single laser into 16 different modes of light. Each channel is then routed to independent optical fiber-based modules providing rapid control over each laser beam’s intensity, frequency, and phase. The laser beams are then focused down into a small space using a series of telescope-like optical lenses. The researchers verified each laser’s focus and control by measuring them with precision camera sensors.

“This work is part of our effort at the University of Waterloo to build barium ion quantum processors using atomic processes,” said Dr. Crystal Senko, principal investigator of Islam and faculty member at IQC and Waterloo’s Department of Physics and Astronomy. “We use ions because they are the same, qubits that are made by nature, we don’t have to make them. Our job is to find ways to control them.”

The new waveguide method presents a simple and precise control method, which shows the promise of ion control for embedding and processing of quantum data and implementation in quantum simulation and computing.

Reference: “A guided light system for a dynamic interface of Ba+ qubits by 10^-4 Level of intensity crosstalk” by Ali Binai-Motlagh, Matthew L Day, Nikolai Videnov, Noah Greenberg, Crystal Senko and Rajibul Islam, 27 July 2023, Quantum Science and Technology.
DOI: 10.1088/2058-9565/ace6cb