• Thu. Nov 23rd, 2023

    Critical Thought

    Critical thoughts on quantum technologies

    Quantum Breakthrough: Waterloo Researchers Revolutionize Qubit Control

    ByByron Bekker

    Nov 14, 2023
    Quantum Breakthrough: Waterloo Researchers Revolutionize Qubit Control

    A groundbreaking development in the field of quantum computing has been achieved by researchers at the University of Waterloo’s Institute for Quantum Computing (IQC). By utilizing laser light, the team has successfully devised an exceptionally robust method for controlling individual qubits made of barium, an elemental chemical substance.

    Reliably controlling qubits is an essential milestone in the quest to realize fully functional quantum computers. The innovative approach involved using a small glass waveguide to separate laser beams and precisely focus them with a distance of four microns between each beam. This level of precision, which corresponds to around four-hundredths of the width of a single human hair, far exceeds the capabilities of previous methods.

    The study’s lead author, Dr. K. Rajibul Islam, a professor at IQC and Waterloo’s Department of Physics and Astronomy, highlighted the exceptional control achieved through this new technique. Islam stated that the design significantly minimizes crosstalk, with only a minute 0.01 percent relative intensity falling on neighboring ions. This level of efficiency is deemed among the best in the quantum community. The implementation of fiber-based modulators further ensures that the control of individual ions remains unaffected by one another.

    “This breakthrough allows us to communicate with any ion without any impact on its neighboring ions. Furthermore, it enables us to maximally control each individual ion. To our knowledge, this is the most versatile and precise ion qubit control system available in both academic and industrial settings,” explained Dr. Islam.

    The researchers specifically targeted barium ions due to their increasing prominence in the field of trapped ion quantum computation. These ions possess energy states that can function as zero and one levels of a qubit, and they can be easily manipulated using visible green light. Unlike other atom types, which require higher energy ultraviolet light for manipulation, barium ions allow the use of readily available optical technologies.

    To achieve their objective, the team developed a waveguide chip capable of dividing a single laser beam into 16 separate channels of light. Each channel is then directed into individual optical fiber-based modulators. These modulators independently provide agile control over the intensity, frequency, and phase of each laser beam. The researchers subsequently focused the laser beams with small spacing through a telescopic arrangement of optical lenses. By employing precise camera sensors, they were able to verify the focus and control of each laser beam.

    Dr. Crystal Senko, co-principal investigator of the study and a faculty member at IQC and Waterloo’s Department of Physics and Astronomy, emphasized that this work aligns with the university’s larger mission of developing barium ion quantum processors. Barium ions are particularly advantageous as qubits due to their identical, nature-made properties, eliminating the need for fabrication. The team’s primary objective is to explore new techniques to control these ions effectively.

    The groundbreaking waveguide method is a major step forward in achieving precise control over qubits and holds tremendous promise for encoding and processing quantum data. Its potential impact extends beyond quantum computing to quantum simulation and computing.

    The research paper, titled “A guided light system for agile individual addressing of Ba+ qubits with 10−4 level intensity crosstalk,” was published in Quantum Science and Technology by Ali Binai-Motlagh, Dr. Matt Day, Nikolay Videnov, Noah Greenberg, Senko, and Islam.


    1. What is a qubit?
    – A qubit, short for quantum bit, is the fundamental unit of information in quantum computing. It can represent both 0 and 1 simultaneously, thanks to the principles of quantum superposition and entanglement.

    2. How is barium utilized in quantum computing?
    – Barium ions possess energy states that can be used as the zero and one levels of a qubit. They offer the advantage of being easily manipulated using visible green light, unlike other types of atoms that require higher energy ultraviolet light.

    3. Why is controlling qubits important?
    – Reliable control over qubits is crucial for the development of functional quantum computers. It enables encoding, processing, and manipulation of quantum information, paving the way for solving complex problems that are currently infeasible with classical computers.

    4. What is quantum simulation?
    – Quantum simulation refers to the process of using quantum systems to simulate, analyze, and understand complex phenomena that are challenging to simulate using classical computers. It holds great potential for advancements in areas such as materials science, drug discovery, and optimization problems.

    5. Who conducted the research?
    – The research was conducted by a team of researchers at the University of Waterloo’s Institute for Quantum Computing (IQC) in collaboration with other institutions.