A leap forward in reliable quantum information processing

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

Researchers have created a pioneering technology that uses laser light to control individual qubits made of barium with greater power than any other method currently known. Reliably controlling qubits is a crucial step toward achieving functional quantum computers in the future.

It was developed in University of WaterlooAt the Institute for Quantum Computing (IQC), this new method uses a tiny glass waveguide to separate and focus laser beams at a distance of four microns, roughly four hundredths the width of a single human hair. The precision and extent to which each laser beam focused on the targeted qubit can be controlled in parallel is unparalleled in previous research.

Accuracy and avoidance of crosstalk

Dr. K said: “Our design limits the amount of interference — the amount of light falling on neighboring ions — to a very small relative density of 0.01 percent, which is among the best in the quantum community,” said Rajibul Islam, a professor at Harvard University. IQC and the Department of Physics and Astronomy at Waterloo. “Unlike previous methods of creating agile controls on individual ions, fiber-based modulators do not influence each other.

“This means that we can talk to any ion without affecting its neighbors while also retaining the ability to control each ion individually to the greatest extent possible. This is the most flexible ion qubit control system with such high precision that we know of anywhere, in every From academia and industry.

Green laser light is the correct energy for manipulating the energy states of barium ions. Credit: University of Waterloo

Barium ions: the new quantum computing favourite

Scientists targeted barium ions, as they have become increasingly popular in the field of confined ion quantum computation. Barium ions have suitable energy states that can be used as zero and one levels of a qubit and can be manipulated with visible green light, as opposed to the higher energy ultraviolet light needed for other ultraviolet light. corn Types of the same manipulation. This allows researchers to use commercially available optical techniques that are not available for ultraviolet wavelengths.

Waveguide chip and its capabilities

The researchers created a waveguide chip that splits a single laser beam into 16 different light channels. Each channel is then routed to individual optical fiber-based modulation modules that independently provide rapid control of the intensity, frequency and phase of each laser beam. The laser beams are then focused into small distances between them using a series of optical lenses similar to a telescope. The researchers confirmed the focus and control of each laser beam by measuring it using tiny camera sensors.

“This work is part of our efforts at the University of Waterloo to build barium ion quantum processors using atomic systems,” said Dr. Crystal Cinco, co-principal investigator of Islam and a faculty member in the IQC and Waterloo’s Department of Physics and Astronomy. “We use ions because they are identical qubits made by nature, so we don’t need to manufacture them. Our job is to find ways to control them.”

The innovative waveguide method demonstrates a simple and precise control method, showing promise for ion manipulation to encode and process quantum data and its implementation in quantum simulation and computing.

Reference: “A directed photonic system for graceful single processing of Ba+ qubits with 10^-4 “Crosstalk Intensity Level” by Ali Binay Mutlaq, Matthew L. Day, Nikolai Vidinov, Noah Greenberg, Crystal Cinco, and Rajib Islam, July 27, 2023, Quantum science and technology.
doi: 10.1088/2058-9565/ace6cb