Implementation of high-fidelity mixed-species entangling gate

Implementation of high-fidelity mixed-species entangling gate - Credit: D. P. Nadlinger

Researchers at the University of Oxford have recently implemented a two-qubit entangling gate between two distinct atomic elements, calcium and strontium.

They used a gate mechanism that requires only a single laser, which they had previously tested on two different calcium isotopes.

One of the greatest challenges in the development of trapped ion quantum computers is scalability: simply adding new qubits to a quantum computing system often results in a rapid decrease in performance, as it introduces new errors and makes it harder to interact with a single qubit without affecting some of the others.

The research team used two methods known as modularization and optical networking. They have ions in separate ion traps and vacuum systems, which are only connected through optical fibers, which limits crosstalk between qubits, retaining only interactions that are desirable and can be controlled.

Previously, other researchers who previously implemented mixed-species two-qubit entangling gates used different lasers to manipulate different elements. To do this, however, they must ensure that the two lasers are well synchronized and calibrated so that they have a similar effect on the two different ion species. The team at the University of Oxford only used a single laser.

This study could contribute to the creation of new trapped ion quantum computing approaches that are easier to scale up. (

The paper has been published in Physical Review Letters.

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