Chip-delivered standing wave cools trapped ion faster across three motional modes

Researchers at Cornell University have shown that light delivered through a microfabricated photonic chip can cool a trapped ion to near its quantum ground state roughly three times faster than a conventional laser arrangement. The technique also cooled all three measured modes of the ion's motion at once. The work, led by Karan Mehta, was published on 9 November in PRX Quantum.

Why cooling is a bottleneck

Trapped-ion quantum computers hold information in individual charged atoms suspended by electromagnetic fields. The approach offers very precise quantum control, but even small amounts of unwanted motion can disrupt calculations. Lasers must therefore repeatedly cool the ions close to their lowest energy state.

Mehta, an assistant professor of electrical and computer engineering in the Cornell Duffield College of Engineering, notes that this step can take up a large share of operating time. Cooling to near the ground state, he said, is a major bottleneck in leading systems, rather than the logic operations themselves.

A standing wave on a chip

Mehta's group develops integrated photonics for atom control, in which light travels through microscopic waveguides on the same chip that hosts the atoms. The stability of these optics allowed the team to produce a carefully controlled standing wave, formed by two laser beams travelling in opposite directions. This creates alternating regions of high and low light intensity.

The researchers placed a trapped calcium ion at a point of minimum intensity. There, the light could still remove energy from the ion's motion, while interactions that would otherwise cause heating were suppressed.

The experimental design builds on theoretical predictions by doctoral student Zhenzhong Xing. Xing and fellow doctoral student Hamim Mahmud Rivy, the co-first authors, carried out the experiments. This included developing packaging that lets the chips handle wavelengths from ultraviolet to near-infrared while operating at cryogenic temperatures.

Faster, and across several modes

Using electromagnetically induced transparency cooling, the team brought the targeted motion close to the quantum ground state in about 150 microseconds. A conventional laser arrangement needed about 500 microseconds.

The method also cooled all three measured motional modes together, covering a frequency range of around 5 megahertz. An ion can oscillate in three dimensions, each with its own frequency, and conventional approaches often need separate cooling steps for different modes. Xing said the approach works effectively when the motional frequencies are not too far apart.

The team also reported cooling below the conventional Doppler limit, which they describe as an experimental confirmation of a longstanding theoretical prediction.

Limits and next steps

The demonstration used a single ion, so performance in larger systems remains to be tested, although the authors state that the approach applies to larger trapped-ion machines. The chips were fabricated commercially in the Netherlands through a collaboration with ETH Zurich, and Cornell facilities, including the Cornell NanoScale Science and Technology Facility, were used for packaging and preparation.

The result is relevant to a wider effort by several groups to build photonic delivery of multiple wavelengths into trap chips, as a route to systems with many more qubits. Mehta argues that the work shows how technologies developed for scaling up can also improve the basic operations on which quantum computers depend. The key tests ahead are likely to be multi-ion chains, where many motional modes must be cooled together without added crosstalk.

The paper is: Zhenzhong Xing et al., "Rapid Multi-Mode Trapped-Ion Laser Cooling in a Phase-Stable Standing Wave", PRX Quantum (2026), DOI 10.1103/5btm-vwgy.

Source: Chip-based laser cooling could ease quantum computing bottleneck (Phys.org, 13 November 2026).

Image: AI-generated illustration.