Faster, energy efficient cooling for trapped-ion quantum computing

Quantum bits (or qubit) are the basic units to process information in quantum computers. While the building blocks of a classical computer — bits — can take a value of either 0 or 1, qubits can have a value of 0 and 1 simultaneously. This superposition enables quantum computers to perform parallel computations and therefore solve problems that are too complex for classical computers.

 

There are several forms of quantum bits, including superconducting, photonic, neutral atoms, trapped ions and quantum dots ^[1]. All of them require cryogenic cooling to perform without errors for long periods of time.

 

High-fidelity trapped-ion control in quantum computing systems typically requires laser cooling to near the motional ground state ^[2], in order to reduce the motion of a trapped ion until it occupies the lowest possible quantum state of motion. To enable fast and accurate quantum operations, researchers use laser light to reduce the kinetic energy of the trapped ion. This causes the ion to cool to nearly absolute zero, an effective temperature even colder than cryostats can achieve.

 

Traditionally, trapped-ion systems have been implemented using complex configurations, whose large size and susceptibility to vibrations and drift can limit the fidelity and addressability of ion arrays, inhibiting scaling to large numbers of qubits ^[3]. Developing trapped-ion quantum computers based on ultra-compact photonic chips can offer a scalable alternative to existing trapped-ion quantum computers, which rely on bulky optical equipment.

 

A team of researchers at Massachusetts Institute of Technology (MIT) and MIT Lincoln Laboratory has implemented a much faster and more energy-efficient method for cooling trapped ions using photonic chips ^[4].

 

With common cooling methods, the ion still has a lot of vibrational energy after the cooling process completes. This would make it hard to use the qubits for high-quality computations. The MIT researchers used an approach known as polarization-gradient cooling, which involves the precise interaction of two beams of light. Each light beam has a different polarization, which means the field in each beam is oscillating in a different direction (up and down, side to side, etc.). Where these beams intersect, they form a rotating vortex of light that can force the ion to stop vibrating even more efficiently.

 

To enable this more complex interaction, the researchers designed a chip with two nanoscale antennas, which emit beams of light out of the chip to manipulate the ion above it.

 

The researchers demonstrated ion cooling that was nearly 10 times below the limit of standard laser cooling, referred to as the Doppler limit. Their chip was able to reach this limit in about 100 microseconds, several times faster than other techniques.

This demonstration marks a significant advance toward scalable, chip-based architectures capable of enabling more efficient and stable quantum computing systems.

 

 

For more information, visit the MIT website.

 

 

Sources

[1] XU C., QIAN N., LIANG K. A mixed refrigerant Joule-Thomson cryocooler for trapped-ion quantum chips. Cryogenics 2025. Proceedings of the 18th IIR International Conference on Cryogenics, Prague, Czech Republic, 7-11 April 2025. http://dx.doi.org/10.18462/iir.cryo.2025.0014

[2] Xing, Z., & Mehta, K. K. (2025). Trapped-ion laser cooling in structured light fields. Physical Review Applied, 24(1), 014034. https://doi.org/10.48550/arXiv.2411.08844

[3] Corsetti, S.M., Hattori, A., Clements, E.R. et al. Integrated-photonics-based systems for polarization-gradient cooling of trapped ions. Light Sci Appl 15, 57 (2026). https://doi.org/10.1038/s41377-025-02094-4

[4] https://news.mit.edu/2026/efficient-cooling-method-could-enable-chip-based-quantum-computers-0115