Liquid metal offers fluid replacement of quantum chip interconnects

Qubits, the basic units of a quantum computer, can break. If one qubit in a system breaks and all the qubits are on one chip, the entire chip must be replaced. For smaller systems, this might not be a major concern, but it becomes increasingly problematic as the quantum computing field designs larger computers.

For these larger systems, a modular architecture of smaller interconnected chips allows a broken qubit on one chip to be replaced without scrapping the entire system, saving resources. However, these modules are traditionally connected with solid-state galvanic interconnects, which must be broken to replace a chip. Inspired by stretchable electronics, Yao et al. proposed using a liquid metal for the interconnects. Gallium alloy is a liquid at room temperature and can be self-healing, potentially allowing non-destructive chip replacement.

To test the performance of these liquid metal interconnects, the authors built coplanar waveguide resonators connected by gallium alloy droplets. They found the performance of the liquid metal was similar to that of solid-state interconnects.

“We think it’s promising,” said author Zhancheng Yao. “No one has ever explored liquid metal in the quantum computing application, and it’s important to introduce this new method without compromising the performance.”

Next, the authors will build and test an actual modular quantum system of two chips connected by the liquid metal. This method has potential applications in scaled-up quantum circuits, such as those being built in industry.

“I would argue this work will be important when making a larger quantum system,” Yao said.

Source: “Low-loss liquid metal interconnects for superconducting quantum circuits,” by Zhancheng Yao, Martin Sandberg, David W. Abraham, and David J. Bishop, Applied Physics Letters (2024). The article can be accessed at https://doi.org/10.1063/5.0211244 .