Zhancheng Yao

Reconfigurable Superconducting Quantum Circuits Enabled by Micro-Scale Liquid-Metal Interconnects

  1. Zhancheng Yao,
  2. Nicholas E. Fuhr,
  3. Nicholas Russo,
  4. David W. Abraham,
  5. Kevin E. Smith,
  6. and David J. Bishop
Modular architectures are a promising route toward scalable superconducting quantum processors, but finite fabrication yield and the lack of high quality temporary interconnects impose
fundamental limitations on system size. Here, we demonstrate chip-scale liquid-metal interconnects that show promise for plug-and-play superconducting quantum circuits by enabling non-destructive module replacement while maintaining high microwave performance. Using gallium-based liquid metals, we realize high-quality inter-module signal and ground interconnects, comparable in performance to conventional coplanar waveguide resonators. We illustrate consistent device characteristics across three thermal cycles between room temperature and 15 mK, as well as the ability to reform superconducting connections following module replacement. A width-dependent resonance frequency shift reveals a significant kinetic inductance fraction, which we attribute to the presence of β-phase tantalum as confirmed by X-ray characterization. Finally, we investigate power-dependent loss mechanisms and observe high-power dissipative nonlinearities qualitatively consistent with a readout-power heating model. These results establish liquid metals as viable chip-scale interconnects for reconfigurable, modular superconducting quantum systems.
arxiv pdf

Low-loss liquid metal interconnects for modular superconducting quantum systems

  1. Zhancheng Yao,
  2. Martin Sandberg,
  3. David W. Abraham,
  4. and David J. Bishop
Building modular architecture with superconducting quantum computing chips is one of the means to achieve qubit scalability, allowing the screening, selection, replacement, and integration
of individual qubit modules into large quantum systems. However, the non-destructive replacement of modules within a compact architecture remains a challenge. Liquid metals (LM), specifically gallium alloys, can be alternatives to solid-state galvanic interconnects. This is motivated by their self-healing, self-aligning, and other desirable fluidic properties, potentially enabling non-destructive replacement of modules at room temperatures, even after operating the entire system at millikelvin regimes. In this study, we present high-internal-quality-factor coplanar waveguide resonators (CPWR) interconnected by gallium alloy droplets, demonstrating performance on par with the continuous solid-state CPWRs. Leveraging the desirable fluidic properties of gallium alloys at room temperature and their compact design, we envision a modular quantum system enabled by liquid metals.
arxiv pdf