Scientists and engineers worldwide are harnessing the unique properties of quantum mechanics to develop systems with extraordinary capabilities, particularly quantum computers that can perform complex calculations at unprecedented speeds. These computers are designed to meet the growing computational demands of scientific research and data-intensive industries like finance, cybersecurity, and medicine.
The development of quantum systems requires an environment that stabilizes the fragile nature of quantum bits (qubits) and dampens the thermal noise (current/voltage fluctuations) inherent in superconducting electronics. This environment necessitates cryogenic temperatures, specifically between 5 to 10 millikelvins, colder than extreme temperatures found in space. Dilution refrigerators create this required cryogenic condition.
For quantum R&D, dilution refrigerators need a wiring system that operates at cryogenic temperatures, maintains a power-efficient direct current, and supports high-speed data transmission. Researchers at MIT Lincoln Laboratory have prototyped flexible, ribbon-like, low-frequency (LF) cables that not only meet these demands but are also compatible with commercial circuit-board manufacturing processes. Maybell Quantum, a Colorado-based company supplying hardware for developing quantum systems, has licensed the design of these cables and is adapting them for use in their dilution refrigerators.
Lasse Nielsen, strategy and operations lead at Maybell Quantum, stated, "We’re planning to integrate Maybell LF CryoTrace, the ribbon wiring system transferred from MIT Lincoln Laboratory, across all thermal stages of our dilution refrigerators. Initially, the cables will be used for LF services, such as thermometry, heaters, and sensors, with feasibility studies planned for additional functions."
To support government initiatives in quantum computing, the Lincoln Laboratory research team investigated alternatives to conventional coaxial cables for use in hardware like dilution refrigerators. Coaxial cables can generate significant heat loads for cryogenic hardware. As the number of qubits in quantum computers increases, so will the number of coaxial cables in the infrastructure, complicating the integration of stiff, bulky cable arrays into hardware supporting superconducting qubits.
The team opted for a stripline cable configuration with conductive layers positioned between flexible polymer layers that shield against electromagnetic interference (crosstalk). Striplines offer consistency across different frequencies and minimal signal loss. The new cables were designed to accommodate large numbers of simultaneous signal transmissions, support direct-current operation without warming the cryogenic environment, and crucially, provide easier integration into hardware than brittle coaxial cables.
John Cummings, a principal investigator in the flexible cables project at Lincoln Laboratory, noted, "The main innovation is that the laboratory's cables can be fabricated by a traditional printed-circuit-board manufacturer. They're cheaper to fabricate and easier to install than traditional coaxial cables." Maybell Quantum emphasizes that the ribbon format is mechanically robust, reducing handling-related breakages common with thin coaxials and improving production repeatability.
Looking ahead, Maybell Quantum aims to support the transition of quantum computing from a laboratory-based capability to an industrial, commercially viable one. The significant gap between the current highly specialized quantum-laboratory environment and the robust infrastructure required for future industrial quantum computing lies in the hardware that promotes the development of functional chips. Maybell's mission is to develop reliable tools that commercial developers of quantum computers can use easily and without the high costs and expert training associated with today's quantum labs.
Kyle Thompson, founder and chief technology officer of Maybell Quantum, remarked, "If you want to scale to hundreds of chips, you need interconnects that can handle more signals more reliably. That’s why the Lincoln Laboratory cables are so exciting for us — they enable true scalability." He further stated, "We believe this technology will materially improve our systems and strengthen the broader U.S. quantum ecosystem by moving federally funded innovation into American manufacturing."
Blogger's Review: The development of flexible cryogenic cables marks a significant advancement in the infrastructure for quantum computing hardware. By addressing the thermal load issues associated with traditional coaxial cables and reducing manufacturing and installation costs, this innovation paves the way for the industrialization of quantum computing. As quantum technology continues to evolve, such advancements will facilitate the widespread application of quantum computers.