Fraunhofer Institute for Electronic Microsystems and Solid State Technologies EMFTInnovative interconnection technology is an "enabler" for realizing quantum computers with 100 qubits or more. Solutions currently used in quantum computers, such as coaxial cables, have limited capabilities. Fraunhofer research teams are working on extremely thin, flexible superconducting cables, enabling a high density of signal connections. At the same time, thermal loads can be considerably reduced by decreasing the total cable cross section. Moreover, a PCB direct interconnection customized for the cables provides a space-optimized wiring system.
Flexible Superconducting Interconnects
Thin, flexible RF transmission lines for superconducting quantum circuits fabricated at Fraunhofer EMFT using roll-to-roll technology to enable upscaling of parallel interconnects (1000+) in the cryostat.
Fraunhofer EMFT's roll-to-roll pilot line is used to realize thin and flexible RF signal lines for superconducting quantum circuits. This allows cost-effective processing using lithography, laser structuring, printing, vacuum-based processes and system integration and enables the realization of electronic systems that are thin, flexible and large-area. Extremely precise structures with high repeat accuracy can be produced.
With Fraunhofer EMFT´s “endless electronics” roll-to-roll line, cables of any desired length can be realized. The welding together of sections, as is done with currently available solutions, is no longer necessary - a considerable quality, cost and time advantage.
Fraunhofer EMFT draws on years of experience in the field of assembly and connection technology. With a customized direct contacting between cable and PCB, Fraunhofer EMFT offers a space-saving contacting solution that is optimally adapted to flexible cable designs and thus offers a high signal integrity and reliability. Special contact elements ensure optimum signal transfer even at very low temperatures.
1.25 m long copper conducting paths with a width and spacing down to 20 µm were fabricated on polyimide foil by digital photolithography and wet chemical etching of the copper. By lithographically stitching consecutive images of 10 cm long line segments, copper lines of any length can be generated.
Springloaded direct contacting of flexible cable with printed circuit board
High density superconducting cables: 80 individually shielded signal lines per inch
With the number of qubits, the number of required cables also increases. This makes a space-saving cabling solution mandatory for large-scale quantum computers. Our cable design with a thickness of less than 100 micrometers, jointly developed with Fraunhofer IIS, allows for a large number of signal lines to be provided in a very small space. The flexible high density interconnects provide over 80 individually shielded signal lines per inch. This is essential for both the transmission of control and readout signals of the qubits.
Signal integrity in terms of cross talk and signal losses is ensured by using superconducting materials and an innovative shielding concept. Furthermore, the team is developing additional specific functions such as bandpass/lowpass filters or attenuators that can be integrated directly into the cable.
Another advantage of this technology: Significantly less heat is passively transferred. Fraunhofer EMFT´s high-density superconducting cables therefore allow for optimum use of the limited cooling power in quantum computer cryostats.
Fraunhofer EMFT offers a complete solution consisting of flexible high density superconducting cables and interconnects that is unique in terms of signal density. The cable design is highly scalable and can therefore be adapted to customer requirements at any time.