Hybrid quantum computing circuit combines quantum devices with readout amplifier
Hybrid quantum computing circuit combines quantum devices with readout amplifier lead image
A central challenge in building commercially viable quantum computers is the ability to combine quantum and classical hardware components. Taking a step in solving this problem, Le Guevel et al. developed hybrid circuit prototypes that integrate transimpedance amplifiers (TIAs) with quantum devices.
Quantum devices are kept ultracold via cryostat machines. The quantum state of qubits is coherently controlled and read out using microwave signals, which are typically generated and measured by room-temperature electronics, such as TIAs, located at meter-scale distances.
As more qubits are added to form large-scale processors for complex quantum algorithms, the heat load and time delays associated with the measurement and control wiring are expected to pose serious technical challenges, thereby hindering scalability.
The researchers fabricated a TIA that was able to withstand cryogenic temperatures using complementary metal-oxide semiconductor fully depleted silicon on insulator (CMOS FD-SOI) technology with a 28-nanometer feature size.
“The characteristic transistor size is a critical factor here,” author Loïck Le Guevel said. “We’ve seen more circuits operating well at cryogenic temperatures thanks to recent sub-65-nanometer technologies, such as CMOS FD-SOI.”
The TIA was used to measure a silicon quantum-dot device fabricated on a different chip and connected to the CMOS chip with millimeter-long bonding wires. The results were compared to TIA operation at room temperature. The researchers then demonstrated the integration of TIA with a quantum-dot structure made in the same silicon substrate a micrometer away.
The cryogenic TIA fully operated at a fraction of a degree above absolute zero, achieving better bandwidth and leakage-current reduction because of the reduced cable length. The researchers plan to improve the TIA performance to speed up qubit measurements.
Source: “Low-power transimpedance amplifier for cryogenic integration with quantum devices,” by L. Le Guevel, G. Billiot, B. Cardoso Paz, M. L. V. Tagliaferri, S. De Franceschi, R. Maurand, M. Cassé, M. Zurita, M. Sanquer, M. Vinet, X. Jehl, A. G. M. Jansen, and G. Pillonnet, Applied Physics Reviews (2020). The article can be accessed at https://doi.org/10.1063/5.0007119 .
