Performance characterization of Altera and Xilinx 28 nm FPGAs at cryogenic temperatures

Quantum computers enable a massive speed-up in calculations, thanks to the nature of quantum operations. To unlock quantum computation, a classical system infrastructure is required for the control of qubits and processing of their data. While qubits are generally operating at extremely low temperatures, the implementation of such a control interface is especially challenging for large scale systems, requiring significant physical interconnects between room temperature and the quantum devices. A cryogenic control interface is beneficial due to the closer qubit proximity, reduced thermal heat load, and potentially the integration with qubits at a single temperature. The basis for any such control interface is the error-correction loop, required for a longer coherence time of the qubits. The data processing, in the digital domain, can be completely implemented on an FPGA, operating at cryogenic temperatures. We report on the performance of FPGAs from Altera and Xilinx operating at cryogenic temperatures. A Cyclone V and Artix 7 were implemented on dedicated PCBs and extensive logic characterization was executed to investigate performance changes from room temperature towards 4 Kelvin. According to our extensive and systematic analysis, the Cyclone V is limited in operation down to 30 K, whereas the Artix 7 is fully functional down to 4 K.