A Ring Temperature Sensor for Quantum Applications

In this paper, we present a fully integrated ring-oscillator (RO)-based temperature sensor for quantum computing applications. As the quantum states exhibit an exponential sensitivity to the on-die cryogenic temperature change, any such temperature variation due to, for example, local heating islands arising from the poor thermal conductivity of silicon should be monitored. For this purpose, we exploit a compact RO sensor placed in the vicinity of qubits. The proposed approach employs four differently sized oscillators and two VBGs to generate, in total, eight different temperature-dependent oscillating frequency signals. Then, by performing their polynomial fitting, a linear temperature-frequency compensating model for the proposed sensor is derived. Fabricated in 22 nm FD-SOI technology, the proposed sensor occupies 0.0016 mm², consumes 128 μW and achieves maximum inaccuracy of ± 2.1 K in a wide temperature range from 3 to 270 K.