Universal quantum logic in hot silicon qubits

Large scale quantum computation can leverage significantly from semiconductor fabrication technology, to allow for quantum integrated circuits, hosting quantum hardware and control circuitry all on the same chip. However, leading qubit approaches operate at very low temperatures below 100 mK, where cooling power is extremely limited, and this severely impacts the perspective for practical quantum computation. Demonstrating qubit operation at elevated temperatures would therefore be a major breakthrough in the effort towards scalable quantum systems.
Here, we study quantum operations in a silicon two-qubit system, operated at a temperature of 1.1 K. We perform readout using Pauli spin blockade and obtain coherent single-qubit control via electron-spin-resonance, with fidelities exceeding 99 %. We show tunability of the exchange interaction between the two spins from 0.5 up to 18 MHz and use this mechanism to execute coherent two-qubit controlled rotations (CROT). We additionally investigate the temperature dependence of the coherence times, which we find surprisingly robust against thermal noise.
Our results mark an important step for the realization of quantum integrated circuits, a scalable approach towards practical quantum computation.