  Quantum computation requires many qubits that can be coherently controlled
and coupled to each other. Qubits that are defined using lithographic
techniques are often argued to be promising platforms for scalability, since
they can be implemented using semiconductor fabrication technology. However,
leading solid-state approaches function only at temperatures below 100 mK,
where cooling power is extremely limited, and this severely impacts the
perspective for practical quantum computation. Recent works on spins in silicon
have shown steps towards a platform that can be operated at higher temperatures
by demonstrating long spin lifetimes, gate-based spin readout, and coherent
single-spin control, but the crucial two-qubit logic gate has been missing.
Here we demonstrate that silicon quantum dots can have sufficient thermal
robustness to enable the execution of a universal gate set above one Kelvin. We
obtain single-qubit control via electron-spin-resonance (ESR) and readout using
Pauli spin blockade. We show individual coherent control of two qubits and
measure single-qubit fidelities up to 99.3 %. We demonstrate tunability of the
exchange interaction between the two spins from 0.5 up to 18 MHz and use this
to execute coherent two-qubit controlled rotations (CROT). The demonstration of
`hot' and universal quantum logic in a semiconductor platform paves the way for
quantum integrated circuits hosting the quantum hardware and their control
circuitry all on the same chip, providing a scalable approach towards practical
quantum information.
