Abstract
We present the experimental observation of a large exchange coupling between two electron spin qubits in silicon. The singlet and triplet states of the coupled spins are monitored in real time by a single-electron transistor, which detects ionization from tunnel-rate-dependent processes in the coupled spin system, yielding single-shot readout fidelities above 95%. The triplet to singlet relaxation time at zero magnetic field agrees with the theoretical prediction for -coupled dimers in silicon. The time evolution of the two-electron state populations gives further insight into the valley-orbit eigenstates of the donor dimer, valley selection rules and relaxation rates, and the role of hyperfine interactions. These results pave the way to the realization of two-qubit quantum logic gates with spins in silicon and highlight the necessity to adopt gating schemes compatible with weak -coupling strengths.
- Received 28 February 2014
DOI:https://doi.org/10.1103/PhysRevLett.112.236801
© 2014 American Physical Society