Single-donor Electron and Nuclear Spin Qubits in Silicon Andrea Morello ARC Centre of Excellence Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney NSW 2052, Australia The idea of using the nuclear spin of a single phosphorus atom in silicon as the building block of scalable solid-state quantum computer was proposed by Kane in 1998 [1]. The proposal appeared wild at the time, but very appealing if realized. Silicon is, at the same time, the platform of choice for the microelectronic industry, and an excellent solid-state environment to host highly coherent spin qubits. We have now experimentally demonstrated the full quantum control and readout of both the electron and the nuclear spin of a single P atom, implanted in a silicon chip [2]. The device structure is compact and fully compatible with standard silicon nanoelectronics [3]. It consists of the P atom, a silicon single-electron transistor for charge sensing, and a nanofabricated microwave transmission line to perform spin resonance. The electron spin of the single P atom can be readout in single-shot with fidelity > 90% on ~10 μs time scales. Its relaxation time can be as long T1e ~ 6 s at B = 1.5 T [4]. More recently, we have demonstrated coherent Rabi oscillations and spin echo, with coherence times T2e ~ 200 μs as expected from the coupling to the 29Si nuclear spins in the bulk. In addition, we have gained full control and single-shot readout of the nuclear spin qubit as well. The readout fidelity is > 99.9%, and we observe quantum jumps on ~10 minutes time scales, which is a measure of the nuclear T1n. Nuclear Rabi oscillations, Ramsey fringes and spin echo have been demonstrated, with T2n ~ 60 ms. [1] B. E. Kane, Nature 393, 133 (1998). [2] D. N. Jamieson et al., Appl. Phys. Lett. 86, 202101 (2005). [3] A. Morello et al., Phys. Rev. B 80, 081307(R) (2009). [4] A. Morello et al., Nature 467, 687 (2010). .