RT Journal Article SR Electronic T1 Atomically engineered electron spin lifetimes of 30 s in silicon JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP e1602811 DO 10.1126/sciadv.1602811 VO 3 IS 3 A1 Watson, Thomas F. A1 Weber, Bent A1 Hsueh, Yu-Ling A1 Hollenberg, Lloyd C. L. A1 Rahman, Rajib A1 Simmons, Michelle Y. YR 2017 UL http://advances.sciencemag.org/content/3/3/e1602811.abstract AB Scaling up to large arrays of donor-based spin qubits for quantum computation will require the ability to perform high-fidelity readout of multiple individual spin qubits. Recent experiments have shown that the limiting factor for high-fidelity readout of many qubits is the lifetime of the electron spin. We demonstrate the longest reported lifetimes (up to 30 s) of any electron spin qubit in a nanoelectronic device. By atomic-level engineering of the electron wave function within phosphorus atom quantum dots, we can minimize spin relaxation in agreement with recent theoretical predictions. These lifetimes allow us to demonstrate the sequential readout of two electron spin qubits with fidelities as high as 99.8%, which is above the surface code fault-tolerant threshold. This work paves the way for future experiments on multiqubit systems using donors in silicon.