المؤلفون: Juan P Dehollain, Juha T Muhonen, Robin Blume-Kohout, Kenneth M Rudinger, John King Gamble, Erik Nielsen, Arne Laucht, Stephanie Simmons, Rachpon Kalra, Andrew S Dzurak, Andrea Morello

المصدر: New Journal of Physics, Vol 18, Iss 10, p 103018 (2016)

مصطلحات موضوعية: quantum computing, silicon, tomography, 03.65.Wj, 03.67.Ac, 03.67.Lx, Science, Physics, QC1-999

الوصف: State of the art qubit systems are reaching the gate fidelities required for scalable quantum computation architectures. Further improvements in the fidelity of quantum gates demands characterization and benchmarking protocols that are efficient, reliable and extremely accurate. Ideally, a benchmarking protocol should also provide information on how to rectify residual errors. Gate set tomography (GST) is one such protocol designed to give detailed characterization of as-built qubits. We implemented GST on a high-fidelity electron-spin qubit confined by a single ^31 P atom in ^28 Si. The results reveal systematic errors that a randomized benchmarking analysis could measure but not identify, whereas GST indicated the need for improved calibration of the length of the control pulses. After introducing this modification, we measured a new benchmark average gate fidelity of $99.942(8) \% $ , an improvement on the previous value of $99.90(2) \% $ . Furthermore, GST revealed high levels of non-Markovian noise in the system, which will need to be understood and addressed when the qubit is used within a fault-tolerant quantum computation scheme.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1367-2630Test

الوصول الحر: https://doaj.org/article/20b88b157e5442c5afdf73124287b1b5Test

المؤلفون: Gary Wolfowicz, Pierre-André Mortemousque, Roland Guichard, Stephanie Simmons, Mike L W Thewalt, Kohei M Itoh, John J L Morton

المصدر: New Journal of Physics, Vol 18, Iss 2, p 023021 (2016)

مصطلحات موضوعية: nuclear spins, decoherence, quantum error correction, donors in silicon, Science, Physics, QC1-999

الوصف: Nuclear spin registers in the vicinity of electron spins in solid state systems offer a powerful resource to address the challenge of scalability in quantum architectures. We investigate here the properties of ^29 Si nuclear spins surrounding donor atoms in silicon, and consider the use of such spins, combined with the donor nuclear spin, as a quantum register coupled to the donor electron spin. We find the coherence of the nearby ^29 Si nuclear spins is effectively protected by the presence of the donor electron spin, leading to coherence times in the second timescale—over two orders of magnitude greater than the coherence times in bulk silicon. We theoretically investigate the use of such a register for quantum error correction (QEC), including methods to protect nuclear spins from the ionisation/neutralisation of the donor, which is necessary for the re-initialisation of the ancillae qubits. This provides a route for multi-round QEC using donors in silicon.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1367-2630Test

الوصول الحر: https://doaj.org/article/9b696b9cc8a1498e9c9191e45b8ac8d9Test