Driven Spin Arrays for Quantum Computing and Measurement
Speaker: Brendon Lovett, Heriot-Watt University, Edinburgh
Department: Electrical Engineering
Location: Bowen Hall Auditorium 222
Date/Time: Thursday, March 28, 2013, 12:00 p.m. - 1:00 p.m.
In this talk, I will present two ideas which exploit different patterns of spins in crystals, for quantum computing and quantum signal amplification and measurement.
First, nitrogen vacancy (NV) centres in diamond are one of the most promising candidates for embodying small numbers of spin qubits in simple quantum processors. How to upsize such systems into full scale quantum computers is not yet clear. Here, I will discuss the recent idea that two nitrogen-vacancy (NV) defect centers in diamond can be connected by a chain of implanted nitrogen impurities, and when driven by suitable global fields the chain can potentially enable quantum state transfer at room temperature . However, our detailed analysis of error effects suggests that foreseeable systems using this idea may fall far short of the fidelities required for full quantum computing . Fortunately, I will go on to demonstrate that instead the chain can function in the more modest role as a mediator of noisy entanglement, and so can function as a quantum computer provided that subsequent
purification is used .
Second, single electron spins are difficult to measure, though such a single spin measurement is a key enabling technology for a quantum processor. I will discuss a new approach to measuring single spins which relies on spin amplification . We show that it is possible to rapidly and robustly amplify a spin state using a lattice of ancillary spins. The model we employ corresponds to an extremely simple system: a homogenous Ising-coupled spin lattice in one, two, or three dimensions, driven by a continuous microwave field. We hope that the simplicity of the model makes this approach amenable to experimental testing in the near future.
 N. Y. Yao, L. Jiang, A. V. Gorshkov, P. C. Maurer, G. Giedke, J. I. Cirac and M. D. Lukin, Nature Communications 3, 800 (2012)
 Y. Ping, B. W. Lovett, S. C. Benjamin and E. M. Gauger, Phys. Rev. Lett. 110 100503 (2013)
 Rapid and robust spin state amplification, T. Close, F. Fadugba. J. Fitzsimons, S. C. Benjamin and B. W. Lovett, Phys. Rev. Lett. 106 110504 (2011)