Negoro, M., et al., Scalable Spin Amplification with a Gain Over a Hundred. Phys. Rev. Lett., 2011. 107(5): p. 050503.
http://link.aps.org/doi/10.1103/PhysRevLett.107.050503
We propose a scalable and practical implementation of spin amplification which does not require individual addressing nor a specially tailored spin network. We have demonstrated a gain of 140 in a solid-state nuclear spin system of which the spin polarization has been increased to 0.12 using dynamic nuclear polarization with photoexcited triplet electron spins. Spin amplification scalable to a higher gain opens the door to the single spin measurement for a readout of quantum computers as well as practical applications of nuclear magnetic resonance spectroscopy to infinitesimal samples which have been concealed by thermal noise.