NMR Sees the Spin of a Single Proton
Figure 2(a): Coherent control of reporter spins. Rabi oscillations between spin states with a variable-width pulse (red points) with an exponentially damped fit (blue line). Inset: rf pulse sequence. [From: A. Sushkov, I. Lovchinsky, N. Chisholm, R.L. Walsworth, H. Park, and M.D. Lukin, "Magnetic Resonance Detection of Individual Proton Spins Using Quantum Reporters," Phys. Rev. Lett. 113, 197601 | DOI: http://dx.doi.org/10.1103/PhysRevLett.113.197601. Copyright ©2014 by The American Physical Society]
A team of researchers, including Professors Walsworth, Park, and Lukin, published an article in Physical Review Letters in which they demonstrate a method of magnetic resonance imaging with single nuclear-spin sensitivity under ambient conditions. Their method employs isolated electronic-spin quantum bits (qubits) as magnetic resonance “reporters” on the surface of high purity diamond. These spin qubits are localized with nanometer-scale uncertainty, and their quantum state is coherently manipulated and measured optically via a proximal nitrogen-vacancy color center located a few nanometers below the diamond surface. This system is then used for sensing, coherent coupling, and imaging of individual proton spins on the diamond surface with angstrom resolution. The authors believe their approach may enable direct structural imaging of complex molecules that cannot be accessed from bulk studies. It realizes a new platform for probing novel materials, monitoring chemical reactions, and manipulation of complex systems on surfaces at a quantum level.