Towards a large scale simulation of many body ground states by measurement induced back action

Singlet pairing is a well-studied physical mechanism in strongly correlated systems. Quantum particles paired in singlets share maximal entanglement and their total vanishing spin renders them robust to external noise. Inducing such pairing in any random spin ensemble has many potential applications in the field of quantum limited sensing$[1,2]$ and quantum information processing$[3]$. We show here how singlet pairing can be generated in an unpolarized nuclear spin ensemble which is dipolar coupled to a Nitrogen Vacancy (NV) center in diamond. Alongside the singlet formation, the long life times of these spins constitute a potential test bed for simulating quantum correlations of dimer compounds crystallizing into singlet pairs.$[4]$\\ $[1]$ Wrachtrup, J. & Finkler, A. Single spin magnetic resonance. Journal of Magnetic Resonance 269, 225–236 (2016).$[2]$ Zaiser, S. et al. Enhancing quantum sensing sensitivity by a quantum memory. Nature Communications 7, 12279 (2016).$[3]$ Waldherr, G. et al. Quantum error correction in a solid-state hybrid spin register. Nature 506, 204–207 (2014).\\ $[4]$ Greiner, J. N., Rao, D. D. B. & Wrachtrup, J. Purification of an unpolarized spin ensemble into entangled singlet pairs. arXiv:1610.08886 [quant-ph] (2016).