Estimation of Coupling Constants of a Three-Spin Chain: Case Study of   Hamiltonian Tomography with NMR
  It has been shown that inter-spin interaction strengths in a spins-1/2 chain can be evaluated by accessing one of the edge spins only. We demonstrate this experimentally for the simplest case, a three-spin chain, with nuclear magnetic resonance (NMR) technique. The three spins in the chain interact through nearest-neighbor Ising interactions under site-dependent transverse fields. The employed molecule is an alanine containing three $^{13}$C nuclei, each of which has spin-1/2. 
Elham Hosseini Lapasar, Koji Maruyama, Daniel Burgarth, Takeji Takui,   Yasushi Kondo, and Mikio Nakahara
quant-ph