  Quantum simulators are controllable quantum systems that can reproduce the
dynamics of the system of interest, which are unfeasible for classical
computers. Recent developments in quantum technology enable the precise control
of individual quantum particles as required for studying complex quantum
systems. Particularly, quantum simulators capable of simulating frustrated
Heisenberg spin systems provide platforms for understanding exotic matter such
as high-temperature superconductors. Here we report the analog quantum
simulation of the ground-state wavefunction to probe arbitrary Heisenberg-type
interactions among four spin-1/2 particles . Depending on the interaction
strength, frustration within the system emerges such that the ground state
evolves from a localized to a resonating valence-bond state. This spin-1/2
tetramer is created using the polarization states of four photons. The
single-particle addressability and tunable measurement-induced interactions
provide us insights into entanglement dynamics among individual particles. We
directly extract ground-state energies and pair-wise quantum correlations to
observe the monogamy of entanglement.
