  Drawing fair samples from the Boltzmann distribution of a statistical model
is a challenging task for modern digital computers. We propose a physical
implementation of a Boltzmann sampler for the classical XY model by using a
laser network. The XY spins are mapped onto the phases of multiple laser pulses
in a fiber ring cavity and the steady-state distribution of phases naturally
realizes the Boltzmann distribution of the corresponding XY model. We
experimentally implement the laser network by using an actively mode-locked
fiber laser with optical delay lines, and demonstrate Boltzmann sampling for a
one-dimensional XY ring.
