A quantum simulator includes a pseudo speckle pattern generator, a main vacuum chamber, an atomic gas supply unit, a light beam generator, a photodetector, and an atom number detector. The pseudo speckle pattern generator generates a pseudo speckle pattern in the inside of the main vacuum chamber by light allowed to enter the inside of the main vacuum chamber through the second window. The pseudo speckle pattern generator includes a controller, a light source, a beam expander, a spatial light modulator, and a lens. The controller sets a modulation distribution of the spatial light modultor based on a two-dimensional pseudo random number pattern.