tqix.pis: A toolbox for quantum dynamics simulation of spin ensembles in Dicke basis

We introduce tqix.pis, a library of tqix, for quantum dynamics simulation of spin ensembles. The library emulates a dynamic process by a quantum circuit, including initializing a quantum state, executing quantum operators, and measuring the final state. It utilizes collective processes in spin ensembles to reduce the dimension from exponentially to quadratically with the number of particles, i.e., the quantum state spans in Dicke basis. It also facilitates the simulation time with multi-core processors and Graphics Processing Units. The library is thus applicable for the simulation of ensembles of large number of particles that have collective properties. Various phenomena, such as spin squeezing, variational quantum squeezing, quantum phase transition, and many-body quantum dynamics, can be simulated using the library.