The Multiphoton Boson Sampling Machine Doesn't Beat Early Classical Computers for Five-boson Sampling.

An ignored algorithm called Store-reuse for calculating the permanent of an n * n matrix is considered. It utilizes computer storages sufficiently, and uses stored data repetitively. The analysis manifests that the numbers of multiplications and additions taken by the Store-reuse algorithm are respectively far smaller than those taken by the famous Ryser's algorithm. As to the 5-boson sampling, the running times of the Store-reuse algorithm for a related permanent on ENIAC and TRADIC are each lower than the that of the sampling operation on the multiphoton boson sampling machine (shortly MPBSM), and thus MPBSM does not beat the early classical computers. However, this does not mean that a quantum boson sampling machine will be beaten by a classical computer when n gets large enough. On a computer, people can design an algorithm that exchanges space for time while on MPBSM, people can not do so, which is the greatest difference between a universal computer and MPBSM. This difference is right the reason why MPBSM may not be called a (photonic) quantum computer.