A calculation apparatus according to an embodiment includes matrix multiplication circuitry, time evolution circuitry, management circuitry, and output circuitry. The matrix multiplication circuitry calculates N second intermediate variables at a first time point by matrix multiplication between N (N>=2) first intermediate variables at the first time point and a preset coefficient matrix in N rows and N columns. The time evolution circuitry calculates N first variables at a second time point and N first intermediate variables at the second time point, the second time point being a time point following one sampling period after the first time point. The management circuitry increments time point from a start time point for each sampling period and controls the above circuitry to perform a process for each time point. The output circuitry outputs N first variables at a preset end time point.