Playing cards trivia:How many times does the playing card have to be shuffled to be random?

How many times does the playing card need to be washed to wash? In 1992, Percy Deaconis, an American mathematician and professional magician, worked with Dave Bayer of Columbia University to create a mathematical model for cross-shuffling.

Finally, a 20-page long paper was published. They calculated that when there were 52 cards, the seven shuffles were random enough.