quantamagazine.orgFreedom and restraint seem like opposing forces, but to Yu Deng, they go hand in hand. Take the poem he's just pulled up on his computer screen: a dense forest of Chinese characters corralled into eight lines of equal length - a perfect, symmetric block of text. Written in the ninth century by the Tang Dynasty poet Li Shangyin, as China teetered on the brink of civil war, "The Brocade Zither" is…