Quant funds in China have become so popular that they are being deluged with investors’ money. Ubiquant, one of the top players, raised 2.6 billion yuan ($384 million) in less than two hours for a new fund in May, according to people familiar with the matter. Investors also snapped up over 100 million yuan of a product from Shenzhen ChengQi Asset Management Ltd. within seconds, a product distributor said....