A research team in China has built a quantum dot device that produces photon pairs with record-setting purity, achieving a two-photon fraction of 0.983(1). The work, published in Nature Materials, ...

The S&P 500 closed at 6,740 on Friday, its lowest level since mid-December, as technical deterioration, collapsing payrolls, and $90 oil converged on the charts. Every major moving average has broken.