https://www.engadget.com/2017/11/26/scientists-develop-fast-quantum-encryption/

"Quantum encryption is theoretically a dream for security, as you can't even inspect the data without altering it. However, it's currently several times slower than the conventional kind, which makes it impractical for voice calls or streaming video. Science may have come to the rescue, though: researchers have developed a quantum encryption key distribution system that promises to be five to 10 times faster than existing methods, or roughly on par with conventional encryption when run in parallel. The trick was to cram more data into each photon."

They still need to work on some problems before it becomes practical, size of machines is one.