When Did Quantum Computing Start to Look Like a Real Threat to Cryptography?

Short answer: Not early enough to make us not panic.

Source: https://www.quantamagazine.org/mathematicians-seal-back-door-to-breaking-rsa-encryption-20181217/

A quantum revolution is in the air, powered by formidable computing power and counterintuitive subatomic properties. While many are looking forward to the quantum magic that can dramatically accelerate computations, we may also be launching…