Jean-Claude Besse

An ordinary envelope has a rectangular shape, and the letter inside does not change the envelope's properties. With photons, particles of light, the situation is different: their 'shape' in time can vary, and this shape itself carries information.

Quantum computers in the cloud are like a post office: you send a letter, and someone else reads the address and the contents. In ordinary computing, the server sees your data and algorithm. Blind quantum computing is an unopenable envelope: the server does the work but doesn't know what it's doing.