In 1982, a paper entitled “FLASH – A Superluminal Communicator Based Upon a New Kind of Quantum Measurement” was published by Nick Herbert, an American physicist who meant to prove that by using EPR entangled pairs and quantum effects, a superluminial communicator could be built to transmit information at speeds faster than the speed of light . Such a statement caused quite some uproar in the scientific community, because, as you may know, there are no signals than can travel faster than light.
The story of Herbert’s paper is not a story of an experimental proposal with a fundamental error, but the story of scientific progress and how, by studying the possibility of a superluminial communicator, the no-cloning theorem came to be. We will see in this article how the resolution of this problem improved our understanding of physics by showing that we cannot copy an unknown quantum state.
Now, before proceeding to review Herbert’s paper, we should first answer the question:
Could there be superluminial velocities?
The answer to this questions is no… and yes… (of course it is, isn’t it?). Let’s first try to understand why it is that the answer to this question should be no.