Subtle Technologies 2003

Quantum theory is that part of theoretical physics which describes small things like atoms, electrons, and photons (particles of light). The theory doesn’t fit comfortably with our usual intuitions about the world. It has many deeply strange features such as quantum superposition in which a quantum particle can be in two places at once and quantum entanglement in which two quantum particles display a kind of spooky action at a distance. And yet quantum theory seems to be the correct theory of nature. It seems to me that the really interesting question to ask is “Why is nature described by this deeply weird theory?” This is a difficult question. We cannot ask nature herself or god himself (at least I don’t know how to do this). The best we can do in physics is to try to find simple principles from which the more complicated equations of physics follow. If we are satisfied that these principles are sufficiently simple and reasonable then it seems plausible that they represent the reason nature is described by such equations. A few years ago I embarked a project to find some simple reasonable principles that give rise to quantum theory. Eventually I found a set of such principles which, I am convinced, give us a deep insight into why the world is described by quantum theory. Having got that far I started to think about what these principles might be telling us about the nature of reality. I still haven’t reached any definite opinion about this, but the more I think about it the more disturbed and amazed I am. It seems to me that there is a certain sense in which the human condition determines the laws of quantum theory. Actually, this might sound more radical than it is (though from the viewpoint of a scientist it is radical enough) so I had better explain a little more carefully what I mean. In referring to the human condition I am not referring to pain, suffering, and all the difficulties of human existence that make life so difficult and great art so great. Indeed that part of the human condition I am referring to is shared with the animals and even with robots. What I am referring to is that the human condition involves us as actor/observers in the world. We observe the world through our eyes, ears and other senses. And we can act on the world with our hands, feet, voice, and so on. This relatively banal aspect of our existence might be thought to be entirely incidental in the grand scheme of things. But I have come to believe that it is actually central and that the laws of quantum physics are, to a large extent, determined by the fact that we are observer-actors immersed in the world.

Biography
Lucien Hardy received his PhD in theoretical physics in England in 1992. He has held research and lecturing positions in a number of cities across Europe and is now a Long-Term researcher at the Perimeter Institute in Waterloo. He works on conceptual and philosophical issues relating to quantum theory.