Consider the following three statements. A implies B. B implies C. C implies D. If these three statements are true then it follows from elementary logic that A implies D (this is just the transitivity of implication). I will discuss an example in quantum theory which appears to contradict this elementary logic. To get there we will consider the Elitzur-Vaidman bomb testing problem, quantum interference for electrons and then quantum interference with a double interferometer for an electron and a positron. With this interferometer we get an set of statements that appear to violate the transitivity of implication. However, there cannot exist genuine paradoxes and so this apparent paradox must have a resolution. I will discuss the resolution and what it implies for the picture of reality afforded by quantum theory. The quantum theory we need to employ is very basic and so the ideas in this talk will be readily accessible to non-specialists.
gkarl synopsis: This paradox is known as Hardy's Paradox. It has been checked experimentally in the recent 12 months, we will also have an experimental talk from Steinberg in Toronto, on the experiment.
Host: Gabriel Karl