This paper explains the delayed choice quantum eraser of Kim et al. in terms of the transactional interpretation of quantum mechanics by Cramer. It is kept deliberately mathematically simple to help explain the transactional technique. The emphasis is on a clear understanding of how the instantaneous “collapse” of the wave function due to a measurement at a specific time and place may be reinterpreted as a relativistically well-defined collapse over the entire path of the photon and over the entire transit (...) time from slit to detector. This is made possible by the use of a retarded offer wave, which is thought to travel from the slits to the detector and an advanced counter wave traveling backward in time from the detector to the slits. The point here is to make clear how simple the transactional picture is and how much more intuitive the collapse of the wave function becomes if viewed in this way. Also, any confusion about possible retro-causal signaling is put to rest. A delayed choice quantum eraser does not require any sort of backward in time communication. This paper makes the point that it is preferable to use the TI over the usual Copenhagen interpretation for a more intuitive understanding of the quantum eraser delayed choice experiment. Both methods give exactly the same end results and can be used interchangeably. (shrink)

We take for granted that Gravitational Waves (GWs) exist, but examine critically the possibility for their direct observation with ground and space-based laser interferometers. It is argued that the detection of GWs can, at least theoretically, be achieved iff three requirements are met en bloc. Alternatively, a hypothetical case related to the so-called dark energy would render the task impossible in principle. The discussion is kept at conceptual level, to make it accessible to the general audience.