HUP --> Heisenberg Uncertainty Principle The below questions maybe a bit amateurish. 1. Can two photons be entangled on both position and momentum?....for a same time period I think not because: To entangle on momentum (or any property) we need a broad distribution of momentum for the photon. Same for position. However a photon cannot have a broad distribution for both (?). 2. why is a broad distribution (for the property on which the two photons will be entangled) needed for entanglement? or in other words why are we not able to violate bell inequalities when the distribution is narrow? 3. In a single particle, double-slit experiment, when we do which-way: at that point do we have a broader distribution for momentum since the positions has been narrowed? 4. Most of the mystery lies in HUP it seems. For example complimentarity is just an expression/corollary of HUP. Position & momentum are entangled Time & energy are entangled (?) Would a dimension analysis, like the one below, throw some light on HUP? Can one find similarities between position-momentum AND time-energy via dimensional analysis? What position (meters) is to (kgs*(meters/sec) ---> position is to momentum Time (sec) is to Energy (kg*(meters^2/sec) -----> Time is to energy It does not seem to work. Dimension analysis does not shed any light on HUP. 4 b) are all complimentarities reducible to one complimentarity? 5. We say position and momentum are complimentary. Since the velocity of the photon is always c, Is (relativistic) mass not constant?...in the case of a photon Thus why can we not say position and velocity are complimentary? 6. when we narrow the position distribution, the momentum distribution must spread out. Is there any analogy in classical mechanics? 7. For a single photon -- what does it mean to be incoherent (or coherent)? I guess - for a single photon -- the wave-function travelling the various paths can be made incoherent and that would somehow make the single photon incoherent. 8. Coherency between two "self-coherent" photons means that they have a fixed phase relationship (?) The photons are self coherent and photon A has a fixed phase relationship with photon B. Does Coherency between two self-incoherent photons again mean there is a fixed phase relationship between photon A and photon B however photon A and photon B are "individually" self-incoherent? 9. In case of photon A being entangled with photon B: the more entangled (and hence coherent?) photon A is with B the less coherent it is with self. In other words: for A to be more coherent with B A needs to be less coherent with itself...... what does being less coherent with itself mean?