[CraigS]

Originally Posted by sjastro

This is the uncertainty principle at work.

delta(x).delta(p)>h/2 x and p are position and momentum respectively.

In a weak measurement for x, the uncertainty in the measurement of x (delta x) is small hence the uncertainty in the measurement of p (delta p) is large for the inequality to hold.

Aha !! … ok … that makes sense, now !

Originally Posted by sjastro

I don't fully understand what is going on here. Perhaps I should take Richard Feynman's advice and go to another Universe where the physics is easier.

Ya caught me out before I could eliminate the 'eigenvalue' "furphie" which sneaked into my reply post .. (later stealthily removed .. ) …
Undeterred by this however, I'll assume that you mean the bit about how they're associating the real and imaginary parts with position and momentum, though ..(??)..

Originally Posted by sjastro

A wavefunction can be expressed in either position space (x-space) or momentum space (k-space).
The relationship between position and momentum operators is given by
p=-ih(d/dx). That is where your imaginary i term comes into it.

Unfortunately it's not that simple to state your real terms correspond to position and imaginary terms to momentum.
In both x-space and k-space the wavefunctions are complex valued.

It seems the key to this is the coupling of the wavefunction of the photons to the pointer (which is also a wavefunction).

I notice the use of the term 'pointer' .. it seems to be defined a bit like an index 'pointer' in database terminology … the coupling would seem to be the source of establishing the weak part. This 'weak theory' stuff is pretty controversial too, I notice. Not much agreement on its application by QM theorists, apparently ...

Originally Posted by sjastro

That would be great Carl.

Ditto .. thanks Carl .. (although I fear what's in it )!!
Cheers
PS: I'm having recall here at present … this mathematics is so close to applied maths in electrical engineering it ain't funny .. if only my memory was better ..