keithlucas1947

I am not a physicist and have met quantum mechanics only as part of an engineering course - but I do have training in field theory and a PhD in maths. I am familiar with the solution of Maxwells equations in specific cases including circular polarisation. I am trying to understand the Quantum Eraser. My first question is to understand where classical field theory departs from Quantum theory. It seems to me that Maxwells equations (viewing light only as a wave) would predict interference fringes in every case for the dual slit experiment. The Quarter Wave Plates would introduce equal and opposite orthogonal vectors which would cancel out at the target, leaving normal interference fringes. Is that correct? Does the Quantum Eraser indicate that Maxwells equations break down in the case of single photons? If so - what are the limits of the validity of Maxwells equations?