λDiffraction and the nanoscale

Physical intuition

A propagating far-field wave cannot freely resolve arbitrary subwavelength detail. This is the starting point for understanding how nanoscale optical geometry changes the states or dynamics accessible to light and matter.

Deep dive: how the mechanism works

An objective accepts only a finite range of transverse wavevectors; subwavelength spatial frequencies are typically evanescent and decay before reaching the detector.

How the quantum phenomenon appears

Near-field scanning optical microscopy accesses evanescent information close to a sample. To distinguish a genuinely quantum signal from a classical optical response, connect the device physics to a measurement such as photon correlations, interference visibility, energy-level structure or quantum-state tomography where appropriate.

Assumptions and limitations

Research and simulation exercise

Identify the tunable parameters, predict the observable from the stated model, and sweep one parameter while holding the others fixed. Compare against a simpler reference model, quantify loss and uncertainty, and state which observations would falsify the hypothesis.

Connect the ideas

See the chapter guide and further reading.