(app:g)=
# Reading Guide
This guide groups references by reading purpose. The main chapters contain denser citations; this appendix gives a starting set for entering each topic. All entries use NASA ADS BibTeX keys and are maintained in `references.bib`.

(appsec:g-classic)=
## Classic Starting Points
The historical starting point for intensity interferometry is the experiment and astronomical implementation by Hanbury Brown and Twiss {cite:p}`1956Natur.178.1046H,1957RSPSA.242..300B,1974iiia.book.....H`. Read these papers for how they connect the correlation peak, telescope area, baseline, bandwidth, and integration time into an executable observation; do not stop at the name $g^{(2)}$. For the quantum-optics foundation, start with Glauber and Sudarshan on optical coherence, then Mandel--Wolf and Gerry--Knight for textbook treatments {cite:p}`1963PhRv..130.2529G,1963PhRvL..10..277S,1995ocqo.book.....M,1985stop.book.....G`.

(appsec:g-sii)=
## The Modern Revival of Intensity Interferometry
The modern revival combines Cherenkov arrays, large collecting area, digital correlators, and calibrator-star catalogs. Early concepts and instrumental paths are discussed by {cite:t}`2009A&A...508..531N` {cite:p}`2017MNRAS.472.4126G`; real astronomical results from VERITAS, MAGIC, and later samples mark the transition into systematic measurement {cite:p}`2020NatAs...4.1164A,2021MNRAS.506.1585Z,2022MNRAS.512.1722K,2024MNRAS.529.4387A,2024ApJ...966...28A,2025ApJ...995..191A`. When reading these papers, focus first on data rates, zero-baseline calibration, background subtraction, systematic floors, and target selection. Angular-diameter tables make sense only in that context.

(appsec:g-instrument)=
## Detectors, Timing, and Event Tables
Event-table astronomy requires optics, electronics, and time standards to be read together. Papers on AQuEye, IquEye, and related photon-counting instruments are useful for understanding ps--ns time tagging, absolute synchronization, and high-photon-rate data streams {cite:p}`2015SPIE.9504E..0CZ,2016SPIE.9907E..0NZ,2013NIMPA.725..187J,2020RScI...91a3108W`. For each paper, make a separate table of detector efficiency, dead time, afterpulsing, TDC resolution, GPS or White Rabbit synchronization, and data format. Those quantities later enter the data models of Chapters {ref}`chap:06`--{ref}`chap:07`.

(appsec:g-estimation)=
## Quantum Estimation and Sub-Resolution Measurements
The core papers on the Rayleigh curse and SPADE show that traditional resolution criteria are not the information limit for every parameter-estimation problem {cite:p}`2015Optic...2..646T,2016PhRvX...6c1033T,2017PhRvL.118g0801T,2017NJPh...19b3054T`. When reading them, list the source model, PSF, background, available modes, and Fisher-information definition for each paper. Results for two weak incoherent point sources should be used only under the corresponding assumptions.

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## Astrophysical Radiation Mechanisms and Source Models
The chapters on stars, masers, natural lasers, Crab photon statistics, and compact objects require both classical radiation physics and modern observations. Quantum-optics language does not replace ordinary astrophysical source modeling; it identifies which photon-statistical quantities have not already been averaged away. For this reading group, record three quantities for each source class: brightness or photon rate, angular or temporal scale, and the mixed components most likely to break ideal statistics. For stimulated emission and natural-laser candidates, distinguish especially among narrow lines, high brightness temperature, pump fluctuations, and a stable coherent state {cite:p}`1982RvMP...54.1225E,1992ARA&A..30...75E,2004A&A...428..497J,2005MNRAS.364..731J,2005NewA...10..361J,2008AIPC..984..216D`.

(appsec:g-propagation)=
## Propagation, Lensing, Polarization, and Cosmology
Read the propagation literature by observable: DM and dispersive delay, RM and polarization angle, scattering broadening, dust extinction, gravitational-lens time delay, wave-optics lensing, CMB polarization, and cosmic birefringence. For each topic, ask what changes in the data: arrival time, frequency, polarization, phase, or intensity correlation. Without that distinction, propagation effects are easy to miswrite as source photon statistics.

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## Science Cases and Long-Term Networks
First-generation science cases can begin with bright-star angular diameters, rapid rotators, Be-star disks, binaries, Crab photon statistics, natural lasers, and nearby transients. The Type Ia supernova distance idea shows how intensity interferometry could enter cosmological distance work, while also exposing the pressure from baseline, photon rate, trigger time, and model systematics {cite:p}`2025PhRvD.111h3047K`. Quantum-network telescopes should be read through pathfinder proposals: two-photon astrometry, entanglement-assisted interferometry, memories, and frequency-conversion resource limits are discussed in {cite:t}`2023PhRvL.130p0801M` {cite:p}`2025PhRvA.111d3701M,2025PhRvR...7d3278Z,2026PhRvA.113a2608P,2026Natur.651..326S`. This group belongs near the end of a course, after event tables, coherence functions, instrumental errors, and error budgets are familiar enough for the resource pressure to be visible.

(appsec:g-reading-template)=
## Template for Reading Papers
| Item | How to record it |
|:----------------|:-----------------------------------------------|
| Observable | Write the quantity the paper actually measures, such as $g^{(2)}(\tau)$, $|V|^2$, angular diameter, polarization angle, delay, or event rate. |
| Data product | Note whether the paper releases event tables, correlation histograms, calibration tables, posterior samples, or code. |
| Main scales | Photon rate, bandwidth, time resolution, baseline, target magnitude, background, and integration time. |
| Core assumptions | Thermal light, Gaussian PSF, uniform disk, incoherent source, stable response, weak signal, and so on. |
| Systematic errors | Background, dead time, afterpulsing, crosstalk, calibrator stars, model error, and selection effects. |
| Reusable figures | Identify figures that can inspire teaching plots, without copying them. |