Book Recommendation: Quantum optics Could you suggest me a list of books for understanding Quantum Optics for students who have studied Introductory Q.M. (such as Griffiths). 
It would be grateful if you distinguish between readable one (might be easier) and one for hard-practice (might be harder).
 A: *

*For a beginner in this field may start with the book named Quantum Optics for Beginners, by Zbigniew Ficek and Mohamed Ridza Wahiddin (CRC Press). I think it is most easiest and reader friendly book . Although this book is not very popular and may not be available.

*Introductory Quantum Optics, by C. C. Gerry and P. L. Knight is also very easy book to start.

*Some very good standard books at medium and harder level:


*

*Quantum Optics by Girish S Agarwal

*Quantum Optics by Scully and Zubairy

*Elements of Quantum Optics by Pierre Meystre & Murray Sargent III


*If you are interested in mathematical background you can follow
Mathematical Methods of Quantum Optics by Ravinder R. Puri (Springer).

*For specialisation and  advanced in coherent states: Coherent States in Quantum Physics, by Jean-Pierre Gazeau

*If you are interested in statistical properties of quantum optics then the best book is Quantum statistical properties of radiation, by W. H. Louisell. This is easy and very much reader friendly. Since my PhD work based on partly quantum optics I have personally used this book. Almost all the derivation are done in the book. 

*An equally important book is Statistical Methods in Quantum Optics 1 by Howard J Carmichael.
A: Most of the classics have already been posted, but I want to make the case for one more book, namely

Photons and Atoms: Introduction to Quantum Electrodynamics. Claude Cohen-Tannoudji, Jacques Dupont-Roc and Gilbert Grynberg (Wiley, 1997).

Like most works by Cohen-Tannoudji, it is extremely thorough and complete, but it is also a complex work to navigate, with an intricate chapter-plus-supplements structure that requires active decision-taking on the part of the reader as to which parts to read and which part to leave for a second go-through. As such, it can be demanding to read, but it repays that attention with a thorough construction of the material from a very solid basis all the way through to the full corpus of standard materials in quantum optics. (Indeed, much of the stuff there was probably cutting-edge at the time, and it's a testament to how well they chose their material that the cutting-edge stuff they included has gone on to be standard.)
A: *

*Introduction to Quantum Optics - Grynberg, Aspect, Fabre: I found this book to be a very good introduction for someone with some background in QM at undergrad level. As the subtitle suggests, the authors first start with the semi-classical description of light-matter interactions before moving on to the fully quantised treatment. This is a very comprehensive book that uses many examples to illustrate the theory.

*Introductory Quantum Optics - Gerry, Knight: Similar level as the above book, but less comprehensive. Still sufficient detail and in-between steps in derivations so that it's possible to follow without having to use additional resources. Interesting examples and applications in the appendix.

*Methods in Theoretical Quantum Optics - Barnett, Radmore: Advanced QO book, quite mathematical, includes an introduction to basic quantum theory using bra-ket notation.

A: My experience here is that quantum mechanics is widely spoken about by people in the optics field, but poorly understood. I wouldn't be in a hurry to shift to a QM book specialized to optics; rather I would deepen one's understanding of fundamental principles through a more advanced book such as 
"Quantum Mechanics", Vol. 1 and 2.
by Claude Cohen-Tannoudji. One needs to have a deep and thorough understanding of experimental results and to be comfortable with clean mathematical abstractions we make of these results. Preferably several mathematical abstractions. Because we have no everyday intuition for QM, some of these abstractions are perhaps more advanced than you'll find in Griffiths. Cohen-Tannoudji is a bit light on on things like the Bell inequality and entanglement in general. So you'll need another text as well for this.
One of the standard quantum optics texts is 
Scully and Zubairy, "Quantum Optics"
but I found this one full of fearsome and tiresome equations but lacking in either mathematical or physical insight. You need to have a thorough grasp of fundamentals before you can use this book, and even then I only find it useful as a reference and a starting point for branching into other literature.
A: I have two go-to books.
Quantum Theory of Light, by Rodney Loudon.  This is your readable one.  It really covers a lot of stuff, including noise (including relative intensity noise), amplitude correlation functions, intensity correlation, quantization of the Maxwell fields, nonlinear optics an higher-order correlations, and more.  You can just sit down and read it.
Optical Coherence and Quantum Optics, by Mandel and Wolf.    The details, in detail.  This one you need to sit down and study.  I think it's rather complete, and as rigorous as a physicist gets.  As an experimentalist, I learned an awful lot from this book, and gained much deeper understanding of things.  It's very clearly written, without the ambiguity of language or notation that some books have.  This is a real classic in the same league as Born and Wolf.
These are both older books, and the editions I have don't cover entanglement, and probably many other currently-relevant topics.  But don't pass on them for that reason.  Get another book for whatever extensions you need.
A: I'm surprised nobody has mentioned
Modern Foundations Of Quantum Optics by Vedral Vlatko.
It is very easy to read,  probably not enough for everything but an excellent starting point.
