Add Quantum Computing (#6767)

* Add Quantum Computing

* fixes alphabetical order

* Update books/free-programming-books-subjects.md

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

* Update books/free-programming-books-subjects.md

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

* Use book landing page instead of PDF direct download link

Co-authored-by: Eric Hellman <eric@hellman.net>

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>
Co-authored-by: Eric Hellman <eric@hellman.net>

books/free-programming-books-subjects.md

@@ -36,6 +36,7 @@ Books that cover a specific programming language can be found in the  [BY PROGRA
 * [Partial Evaluation](#partial-evaluation)
 * [Professional Development](#professional-development)
 * [Programming Paradigms](#programming-paradigms)
+* [Quantum Computing](#quantum-computing)
 * [Regular Expressions](#regular-expressions)
 * [Reverse Engineering](#reverse-engineering)
 * [Search Engines](#search-engines)
@@ -670,6 +671,13 @@ Kerridge (PDF) (email address *requested*, not required)
 * [Type Theory and Functional Programming](https://www.cs.kent.ac.uk/people/staff/sjt/TTFP/)
 
 
+### Quantum Computing
+
+* [Introduction to Classical and Quantum Computing](http://www.thomaswong.net/introduction-to-classical-and-quantum-computing-1e2p.pdf) - Thomas G. Wong (PDF)
+* [Learn Quantum Computation using Qiskit](https://qiskit.org/textbook/preface.html) - Frank Harkins et al. (HTML)
+* [Quantum Computing for the Quantum Curious](https://link.springer.com/book/10.1007/978-3-030-61601-4) - Ciaran Hughes, Joshua Isaacson, Anastasia Perry, Ranbel F. Sun, Jessica Turner (HTML, PDF, EPUB)
+
+
 ### Regular Expressions
 
 * [JavaScript RegExp](https://learnbyexample.github.io/learn_js_regexp/) - Sundeep Agarwal