Bengaluru (Karnataka) [India]: Somewhere in a fiber under a city, a single photon is carrying a secret. Copy it and it changes; measure it and it tells. Rajesh Kumar Krishnan has spent nearly a decade turning that law into working machines — not from a whiteboard, but at the bench. He has designed the laser drivers, modulator electronics and single-photon detector circuits that make quantum key distribution run, written the FPGA logic that times them to the picosecond, hardened post-quantum cryptography against side-channel attack, and stood in the field at 2 a.m. coaxing a link back to life. Today, as Senior VP – Innovation at QNu Labs, the physicist who still aligns his own optics and reads his own oscilloscope puts it all into a book. The Unclonable Photon headlines a stack of five titles by Krishnan, out now in print and e-book, that reads like the inside of a very unusual head.
The Unclonable Photon — Physics · Engineering · Security. The book its author wishes had existed when he started. It opens with the no-cloning theorem and never lets go of the reader’s hand: every protocol derived, every detector quirk explained, every security proof pushed all the way to a key rate you could measure on a bench. Worked numbers, corrected in-depth diagrams and the hard-won intuition of someone who has watched these systems fail in the field and fixed them.
“Most books on quantum communication stop at the idea. Most papers start after it,” Krishnan said. “Nobody stays with you through the middle — why a detector’s dead time quietly eats your key, what a decoy state is really doing, how a proof on paper becomes bits in a box. This book lives in the middle.”
Quantum Physics in 300 Formulas — Two Places at Once. Three hundred results of quantum mechanics, each derived step by step, each with a picture, a story and a worked example with real numbers. The Schrödinger equation built from operators; the uncertainty principle as a bargain you can’t escape. A book to be read with a pencil.
The Physics of Time — Running Late Since the Big Bang. Graduate-level depth, full derivations, and a narrator who refuses to be solemn about entropy. Why time has an arrow, why your GPS would drift without relativity, and why the universe has been running late for 13.8 billion years.
Lift the Bow — Sanskrit · Tamil · English. Verses on work, duty, focus and courage from the Gita, the Tirukkural and the Upanishads, set in three languages. Its old title, Where the Hand Goes, survives as the subtitle — the lines, Krishnan says, that got him through long nights of debugging.
How to Get a Cute Wife. The delightful outlier. A funny, entirely non-quantum book of management secrets, hiding behind a title that is anything but boring — written, the author insists, from field experience.
“Quantum technology is leaving the lab, and India has a real shot at building this rather than buying it,” Krishnan said. “But you can’t build what you can’t derive. The technical books are for the next hundred engineers who will. The other two are for everyone who has to live with them.”
Krishnan is that rare combination: a leader who builds. He began as a hardware design engineer, founded an embedded-systems company, and in 2017 joined QNu Labs as a project lead — rising through product management and heading engineering to lead innovation across the company’s entire quantum portfolio. Today he directs teams spanning quantum information, atomic physics and post-quantum cryptography, drives research partnerships with universities in India and Europe, and holds patents in quantum security. He is as likely to be found reviewing a security proof as probing a photodiode, and has long insisted that the two are the same job. He also writes physics problems and workshop material for students.
All five titles are on sale now in print and e-book on Amazon and Flipkart, with worldwide distribution across 150+ countries. Sample chapters, talks and the author’s blog are at rajeshkumarkrishnan.com.
Boilerplate and contact
About the author: Rajesh Kumar Krishnan is Senior VP – Innovation at QNu Labs, a Bengaluru-based quantum security company incubated at IIT Madras. He began as a hardware design engineer, founded an embedded-systems company, and has worked in quantum key distribution, quantum random number generation, post-quantum cryptography and quantum sensing since 2017. He holds patents in quantum security and writes on physics, engineering and the verse traditions of India. More at rajeshkumarkrishnan.com.
Media contact: Rajesh Kumar Krishnan
Email : rajeshkumarkrishnan.com
