This book is the first comprehensive monograph focusing on the recent developments of quantum white noise calculus and its applications. Quantum white noise calculus is a quantum extension of the Gaussian white noise calculus and provides a useful toolbox for the analysis of operators on Boson Fock space based on an infinite dimensional distribution theory of Schwartz type. This volume starts with the famous Wiener–Ito–Segal isomorphism between the Fock space and the L2-space over a Gaussian space, and systematically constructs Gelfand triples along which white noise operators are defined. The white noise operators cover a wide class of operators on Fock space including pointwisely defined annihilation and creation operators called quantum white noise and a white noise operator is regarded as a function of quantum white noise. The main purpose of this volume is to describe the new concept of quantum white noise derivatives, a kind of functional derivative for white noise operators. This idea leads to a new type of differential equations for white noise operators with applications in stochastic analysis and quantum physics. In particular, transforms of white noise functions and operators such as Fourier–Gauss transform, Fourier–Mehler transform, Bogoliubov transform, and quantum Girsanov transform are characterized as solutions to differential equations of new type. The development of quantum white noise derivative sheds fresh light on the study of Fock space operators.