Quantum Theory of Light: Light Quantum and Field Quantization

Hermann Haken

Preface. List of symbols. 1. What is light? 2. The nature of light: waves or particles? 3. The nature of matter. Particles or waves? 4. Response of quantum systems to classical electromagnetic oscillations. 5. Quantization of the light field. 6. Quantization of electron wave field. 7. The interaction between light field and matter. 8. Quantum theory of coherence. 9. Dissipation and fluctuations in quantum optics. References. Subject index.

Michael Kreshchuk, Shaoyang Jia, William Kirby +3 more

We present a quantum algorithm for simulation of quantum field theory in the light-front formulation and demonstrate how existing quantum devices can be used to study the structure of bound states in relativistic nuclear physics. Specifically, we apply the Variational Quantum Eigensolver algorithm to find the ground state of the light-front Hamiltonian obtained within the Basis Light-Front Quantization (BLFQ) framework. The BLFQ formulation of quantum field theory allows one to readily import techniques developed for digital quantum simulation of quantum chemistry. This provides a method that can be scaled up to simulation of full, relativistic quantum field theories in the quantum advantage regime. As an illustration, we calculate the mass, mass radius, decay constant, electromagnetic form factor, and charge radius of the pion on the IBM Vigo chip. This is the first time that the light-front approach to quantum field theory has been used to enable simulation of a real physical system on a quantum computer.

Marc-Oliver Pleinert

Michael Kreshchuk, Shaoyang Jia, William M. Kirby +3 more

The analogy between quantum chemistry and light-front quantum field theory, first noted by Wilson, serves as motivation to develop light-front quantum simulation of quantum field theory. We demonstrate how calculations of hadron structure can be performed on noisy intermediate-scale quantum devices within the basis light-front quantization (BLFQ) framework. Within BLFQ, relativistic quantum field theories take a form that permits direct application of methods for digital quantum simulation of quantum chemistry, which can be readily scaled into the quantum advantage regime. We calculate the light-front wave functions of pions using an effective light-front Hamiltonian in a basis representation on a current quantum processor. We use the variational quantum eigensolver to find the ground-state energy and the corresponding wave function, which is subsequently used to calculate pion mass radius, decay constant, elastic form factor, and charge radius.