First detection problems in quantum physics

• Applicant: Dr. Felix Thiel
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Theoretical Condensed Matter Physics
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329823323

"At what time does a particle reach its destination?" Students are confronted with this question as early as in high-school physics. By the name "first-passage problem" this question is also part of diffusion theory and gives the theoretical basis for many applications, e.g. chemical reactions. When the particle is not moving classically, but according to quantum theory, the question may be ill-posed. Because the measurement - which is necessary to infer the particle's position - perturbes the particle itself. A continuous observation, like we do with a sample under a microscope, is not possible just like that. The solution is specifying the temporal sequence of measurements, the measurement protocol. Now it is clear when measurement and system interact and one may ask: "What is the first detection attempt, that finds the particle in its destination?" This project is devoted to exactly this question and tackles it with generating function techniques, which are also popular in classical first-passage theory. The properties of first detection time will be found and compared to the first passage time. Similarities and differences between both shall be worked out. This way, we obtain a better understanding of the interplay between measurement and quantum system. This is elementary for e.g. the construction of quantum computers.

• DFG Programme: Research Fellowships
• International Connection: Israel
• Host: Professor Eli Barkai, Ph.D.