Date and Time:  3-Nov-2023  10am 

Speaker:  Prof. Mariusz Gajda, Institute of Physics Polish Academy of Sciences, Warsaw, Poland

Host: Li You (Tsinghua Univ.& BAQIS）

Title: Time-continuous measurement of position and momentum of a quantum particle

Venue: Room 526

Abstract: 

In my talk I will present a model of frequently repeated measurement of position and momentum of a quantum particle. I will shortly discuss the measurement problem in quantum mechanics. Then I will formulate an open system formalism suited for description of a particle interrogated by a grid of detectors distributed uniformly in the phase space. The formalism incorporates a wavefunction collapse postulate: after a measurement the system is assumed to be in one of a meter’s state which is a coherent state of a local quantum oscillator. Trajectories of observables are generated using Wave Function Quantum Monte Carlo method.  Some simple illustrative examples will be given. The Zeno effect, for a relatively sparse spatial grid of detectors, as well as emergence of classical trajectories, for densely distributed meters, will be discussed. Analogy to classical dynamics of a particles subject to the Brownian motion will be pointed out.

About the Speaker:

I got my PhD presenting the thesis: Light scattering by trapped ions, under supervision of Jan Mostowski in 1985. At the early stages of my scientific carrier I worked on problems related to interaction of atoms with ultra-strong e-m field and stabilization phenomenon.  I spent two years as post-doc at the Department the Physics of the University of Arizona in Tucson.  I received the professor title from the president of Poland in 2011.

Most of my work is related to the theory of ultra-cold degenerate atomic quantum gases: fluctuations of a BEC, creation of vortices, description of a BEC at non-zero temperature, to this end I formulated with K. Rz??ewski the classical fields method. Then I studied spinor and dipolar condensates, lattice models, quantum droplets in a Bose-Bose and Bose-Fermi mixtures. I was a visiting professor at Paris Sorbonne University – Paris Nord XIII, collaborating with prof. Bruno Laburthe-Tolra.  I also collaborated with ICFO group of prof. M. Lewenstein.