Extracting the Field Theory Description of a Quantum ManyBody System from Experimental Data
Abstract
Quantum field theory is a powerful tool to describe the relevant physics governing complex quantum manybody systems. Here, we develop a general pathway to extract the irreducible building blocks of quantum field theoretical descriptions and its parameters purely from experimental data. This determination is accomplished by extracting the oneparticle irreducible (1PI) correlation functions from which one can construct all physical observables. To match the capabilities of experimental techniques, our approach employs a formulation of quantum field theory based on equaltime correlation functions only. We illustrate the theoretical foundations of our procedure by applying it to the sineGordon model in thermal equilibrium and then demonstrate explicitly how to extract these quantities from an experiment where we quantum simulate the sineGordon model by two tunnelcoupled superfluids. We extract all 1PI correlation functions up to the 1PI fourpoint function (interaction vertex) and their variation with momentum, encoding the "running" of the couplings. The measured 1PI correlation functions are compared to the theoretical estimates, verifying our procedure. Our work opens new ways of addressing complex manybody questions emerging in a large variety of settings from fundamental science to practical quantum technology.
 Publication:

Physical Review X
 Pub Date:
 January 2020
 DOI:
 10.1103/PhysRevX.10.011020
 arXiv:
 arXiv:1909.12815
 Bibcode:
 2020PhRvX..10a1020Z
 Keywords:

 Condensed Matter  Quantum Gases;
 Quantum Physics
 EPrint:
 18 pages, 11 figures. Updated Phys. Rev. X version with minor changes