Atom-chip experiment : a new experimental setup to probe 1D Bose gases

Julien Armijo, Carlos L. Garrido Alzar, Isabelle Bouchoule

Tarik Berrada, T. Jacqmin, Isabelle Bouchoule

Aaldert H. van Amerongen, J.J.P. van Es, N. J. van Druten

Isabelle Bouchoule, Julien Armijo, T. Jacqmin +1 more

In this seminar, we present results obtained on our atom-chip setup. Measuring in situ density fluctuations in very elongated gases we probe the physics of 1D Bose gases with repulsive interactions. We investigate the crossover from weakly to strongly interacting gases. For weakly interacting gases, we probed the transition from 1D physics to 3D physics.

T. Jacqmin, Bess Fang, Tarik Berrada +1 more

Muhammad Taufiq Murtadho

Quantum state tomography provides a powerful and versatile framework for characterizing quantum states across diverse quantum systems. However, tomography is still largely restricted to systems with a few degrees of freedom, while for continuous systems, it is typically tailored to quantum-optical platforms. For other many-body systems described by continuous quantum fields such as ultracold atomic gases, tomographic technique is not as well-established. The present thesis addresses this gap by providing new approaches to measurement and tomography of ultracold Bose gases trapped in one (1D) and two dimensions (2D). These systems serve as analog quantum field theory (QFT) simulators and exhibit novel physics absent in higher dimensions. We begin by systematically assessing state-of-the-art method for extracting the relative phase field in parallel 1D Bose gases with matter-wave interference. In particular, we derive a formula for the systematic phase shift due to longitudinal dynamics, a factor that is often ignored in previous modeling of the measurement. We further examine how the single-shot readout error propagates to correlation and distribution functions of the relative phase. Then, we broaden the scope of experimentally accessible quantities by developing a new methodology to extract the common phase field---the sum of the phase fields of the two parallel gases---from the already available density ripple data. We rigorously benchmark this new readout with numerical simulations and experimental data in 1D systems and further generalize it to 2D systems. By combining the relative and common phases information, we improve Gaussian state tomography in parallel 1D Bose gases and apply it to probe new physical phenomena in quantum field simulators. Specifically, we focus on two applications: (i) field-space entanglement detection at finite temperatures and out of equilibrium, and (ii) probing non-linear relaxation in near-integrable quantum systems. This thesis bridges theory and experiment in the simulation of QFTs and reveals new opportunities for exploring many-body quantum effects in ultracold bosonic gases.