Debayan Mitra

Phase Separation and Pair Condensation in a Spin-Imbalanced 2D Fermi Gas.

We study a two-component quasi-two-dimensional Fermi gas with imbalanced spin populations. We probe the gas at different interaction strengths and polarizations by measuring the density of each spin component in the trap and the pair momentum distribution after time of flight. For a wide range of experimental parameters, we observe in-trap phase separation characterized by the appearance of a spin-balanced core surrounded by a polarized gas. Our momentum space measurements indicate pair condensation in the imbalanced gas even for large polarizations where phase separation vanishes, pointing to the presence of a polarized pair condensate. Our observation of zero momentum pair condensates in 2D spin-imbalanced gases opens the way to explorations of more exotic superfluid phases that occupy a large part of the phase diagram in lower dimensions.

Quantum gas microscopy of an attractive Fermi–Hubbard system

The simplest lattice model that allows the investigation of superconductivity with attractive interactions is realized using ultracold quantum gas. The experimental observation provides a lower bound on the strength of s-wave pairing correlations.

Pair condensation in a spin-imbalanced two-dimensional Fermi gas

A prediction and observational evidence for the mass of a dark matter particle are presented.T validity of quantum-mechanical predictions has been confirmed with a high degree of accuracy in a wide range of experiments. Although the statistics of the outcomes of a measuring apparatus have been studied intensively, little has been explored and is known regarding the accessibility of quantum dynamics and the evolutions of a quantum system during measurements. For this sort of fundamental studies of quantum mechanics, interferometric and polarimetric approaches, in particular by the use of neutron’s matter-waves, provide almost ideal experimental circumstances. The former device explicitly exhibits quantum interference between spatially separated beams in a macroscopic scale. In contrast, interference effects between two spin eigenstates are exposed in the latter apparatus. Exploiting both strategies, alternative theories of quantum mechanics, Kochen-Specker theorem and so on are studied. Recently, as a study of quantum dynamics, neutron interferometer experiments are carried out: A new counter-intuitive phenomenon, called quantum Cheshire-cat, is observed. Moreover, extending the first experimental test of the new error-disturbance uncertainty relation by using a modified neutron polarimeter setup, we performed experiments investigating the validity of an extended uncertainty relation for mixed ensemble as well as a new noise-disturbance uncertainty relation in an entropic form. In my talk, I am going to give an overview of matter-wave optical approach to investigations of fundamental aspect of quantum mechanics.We will discuss a novel entangled photon pair source based on an on-chip silicon ring resonator, enabling the distribution of wavelength multiplexed quantum information in standard telecommunication channels. This source opens the route towards out-of-the laboratory quantum cryptography systems showing augmented bit rates.