Squeezed Light from a Levitated Nanoparticle at Room Temperature.

Quantum measurements of mechanical systems can generate optical squeezing via ponderomotive forces. Its observation requires high environmental isolation and efficient detection, typically achieved by using cryogenic cooling and optical cavities. Here, we realize these conditions by measuring the position of an optically levitated nanoparticle at room temperature and without the overhead of an optical cavity.

Collective Radiative Dynamics of an Ensemble of Cold Atoms Coupled to an Optical Waveguide.

We experimentally and theoretically investigate collective radiative effects in an ensemble of cold atoms coupled to a single-mode optical nanofiber. Our analysis unveils the microscopic dynamics of the system, showing that collective interactions between the atoms and a single guided photon gradually build up along the atomic array in the direction of propagation of light. These results are supported by time-resolved measurements of the light transmitted and reflected by the ensemble after excitation via nanofiber-guided laser pulses, whose rise and fall times are shorter than the atomic lifetime.

Observation of Collective Superstrong Coupling of Cold Atoms to a 30-m Long Optical Resonator.

We report on the observation of collective superstrong coupling of a small ensemble of atoms interacting with the field of a 30-m long fiber resonator containing a nanofiber section. The collective light-matter coupling strength exceeds the free-spectral range and the atoms couple to consecutive longitudinal resonator modes. The measured transmission spectra of the coupled atom-resonator system provide evidence of this regime, realized with a few hundred atoms with an intrinsic single-atom cooperativity of 0.

Momentum-Space Correlations of a One-Dimensional Bose Gas.

Analyzing the noise in the momentum profiles of single realizations of one-dimensional Bose gases, we present the experimental measurement of the full momentum-space density correlations ⟨δn_{p}δn_{p^{'}}⟩, which are related to the two-body momentum correlation function. Our data span the weakly interacting region of the phase diagram, going from the ideal Bose gas regime to the quasicondensate regime. We show experimentally that the bunching phenomenon, which manifests itself as super-Poissonian local fluctuations in momentum space, is present in all regimes.

Quench-induced breathing mode of one-dimensional Bose gases.

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided.