arXiv subjects

Hagai Edri

Publications and source records attributed to Hagai Edri.

3 recordsLinked to original sources

arXiv2020

Observation of nonlinear spin dynamics and squeezing in a BEC using dynamic decoupling

We study the evolution of a Bose-Einstein Condensate (BEC) in a two-state superposition due to inter-state interactions. Using a population imbalanced dynamic decoupling scheme, we measure inter-state interactions while canceling intra-state density shifts and external noise sources. Our measurements show low statistical uncertainties for both magnetic sensitive and insensitive superpositions, indicating that we successfully decoupled our system from strong magnetic noises. We experimentally show that the Bloch sphere representing general superposition states is "twisted" by inter-state interactions, and that the twist rate depends on the difference between inter-state and intra-state scattering lengths $a_{22}+a_{11}-2a_{12}$. We use the non-linear spin dynamics in our scheme to demonstrate squeezing of gaussian noise, showing $2.79 \pm 0.43$ dB squeezing when starting with a noisy state and applying 160 echo pulses. Which can be used to increase sensitivity when there are errors in state preparation. Our results allow for a better understanding of inter-atomic potentials in \textsuperscript{87}Rb. Our scheme can be used for spin squeezing beyond the standard quantum limit and observing polaron physics close to a Feshbach resonance, where interactions diverge, and strong magnetic noises are ever present.

physics.atom-ph↗

arXiv2020

Observation of spin-spin fermion-mediated interactions between ultracold bosons

Interactions in an ultracold boson-fermion mixture are often manifested by elastic collisions. In a mixture of a condensed Bose gas (BEC) and spin polarized degenerate Fermi gas (DFG), fermions can mediate spin-spin interactions between bosons, leading to an effective long-range magnetic interaction analogous to Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in solids. We used Ramsey spectroscopy of the hyperfine clock transition in a $^{87}$Rb BEC to measure the interaction mediated by a $^{40}$K DFG. By controlling the bosons density we isolated the effect of mediated interactions from mean-field frequency shifts due to direct collision with fermions. We measured an increase of boson spin-spin interaction by a factor of $η=1.45\pm 0.05^{stat} \pm 0.13^{sys}$ in the presence of the DFG, providing a clear evidence of spin-spin fermion mediated interaction. Decoherence in our system was dominated by inhomogeneous boson density shift, which increased significantly in the presence of the DFG, again indicating mediated interactions. We also measured a frequency shift due to boson-fermion interactions in accordance with a scattering length difference of $a_{bf_2}-a_{bf_1}=-5.36 \pm 0.44^{stat} \pm 1.43^{sys}~a_0$ between the clock-transition states, a first measurement beyond the low-energy elastic approximation in this mixture. This interaction can be tuned with a future use of a boson-fermion Feshbach resonance. Fermion-mediated interactions can potentially give rise to interesting new magnetic phases and extend the Bose-Hubbard model when the atoms are placed in an optical lattice.

physics.atom-ph↗

arXiv2017

Observation of Optomechanical Strain in a Cold Atomic Cloud

We report the observation of the optomechanical strain applied to thermal and to quantum degenerate $^{87}\text{Rb}$ atomic clouds when illuminated by an intense, far detuned homogenous laser beam. In this regime the atomic cloud acts as a lens which focuses the laser beam. As a back action, the atoms experience a force opposite to the beam deflection, which depends on the atomic cloud density profile. We experimentally demonstrate the basic features of this force, distinguishing it from the well-established scattering and dipole forces. The observed strain saturates, ultimately limiting the momentum impulse that can be transferred to the atoms. This optomechanical force may effectively induce inter-particle interactions, which can be optically tuned.

physics.atom-ph↗