arXiv subjects

Boaz Raz

Publications and source records attributed to Boaz Raz.

3 recordsLinked to original sources

arXiv2024

A new technique to measure gravitational mass of ultra-cold matter and its implications for antimatter studies

Measuring the effect of gravity on antimatter is a longstanding problem in physics that has significant implications for our understanding of the fundamental nature of the universe. Here, we present a technique to measure the gravitational mass of atoms, motivated by a recent measurement of antimatter atoms in CERN [1]. We demonstrate the results on ultra-cold atoms by measuring the surviving fraction of atoms gradually released from a quadrupole magnetic trap, which is tilted due to gravitational potential. We compare our measurements with a Monte Carlo simulation to extract the value of the gravitational constant. The difference between the literature value for g, the local acceleration due to gravity, and the measured value is $(-1.9 \pm 12^{stat} \pm 5^{syst}) \times 10^{- 4} g$. We demonstrate the importance of various design parameters in the experiment setup, and estimate their contribution to the achievable accuracy in future experiments. Our method demonstrates simplicity, precision, and reliability, paving the way for future precision studies of the gravitational force on antimatter. It also enables a precise calibration of atom traps based on the known gravitational attraction of normal matter to Earth.

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↗

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↗