<i>In situ</i>
 momentum-distribution measurement of a quantum degenerate Fermi gas using Raman spectroscopy

Shkedrov, Constantine; Ness, Gal; Florshaim, Yanay; Sagi, Yoav

doi:10.1103/physreva.101.013609

Cited by 9 publications

(12 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In summary, we have proposed a minimally destructive and local thermometry protocol based on the decoherence of immersed impurities, which offers a solution to the challenge of in situ thermometry for homogeneous Fermi gases. This complements recently developed techniques based on two-photon spectroscopy [84,85]. Future work could address the effect of impurity motion [86,87] and correlations between probes generated via their mutual interaction with the gas [25,88,89].…”

mentioning

confidence: 71%

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

et al. 2020

View full text Add to dashboard Cite

The precise measurement of low temperatures is a challenging, important, and fundamental task for quantum science. In particular, in situ thermometry is highly desirable for cold atomic systems due to their potential for quantum simulation. Here, we demonstrate that the temperature of a noninteracting Fermi gas can be accurately inferred from the nonequilibrium dynamics of impurities immersed within it, using an interferometric protocol and established experimental methods. Adopting tools from the theory of quantum parameter estimation, we show that our proposed scheme achieves optimal precision in the relevant temperature regime for degenerate Fermi gases in current experiments. We also discover an intriguing trade-off between measurement time and thermometric precision that is controlled by the impurity-gas coupling, with weak coupling leading to the greatest sensitivities. This is explained as a consequence of the slow decoherence associated with the onset of the Anderson orthogonality catastrophe, which dominates the gas dynamics following its local interaction with the immersed impurity.

show abstract

mentioning

confidence: 71%

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The beam parameters are the same as described in Ref. [57]. We denote their frequencies by ω 1 and ω 2 and their wave vectors by k 1 and k 2 .…”

Section: Methodsmentioning

confidence: 99%

“…The measurement is performed by recording the number of atoms transferred to the state j3i versus the two-photon detuning, ω ¼ ω 1 − ω 2 − E 0 =ℏ, where E 0 is the bare transition energy between states j2i and j3i. To achieve the utmost sensitivity, we measure the atoms using a highsensitivity fluorescence detection scheme we recently developed [56,57].…”

Section: Methodsmentioning

confidence: 99%

Observation of a Smooth Polaron-Molecule Transition in a Degenerate Fermi Gas

et al. 2020

Self Cite

View full text Add to dashboard Cite

Understanding the behavior of an impurity strongly interacting with a Fermi sea is a long-standing challenge in many-body physics. When the interactions are short ranged, two vastly different ground states exist: a polaron quasiparticle and a molecule dressed by the majority atoms. In the single-impurity limit, it is predicted that at a critical interaction strength, a first-order transition occurs between these two states. Experiments, however, are always conducted in the finite temperature and impurity density regime. The fate of the polaron-to-molecule transition under these conditions, where the statistics of quantum impurities and thermal effects become relevant, is still unknown. Here, we address this question experimentally and theoretically. Our experiments are performed with a spin-imbalanced ultracold Fermi gas with tunable interactions. Utilizing a novel Raman spectroscopy combined with a high-sensitivity fluorescence detection technique, we isolate the quasiparticle contribution and extract the polaron energy, spectral weight, and the contact parameter. As the interaction strength is increased, we observe a continuous variation of all observables, in particular a smooth reduction of the quasiparticle weight as it goes to zero beyond the transition point. Our observation is in good agreement with a theoretical model where polaron and molecule quasiparticle states are thermally occupied according to their quantum statistics. At the experimental conditions, polaron states are hence populated even at interactions where the molecule is the ground state and vice versa. The emerging physical picture is thus that of a smooth transition between polarons and molecules and a coexistence of both in the region around the expected transition. Our findings establish Raman spectroscopy as a powerful experimental tool for probing the physics of mobile quantum impurities and shed new light on the competition between emerging fermionic and bosonic quasiparticles in non-Fermi-liquid phases.

show abstract

“…The one-dimensional momentum distribution of a uniform periodically-driven Fermi gas. The distribution, measured by Raman spectroscopy [60], is fitted with the homogeneous Fermi-Dirac distribution given by Eq. ( 5) (black solid line).…”

Section: Resultsmentioning

confidence: 99%

Absence of heating in a uniform Fermi gas created by periodic driving

Shkedrov,

Menashes,

Ness

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Ultracold atoms are a powerful resource for quantum technologies. As such, they are usually confined in an external potential that often depends on the atomic spin, which may lead to inhomogeneous broadening, phase separation and decoherence. Dynamical decoupling provides an approach to mitigate these effects by applying an external field that induces rapid spin rotations. However, a continuous periodic driving of a generic interacting many-body system eventually heats it up. The question is whether dynamical decoupling can be applied at intermediate times without altering the underlying physics. Here we answer this question affirmatively for a strongly interacting degenerate Fermi gas held in a flat box-like potential. We counteract most of the gravitational force by applying an external magnetic field with an appropriate gradient. Since the magnetic force, and consequently, the whole potential, is spin-dependent, we employ rf to induce a rapid spin rotation. The driving causes atoms in both spin states to experience the same time-average flat potential, leading to a uniform cloud. Most importantly, we find that when the driving frequency is high enough, there is no heating on experimentally relevant timescales, and physical observables are similar to those of a stationary gas. In particular, we measure the pair-condensation fraction of a fermionic superfluid at unitarity and the contact parameter in the BEC-BCS crossover. The condensate fraction exhibits a non-monotonic dependence on the drive frequency and reaches a value higher than its value without driving. The contact agrees with recent theories and calculations for a uniform stationary gas. Our results establish that a strongly-interacting quantum gas can be dynamically decoupled from a spin-dependent potential for long periods of time without modifying its intrinsic many-body behavior.

show abstract

In situ momentum-distribution measurement of a quantum degenerate Fermi gas using Raman spectroscopy

Cited by 9 publications

References 37 publications

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities

Observation of a Smooth Polaron-Molecule Transition in a Degenerate Fermi Gas

Absence of heating in a uniform Fermi gas created by periodic driving

Contact Info

Product

Resources

About