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The fine-structure constant, α, is a dimensionless constant that characterizes the strength of the electromagnetic interaction between charged elementary particles. Related by four fundamental constants, a precise determination of α allows for a test of the Standard Model of particle physics. Parker et al. used matter-wave interferometry with a cloud of cesium atoms to make the most accurate measurement of α to date. Determining the value of α to an accuracy of better than 1 part per billion provides an independent method for testing the accuracy of quantum electrodynamics and the Standard Model. It may also enable searches of the so-called “dark sector” for explanations of dark matter. Science , this issue p. 191 Atom interferometry provides a precise measurement of the fine-structure constant. Measurements of the fine-structure constant α require methods from across subfields and are thus powerful tests of the consistency of theory and experiment in physics. Using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: α = 1/137.035999046(27) at 2.0 × 10 −10 accuracy. Using multiphoton interactions (Bragg diffraction and Bloch oscillations), we demonstrate the largest phase (12 million radians) of any Ramsey-Bordé interferometer and control systematic effects at a level of 0.12 part per billion. Comparison with Penning trap measurements of the electron gyromagnetic anomaly g e − 2 via the Standard Model of particle physics is now limited by the uncertainty in g e − 2; a 2.5σ tension rejects dark photons as the reason for the unexplained part of the muon’s magnetic moment at a 99% confidence level. Implications for dark-sector candidates and electron substructure may be a sign of physics beyond the Standard Model that warrants further investigation.

We present a new framework to study the time variation of fundamental constants in a model-independent way. Model independence implies more free parameters than assumed in previous studies. Using data from atomic clocks based on 87 Sr, 171 Yb + and 133 Cs, we set bounds on parameters controlling the variation of the fine-structure constant, α , and the electron-to-proton mass ratio, µ . We consider variations on timescales ranging from a minute to almost a day. In addition, we use our results to derive some of the tightest limits to date on the parameter space of models of ultralight dark matter and axion-like particles.

The COHERENT collaboration observed coherent elastic neutrino nucleus scattering using a 14.6 kg cesium-iodide (CsI) detector in 2017 and recently published the updated results before decommissioning the detector. Here, we present the legacy determination of the weak mixing angle and of the average neutron rms radius of 133 Cs and 127 I obtained with the full CsI dataset, also exploiting the combination with the atomic parity violation (APV) experimental result, that allows us to achieve a precision as low as ∼  4.5% and to disentangle the contributions of the 133 Cs and 127 I nuclei. Interestingly, we show that the COHERENT CsI data show a 6 σ evidence of the nuclear structure suppression of the full coherence. Moreover, we derive a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of 133 Cs and 127 I , that is allowed to vary freely in the fit. Additionally, we extensively discuss the impact of using two different determinations of the theoretical parity non-conserving amplitude in the APV fit. Our findings show that the particular choice can make a significant difference, up to 6.5% on R n (Cs) and 11% on the weak mixing angle. Finally, in light of the recent announcement of a future deployment of a 10 kg and a ∼  700 kg cryogenic CsI detectors, we provide future prospects for these measurements, comparing them with other competitive experiments that are foreseen in the near future.

Quantum matter interacting with gauge fields, an outstanding paradigm in modern physics, underlies the description of various physical systems. Engineering artificial gauge fields in ultracold atoms offers a highly controllable access to the exotic many-body phenomena in these systems, and has stimulated intense interest. Here we implement a triangular flux ladder in the momentum space of ultracold 133 Cs atoms, and study the chiral dynamics under tunable interactions. Through measurements of the site-resolved density evolutions, we reveal how the competition between interaction and flux in the frustrated triangular geometry gives rise to flux-dependent localization and biased chiral dynamics. For the latter in particular, the symmetry between the two legs is dynamically broken, which can be attributed to frustration. We then characterize typical dynamic patterns using complementary observables. Our work opens the avenue toward exploring correlated transport in frustrated geometries, where the interplay between interactions and gauge fields plays a key role. Synthetic gauge field in ultracold atoms provides a controllable platform for the study of quantum many-body physics. Here the authors demonstrate frustrated chiral dynamics in synthetic triangular flux ladder under strong interaction using ultracold Cs atoms.

The emergence of Efimov states in ultracold atomic systems is expected to have a universal behaviour, but a new experimental study defies this expectation, reporting a clear deviation around a narrow Feshbach resonance. Efimov physics is a universal phenomenon in quantum three-body systems. For systems with resonant two-body interactions, Efimov predicted an infinite series of three-body bound states with geometric scaling symmetry 1 . These Efimov states, first observed in cold caesium atoms 2 , have been recently reported in a variety of other atomic systems 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 . The intriguing prospect of a universal absolute Efimov resonance position across Feshbach resonances remains an open question. Theories predict a strong dependence on the resonance strength for closed-channel-dominated Feshbach resonances, whereas experimental results have so far been consistent with the universal prediction. Here we directly compare the Efimov spectra in a 6 Li– 133 Cs mixture near two Feshbach resonances which are very different in their resonance strengths, but otherwise almost identical. Our result shows a clear dependence of the absolute Efimov resonance position on Feshbach resonance strength and a clear departure from the universal prediction for the narrow Feshbach resonance.

Recently, competing electronic instabilities, including superconductivity and density-wave-like order, have been discovered in vanadium-based kagome metals A V 3 Sb 5 ( A = K, Rb, Cs) with a nontrivial band topology. This finding stimulates considerable interest to study the interplay of these competing electronic orders and possible exotic excitations in the superconducting state. Here, we performed 51 V and 133 Cs nuclear magnetic resonance (NMR) measurements on a CsV 3 Sb 5 single crystal to clarify the nature of density-wave-like transition in these kagome superconductors. A first-order structural transition is unambiguously revealed below T s ∼ 94 K by observing the sudden splitting of Knight shift in 51 V NMR spectrum. Moreover, combined with 133 Cs NMR spectrum, the present result confirms a three-dimensional structural modulation. By further analyzing the anisotropy of Knight shift and 1/ T 1 T at 51 V nuclei, we proposed that the orbital order is the primary electronic order induced by the first-order structural transition, which is supported by further analysis on electric field gradient at 51 V nuclei. In addition, the evidence for possible orbital fluctuations is also revealed above T s . The present work sheds light on a rich orbital physics in kagome superconductors A V 3 Sb 5 .

The FNAL+BNL measurements for muon g-2 is 4.2σ above the SM prediction, and the Berkeley 133Cs measurement for the fine-structure constant αem leads to the SM prediction for electron g-2 which is 2.4σ above the experimental value. Hence, a joint explanation of both anomalies requires a positive contribution to muon g-2 and a negative contribution to electron g-2, which is rather challenging. In this work we explore the possibility of such a joint explanation in the minimal supersymmetric standard model (MSSM). Assuming no universality between smuon and selectron soft masses, we find out a part of parameter space for a joint explanation at 2σ level, i.e., μM1,μM2<0, mL1,mE2<200 GeV, mL2 being much larger than the soft masses of other sleptons, |M1|<125 GeV and μ<400 GeV. This part of parameter space can survive LHC and LEP constraints, but gives an over-abundance for dark matter if the bino-like lightest neutralino is assumed to be the dark matter candidate. With the assumption that the dark matter candidate is a superWIMP (say a pseudo-goldstino in multi-sector SUSY breaking scenarios, whose mass can be as light as GeV and produced from the late-decay of the thermally freeze-out lightest neutralino), the dark matter problem can be avoided. So, we conclude that the MSSM may give a joint explanation for the muon and electron g-2 anomalies at 2σ level (the muon g-2 anomaly can be even ameliorated to 1σ).

We report simultaneous Raman sideband cooling of a single 87Rb atom and a single 133Cs atom held in separate optical tweezers at 814 nm and 938 nm, respectively. Starting from outside the Lamb-Dicke regime, after 45 ms of cooling we measure probabilities to occupy the three-dimensional motional ground state of 0.86−0.04+0.03 for Rb and 0.95−0.04+0.03 for Cs. Our setup overlaps the Raman laser beams used to cool Rb and Cs, reducing hardware requirements by sharing equipment along the same beam path. The cooling protocol is scalable, and we demonstrate cooling of single Rb atoms in an array of four tweezers. After motional ground-state cooling, a 938 nm tweezer is translated to overlap with a 814 nm tweezer so that a single Rb and a single Cs atom can be transferred into a common 1064 nm trap. By minimising the heating during the merging and transfer, we prepare the atoms in the relative motional ground state with an efficiency of 0.81−0.08+0.08. This is a crucial step towards the formation of single RbCs molecules confined in optical tweezer arrays.

The cross sections of 127I(n,γ)128I and 133Cs(n,γ)134Cs play a critical role in the s-process of nuclear astrophysics, the iodine–xenon chronometer on early meteorite evolution, and understanding the performance of CsI crystal detectors for Dark Matter Detection Experiment and Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) experiments. The neutron capture cross sections of 127I and 133Cs were measured from 1 eV to 1 MeV using the time-of-flight method at China Spallation Neutron Source Back-n facility. The neutron capture yield was derived via the pulse-height weighting technique based on the total energy detection principle of C6D6 detectors. In the resolved resonance region (RRR), some new resonance peaks of 133Cs(n,γ) were observed for the first time. Resonance parameters for the neutron capture cross section were extracted using the SAMMY code from 1 eV to 4 keV, while averaged capture cross sections in the unresolved resonance region (URR) from 4 keV to 1 MeV were analyzed with TALYS. Results were compared with evaluated libraries and previous work in both RRR and URR. Astrophysical Maxwellian-averaged cross sections (MACS) were calculated for kT = 5–100 keV. At kT = 30 keV, the MACS of both 127I(n,γ)128I and 133Cs(n,γ)134Cs were slightly higher than those of the KADoNiS v0.3 recommended value. And the reaction rates were derived over the astrophysically relevant temperature range of s-process nucleosynthesis models. The uncertainties of present reaction rates are significantly reduced.

We report the preparation of exactly one 87Rb atom and one 133Cs atom in the same optical tweezer as the essential first step towards the construction of a tweezer array of individually trapped 87Rb133Cs molecules. Through careful selection of the tweezer wavelengths, we show how to engineer species-selective trapping potentials suitable for high-fidelity preparation of Rb + Cs atom pairs. Using a wavelength of 814 nm to trap Rb and 938 nm to trap Cs, we achieve loading probabilities of 0.508(6) for Rb and 0.547(6) for Cs using standard red-detuned molasses cooling. Loading the traps sequentially yields exactly one Rb and one Cs atom in 28.4(6)% of experimental runs. Using a combination of an acousto-optic deflector and a piezo-controlled mirror to control the relative position of the tweezers, we merge the two tweezers, retaining the atom pair with a probability of \\(0.99_(-0.02)^(+0.01)\\). We use this capability to study hyperfine-state-dependent collisions of Rb and Cs in the combined tweezer and compare the measured two-body loss rates with coupled-channel quantum scattering calculations.