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We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating timereversal invariance. The salient features of this experiment were the use of a 199 Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d n ¼ ð0.0 AE 1.1 stat AE 0.2 sys Þ × 10 −26 e:cm.

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We report results of a new technique to measure the electric dipole moment of 129 Xe with 3 He comagnetometry. Both species are polarized using spin-exchange optical pumping, transferred to a measurement cell, and transported into a magnetically shielded room, where SQUID magnetometers detect free precession in applied electric and magnetic fields. The result from a one week measurement campaign in 2017 and a 2.5 week campaign in 2018, combined with detailed study of systematic effects, is dA( 129 Xe) = (1.4 ± 6.6stat ± 2.0syst) × 10 −28 e cm. This corresponds to an upper limit of |dA( 129 Xe)| < 1.4 × 10 −27 e cm (95% CL), a factor of five more sensitive than the limit set in 2001.Searches for permanent electric dipole moments (EDMs) are a powerful way to investigate beyondstandard-model (BSM) physics. An EDM is a charge asymmetry along the total angular momentum axis of a particle or system and is odd under both parity reversal (P) and time reversal (T). Assuming CPT conservation (C is charge conjugation), an EDM is a direct signal of CP violation (CPV), a condition required to generate the observed baryon asymmetry of the universe [1]. The Standard Model incorporates CPV through the phase in the CKM matrix and the QCD parameterθ. However, the Standard Model alone is insufficient to explain the size of the baryon asymmetry [2]. BSM scenarios that generate the observed baryon asymmetry [3] generally also provide for EDMs larger than the SM estimate, which for 129 Xe is |d A ( 129 Xe) SM | ≈ 5 × 10 −35 e cm [4].EDM measurements have provided constraints on how BSM CPV can enter low-energy physics [4]. Diamagnetic systems such as 129 Xe and 199 Hg are particularly sensitive to CPV nucleon-nucleon interactions that induce a nuclear Schiff moment and CPV semileptonic couplings [7]. While the most precise atomic EDM measurement is from 199 Hg [8], there are theoretical challenges to constraining hadronic CPV parameters from 199 Hg alone, and improved sensitivity to the 129 Xe EDM would tighten these constraints [7,9]. Additionally, recent work has shown that contributions from light-axion-induced CPV are significantly stronger for 129 Xe than for 199

A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.