Ultrasensitive atomic comagnetometer with enhanced nuclear spin coherence

Abstract

Achieving high energy resolution in spin systems is important for fundamental physics research and precision measurements, with alkali-noble-gas comagnetometers being among the best available sensors. We found a new relaxation mechanism in such devices, the gradient of the Fermi-contactinteraction field that dominates the relaxation of hyperpolarized nuclear spins. We report on precise control over spin distribution, demonstrating a tenfold increase of nuclear spin hyperpolarization and transverse coherence time with optimal hybrid optical pumping. Operating in the self-compensation regime, our 21 Ne-Rb-K comagnetometer achieves an ultrahigh inertial rotation sensitivity of 3 × 10 −8 rad/s/Hz 1/2 in the frequency range from 0.2 to 1.0 Hz, which is equivalent to the energy resolution of 3.1 × 10 −23 eV/Hz 1/2 . We propose to use this comagnetometer to search for exotic spin-dependent interactions involving proton and neutron spins. The projected sensitivity surpasses the previous experimental and astrophysical limits by more than four orders of magnitude.Coherent control of electron and nuclear spins via lightmatter interactions is an important platform for fundamental physics research [1], and an essential tool for quantum sensors [2-4] and quantum information processing [5]. Dense mixture of vapors of polarized alkali-metal atoms and noble gases with hyperpolarized nuclei have found prominent use in quantum-technology devices such as atomic magnetometers and comagnetometers. Particularly, atomic comagnetometers with hybrid spin ensembles are used to search for "new physics", including fifth forces [6,7], axion-like particles [8,9], permanent electric dipole moments [10,11], and to test thee combined charge-paritytime (CPT) and Lorentz symmetries [12,13].These applications have long been limited by systematic errors and spurious signals due to magnetic field from ambient environment or interactions between atoms [14,15]. A typical approach for addressing this problem is to isolate the magnetic-field effect by using two species with different gyromagnetic ratio, for example, 129 Xe and 131 Xe [8, 16], 3 He and 129 Xe [10, 11], 85 Rb and 87 Rb [17], different nuclear spins in the same molecule [15] or different hyperfine levels of single-species atoms [18]. Another approach is operating the alkali-noble gas atomic comagnetometer in the self-compensation (SC) regime [4,19], where noble gas nuclear spins interact with alkali electron spins by spin-exchange (SE) interactions and adiabatically cancel slowly changing magnetic fields. Another advantage of SC comagnetometer is that the alkali atoms are in the spin-exchange relaxation free (SERF) regime, one can achieve sub-femtotesla magnetic sensitivity [20].