A physics cell includes a sealed glass vial that contains a high-purity dipolar gas (e.g., OCS) at a low pressure (e.g., between about 0.01 millibar and 0.2 millibar). The vial can be sealed using a laser cutting process that involves only local heating of the vial that does not denature the bulk of the contained gas. One or more electromagnetically translucent windows or vial-end access points provide access to electromagnetic waves launched or received by one or more electromagnetic antennas at a frequency that is adjusted to match the quantum transition frequency of the gas based on a detected maximum absorption frequency. The glass-vial physics cell can be fabricated at lower cost than physics cells fabricated from bonded wafers. Multiple vials can be joined by a waveguide in an enclosure so that launch and receive antennas can be provided at a single end of the vials.