Atomic clock system

A method for stabilizing a local oscillator of an atomic clock system, the method comprising:

• trapping alkali metal atoms in a cell during a trapping stage of each of sequential coherent population trapping (CPT) cycles to provide a source of cold alkali atoms and a baseline optical response of the alkali metal atoms;
• generating an optical difference beam comprising a first optical beam having a first frequency and a second optical beam having a second frequency different from the first frequency;
• periodically alternating a direction of the optical difference beam through the cell during a CPT interrogation stage of each of the sequential clock measurement cycles to drive CPT interrogation of the trapped alkali metal atoms based on relative circular polarizations of the first and second optical beams;
• monitoring an optical response of the CPT interrogated alkali metal atoms during a state readout stage in each of the sequential clock measurement cycles;
• and
• adjusting a frequency of the local oscillator based on the optical response of the CPT interrogated alkali metal atoms of each of the sequential clock measurement cycles relative to the baseline optical response.

An atomic clock system comprising:

• a magneto-optical trap (MOT) system configured to trap alkali metal atoms in a cell during a trapping stage of each of sequential coherent population trapping (CPT) cycles to provide a source of cold alkali atoms and a baseline optical response of the alkali metal atoms;
• an interrogation system configured to generate an optical difference beam comprising a first optical beam having a first frequency and a second optical beam having a second frequency different from the first frequency and having a variable relative intensity proportion, the optical difference beam having a frequency that is off-resonance of a frequency associated with a peak corresponding to a maximum excitation of a population of the alkali metal atoms from a first energy state to a second energy state, the interrogation system comprising a direction controller configured to periodically alternate a direction of the optical difference beam through the cell during a CPT interrogation stage of each of the sequential clock measurement cycles to drive CPT interrogation of a population of the alkali metal atoms from a first energy state to a second energy state in the presence of a uniform clock magnetic field having an amplitude based on Zeeman-shift characteristics of the alkali metal atoms;
• and
• an oscillator system configured to adjust a frequency of a local oscillator based on an optical response of the CPT interrogated alkali metal atoms relative to the baseline optical response during a state readout stage in each of the sequential clock measurement cycles.