An atomic clock employs hybrid long/short quantum clock frequency regulation wherein each of a series of regulation cycles includes a relatively long (four Ramsey-cycle) combination error signal (CES) cycle and plural relatively short (two Ramsey-cycle) single error signal (SES) cycles. The CES cycles provide for better long-term stability than can be provided using only SES cycles. However, including the SES cycles between CES cycles improves short term stability with negligible diminishment of long-term stability.