Optical atomic clocks with eighteen significant digits are the most accurate measurement devices available to us with applications ranging from tests of fundamental physics to height difference measurements in relativistic geodesy. The uncertainty in trapped-ion clocks is limited by systematic frequency shifts and quantum projection noise. In my presentation, I will show how quantum engineering techniques can overcome these limitations. Quantum algorithms provide access to new clock species such as highly charged ions with reduced systematic shifts and high sensitivity to searches for new physics, including hypothetical fifth forces, variation of fundamental constants and dark matter candidates. Dynamical decoupling and entangled state spectroscopy in a multi-ion frequency reference offer suppression of systematic shifts, while improving the signal-to-noise ratio of the clock and thus the required averaging time to reach a certain resolution. These developments will pave the way towards a next generation of quantum-enhanced clocks that enter the 10-19 relative frequency uncertainty regime.
a joint institute of 
and 
and