Hyperfine Averaging by Dynamic Decoupling in a Multi-Ion Lutetium Clock

Abstract

We propose and experimentally demonstrate a scheme which effects hyperfine averaging during a Ramsey interrogation of a clock transition. The method eliminates the need to average over multiple optical transitions, reduces the sensitivity of the clock to its environment, and reduces inhomogeneous broadening in a multi-ion clock. The method is compatible with auto-balanced Ramsey spectroscopy, which facilitates elimination of residual shifts due to imperfect implementation and ac stark shifts from the optical probe. We demonstrate the scheme using correlation spectroscopy of the 1 S0 ↔ 3 D1 clock transition in a three-ion Lu + clock. From the demonstration we are able to provide a measurement of the 3 D1 quadrupole moment, Θ( 3 D1) = 0.634(9)ea 2 0 .

Coherent Suppression of Tensor Frequency Shifts through Magnetic Field Rotation

“…Coherent suppression is another form of shift elimination that relies on dynamic modification of experimental parameters during the atomic state evolution, providing the advantages of a fixed clock sequence and shift suppression within a single cycle. For optical clocks, different types of dynamic decoupling schemes have been investigated in which sublevels of the clock states are coherently coupled during the dark time of a Ramsey interrogation for cancellation of various shifts [11][12][13]. Further examples of coherent suppression can be found in hyper-Ramsey spectroscopy dealing with light shifts [14], and entangled many-atom states designed to provide immunity from selected perturbations [15].…”

“…Here, the radio frequency trapping field and large static electric field gradients typically cause tensor frequency shifts that exceed the resolvable linewidth resulting in inhomogeneous broadening, thus preventing long coherent interrogation. In contrast to dynamic decoupling schemes [11][12][13], our method does not require any additional drive field that can also cause frequency shifts, but provides a straightforward solution for different optical clock systems seeking to mitigate tensor shifts.…”

Simultaneous bicolor interrogation in thulium optical clock providing very low systematic frequency shifts

“…The synthetic frequency ν s is found to be insensitive to a magnetic field because of the equal but opposite Zeeman shifts of the “4-3” and “3-2” clock transitions (see the “Methods” section for details). We note here, that recently implemented dynamic decoupling scheme 40 , 44 allows one to average out the second-order Zeeman shift and quadrupole electric shift.…”

Coherent suppression of tensor frequency shifts through magnetic field rotation

“…Coherent suppression is another form of shift elimination that relies on dynamic modification of experimental parameters during the atomic state evolution, providing the advantages of a fixed clock sequence and shift suppression within a single cycle. For optical clocks, different types of dynamic decoupling schemes have been investigated in which sublevels of the clock states are coherently coupled during the dark time of a Ramsey interrogation for cancellation of various shifts [11][12][13]. Further examples of coherent suppression can be found in Hyper-Ramsey spectroscopy dealing with light shifts [14], and entangled many-atom states designed to provide immu-nity from selected perturbations [15].…”

“…Here, the radio-frequency (RF) trapping field and large static electric field gradients typically cause tensor frequency shifts that exceed the resolvable linewidth resulting in inhomogeneous broadening, thus preventing long coherent interrogation. In contrast to dynamic decoupling schemes [11][12][13], our method does not require any additional drive field that can also cause frequency shifts, but provides a straightforward solution for different optical clock systems seeking to mitigate tensor shifts.…”