King plots constructed from combinations of mass-weighted atomic isotope shifts provide a sensitive technique to search for electron-neutron interactions beyond the standard model mediated by a light boson. Using high-precision variational wave functions in Hylleraas coordinates, we present a comprehensive survey of all possible King plots arising from states of ${\mathrm{Li}}^{+}$ up to principal quantum number $n=10$ and angular momentum $L=7$ in order to identify the ones most sensitive to new physics. A major limitation in previous work due to second-order mass polarization is eliminated by the introduction of a second-King plot defined in terms of second differences. The residual theoretical uncertainty is then of the order of ${\alpha }^2{(\mu /M)}^3\sim 0.4$ Hz, where $\alpha$ is the fine-structure constant and $\mu$ is the reduced electron mass for a nucleus of mass $M$. Test results are presented for the ${}^A{\mathrm{Li}}^{+}$ isotope sequence with $A=6,7,8,9,11$ and are compared with other methods, including the ${\mathrm{Yb}}^{+}$ case recently studied both experimentally and theoretically. It is shown that the second-King plots for ${\mathrm{Li}}^{+}$ have about the same sensitivity to new physics as the ${\mathrm{Yb}}^{+}$ case for boson masses up to about 10 keV, and nuclear size uncertainties (including nuclear polarization) are suppressed. This greatly extends the sensitivity to new physics for light two-electron systems.

We present an experimental study of the coherence properties of a single heavy-hole spin qubit formed in one quantum dot of a gated GaAs/AlGaAs double quantum dot device. We use a modified spin-readout latching technique in which the second quantum dot serves both as an auxiliary element for a fast spin-dependent readout within a 200 ns time window and as a register for storing the spin-state information. To manipulate the single-spin qubit, we apply sequences of microwave bursts of various amplitudes and durations to make Rabi, Ramsey, Hahn-echo, and CPMG measurements. As a result of the qubit manipulation protocols combined with the latching spin readout, we determine and discuss the achieved qubit coherence times: $T_1$, $T_{Rabi}$, $T_2^{*}$, and $T_2^{CPMG}$ vs. microwave excitation amplitude, detuning, and additional relevant parameters.

We present an experimental study of the coherence properties of a single heavy-hole spin qubit formed in one quantum dot of a gated GaAs/AlGaAs double quantum dot device. We use a modified spin-readout latching technique in which the second quantum dot serves both as an auxiliary element for fast spin-dependent readout within a 200ns time window and also as a register for storing the spin-state information. To manipulate the single-spin qubit we apply sequences of microwave bursts of various amplitudes and durations to make Rabi, Ramsey, Hahn-echo, and CPMG measurements. As a result of the qubit manipulation protocols combined with the latching spin readout, we determine and discuss the achieved qubit coherence times: T1, T_Rabi, T2*, and T_CPMG vs microwave excitation amplitude, detuning and additional relevant parameters