Speaker
Description
We report progress on quantum logic implemented using microwave and radiofrequency
magnetic fields together with magnetic field gradients in a mixed-species trapped-ion
system. This approach avoids direct optical interactions on the data ion, thereby
mitigating spontaneous-emission-induced errors and surface charging associated with
short-wavelength laser light, and offers a path toward scalable laser-free quantum
information processing. Our platform consists of a co-trapped $^{25}$Mg$^{+}$ data
ion and $^{40}$Ca$^{+}$ helper ion confined in a surface-electrode trap. The
charge-to-mass ratio mismatch between species leads to imbalanced participation in
the shared motional modes, particularly the radial modes relevant for
magnetic-field-gradient-based spin--motion coupling. We implement mode--mode coupling
between Mg-dominant and Ca-dominant motional modes to achieve controlled
hybridization and redistribution of mode participation, enabling sympathetic cooling
of data-ion-dominant modes via the Ca$^{+}$ helper ion and providing a means of
tuning the effective spin--motion coupling in the mixed-species crystal. Building on
this, we pursue quantum logic state preparation of $^{25}$Mg$^{+}$ via microwave
sideband pumping within its hyperfine manifold, with dissipation provided indirectly
through repeated Ca$^{+}$-based ground-state cooling of the shared motional modes.
Together, mode--mode coupling, microwave-driven spin--motion interactions, and
helper-ion-mediated state preparation and readout establish the essential ingredients
for mixed-species quantum logic and provide a pathway toward entangling gate
operations between data and helper ions mediated by magnetic field gradients.
| Academic level | Postdoctoral researcher |
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