Speaker
Description
Being a prospective platform for quantum computing and metrology, Coulomb
crystals of ultracold trapped ions currently reach sizes of hundreds of
individual particles. Such systems require high level of control over their
motional temperature in order to account for the second-order Doppler shift in
atomic clocks and implement high-fidelity entangling gates in quantum
computers. However, the existing ion crystal thermometry tools struggle to
provide an accurate temperature estimation for large ground-state cooled Coulomb
crystals, either focusing only on the symmetric center-of-mass vibrational
mode of motion or neglecting the involved spin-spin correlations between
the trapped ions. To resolve the arising thermometry bottleneck, we consider
the many-body dynamics of an ion crystal, arising when motional sideband
transitions are driven in a near ground-state regime. In the single ion case,
thermometry methods based on the motional sidebands are widely used and
are thus of interest in the ion crystal case. The conducted study of the
single-ion case from the Fisher Information prospective gives us some valuable
insights for extending the approach further towards ion crystals. In our
work we account for entanglement created between the ions in a Coulomb crystal
to derive a new reliable temperature estimator, insensitive to the number
of ions, and field-test in experiments with 4- and 19-ion crystals done by
our colleagues from PTB Braunschweig and University of Innsbruck.
