  A mixed-species geometric phase gate has been proposed for implementing
quantum logic spectroscopy on trapped ions that combines probe and information
transfer from the spectroscopy to the logic ion in a single pulse. We
experimentally realize this method, show how it can be applied as a technique
for identifying transitions in currently intractable atoms or molecules,
demonstrate its reduced temperature sensitivity, and observe quantum-enhanced
frequency sensitivity when it is applied to multi-ion chains. Potential
applications include improved readout of trapped-ion clocks and simplified
error syndrome measurements for quantum error correction.
