title: Quantum Algorithmic Readout in Multi-Ion Clocks.
abstract: Optical clocks based on ensembles of trapped ions promise record frequency accuracy with good short-term stability. Most suitable ion species lack closed transitions, so the clock signal must be read out indirectly by transferring the quantum state of the clock ions to cotrapped logic ions of a different species. Existing methods of quantum logic readout require a linear overhead in either time or the number of logic ions. Here we describe a quantum algorithmic readout whose overhead scales logarithmically with the number of clock ions in both of these respects. The scheme allows a quantum nondemolition readout of the number of excited clock ions using a single multispecies gate operation which can also be used in other areas of ion trap technology such as quantum information processing, quantum simulations, metrology, and precision spectroscopy.
authors.affiliation: Institute for Theoretical Physics and Institute for Gravitational Physics (Albert-Einstein-Institute), Leibniz University Hannover, Callinstrasse 38, 30167 Hannover, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schulte
authors.affiliation: Institute for Theoretical Physics and Institute for Gravitational Physics (Albert-Einstein-Institute), Leibniz University Hannover, Callinstrasse 38, 30167 Hannover, Germany.|Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Lörch
authors.affiliation: QUEST Institut, Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany.
authors.forename: I D
authors.initials: ID
authors.lastname: Leroux
authors.affiliation: QUEST Institut, Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany.|Institute for Quantum Optics, Leibniz University Hannover, Welfengarten 1, 30167 Hannover, Germany.
authors.forename: P O
authors.initials: PO
authors.lastname: Schmidt
authors.affiliation: Institute for Theoretical Physics and Institute for Gravitational Physics (Albert-Einstein-Institute), Leibniz University Hannover, Callinstrasse 38, 30167 Hannover, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Hammerer