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arXiv · 1709.10469

Sequential modular position and momentum measurements of a trapped ion mechanical oscillator

C. Flühmann·V. Negnevitsky·M. Marinelli·J. P. Home
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Abstract

The non-commutativity of position and momentum observables is a hallmark feature of quantum physics. However this incompatibility does not extend to observables which are periodic in these base variables. Such modular-variable observables have been suggested as tools for fault-tolerant quantum computing and enhanced quantum sensing. Here we implement sequential measurements of modular variables in the oscillatory motion of a single trapped ion, using state-dependent displacements and a heralded non-destructive readout. We investigate the commutative nature of modular variable observables by demonstrating no-signaling-in-time between successive measurements, using a variety of input states. In the presence of quantum interference, which we enhance using squeezed input states, measurements of different periodicity show signaling-in-time. The sequential measurements allow us to extract two-time correlators for modular variables, which we use to violate a Leggett-Garg inequality. The experiments involve control and coherence of multi-component superpositions of up to 8 coherent, squeezed or Fock state wave-packets. Signaling-in-time as well as Leggett-Garg inequalities serve as efficient quantum witnesses which we probe here with a mechanical oscillator, a system which has a natural crossover from the quantum to the classical regime.

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C. Flühmann, V. Negnevitsky, M. Marinelli, J. P. Home. 2017-09-29. Sequential modular position and momentum measurements of a trapped ion mechanical oscillator. https://doi.org/10.1103/physrevx.8.021001

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