Rolf Landauer and Charles H. Bennett Award in Quantum Computing talk: Repeated parity measurement and feedback in a mixed-species trapped ion register

Quantum error correction is essential for realizing the full potential of large-scale quantum information processing devices. Fundamental to its experimental realization is the repetitive detection of errors via projective measurements of quantum correlations among qubits, as well as corrections using conditional feedback. I will describe experiments in which we demonstrate up to 50 sequential measurements of correlations between two beryllium ion microwave qubits using an ancillary optical-frequency qubit in a calcium ion, and implement feedback that allows us to stabilize two-qubit subspaces as well as maximally entangled Bell states [1]. The use of multiple ion species allows us to completely reset the ancilla after measurement and completely mitigate any unwanted effects. Looking towards further scaling, many apparent challenges appear to lie in the use of radio-frequency traps, including power-dissipation and the need to co-align microscopically varying potentials. I will describe how this might be mitigated using micro-fabricated arrays of Penning traps, which would also provide a powerful tool for implementing trapped-ion quantum simulation on a variety of two-dimensional lattices.

[1] V. Negnevitsky, M. Marinelli et al. Nature 563, 527–531 (2018)