Speaker
Description
Trapped $^{137}\textrm{Ba}^+$ ions possess two long-lived hyperfine manifolds in which quantum information can be stored: the ground $S_{1/2}$ level and the metastable $D_{5/2}$ level. The metastable level does not couple to the fluorescence beams, so information stored there is protected during dissipative operations such as cooling, state preparation or readout. This allows for these operations to be performed mid-circuit, a requirement for most error correction schemes. In addition, gates can be driven via two-photon Raman transitions using light at 532 nm in both levels, simplifying experimental setups.
Here, we present a system for quantum computation experiments with chains of $^{137}\textrm{Ba}^+$. A fibre network coupled to a novel photonic chip is used to generate an array of 532 nm beams that are individually focused on each of the ions. This enables the implementation of all logical and dissipative operations on a target subset of qubits. Furthermore, the ions are stored in a microfabricated linear trap with a segmented electrode structure [1] that can generate complex DC potentials. This allows us to modify the axial position of the ions to match the addressing beam array, as well as rotate the direction of the crystal's radial modes of motion to optimise high-fidelity two-qubit operations.
Additionally, we use the system and our control of the ground and metastable levels to implement a novel state-preparation and measurement (SPAM) protocol based on the detection of population leakages. We achieve SPAM infidelities as low as $5 \times 10^{-6}$, the lowest reported. We also discuss how information processing using multi-dimensional quantum systems could be implemented in this system.
[1] K. Choonee, G. Wilpers and A. G. Sinclair, doi: 10.1109/TRANSDUCERS.2017.7994124.
