Crosstalk mitigation and in-sequence detection in a dual-isotope trapped ion register
Roland Matt
I present experimental work performed in a cryogenic apparatus exploiting a segmented ion trap architecture for the implementation of quantum algorithms. The quantum register consists of a linear string of Ca+ ions which are individually controlled by tightly focused laser beams perpendicular to the crystal axis. Light is delivered by a waveguide array allowing to individually feed each ion with a separately controlled tightly focused laser beam. However, the spatial profile of the addressing beams is fundamentally limited by diffraction, therefor leading to significant optical crosstalk for closely spaced ion strings. This will lead to unwanted errors on spectator qubits which can be suppressed at the gate level. This class of errors are of particular interest as they can create correlations between qubits that may render a quantum circuit no longer fault-tolerant.
I will start by presenting a coherent optical cancellation method which relies on applying parallel compensation pulses on spectator ion(s) and compare this method against known techniques such as composite pulse sequences and noise refocusing methods.
The second part of the talk will focus on presenting recent results from a novel back-ground free detection scheme implemented on the narrow S1/2 -D3/2 quadrupole transition. We show that high scattering rates can be achieved with low levels of heating on the ions’ motion. This reduces the overhead for recooling greatly, making this scheme an excellent candidate for in-sequence detection in future quantum error correction routines.