Yep, still a major issue. This was run at 0.15 kelvin (-273c/-459.4f) and they'd like to get it colder: In these experiments, the electron temperature accounts

Yep, still a major issue. This was run at 0.15 kelvin (-273c/-459.4f) and they'd like to get it colder: In these experiments, the electron temperature accounts for 10% of the reduction in our visibility, and spin relaxation accounts for the remaining 5-10%. In our experiment we readout the qubits sequentially, reading the left qubit first. Relaxation of the right qubit during the readout of the left qubit is what leads to the asymmetry of the expected visibilities. Relaxation contributions to the readout fidelity can be mitigated by using a faster readout technique such as RF reflectometry or by incorporating a cold amplifier into the readout circuit (9, 10). Further improvements can be made by reducing the electron temperature or using cavity-based measurement approaches (11).