APS March Meeting 2023, Day 3

There is vigorous discussion taking place on the Day 2 link regarding the highly controversial claim of room temperature superconductivity.  

Highlights from Wednesday are a hodgepodge because of my meanderings:

• The session about quantum computing hardware was well attended, though I couldn't stay for the whole thing.  The talk by Christopher Eichler about the status of superconducting qubit capabilities was interesting, arguing the case that SC devices can credibly get to the thresholds needed for error correction, though that will require improvements in just about every facet to get there with manageable overhead.  The presentation by Anausa Chatterjee about the status of silicon spin qubits was similarly broad.  The silicon implementation faces major challenges of layout, exacerbated (ironically) by the small size of the physical dots.  There have been some recent advances in fab that are quite impressive, like this 4 by 4 crossbar.  
• Speaking of impressive capabilities, there were two talks (1, 2) by members of the Yacoby group at Harvard about using a scanning NV center to image the formation and positions of vortices in planar Josephson junctions.  They can toggle between 0 and 1 vortices in the junction and can see some screening effects that you can't just get from the transport data.  Pretty images.
• Switching gears, I heard a couple of talks in an invited session about emergent phenomena in strongly correlated materials.  From Paul Goddard at Warwick I learned about charge transport in some pyrochlore iridates that I didn't realize had so much residual conduction at low temperatures.  See here.  Likewise, James Analytis gave a characteristically clear talk about interesting superconductivity in Ni(x)Ta4Se8 (arxiv version here), an intercalated dichalcogenide that has magnetism as well as re-entrant superconductivity up at the magnetic field that kills the magnetically ordered state.
• Later in the day, there was a really interesting session about measuring entropy, which is notoriously difficult to do.  As I've told students for years, you can't go to Keysight and buy an entropy-meter.  There was some extremely pretty data presented by Shahal Ilani using a variant of their new scanning probe technique.

Morning of Day 4 is being taken up by a bunch of other tasks, so the next writeup may be sparse.