Lots to read, including fab for quantum and "Immaterial Science"

Sometimes there are upticks in the rate of fun reading material.  In the last few days:

• A Nature paper has been published by a group of authors predominantly from IMEC in Belgium, in which they demonstrate CMOS-compatible manufacturing of superconducting qubit hardware (Josephson junctions, transmon qubits, based on aluminum) across 300 mm diameter wafers.  This is a pretty big deal - their method for making the Al/AlOx/Al tunnel junctions is different than the shadow evaporation method routinely used in small-scale fab.  They find quite good performance of the individual qubits with strong uniformity across the whole wafer, testing representative random devices.  They did not actually do multi-qubit operations, but what they have shown is certainly a necessary step if there is ever going to be truly large-scale quantum information processing based on this kind of superconducting approach.
• Interestingly, Friday on the arXiv, a group led by researchers at Karlsruhe demonstrated spin-based quantum dot qubits in Si/SiGe, made on 300 mm substrates.  This fab process comes complete with an integrated Co micromagnet for help in conducting electric dipole spin resonance.  They demonstrate impressive performance in terms of single-qubit properties and operations, with the promise that the coherence times would be at least an order of magnitude longer if they had used isotopically purified 28Si material.  (The nuclear spins of the stray 29Si atoms in the ordinary Si used here are a source of decoherence.)  

So, while tremendous progress has been made with atomic physics approaches to quantum computing (tweezer systems like this; ion trapping), it's not wise to count out the solid-state approaches.  The engineering challenges are formidable, but solid-state platforms are based on fab approaches that can make billions of transistors per chip, with complex 3D integration.

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  On the arXiv this evening is also this review about "quantum geometry", which seems like a pretty readable overview of how the underlying structure of the wavefunctions in crystalline solids (the part historically neglected for decades, but now appreciated through its relevance to topology and a variety of measurable consequences) affects electronic and optical response.  I just glanced at it, but I want to make time to look it over in detail.
• Almost 30 years ago, Igor Dolgachev at Michigan did a great service by writing up a brief book entitled "A Brief Introduction to Physics for Mathematicians".  That link is to the pdf version hosted on his website.  Interesting to see how this is presented, especially since a number of approaches routinely shown to undergrad physics majors (e.g., almost anything we do with Dirac delta functions) generally horrify rigorous mathematics students.
• Also fun (big pdf link here) is the first fully pretty and typeset issue of the amusing Journal of Immaterial Science, shown at right.  There is a definite chemistry slant to the content, and I encourage you to read their (satirical) papers as they come out on their website.