The basis for much of modern electronics is a set of silicon technologies called CMOS, which stands for complementary metal oxide semiconductor devices and processes.  "Complementary" means using semiconductors (typically silicon) that is locally chemically doped so that you can have both n-type (carriers are negatively charged electrons in the conduction band) and p-type (carriers are positively charged holes in the valence band) material on the same substrate.  With field-effect transistors (using oxide gate dielectrics), you can make very compact, comparatively low power devices like inverters and logic gates.   There are multiple different approaches to try to implement quantum information processing in solid state platforms, with the idea that the scaling lessons of microelectronics (in terms of device density and reliability) can be applied.  I think that essentially all of these avenues require cryogenic operating conditions; all superconducting qubits need ultracold conditions for both superconductivity and to minimize extraneous quasiparticles and other decoherence sources.  Semiconductor-based quantum dots (Intel's favorite) similarly need thermal perturbations and decoherence to be minimized.  The wealth of solid state quantum computing research is the driver for the historically enormous (to me, anyway) growth of dilution refrigerator manufacturing (see my last point here). So you eventually want to have thousands of error-corrected logical qubits at sub-Kelvin temperatures, which may involve millions of physical qubits at sub-Kelvin temperatures, all of which need to be controlled.  Despite the absolute experimental fearlessness of people like John Martinis, you are not going to get this to work by running a million wires from room temperature into your dil fridge.   Fig. 1 from here. The alternative people in this area have converged upon is to create serious CMOS control circuitry that can work at 4 K or below, so that a lot of the wiring does not need to go from the qubits all the way to room temperature.  The materials and device engineering challenges in doing this are substantial!  Power dissipation really needs to be minimized, and material properties to work at cryogenic conditions are not the same as those optimized for room temperature.  There have been major advances in this - examples include Google in 2019, Intel in 2021, IBM in 2024, and this week, folks at the University of New South Wales supported by Microsoft.   In this most recent work, the aspect that I find most impressive is that the CMOS electronics are essentially a serious logic-based control board operating at milliKelvin temperatures right next to the chip with the qubits (in this case, spins-in-quantum-dots).  I'm rather blown away that this works and with sufficiently low power dissipation that the fridge is happy.  This is very impressive, and there is likely a very serious future in store for cryogenic CMOS.

As usual, I hope to write more about particular physics topics soon, but in the meantime I wanted to share a sampling of news items: First, it's a pleasure to see new long-form writing about condensed matter subjects, in an era where science blogging has unquestionably shrunk compared to its heyday.  The new Quantum Matters substack by Justin Wilson (and William Shelton) looks like it will be a fun place to visit often. Similar in spirit, I've also just learned about the Knowmads podcast (here on youtube), put out by Prachi Garella and Bhavay Tyagi, two doctoral students at the University of Houston.  Fun Interviews with interesting scientists about their science and how they get it done.   There have been some additional news bits relevant to the present research funding/university-govt relations mess.  Earlier this week, 200 business leaders published an open letter about how the slashing support for university research will seriously harm US economic competitiveness.  More of this, please.  I continue to be surprised by how quiet technology-related, pharma, and finance companies are being, at least in public.  Crushing US science and engineering university research will lead to serious personnel and IP shortages down the line, definitely poor for US standing.  Again, now is the time to push back on legislators about cuts mooted in the presidential budget request.   The would-be 15% indirect cost rate at NSF has been found to be illegal, in a summary court judgment released yesterday.  (Brief article here, pdf of the ruling here.) Along these lines, there are continued efforts for proposals about how to reform/alter indirect cost rates in a far less draconian manner.  These are backed by collective organizations like the AAU and COGR.  If you're interested in this, please go here, read the ideas, and give some feedback.  (Note for future reference:  the Joint Associations Group (JAG) may want to re-think their acronym.  In local slang where I grew up, the word "jag" does not have pleasant connotations.) The punitive attempt to prevent Harvard from taking international students has also been stopped for now in the courts.

A very quick summary of some non-negative news developments: The NSF awarded 500 more graduate fellowships this week, bringing the total for this year up to 1500.  (Apologies for the X link.)  This is still 25% lower than last year's number, and of course far below the original CHIPS and Science act target of 3000, but it's better than the alternative.  I think we can now all agree that the supposed large-scale bipartisan support for the CHIPS and Science act was illusory. There seems to be some initial signs of pushback on the senate side regarding the proposed massive science funding cuts.  Again, now is the time to make views known to legislators - I am told by multiple people with experience in this arena that it really can matter. There was a statement earlier this week that apparently the US won't be going after Chinese student visas.  This would carry more weight if it didn't look like US leadership was wandering ergodically through all possible things to say with no actual plan or memory. On to the main topic of this post.  Thanks to my professional age (older than dirt) and my experience (overseeing shared research infrastructure; being involved in a couple of building design and construction projects; and working on PI lab designs and build-outs), I have some key advice and lessons learned for anyone designing a new big science/engineering research building.  This list is by no means complete, and I invite readers to add their insights in the comments.  While it seems likely that many universities will be curtailing big capital construction projects in the near term because of financial uncertainty, I hope this may still come in handy to someone.   Any big laboratory building should have a dedicated loading dock with central receiving.  If you're spending $100M-200M on a building, this is not something that you should "value engineer" away.  The long term goal is a building that operates well for the PIs and is easy to maintain, and you're going to need to be able to bring in big crates for lab and service equipment.  You should have a freight elevator adjacent to the dock.   You should also think hard about what kind of equipment will have to be moved in and out of the building when designing hallways, floor layouts, and door widths.  You don't want to have to take out walls, doorframes, or windows, or to need a crane to hoist equipment into upper floors because it can't get around corners. Think hard about process gasses and storage tanks at the beginning.  Will PIs need to have gas cylinders and liquid nitrogen and argon tanks brought in and out in high volumes all the time, with all the attendant safety concerns?  Would you be better off getting LN2 or LAr tanks even though campus architects will say they are unsightly?   Likewise, consider whether you should have building-wide service for "lab vacuum", N2 gas, compressed air, DI water, etc.  If not and PIs have those needs, you should plan ahead to deal with this. Gas cylinder and chemical storage - do you have enough on-site storage space for empty cylinders and back-up supply cylinders?  If this is a very chemistry-heavy building, think hard about safety and storing solvents.  Make sure you design for adequate exhaust capacity for fume hoods.  Someone will always want to add more hoods.  While all things are possible with huge expenditures, it's better to make sure you have capacity to spare, because adding hoods beyond the initial capacity would likely require a huge redo of the building HVAC systems. Speaking of HVAC, think really hard about controls and monitoring.  Are you going to have labs that need tight requirements on temperature and humidity?  When you set these up, put have enough sensors of the right types in the right places, and make sure that your system is designed to work even when the outside air conditions are at their seasonal extremes (hot and humid in the summer, cold and dry in the winter).  Also, consider having a vestibule (air lock) for the main building entrance - you'd rather not scoop a bunch of hot, humid air (or freezing, super-dry air) into the building every time a student opens the door. Still on HVAC, make sure that power outages and restarts don't lead to weird situations like having the whole building at negative pressure relative to the outside, or duct work bulging or collapsing. Still on HVAC, actually think about where the condensate drains for the fan units will overflow if they get plugged up or overwhelmed.  You really don't want water spilling all over a rack of networking equipment in an IT closet.  Trust me. Chilled water:  Whether it's the process chilled water for the air conditioning, or the secondary chilled water for lab equipment, make sure that the loop is built correctly.   Incompatible metals (e.g., some genius throws in a cast iron fitting somewhere, or joints between dissimilar metals) can lead to years and years of problems down the line.  Make sure lines are flushed and monitored for cleanliness, and have filters in each lab that can be checked and maintained easily. Electrical - design with future needs in mind.  If possible, it's a good idea to have PI labs with their own isolation transformers, to try to mitigate inter-lab electrical noise issues.  Make sure your electrical contractors understand the idea of having "clean" vs. "dirty" power and can set up the grounding accordingly while still being in code. Still on electrical, consider building-wide surge protection, and think about emergency power capacity.  For those who don't know, emergency power is usually a motor-generator that kicks in after a few seconds to make sure that emergency lighting and critical systems (including lab exhaust) keep going. Ceiling heights, duct work, etc. - It's not unusual for some PIs to have tall pieces of equipment.  Think about how you will accommodate these.  Pits in the floors of basement labs?  5 meter slab-to-slab spacing?  Think also about how ductwork and conduits are routed.  You don't want someone to tell you that installation of a new apparatus is going to cost a bonus $100K because shifting a duct sideways by half a meter will require a complete HVAC redesign. Think about the balance between lab space and office space/student seating.  No one likes giant cubicle farm student seating, but it does have capacity.  In these days of zoom and remote access to experiments, the way students and postdocs use offices is evolving, which makes planning difficult.  Health and safety folks would definitely prefer not to have personnel effectively headquartered directly in lab spaces.  Seriously, though, when programming a building, you need to think about how many people per PI lab space will need places to sit.  I have yet to see a building initially designed with enough seating to handle all the personnel needs if every PI lab were fully occupied and at a high level of research activity.  Think about maintenance down the line.  Every major building system has some lifespan.  If a big air handler fails, is it accessible and serviceable, or would that require taking out walls or cutting equipment into pieces and disrupting the entire building?  Do you want to set up a situation where you may have to do this every decade?  (Asking for a friend.) Entering the realm of fantasy, use your vast power and influence to get your organization to emphasize preventative maintenance at an appropriate level, consistently over the years.  Universities (and national labs and industrial labs) love "deferred maintenance" because kicking the can down the road can make a possible cost issue now into someone else's problem later.  Saving money in the short term can be very tempting.  It's also often easier and more glamorous to raise money for the new J. Smith Laboratory for Physical Sciences than it is to raise money to replace the HVAC system in the old D. Jones Engineering Building.  Avoid this temptation, or one day (inevitably when times are tight) your university will notice that it has $300M in deferred maintenance needs. I may update this list as more items occur to me, but please feel free to add input/ideas.

Again, as a distraction from persistently concerning news, here is a science mystery of which I was previously unaware. The role of approximations in physics is something that very often comes as a shock to new students.  There is this cultural expectation out there that because physics is all about quantitative understanding of physical phenomena, and the typical way we teach math and science in K12 education, we should be able to get exact solutions to many of our attempts to model nature mathematically.   In practice, though, constructing physics theories is almost always about approximations, either in the formulation of the model itself (e.g. let's consider the motion of an electron about the proton in the hydrogen atom by treating the proton as infinitely massive and of negligible size) or in solving the mathematics (e.g., we can't write an exact analytical solution of the problem when including relativity, but we can do an order-by-order expansion in powers of \(p/mc\)).  Theorists have a very clear understanding of what means to say that an approximation is "well controlled" - you know on both physical and mathematical grounds that a series expansion actually converges, for example.   Some problems are simpler than others, just by virtue of having a very limited number of particles and degrees of freedom, and some problems also lend themselves to high precision measurements.  The hydrogen atom problem is an example of both features.  Just two spin-1/2 particles (if we approximate the proton as a lumped object) and readily accessible to optical spectroscopy to measure the energy levels for comparison with theory.  We can do perturbative treatments to account for other effects of relativity, spin-orbit coupling, interactions with nuclear spin, and quantum electrodynamic corrections (here and here).  A hallmark of atomic physics is the remarkable precision and accuracy of these calculations when compared with experiment.  (The \(g\)-factor of the electron is experimentally known to a part in \(10^{10}\) and matches calculations out to fifth order in \(\alpha = e^2/(4 \pi \epsilon_{0}\hbar c)\).).   The helium atom is a bit more complicated, having two electrons and a more complicated nucleus, but over the last hundred years we've learned a lot about how to do both calculations and spectroscopy.   As explained here, there is a problem.  It is possible to put helium into an excited metastable triplet state with one electron in the \(1s\) orbital, the other electron in the \(2s\) orbital, and their spins in a triplet configuration.  Then one can measure the ionization energy of that system - the minimum energy required to kick an electron out of the atom and off to infinity.  This energy can be calculated to seventh order in \(\alpha\), and the theorists think that they're accounting for everything, including the finite (but tiny) size of the nucleus.  The issue:  The calculation and the experiment differ by about 2 nano-eV.  That may not sound like a big deal, but the experimental uncertainty is supposed to be a little over 0.08 nano-eV, and the uncertainty in the calculation is estimated to be 0.4 nano-eV.  This works out to something like a 9\(\sigma\) discrepancy.  Most recently, a quantitatively very similar discrepancy shows up in the case of measurements performed in 3He rather than 4He.   This is pretty weird.  Historically, it would seem that the most likely answer is a problem with either the measurements (though that seems doubtful, since precision spectroscopy is such a well-developed set of techniques), the calculation (though that also seems weird, since the relevant physics seems well known), or both.  The exciting possibility is that somehow there is new physics at work that we don't understand, but that's a long shot.  Still, something fun to consider (as my colleagues (and I) try to push back on the dismantling of US scientific research.)