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These clocks depend dilute gasses of atoms. Usually the process for preparing and probing the atoms takes at least a few hundred milliseconds, and usually in the seconds range. There's a bunch of reasons for this, probably two main reasons IMO:

1. Generally for precision clocks you need "cold" or "ultracold" atoms (essentially random doppler shifts of hot atoms kill your accuracy). This means something like microkelvins - this is hard to prepare quickly. And atoms are constantly lost/heated due to collisions with stray gas molecules, even though the pressure is usually something like a quadrillion times lower than atmosphere. There's research into continuous ultracold atom sources, and you could prepare way more than you need and siphon a few off at a time, but both are technically challenging.

2. The way these clocks work is essentially you have some laser, and an atom that only reacts to laser light of a very specific frequency. If the laser frequency is off from the exact frequency you can tell. A variety of effects means that the measurement process takes some time. It's like trying to accurately measure your heart rate in 1s vs 10s - a lot easier to do in the latter case.

Nothing fundamental, just technically quite painful.

Just judging by the torque specs and comparing to a nema23 stepper, seems like it needs an order of magnitude more torque to compare. Note that in the comparison chart they compare to a nema11, which is tiny compared to the steppers used in most hobby cncs.

Well it depends on what your bar is for a monopoly. E.g. I can only use Comcast where I live. Comcast is not technically a monopoly - I could move somewhere else where other providers are available. But the friction to change is high enough that they effectively are a monopoly to me.

No company is a monopoly if you are flexible enough. Where antitrust starts to become relevant is a bit of an arbitrary line. If you think "mobile phones" is the industry then Apple does not have a monopoly. But there are many people who would put up with a lot before switching from iOS to Android, because of apps, iCloud, iMessaging, or whatever.

You seem to be very convinced of this. At my institution, research activities has resumed for the past month (albeit with restrictions on occupancy).

Definitely not a cubic function though, you can't get a polynomial to hit 0 that nicely. Any polynomial's leading order term will dominate as x increases. Unless they're using a super high order polynomial and hiding the blowup off the edge of the plot.

I'm a physics grad student finishing up a PhD, would you have some time/be willing to chat about industry jobs? Email is in bio.

Practical from a cultural standpoint or in terms of quantity? IIRC, people are required to wear masks when entering businesses in China now.

Those benefits only apply to people who work at companies that have less than 500 employees. Unfortunately, that leaves most people in the lurch.

https://www.nytimes.com/2020/03/14/opinion/coronavirus-pelos...

I've been using this cable: https://www.amazon.com/dp/B074W1G389/ref=cm_sw_r_cp_awdb_t1_...

Haven't used it for 100W charging so I don't know if it stands up to the full rated 5A though.

Interestingly, the 100m record difference is about 10%, which is roughly the same as the gap in the ultramarathon records (and in the record mile time). So the difference is fairly consistent across distances.

I'm pretty sure the way analog degrees are freedom are mapped onto symbols is very important. In principle, if you have infinite SNR over a limited bandwidth, you can have infinite rate of data transfer - e.g. if you can have infinitely fine voltage resolution (in reality limited by the thermal noise floor, but you can always increase transmit power). So in that sense the mapping between information and bandwidth depends on SNR.

From the wiki page on QAM: "Arbitrarily high spectral efficiencies can be achieved with QAM by setting a suitable constellation size, limited only by the noise level and linearity of the communications channel." [https://en.wikipedia.org/wiki/Quadrature_amplitude_modulatio...]

Source for this? I personally need 9+ hours as well but am constantly told I sleep for too long.

If you’re talking about the i9-9900, it’s a very high clock frequency part with “only” 8 cores and part of the consumer line (no ecc support). I’d actually think most people who have it run Windows and use it for things like gaming.

Nature letter here: https://www.nature.com/articles/s41586-018-0707-9

Looks like they developed advancements with lightweight high-voltage converters and performance of the thrusters.

I used to work on trapped ion experiments, and the limitation of the atom size was always the diffraction limit, which is limited by the NA of the lens (f-stop in camera terms) and the wavelength of light. In this case, the optical system (I'm guessing a camera lens) is designed for multiple wavelengths, so it might not reach the diffraction limit at the emission wavelength, which is like 400nm. In that case, the limit would be the aberration of the camera lens, which can be wavelength-dependent. Most camera lenses aren't designed for 400nm light, which is marginally visible.

Your first statement isn't quite true. See, for example, https://www.scottaaronson.com/blog/?p=473

In short, it's hard to classically model pretty simple quantum mechanical systems and sample the probability distribution of outcomes. Using a quantum computer to simulate the system and sample the probability distribution is easy.

Those numbers aren't that bad, actually. A cell phone's peak power draw isn't much more than 5W, so you'd need 10g / efficiency. At 10% efficiency, that's 100g, which is 5 cm^3 for plutonium. A cell phone battery is about 3 times that size, assuming 3000 mAh and an energy density of 600 Wh/L. Of course you'd have to build in a heat engine, but perhaps even a peltier would work given the generous efficiency allowance.

Cambridge (MA) is like this, but housing prices are still pretty unreasonable. You definitely need taller buildings.

Indeed, that's accurate (apart from finite temperature and interaction effects). A BEC is in some ways pretty similar to a laser, where all the photons are in the same state, even quantum mechanically.

But it's important to distinguish between a BEC and a superfluid. Superfluids are the substances with strange collective properties, and these properties come from being cold, bosonic, and interacting. BECs with very low inter-particle interactions do not behave like superfluids, but will exhibit e.g. interference (just like a laser, which is kinda like a non-interacting BEC).

The electric field gets quickly attenuated in saltwater though, especially at high frequency: https://en.wikipedia.org/wiki/Communication_with_submarines

Nice game, but there's nothing intrinsically quantum about anything that happens. Everything is perfectly describable with classical E&M.

Andrea Morello's devices are essentially quantum dots - isolated electrons that behave like they are bound to a single atom. Unfortunately, almost all quantum dots require dilution refrigerators. These things are past liquid nitrogen and even liquid helium - they use interesting phase change properties of a mix of helium-3 and helium-4 to lower the temperature to hundreds of millikelvin.

Really the only game in town currently for room-temperature quantum computing are impurity centers in diamond (most commonly nitrogen-vacancy centers). Unfortunately, there are still many difficulties there, especially since nanofabrication of diamond and precise implantation of the impurities is still a new field.

The real evidence of this is from the last experiment under "Sequential Experiments". Essentially, you only select particles with spin-up in the z direction, then you select particles with spin-up in the x direction. So the resulting particles should be up in both the z and x direction. But if you measure in the z direction again, you find an equal distribution in up and down, indicating that you can't simply treat the spin as both pointed in the x and z direction, and that measuring in the x direction has scrambled the previously well-defined z direction.

This experiment shows that measuring the spin direction in different axes does not commute. Measuring in one direction scrambles the other, which is equivalent to saying measuring in x then z is not the same as measuring in z then x. This fact is inherently related to the notion of a superposition. If a particle's spin direction is well-defined in one measurement basis, it is not well-defined in another - meaning it is in a superposition state in that measurement basis.

You might ask - why can't I describe the system after measuring in the x-direction as just a random mixture of up and down in the z-direction? Physicists use something called a density matrix to describe systems that have both some degree of quantum superposition and classical randomness. One way to measure the degree to which some stream of particles is a random mixture or not is to interfere particles in that stream with each other.

In the Stern-Gerlach experiment, after measuring in the x-direction, if the information in the z-direction was actually simply randomly scrambled, the probability that any two particles from the stream are truly identical is 1/2. If the particles are all identically in a superposition state, then any two particles will always be identical.

You can actually test the indistinguishability of two particles by doing an interference experiment. One very nice example of this is this experiment: https://arxiv.org/pdf/1312.7182.pdf Two atoms were trapped next to each other using lasers. If these atoms have the same spin, they're indistinguishable. If they have different spin, then they are distinguishable, and won't interfere with each other. In fig. 3, you can see varying levels of interference depending on how well-aligned the spins are.

I also had a very different experience, was part of various "gifted" programs from 4th grade until I graduated high school. Many of my classmates are doing extremely well (grad school/consulting/tech) - I don't think problems with these programs are intrinsic. My classmates from high school are on average doing better though, I think there might be some survivorship bias going on.

Regarding your first point: from my experience (working on physics experiments that depend on vacuum <10^-11 torr), the construction of the knife edge that seals against the gasket is fairly important - any chips or imperfections and the part is garbage. Also do people really use stainless for gaskets? I've always used (and seen other people use) copper, stainless sounds like a huge pain to torque down on.

I doubt UHV experience is relevant here though - at 100 torr you can probably get away with simple o-ring seals. And outgassing doesn't matter: even isopropanol has a vapor pressure of only 40 torr.

Edit: The hyperloop design is at ~1 torr, not 100. Still, I'd imagine outgassing is not a huge issue.

Disclaimer: I used to work on trapped-ion systems.

I hear this a lot about trapped-ion qubits, but in their current state, no technology is scalable. The usual suspects are superconducting, quantum dots, or diamond NV-based qubits, but each technology has their own scalability problems. Superconducting qubits suffer from either requiring massive (vacuum tube sized) cavities or a ton of crosstalk. Good luck isolating superconducting LC circuits from one another on one circuit board - a reason why these are limited to only a few qubits. Quantum dots have pretty awful decoherence issues and I'm not sure they can be implanted deterministically. Moreover, I don't think people have demonstrated non-photon mediated entanglement, which is not particularly scalable. NVs have the same implantation and entanglement problems, though at least they can be used at room-temperature. Superconducting and quantum dot technologies require million-dollar dilution refrigerators and large amounts of (expensive!) helium-3.

Obviously, these technologies also have their advantages over trapped-ion qubits. But trapped-ion proponents also have their own roadmaps to scalability (surface traps created using lithiography).

Not quite the same as an ultrasonic bath. This device creates standing waves, so the antinodes (parts of the wave where the amplitude is 0) will not move. I'm pretty sure the waves created by an ultrasonic cleaner are moving. If the wavelength is large enough, you should be able to feel where there is vibration and where there is none.

I'm not sure fiber optics are particularly viable in the next 5-10 years as interconnects between hardware components. Adding photonics to a hardware component increases size and cost fairly significantly, which is why you don't see many fiber optic interconnects yet, even for applications where cable size is important. Moreover, to get the kind of miniaturization you would need for a cell phone, you're talking on-chip photonics (diodes and photodetectors integrated into the IC itself), which still looks like it's in the early R&D phase.

Of course, most of this is probably because copper is still doing just fine in terms of bandwidth. Though some big issues with forcing huge bandwidth over few traces are latency and the additional circuitry needed to translate the signal into the actual components needed to drive RAM chips or a CPU.