[adastra22]

No, we cannot. IBM moved neutral atoms around on an inert surface. No one has demonstrated building covalent structures (or metallic, or ionic for that matter).

My startup is trying to do this, and it is a fiendishly hard problem.

[kev009]

Is this "we" you and your startup or all of humanity? There are a variety of published papers that show simple memories and other structures that are way outside my domain knowledge (qd transistors?).

[adastra22]

No one has ever demonstrated the synthesis of atomically precise structures by positional chemistry.

Quantum dots are not mechanosynthesized, or even atomically precise in many/most instances.

[fooker]

Why though?

[adastra22]

Why is it hard? You need to be able to position things with sub-angstrom precision from a platform that has ~nm uncertainty in the critical z positioning, and in the case of nc-AFM is oscillating to boot.

And you can’t use existing tools. You need an atomically precise scanning probe tip with very specific reactive chemical structure, but NOT react with the surface while scanning with a voltage bias.

And where do you source feedstock from? Needs to be delivered to the surface in passive form but be activated when needed to switch to being chemically reactive in a specific way to get it on the transfer tool and then onto the part being built.

Oh, and this is without even getting into how many electronic structures are entirely invisible at certain voltages, everything looks like an identical blobish shape, surfaces are reconfiguring themselves constantly, and probes randomly crash due to piezo creep, destroying days or weeks of work.

My startup has solutions to all of these problems. And the payoff at the end is reliable, scalable quantum computers, followed by full-on Drexlarian nanotech. But yeah, it’s a fiendishly hard problem.

[fooker]

No, why try doing this?

[adastra22]

In the long run, this:

https://www.youtube.com/watch?v=1bw6Zi17DBI

The story of technological progress is one of shrinking feature sizes in manufacturing. Not just semiconductors, but everything. The Industrial Revolution is really the story of higher tolerance and more reliable manufacturing pins.

You can explore the physical limits of technology by looking at what happens when we reach perfect atomic precision--every atom where we want, in any configuration permitted by physical law. Across nearly every vertical, this represents a 100x to 1000x improvement. In some cases factors of 10^8 to 10^12 over present-day capabilities.

Developing a process to build structures atom-by-atom (essentially 3D printing diamond or other gemstone materials with atomic precision) would enable skipping to these theoretical limits, with the corresponding step function increase in functionality.

It would also move our technological base off being based on rare metals and alloys, and onto an industrial economy built on carbon (diamond and graphene), and other elements commonly available in the Earth's crust and atmosphere. After 3,000 years we will finally move from the Iron Age to the Diamond Age, and with it bring an eventual end to material scarcity and the economic basis for global conflict. You'd seriously need to go back as far as the invention of agriculture or Bronze Age or early Iron Age metallurgy to find a comparably transformative technological advancement.

Within the VC-fundable horizon of the next couple years, early versions of this manufacturing tech will permit making high-value quantum devices like sensors or qubits, as these can be manufactured by introducing certain defects into a growing crystal, with atomic precision relative to other defects or surface features.

[muhdeeb]

What’s the plan for dealing with cosmic rays? I worry about when your beautiful angstrom-precision qubit networks encounter a relativistic proton or muon.

[defrost]

At near surface level ( 80m above ground in clear dry air ) 42 litres of doped Sodium Iodide scintillation crystal will experience ~ one to two thousand gamma events a second .. most of relatively low energy (and ground sourced).

The fall off from low orbit to surface is substantial in both event numbers and energy level.

The higher energy cosmic sourced events at surface level are down in the hundred or less a second (IIRC).

If there's a plan it'd likely include having 9x redundancy hardware surrounded by water deep in a former salt mine .. that'd take cosmic ray events way down and provide a (best of three) x (tell me three times) "just in case" statistical sharpening.

[adastra22]

The liklihood of a particular structure being hit is very, very small. Negligible over the operational lifetime of the device.

In the long-term vision of scaled-up nanotechnology, there will of course have to be redundancy and mechanisms for disabling, removing, and recycling (or incinerating) mechanisms destroyed by cosmic rays.

But in the near-term, it is an ignorable risk.

[lightedman]

Things don't like to move once they're atomically-stuck together. Getting them to stick is another issue altogether. Doing so in reliable locations repeatedly at scale? Good luck.