This is cross-posted from discord and is a follow-up to my recent post where I was looking at the recently leaked photo. In this post, I will talk a bit about the partially obscured page, which I didn’t cover in my post above.
At the top of the page we can see the partially obscured text “Quantum Reciprocal Lo”, which has been established to be referring to Quantum Reciprocal Logic.
Basically, it’s an ultra-low power superconducting digital technology that uses Josephson junctions instead of transistors. It’s based on the idea of encoding information in the presence or absence of a magnetic flux quantum, known as the Single Flux Quantum (SFQ). SFQ pulses are generated across the Josephson junctions. RQL uses reciprocal pairs of SFQ pulses to encode bits. Note that these are classical bits, not quantum bits, or qubits. With this technology you can build superconducting digital logic chips that have ultra-low power dissipation and can operate with clock speeds of tens or hundreds of GHz.
A Josephson junction and how it works is complicated to explain (look up the Josephson effect), but it’s basically two layers of superconducting material with a thin layer of non-superconducting material sandwiched in between, which acts as a non-superconducting barrier. Due to the quantum tunnelling effect, electrons will tunnel through the non-superconductive barrier without resistance, but only as long as the current through the junction is below a certain threshold, the critical current. If the current exceeds the critical current, an AC voltage will develop over the junction, which can be measured.
The superconducting material is usually Niobium, and the non-superconducting material is some kind of Aluminium Oxide. The Niobium needs to be liquid Helium-cooled for it to become superconducting.
The circuit schematic seen in the photo appears to be an example of an RQL shift register. The full circuit can be seen in this paper:
The key thing I note here is that this technology operates on conventional digital bits, and not quantum bits (qubits) (unless I’m missing something), but it can certainly form the basis for building a really fast supercomputer. Imagine what you can do if you can replace the liquid He-cooled Niobium superconductor with a room temperature superconductor.
So, this is likely the technology from which HALOS was built, and we can see how the Niobium fits into this. But there’s probably more to this, and HALOS definitely evolved beyond its original design, and the question is how and why.
There are many more questions, but those are for another post
EDIT: It’s possible that RQL is being used in the support circuitry that controls the operation of the qubits in a quantum processor, sends information in the form of classical bits to the qubits, and reads out the information from the qubits. Qubits are also made up of circuits that uses Josephson junctions, so using RQL in the control circuitry should in theory be ideal as it can all be “easily” integrated on the same chip. This means that the processors that make up HALOS can still be quantum processors (QPUs).