Very recent developments in topological quantum computing ​

[John Clark]

In my opinion a scalable quantum computer could bring about a singularity in human affairs as surely as Drexler's nanotechnology, and the most promising way of achieving this is through a fault tolerant topological quantum computer. In the current issue of the journal Science (August 16 2019) a revolutionary new type of superconductor has been discovered, uranium ditelluride (UTe2), that may turn out to have some considerable bearing on this. Nick Butch, from the National Institute of Standards and one of the authors of the paper says:

"This is potentially the silicon of the quantum information age. You could use uranium ditelluride to build the qubits of an efficient quantum computer."

ferromagnetic spin-triplet superconductivity

Uranium Ditelluride is a very unusual superconductor for several reasons:

1) It is a topological superconductor, meaning that the interior is a insulator but the surface is a superconductor.
2)  It can tolerate enormously strong magnetic fields, much higher than other superconductors.
3) Most superconductors are spin singlet, this means that the spins in the electrons in the Cooper Pairs, which carry the electrical current in all superconductors, are lined up in a antiparallel direction; but Uranium Ditelluride is spin triplet, their electron spins are perpendicular.

All this adds up to the surface of uranium ditelluride being the ideal stage set to produce logic gates made of Majorana pseudoparticles that obey non-Abelian statistics. And that means you could store quantum information topologically which would make it very resistant to quantum decoherence for the same reason you're unlikely to be able to untie a knot by just bumping it, you might change its shape but not its topological properties. And quantum decoherence is by far the most important obstacle we must overcome if we want to build a scalable quantum computer.

And that is not the only new development in the last few weeks, Javad Shaban and his team found something similar in Indium arsenide (InAs) although you must get it much colder before it becomes superconducting, .007 Kelvin verses 1.6 Kelvin for Uranium ditelluride. 

Phase signature of topological transition in Josephson Junctions

Dr. Shabani said:

"We see value in these particles because of their potential to store quantum information in a special computation space where quantum information is protected from the environment noise. As a result, we have sought to engineer platforms on which these calculations could be conducted. The new discovery of topological superconductivity in a two-dimensional platform paves the way for building scalable topological qubits to not only store quantum information, but also to manipulate the quantum states that are free of error. These findings strongly supports the emergence of a topological phase in the system. This offers a scalable platform for detection and manipulation of Majorana bounds states for development of complex circuits for fault-tolerant topological quantum computing."

By the way, the leading company in all this is none other than Microsoft.

John K Clark

[spudb...@aol.com]

Thoughts:

Is this Uranium compound radioactive do you think? As in hazardous? 

Drexler's nanotech looks best used in medical microrobots, and not manufacturing-and that prize goes to 3D-bulk printing.

I believe there has been problems in getting these entanglements in QC to successfully attain actual operations. Does this sound right?

How many successful operations per sec will QC need to do, before it dramatically achieves 'supremacy?'

How many successful operations per sec will it take to achieve a network that improves on, or creates, new inventions for humans?

What I am attempting to do to is ascertain impact on society, how much, and when?  

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[Lawrence Crowell]

Here is a paper by the same authors that appears to address this physics. It is not the science magazine article, but it covers the same material. It is an experimental paper. As a topological superconductor that is defined on edge states on the boundary it appears this is a 2-dimensional surface and there is a mixture between anyonic statistics and fermionic Cooper pairing of electrons with opposite momenta. This has some theoretical implications. The authors talk of nonabelian stats, which I think refer to anyons, and the nonabelian aspects may be with this quantum blurring of anyonic and superconductive physics.

https://arxiv.org/pdf/1908.07396.pdf

LC

[Brent Meeker]

On 8/21/2019 3:55 PM, John Clark wrote:

In my opinion a scalable quantum computer could bring about a singularity in human affairs as surely as Drexler's nanotechnology

It's been 32yrs and it's revolutionized cosmetics.

Brent

[Lawrence Crowell]

I meant to say different authors, but for some reason I wrote the same. This looks like a material that has a lot of interest out there.

LC

[John Clark]

On Wed, Aug 21, 2019 at 8:06 PM spudboy100 via Everything List <everyth...@googlegroups.com> wrote:

> Thoughts: Is this Uranium compound radioactive do you think? As in hazardous? 

It's radioactive but they use depleted Uranium so it's very small, actually Uranium ore that you dig right out of the ground is more radioactive than depleted Uranium because the ore contains U235 and far far more radioactive Polonium and Radium. And besides you don't need much Uranium, just a thin film.

 

> I believe there has been problems in getting these entanglements in QC to successfully attain actual operations. Does this sound right?

Yes, the big problem with Quantum Computers is keeping things entangled and that's the advantage of encoding the quantum information topologically. It's the difference between a pencil balanced on its tip and a knot, the slightest tap will upset the pencil but you have to really work at it to untie the knot, aka change its topological properties.   

> How many successful operations per sec will QC need to do, before it dramatically achieves 'supremacy?'

It depends on how many cycles you need to use for error correction, topological quantum computers don't need nearly as many. Quantum supremacy just means finding something, anything, that a real Quantum Computer can do better than any conventional computer. Even without topology I expect that will be achieved in the next year, maybe two, it will probably just be a proof onf concept and the algorithm will not do anything that is actually useful but it would be a good start.

> What I am attempting to do to is ascertain impact on society, how much, and when?  

Well for one thing it would kill Bitcoin and most forms of encryption that we use today, but that's peanuts. I think the killer application would be in physical simulation, even with today's best supercomputers you need to make big approximations to simulate the simplest quantum interaction. But we really won't know what we can do with a Quantum Computer until we have one we can play around with, its like how we were with conventional computers in the late 1940s

John K Clark   

[Philip Thrift]

Right.

One can write "amazing" quantum programs using Qiskit [ https://qiskit.org/ ]  and run them in the simulator, but they will not be amazing until there is hardware to make them so.

Mathematical fictions can reach for the stars, but matter is a cruel mistress.

@philipthrift