[ExI] Very recent developments in topological quantum computing
John Clark
johnkclark at gmail.com
Tue Aug 20 21:29:37 UTC 2019
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
<https://science.sciencemag.org/content/365/6454/684>
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
<https://arxiv.org/pdf/1906.01179.pdf>
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
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