[ExI] Quantum Supremacy

[John Clark]

Wow, I'm glad the list is back, at least for now. I tried to send the first
part of this a few weeks ago but no joy, and then there were even more
exciting developments.
==
There is a excellent FAQ by Quantum Computer expert Scott Aaronson about
the Google claim of Quantum Supremacy. Aaronson is noted for throwing cold
water over claims of a breakthrough in his field, but not this time!  Aaronson
is clearly excited, he compares Google's Quantum Computer to the Wright
brothers 1903 flyer or Enrico Fermi's 1942 pile, the world's first nuclear
reactor:

Scott’s Supreme Quantum Supremacy FAQ! <https://www.scottaaronson.com/blog/>

==
Here is a copy of that leaked paper:

Quantum Supremacy Using a Programmable Superconducting Processor
<https://drive.google.com/file/d/19lv8p1fB47z1pEZVlfDXhop082Lc-kdD/view>

I found these quotes from it to be particularly interesting:


*"We show that quantum speedup is achievable in a real-world system and
isnot precluded by any hidden physical laws." *

*"Our processor takes about 200 seconds to sample one instance of the
quantum circuit 1 million times, a state-of-the-art supercomputer would
require approximately 10,000 years to perform the equivalent task."*

*"Quantum processors based on superconducting qubits can now perform
computations in a Hilbert space of dimension 2^53 ≈ 9 × 10^15, beyond the
reach of the fastest classical supercomputers available today. To our
knowledge, this experiment marks the first computation that can only be
performed on a quantum processor."*

*"Quantum processors have thus reached the regime of quantum supremacy. We
expect their computational power will continue to grow at a double
exponential rate"*

For me the most stunning thing about the entire article is the 3 words "double
exponential rate"
==
And in a completely different development there is yet more quantum
computing news that happened when the list was dead. For the first time a
fully controllable ten-qubit spin register with a quantum memory of 75
seconds has been developed. And they managed to achieve this without using
any error correcting at all which the researchers believe is the next
step; they
conclude their article in the September 11 2019 Physical review with:

"*our multiqubit register paves the way for the realization of rudimentary
few-node quantum networks comprising tens of qubits. This will enable the
investigation of basic error correction codes and algorithms over quantum
networks*".

A Ten-Qubit Solid-State Spin Register with Quantum Memory Over One Minute
<https://journals.aps.org/prx/pdf/10.1103/PhysRevX.9.031045>

==

And if you want to know who coined the term "Quantum Supremacy and why look
here:

Why I Called It ‘Quantum Supremacy’
<https://www.quantamagazine.org/john-preskill-explains-quantum-supremacy-20191002/>

 John K Clark
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