Quantum computing in silicon hits 99% accuracy

Date:
January 19, 2022
Source:
University of New South Wales
Summary:
Researchers have proven that near error-free quantum computing is
possible, paving the way to build silicon-based quantum devices
compatible with current semiconductor manufacturing technology.



FULL STORY ==========================================================================
UNSW Sydney-led research paves the way for large silicon-based quantum processors for real-world manufacturing and application.


========================================================================== Australian researchers have proven that near error-free quantum computing
is possible, paving the way to build silicon-based quantum devices
compatible with current semiconductor manufacturing technology.

"Today's publication in Nature shows our operations were 99 per cent
error- free," says Professor Andrea Morello of UNSW, who led the work.

"When the errors are so rare, it becomes possible to detect them and
correct them when they occur. This shows that it is possible to build
quantum computers that have enough scale, and enough power, to handle meaningful computation." This piece of research is an important milestone
on the journey that will get us there," Prof. Morello says.

Quantum computing in silicon hits the 99% threshold Morello's paper is
one of three published today in Naturethat independently confirm that
robust, reliable quantum computing in silicon is now a reality.

This breakthrough features on the front cover of the journal.

* Morello et al achieved 1-qubit operation fidelities up to 99.95
per cent,
and 2-qubit fidelity of 99.37 per cent with a three-qubit system
comprising an electron and two phosphorus atoms, introduced in
silicon via ion implantation.

* A Delftteam in the Netherlands led by Lieven Vandersypen achieved
99.87
per cent 1-qubit and 99.65 per cent 2-qubit fidelities using
electron spins in quantum dots formed in a stack of silicon and
silicon-germanium alloy (Si/SiGe).

* A RIKEN team in Japan led by Seigo Tarucha similarly achieved
99.84 per
cent 1-qubit and 99.51 per cent 2-qubit fidelities in a two-electron
system using Si/SiGe quantum dots.



==========================================================================
The UNSW and Delft teams certified the performance of their quantum
processors using a sophisticated method called gate set tomography,
developed at Sandia National Laboratories in the U.S. and made openly
available to the research community.

Morello had previously demonstrated that he could preserve quantum
information in silicon for 35 seconds, due to the extreme isolation of
nuclear spins from their environment.

"In the quantum world, 35 seconds is an eternity," says Prof. Morello. "To
give a comparison, in the famous Google and IBM superconducting quantum computers the lifetime is about a hundred microseconds -- nearly a million times shorter." But the trade-off was that isolating the qubits made it seemingly impossible for them to interact with each other, as necessary
to perform actual computations.

Nuclear spins learn to interact accurately Today's paper describes how
his team overcame this problem by using an electron encompassing two
nuclei of phosphorus atoms.



==========================================================================
"If you have two nuclei that are connected to the same electron, you
can make them do a quantum operation," says Dr Mateusz M?dzik, one of
the lead experimental authors.

"While you don't operate the electron, those nuclei safely store their
quantum information. But now you have the option of making them talk
to each other via the electron, to realise universal quantum operations
that can be adapted to any computational problem." "This really is an unlocking technology," says Dr Serwan Asaad, another lead experimental
author. "The nuclear spins are the core quantum processor. If you
entangle them with the electron, then the electron can then be moved
to another place and entangled with other qubit nuclei further afield,
opening the way to making large arrays of qubits capable of robust
and useful computations." David Jamieson, research leader at the
University of Melbourne, adds: "The phosphorus atoms were introduced
in the silicon chip using ion implantation, the same method used in
all existing silicon computer chips. This ensures that our quantum
breakthrough is compatible with the broader semiconductor industry."
All existing computers deploy some form of error correction and data redundancy, but the laws of quantum physics pose severe restrictions
on how the correction takes place in quantum computer. Prof. Morello
explains: "You typically need error rates below 1 per cent, to apply
quantum error correction protocols. Having now achieved this goal, we
can start designing silicon quantum processors that scale up and operate reliably for useful calculations." Video: https://youtu.be/bjLUhg5mKic ========================================================================== Story Source: Materials provided by University_of_New_South_Wales. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Mateusz T. Mądzik, Serwan Asaad, Akram Youssry, Benjamin
Joecker,
Kenneth M. Rudinger, Erik Nielsen, Kevin C. Young, Timothy
J. Proctor, Andrew D. Baczewski, Arne Laucht, Vivien Schmitt,
Fay E. Hudson, Kohei M.

Itoh, Alexander M. Jakob, Brett C. Johnson, David N. Jamieson,
Andrew S.

Dzurak, Christopher Ferrie, Robin Blume-Kohout, Andrea
Morello. Precision tomography of a three-qubit donor quantum
processor in silicon. Nature, 2022; 601 (7893): 348 DOI:
10.1038/s41586-021-04292-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220119121509.htm

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