RIKEN Research Measures Qubit Spin to 99% Fidelity With Silicon Quantum Dots

Scientists succeed in measuring electron spin qubit without demolishing it

Excerpts and salient points ~

+  A group of scientists from the RIKEN Center for Emergent Matter Science in Japan have succeeded in taking repeated measurements of the spin of an electron in a silicon quantum dot (QD), without changing the spin in the process. This type of “non-demolition” measurement is important for creating quantum computers that are fault tolerant.

“Through this,” explains Group Director Seigo Tarucha, who led the research group, “we were able to achieve a non-demolition fidelity rate of 99%, and by using repeated measurements would get a readout accuracy of 95%. We have also shown that theoretically, this could be increased to out 99.6%, and plan to continue work toward reaching that level.”

+  The key difficulty, however, with developing quantum computers is that they are very sensitive to external noise, making error correction critical. So far, researchers have succeeded in developing single electron spins in silicon QDs with a long information retention time and high-precision quantum operation, but quantum non-demolition measurement–a key to effective error correction–has proven elusive.

+  Essentially, they were able to transfer the spin information–up or down–of an electron in a QD to another electron in the neighboring QD using the Ising type interaction in a magnetic field, and then could measure the spin of the neighbor using the conventional method, so that they could leave the original spin unaffected, and could carry out repeated and rapid measurements of the neighbor.

Source:  nanowerk news.  RIKEN,  Scientists succeed in measuring electron spin qubit without demolishing it…

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