Friday, April 10, 2015

Dialing it up

BRT has talked about quantum computers since 2008 as the potential power of such systems defy imagination. From the Matrix to the ability to create reality in finite space, the tech is disruptive to the max but there are problems. How does one easily control qubits in precise fashion, how does one get them to work in silicon and how does one control said quibits at room temperature, three conditions fiendishly difficult to attain, until now.

Unlike conventional computers that store data on transistors and hard drives, quantum computers encode data in the quantum states of microscopic objects called qubits.

The UNSW team, which is affiliated with the ARC Centre of Excellence for Quantum Computation & Communication Technology, was first in the world to demonstrate single-atom spin qubits in silicon, reported in Nature in 2012 and 2013.

The team has already improved the control of these qubits to an accuracy of above 99% and established the world record for how long quantum information can be stored in the solid state, as published in Nature Nanotechnology in 2014.

It has now demonstrated a key step that had remained elusive since 1998.

"We demonstrated that a highly coherent qubit, like the spin of a single phosphorus atom in isotopically enriched silicon, can be controlled using electric fields, instead of using pulses of oscillating magnetic fields," explained UNSW's Dr Arne Laucht, post-doctoral researcher and lead author of the study.

The donor position can be triangulated from a combination of donor-gate capacitances and the spin readout criterion. This way, it is possible to locate the donor with an accuracy of 4, 2.5 and 3.5 nm in the three cartesian axis x, y and z. Credit: A. Laucht, UNSW Australia
Associate Professor Morello said the method works by distorting the shape of the electron cloud attached to the atom, using a very localized electric field.

"This distortion at the atomic level has the effect of modifying the frequency at which the electron responds.

"Therefore, we can selectively choose which qubit to operate. It's a bit like selecting which radio station we tune to, by turning a simple knob. Here, the 'knob' is the voltage applied to a small electrode placed above the atom."

Click on the graphic to see how the QC can be dialed in using atomic distortion to make it happen.
Very cool research without question. 

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