One electron at a time: Scientists close in on quantum computing

Posted by Wolfgang Gruener

Ann Arbor (MI) – Researchers at the University of Michigan, U.S. Naval Research Laboratory and the University of California at San Diego have made a big step towards quantum computing by trapping the spin of one electron in critical dark state – at rates of about 1 GHz.  

Quantum computing remains one of those science-fiction topics that remain a mystery to most of us. There is this feeling that quantum computing will replace computer technologies as we know it today with monstrous computing power for applications we cannot imagine yet. But if you look to computer science and physics labs across the globe, you will discover a growing effort to solve the mysteries behind quantum computing, with new ideas trying to piece together a huge quantum computing puzzle surfacing almost on a weekly basis.

Researchers at University of Michigan, U.S. Naval Research Laboratory and the University of California at San Diego believe they have created on key puzzle piece by demonstrating the quantum state of a solid-state qubit at rates of about 1 GHz.  

Physics professor Duncan Steel, doctoral student Xiaodong Xu and their colleagues used lasers to stably trap the spin of one electron confined in a single semiconductor quantum dot, which compares to functionality of a transistor in a traditional computer chip. The spin was trapped in a so-called “dark state”, a state in which scientists can arbitrarily and reliably adjust the amount of 0 and 1 the qubit represents, since no light is absorbed. Any reaction to light could potentially destroy the coherence and impact information stored in the qubit.

A conventional bit can be a 0 or a 1. A quantum bit, or qubit, can be both at the same time. Until now, scientists couldn't stabilize that duality. The scientists believe they can use lasers to achieve “fundamental steps” toward programming the qubit. Researchers generally believe that it is the duality of the qubit that may enable much faster and much more secure computers sometime in the future.  Steel said that quantum computers will enable the development of code that would be “impossible to crack” with conventional computers.
 
The scientist noted that spin is an intrinsic property of the electron that isn't a real rotation. He compares it to the magnetic poles, explaining that electrons are said “to have spin up or down”. While traditional bits have 0 or 1 values, the up and down spin directions are the equivalent of 0s and 1s in conventional computing.