All-Semiconductor Quantum CNOT Gate Made

Category: Science & Technology
Posted: May 21, 2012 09:58AM
Author: Guest_Jim_*

The original computers were massive systems that drew unbelievable amounts of power and are easily outperformed by current smartphones, a technology many generations newer. Like the evolution of electronic computers, quantum computers are trying to shrink for large, lab-only systems to smaller devices. Researchers at the University of Cambridge and Toshiba Research Europe Ltd. have successfully created a quantum logic gate, specifically a controlled-NOT (CNOT) gate, from just semiconductors.

As described by the American Institute of Physics in their Applied Physics Letters journal, this discovery brings the possibility of functional and accessible quantum computers closer to reality. The key was developing a way to precisely emit photons with specific characteristics. This was accomplished by placing a quantum dot on the top of a pillar of silicon. For the CNOT function to work, two photons, or qubits in this case, have to be emitted: one target qubit and one control qubit. The control qubit triggers the gate to act on the target qubit, which is what may undergo the quantum operation.

The researchers' next step is to combine the CNOT gate and the quantum dot into a single device, which will be considerably smaller than the current design. Also a second quantum dot may be added, as the CNOT gat requires two photons to operate. Instead of having one dot produce both photons, two could be used to create synchronized pairs of photons.

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