Perfect photons feed new quantum processor

Perfect photons feed new quantum processor

A quantum processor working with photons developed at the University of Twente becomes an ever stronger ‘toolbox’ for doing experiments. The latest version not only has more inputs and outputs, it can also be fed by a photon source that is able to produce identical photons. 

If you want to perform quantum calculations using light, it all starts with the source. The photons you would like to use have to be as identical as possible. If they aren’t identical, then examining typical quantum properties like entanglement and superposition will not be possible.

The researcher has presented a three photon source based on titanylphosphate (KTP) that can, in its current version, be upgraded to 11 photons that are very identical. The next step has been a system with 12 inputs and 12 outputs. In between, there is a system of light-conducting channels, made of silicon nitride that is known for its extremely low losses. The first processor of this type had 8 inputs and 8 outputs, and in fact it was by coincidence that the photonic circuit could be used for quantum experiments.

Thanks to the better photon source and larger processor, the researcher was able to conduct a few experiments. One of them is about retention of information. Quantum mechanics is a theory that stays the same in terms of information: through time, two systems will not look more similar. Thermodynamics, however, is a theory losing information: two systems will, in time, look more and more similar. Quantum mechanics and thermodynamics can’t be true at the same time, you would say. Still, a system that shows quantummechanic behavior as a whole, can have thermodynamic subsystems. So, there must be a way for information to escape within the larger system. (

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