Several solutions for scaling up the quantum computing architecture are under way . Long ion chains in linear Paul traps as shown in \ref{570611} with up to 40 ions are the current 'work-horse'. This is the 'simplest' existing architecture. In such a geometry Shors algorithm was shown for the number 15 \cite{Monz_2016} with five qubits and entanglement between up to 14 qubits was studied \cite{Monz_2011}. However, it reaches its natural limits for entangling distant ions due to cross-talk with other ions during the operation. Therefore, different approaches are currently tested to scale the architecture to larger fault-tolerant geometries \cite{Bermudez_2017}.
By no means we will be able to give a full picture of the booming field. However, a few main players are:
- NIST, JQI and IonQ, which are all strongly connected through their shared past with Dave Wineland.
- Innsbruck, Mainz and AQT which are connected through their shared past and present with Rainer Blatt.
- ETH, Oxford, ...
- The AQTION and the MicroQC network, which are part of the European flagship initiative.