Whats most scalable qubit candidate so far ?
In principle solid state qubits. There are several types that could -in theory- be scaled up to whatever size you want and it would be easy to fabricate a circuit containing hundreds of "potential" qubits. But the circuit would not work.
The problem is of course that decoherence kicks in and makers it difficult to entangle many qubits, the current record for a conventional solid-state qubit is 4.
The current record when it comes to number of entangled qubits of any type is 8, which has been done with a normal ion-trap (of a type that can't really be scaled up much further) and -if I remember correctly- an NMR setup (which again can't be scaled up much further).
Thanks for reply, f95toli. :)
Can you please expand on the upper cap that is restricting Ion Trap... to 8.
Mainly the complexity fo the setup, you need an awful lot of equipment for each qubit (lasers to trap the ions etc) and making ions traps for more than a few ions is very difficult. Even a normal single ion trap is a pretty serious piece of experimental equipment.
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