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When I read about computing using gate based methods, I mainly read about the difficulties with error rates, circuit depth (and connectivity) and not enough qubits.

With computing using quantum annealing, discussion mainly seems to focus on number of qubits and connectivity. It seems error correction is less of an issue here.

Question: Is there an inherent difference in need for error correction between quantum annealing systems (D-Wave etc) and quantum gate based systems?

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The errors from quantum annealing apart from having crappy qubits will come from the imperfect instantiation of the qubit coupling. The first problem i.e having bad qubits can ultimately be mitigated by a kind of error correction look at Error-corrected quantum annealing with hundreds of qubits (Pudenz et al., 2014).

But as it turns out the second problem related to imperfect instantiation of qubit coupling does not need to be perfect, in fact, some disorder can actually help cf. Disorder-assisted graph coloring on quantum annealers (Więckowski et al., 2019).

The ultimate reason for the gap in the models in relation to error correction stems from the fact that the gate model is a well defined computational model that is universal while on the other hand quantum annealing is more of a heuristic. Having a model of error correction really makes sense in a precise model of computation. Quantum Annealing is a method that is really a "physics" idea for arriving at some state (in this case the ground state). Implementing it requires studying the device that implements it and correcting for the "errors" will require knowing your device well. One can't rely on some general notion of errors.

In a sense, all of quantum computing requires knowing your device well, but what helps you in the gate model is that you have a theoretical model of computation while in quantum annealing you are really dealing with some heuristic.

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