1. An analog computer for solving a computational problem, the analog computer comprising a quantum processor, the quantum processor comprising: a first set of qubits and a first set of coupling devices providing communicative coupling between qubits the first set of qubits, the first set of qubits and the first set of coupling devices representing a first instance of the computational problem programmed into the quantum processor; a first set of replica qubits and a first set of replica coupling devices providing communicative coupling between the first set of replica qubits, the first set of replica qubits and the first set of replica coupling devices representing a second instance of the computational problem programmed into the quantum processor, wherein for each qubit in the first set of qubits a corresponding replica qubit exists in the first set of replica qubits, and for each coupling device in the first set of coupling devices a replica coupling device exists in the first set of replica coupling devices; and a second set of coupling devices, wherein each coupling device in the second set of coupling devices provides communicative coupling between a qubit in the first set of qubits and the corresponding replica qubit in the first set of replica qubits, wherein at least some of the coupling devices of each of the first set of coupling devices, the first set of replica coupling devices, and the second set of coupling devices are operable to provide a respective diagonal coupling, and wherein the analog computer is selectively operable perform quantum annealing on the first and the second instances of the computational problem at the same time to reduce the effects of decoherence and noise.