Colorado School of Mines
Is Fault Welcoming Quantum Computing Realistic?
A fault tolerant quantum computer, where arbitrary quantum algorithms can be executed with noisy qubits and gates given polynomial overhead for error correction, is one of the most important long term goals of quantum computing research. In these systems random noise is an obstacle that must be overcome through error correction. In this talk we explore a new possibility, "fault welcoming" quantum computing, where a system can not only maintain a quantum speedup for a given (likely non-universal) class of quantum algorithms against realistic noise, but actually performs better than an idealized copy with all noise sources absent. We consider a modiﬁcation of ﬂux qubit-based quantum annealing which includes random, but coherent, low-frequency oscillations in the directions of the transverse ﬁeld terms as the system evolves. Through extensive analytical and numerical calculations, we show that fault welcoming behavior is plausible given the realistic noise model for these qubits. We show that this system produces a quantum speedup for ﬁnding ground states in the Grover problem and quantum random energy model, and thus should be widely applicable to other hard optimization problems which can be formulated as quantum spin glasses. Further, we show that this speedup should be resilient to two realistic noise channels (1/f-like local potential ﬂuctuations and local heating from interaction with a ﬁnite temperature bath), and that another noise channel, bath-assisted quantum phase transitions, actually accelerates the algorithm and may outweigh the negative eﬀects of the others, thus potentially making the system fault welcoming. The modiﬁcations we consider have a straightforward experimental implementation and could be explored with current technology.