D-Wave Systems Inc., 100-4401 Still Creek Drive, Burnaby, British Columbia, Canada V5C 6G9.
Nat Commun. 2013;4:1903. doi: 10.1038/ncomms2920.
Efforts to develop useful quantum computers have been blocked primarily by environmental noise. Quantum annealing is a scheme of quantum computation that is predicted to be more robust against noise, because despite the thermal environment mixing the system's state in the energy basis, the system partially retains coherence in the computational basis, and hence is able to establish well-defined eigenstates. Here we examine the environment's effect on quantum annealing using 16 qubits of a superconducting quantum processor. For a problem instance with an isolated small-gap anticrossing between the lowest two energy levels, we experimentally demonstrate that, even with annealing times eight orders of magnitude longer than the predicted single-qubit decoherence time, the probabilities of performing a successful computation are similar to those expected for a fully coherent system. Moreover, for the problem studied, we show that quantum annealing can take advantage of a thermal environment to achieve a speedup factor of up to 1,000 over a closed system.
开发有用的量子计算机的努力主要受到环境噪声的阻碍。量子退火是一种量子计算方案，预计对噪声具有更强的鲁棒性，因为尽管热环境以能量基混合系统的状态，但系统在计算基中部分保持相干性，因此能够建立明确定义的本征态。在这里，我们使用超导量子处理器的 16 个量子位来研究环境对量子退火的影响。对于具有最低两个能级之间隔离小能隙反交叉的问题实例，我们通过实验证明，即使退火时间比预测的单量子比特退相干时间长 8 个数量级，成功计算的概率也与完全相干系统预期的概率相似。此外，对于所研究的问题，我们表明量子退火可以利用热环境实现比封闭系统快 1000 倍的加速因子。
