Takita Maika, Cross Andrew W, Córcoles A D, Chow Jerry M, Gambetta Jay M
IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA.
Phys Rev Lett. 2017 Nov 3;119(18):180501. doi: 10.1103/PhysRevLett.119.180501. Epub 2017 Oct 31.
Robust quantum computation requires encoding delicate quantum information into degrees of freedom that are hard for the environment to change. Quantum encodings have been demonstrated in many physical systems by observing and correcting storage errors, but applications require not just storing information; we must accurately compute even with faulty operations. The theory of fault-tolerant quantum computing illuminates a way forward by providing a foundation and collection of techniques for limiting the spread of errors. Here we implement one of the smallest quantum codes in a five-qubit superconducting transmon device and demonstrate fault-tolerant state preparation. We characterize the resulting code words through quantum process tomography and study the free evolution of the logical observables. Our results are consistent with fault-tolerant state preparation in a protected qubit subspace.
强大的量子计算需要将微妙的量子信息编码到环境难以改变的自由度中。通过观察和纠正存储错误，量子编码已在许多物理系统中得到证明，但应用不仅需要存储信息；即使操作有故障，我们也必须准确地进行计算。容错量子计算理论通过提供限制错误传播的基础和技术集合，照亮了前进的道路。在这里，我们在一个五比特超导传输子器件中实现了最小的量子码之一，并演示了容错态制备。我们通过量子过程层析成像来表征所得的码字，并研究逻辑可观测量的自由演化。我们的结果与受保护的量子比特子空间中的容错态制备一致。
