Chiaverini J, Leibfried D, Schaetz T, Barrett M D, Blakestad R B, Britton J, Itano W M, Jost J D, Knill E, Langer C, Ozeri R, Wineland D J
Time and Frequency Division, Mathematical and Computational Sciences Division, NIST, Boulder, Colorado 80305, USA.
Nature. 2004 Dec 2;432(7017):602-5. doi: 10.1038/nature03074.
Scalable quantum computation and communication require error control to protect quantum information against unavoidable noise. Quantum error correction protects information stored in two-level quantum systems (qubits) by rectifying errors with operations conditioned on the measurement outcomes. Error-correction protocols have been implemented in nuclear magnetic resonance experiments, but the inherent limitations of this technique prevent its application to quantum information processing. Here we experimentally demonstrate quantum error correction using three beryllium atomic-ion qubits confined to a linear, multi-zone trap. An encoded one-qubit state is protected against spin-flip errors by means of a three-qubit quantum error-correcting code. A primary ion qubit is prepared in an initial state, which is then encoded into an entangled state of three physical qubits (the primary and two ancilla qubits). Errors are induced simultaneously in all qubits at various rates. The encoded state is decoded back to the primary ion one-qubit state, making error information available on the ancilla ions, which are separated from the primary ion and measured. Finally, the primary qubit state is corrected on the basis of the ancillae measurement outcome. We verify error correction by comparing the corrected final state to the uncorrected state and to the initial state. In principle, the approach enables a quantum state to be maintained by means of repeated error correction, an important step towards scalable fault-tolerant quantum computation using trapped ions.
可扩展的量子计算和通信需要误差控制来保护量子信息免受不可避免的噪声影响。量子纠错通过根据测量结果进行操作来纠正误差，从而保护存储在两能级量子系统（量子比特）中的信息。纠错协议已在核磁共振实验中得到实现，但该技术的固有局限性阻碍了其在量子信息处理中的应用。在此，我们通过实验展示了使用限制在线性多区阱中的三个铍原子离子量子比特进行量子纠错。借助三量子比特量子纠错码，一个编码的单量子比特状态可免受自旋翻转误差的影响。一个主离子量子比特被制备到初始状态，然后被编码为三个物理量子比特（主量子比特和两个辅助量子比特）的纠缠态。以各种速率在所有量子比特中同时引入误差。编码状态被解码回主离子单量子比特状态，使得辅助离子上的误差信息可用，辅助离子与主离子分离并进行测量。最后，根据辅助测量结果对主量子比特状态进行校正。我们通过将校正后的最终状态与未校正状态以及初始状态进行比较来验证纠错。原则上，该方法能够通过重复纠错来维持量子态，这是朝着使用俘获离子进行可扩展容错量子计算迈出的重要一步。
