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arXiv quant-ph/0408128quant-ph
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容错量子动力学解耦

Fault-Tolerant Quantum Dynamical Decoupling

K. Khodjasteh, D. A. Lidar

备注：
5 pages, 4 color eps figures. v3: Minor changes. To appear in Phys. Rev. Lett
发表信息：
Phys. Rev. Lett. 95, 180501 (2005)
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摘要：

自从发现自旋回波效应以来，动态退耦脉冲序列一直被用来延长量子系统的相干时间。在这里，我们介绍了递归级联动态去耦脉冲，旨在克服退相干和操作误差的方法。这对于量子计算机等量子系统的相干控制很重要。对于有界强度，非马尔可夫环境，如自旋浴中出现的电子和核自旋为基础的固态量子计算机的建议，我们表明，它是严格有利的，使用级联，而不是标准的周期性动态去耦脉冲序列。也就是说，级联方案是容错和超多项式更有效的，在相同的成本。我们推导出一个条件下的脉冲噪声水平低于级联保证减少退相干。

英文摘要：

Dynamical decoupling pulse sequences have been used to extend coherence times in quantum systems ever since the discovery of the spin-echo effect. Here we introduce a method of recursively concatenated dynamical decoupling pulses, designed to overcome both decoherence and operational errors. This is important for coherent control of quantum systems such as quantum computers. For bounded-strength, non-Markovian environments, such as for the spin-bath that arises in electron- and nuclear-spin based solid-state quantum computer proposals, we show that it is strictly advantageous to use concatenated, as opposed to standard periodic dynamical decoupling pulse sequences. Namely, the concatenated scheme is both fault-tolerant and super-polynomially more efficient, at equal cost. We derive a condition on the pulse noise level below which concatenated is guaranteed to reduce decoherence.

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