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arXiv quant-ph/0004029quant-ph
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控制相干演化的量子码

Quantum Codes for Controlling Coherent Evolution

Yehuda Sharf, Timothy F. Havel, David G. Cory

摘要:

在核磁共振中,通过相干平均(通过RF脉冲序列实现)和量子码(可以防止非相干演化)获得了对自旋动力学的控制。在这里,我们讨论量子码的设计和实现,以防止相干进化。给出了一个详细的例子,用于保护两个数据量子比特在哈密顿量中的弱耦合(Ising)项下不演化的量子代码,使用一个不在实验时间尺度上演化的“隔离”辅助。该代码是实现在一个三自旋系统的液态NMR光谱13 C-标记的丙氨酸,并测试了两个初始状态。它还表明,相干进化和孤立的附属,代码存在,不需要的附属最初是在一个(伪)纯状态。最后,它表明,即使与非孤立的附属量子码存在,可以防止弱耦合下的进化。给出了一个六量子位代码的例子,该代码保护两个数据自旋到一阶。

英文摘要:

Control over spin dynamics has been obtained in NMR via coherent averaging, which is implemented through a sequence of RF pulses, and via quantum codes which can protect against incoherent evolution. Here, we discuss the design and implementation of quantum codes to protect against coherent evolution. A detailed example is given of a quantum code for protecting two data qubits from evolution under a weak coupling (Ising) term in the Hamiltonian, using an ``isolated'' ancilla which does not evolve on the experimental time scale. The code is realized in a three-spin system by liquid-state NMR spectroscopy on 13C-labelled alanine, and tested for two initial states. It is also shown that for coherent evolution and isolated ancillae, codes exist that do not require the ancillae to initially be in a (pseudo-)pure state. Finally, it is shown that even with non-isolated ancillae quantum codes exist which can protect against evolution under weak coupling. An example is presented for a six qubit code that protects two data spins to first order.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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