Dynamical decoupling and homogenization of continuous variable systems
Dynamical decoupling and homogenization of continuous variable systems
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DOI：
10.1088/1751-8121/aa6017
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发表时间：
2016-05
期刊：
影响因子：
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通讯作者：
C. Arenz;D. Burgarth;R. Hillier
中科院分区：
文献类型：
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作者：
C. Arenz;D. Burgarth;R. Hillier
对于有限维量子系统，如量子位，一种行之有效的策略来保护这样的系统从退相干是动态解耦。然而，许多有前途的量子器件，如振荡器，是无限维的，是否可以应用动态解耦的问题仍然是开放的。本文首先表明，并不是每个无限维系统都可以通过动态解耦来防止退相干。然后研究了用二次哈密顿量描述的连续变量系统的动态解耦问题。我们确定了一个条件和一组操作，使我们能够将一组相互作用的谐振子映射到一组以平均频率旋转的非相互作用的振子上，这个过程我们称之为均匀化。此外，我们还证明了每个二次系统-环境交互作用都可以通过两个简单的操作来抑制。使用随机动态解耦或均匀化方案，我们开发了表征为了实现所需的解耦动力学而必须工作的速度的界限。这使我们能够确定在连续变量系统中均匀化和退相干可以被抑制的程度。
For finite-dimensional quantum systems, such as qubits, a well established strategy to protect such systems from decoherence is dynamical decoupling. However many promising quantum devices, such as oscillators, are infinite dimensional, for which the question if dynamical decoupling could be applied remained open. Here we first show that not every infinite-dimensional system can be protected from decoherence through dynamical decoupling. Then we develop dynamical decoupling for continuous variable systems which are described by quadratic Hamiltonians. We identify a condition and a set of operations that allow us to map a set of interacting harmonic oscillators onto a set of non-interacting oscillators rotating with an averaged frequency, a procedure we call homogenization. Furthermore we show that every quadratic system-environment interaction can be suppressed with two simple operations acting only on the system. Using a random dynamical decoupling or homogenization scheme, we develop bounds that characterize how fast we have to work in order to achieve the desired uncoupled dynamics. This allows us to identify how well homogenization can be achieved and decoherence can be suppressed in continuous variable systems.