Directly comparing entanglement-enhancing non-Gaussian operations
Directly comparing entanglement-enhancing non-Gaussian operations
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DOI：
10.1088/1367-2630/17/2/023038
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发表时间：
2015-02
影响因子：
3.3
通讯作者：
T. Bartley;I. Walmsley
中科院分区：
文献类型：
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作者：
T. Bartley;I. Walmsley
单光子级非高斯运算（光子相加、光子相减及其相干叠加）是增强连续可变光学状态中纠缠的强大工具。尽管此类操作通常不是确定性的，但可能还有其他优点，例如无噪声操作。因此，为了充分考虑实际场景中特定非高斯操作的有效性，我们开发了品质因数，该品质因数权衡了此类协议的优势与其成功概率。具体来说，我们将“纠缠增强率”定义为在双模压缩真空（TMSV）状态下每次尝试通用非高斯操作时纠缠的增加。我们考虑由光子减法、光子加法以及减法和加法的相干叠加产生的态。我们比较了应用于 TMSV 状态的一种或两种模式时以及在操作之前存在通道损耗的情况下的每种策略。在许多情况下，附加属性是可分析计算的，包括操作产生的过量噪声以及结果状态对特定高斯和非高斯状态的保真度。最后，通过合并损失，我们得出每个非高斯操作的最佳交互参数，从而最大限度地提高所研究的特定协议的有效性。
Single-photon-level non-Gaussian operations—photon addition, photon subtraction, and their coherent superposition—are powerful tools with which to increase entanglement in continuous-variable optical states. Although such operations are typically not deterministic, there may be other advantages such as noiseless manipulation. Therefore, to fully account for the efficacy of a particular non-Gaussian operation in a practical scenario, we develop figures of merit which trade off the advantages of such protocols against their success probability. Specifically, we define ‘entanglement enhancement rate’ as the increase in entanglement per trial of a generic non-Gaussian operation on a two-mode squeezed vacuum (TMSV) state. We consider states generated by photon-subtraction, photon-addition and a coherent superposition of subtraction and addition. We compare each strategy when applied to one or both modes of a TMSV state, and also in the presence of channel losses prior to the operation. In many cases, additional properties are analytically calculable, including excess noise arising from the operation and the fidelity of the resulting states to particular Gaussian and non-Gaussian states. Finally, by incorporating loss, we derive optimal interaction parameters for each non-Gaussian operation which maximize the effectiveness of the particular protocol under investigation.