用见证算符检测两个电子自旋量子比特的纠缠
Detecting entanglement of two electron spin qubits with witness operators
摘要：
提出了一种利用纠缠见证算符检测双量子点中两个电子自旋量子比特纠缠的方案。我们首先计算两个电子自旋的最佳配置，定义为能级谱中的位置，在那里，平均在核自旋分布，1）有两个分离的电子的概率，2）由并发量化的量子态的纠缠度都很大。使用密度矩阵的方法，我们然后计算的两个自旋单重态的见证算子的期望值的演变，考虑到退相干的影响，由于量子电荷波动建模为玻色子浴。我们发现，对于大的点间耦合，有可能获得高度纠缠且鲁棒的基态。
英文摘要：
We propose a scheme for detecting entanglement between two electron spin qubits in a double quantum dot using an entanglement witness operator. We first calculate the optimal configuration of the two electron spins, defined as the position in the energy level spectrum where, averaged over the nuclear spin distribution, 1) the probability to have two separated electrons, and 2) the degree of entanglement of the quantum state quantified by the concurrence are both large. Using a density matrix approach, we then calculate the evolution of the expectation value of the witness operator for the two-spin singlet state, taking into account the effect of decoherence due to quantum charge fluctuations modeled as a boson bath. We find that, for large interdot coupling, it is possible to obtain a highly entangled and robust ground state.
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