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arXiv 1005.3976cond-mat.mes-hall
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Mach-Zehnder干涉仪探测宇称和纠缠

Parity detection and entanglement with a Mach-Zehnder interferometer

Géraldine Haack, Heidi Förster, Markus Büttiker

摘要:

奇偶校验计将两个量子比特的状态投影到具有不同奇偶性的两个子空间上,每个奇偶性类中的状态是不可区分的。它的纠缠特性使其在量子信息中具有重要的应用。在我们的工作中,我们考虑电子马赫-曾德尔干涉仪(MZI)耦合电容到两个双量子点(DQD),一个在MZI的每个臂。这些电荷量子位线性耦合到MZI臂中的电荷。MZI的一个关键优势是量子位在距离上很好地分离,从而避免了它们之间的相互作用。假设两个DQD和臂之间的耦合相等,并且每个DQD的偏置相同,这种设置通常检测三个不同的电流,一个用于奇数状态,两个用于每个偶数状态。通过控制MZI的磁通量,我们可以将MZI作为奇偶校验表来操作:在输出端仅测量两个电流,每个电流对应一个奇偶校验类。在这种配置中,MZI充当理想的探测器,其海森堡效率最大。对于一类初始态,初始未纠缠的DQD通过宇称测量过程以概率1纠缠。

英文摘要:

A parity meter projects the state of two qubits onto two subspaces with different parities, the states in each parity class being indistinguishable. It has application in quantum information for its entanglement properties. In our work we consider the electronic Mach-Zehnder interferometer (MZI) coupled capacitively to two double quantum dots (DQDs), one on each arm of the MZI. These charge qubits couple linearly to the charge in the arms of the MZI. A key advantage of an MZI is that the qubits are well separated in distance so that mutual interaction between them is avoided. Assuming equal coupling between both DQDs and the arms and the same bias for each DQD, this setup usually detects three different currents, one for the odd states and two for each even state. Controlling the magnetic flux of the MZI, we can operate the MZI as a parity meter: only two currents are measured at the output, one for each parity class. In this configuration, the MZI acts as an ideal detector, its Heisenberg efficiency being maximal. For a class of initial states, the initially unentangled DQDs become entangled through the parity measurement process with probability one.

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