The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark.
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2015 Mar 20;114(11):110502. doi: 10.1103/PhysRevLett.114.110502. Epub 2015 Mar 17.
We propose and analyze heralded quantum gates between qubits in optical cavities. They employ an auxiliary qubit to report if a successful gate occurred. In this manner, the errors, which would have corrupted a deterministic gate, are converted into a nonunity probability of success: once successful, the gate has a much higher fidelity than a similar deterministic gate. Specifically, we describe that a heralded, near-deterministic controlled phase gate (CZ gate) with the conditional error arbitrarily close to zero and the success probability that approaches unity as the cooperativity of the system, C, becomes large. Furthermore, we describe an extension to near-deterministic N-qubit Toffoli gate with a favorable error scaling. These gates can be directly employed in quantum repeater networks to facilitate near-ideal entanglement swapping, thus greatly speeding up the entanglement distribution.
我们提出并分析了光学腔中量子比特之间的预言量子门。它们采用辅助量子比特来报告门是否成功。通过这种方式，原本会破坏确定性门的错误被转换为成功的概率不是 1：一旦成功，门的保真度就会比类似的确定性门高得多。具体来说，我们描述了一种预言的、近乎确定性的控制相位门（CZ 门），其条件误差可以任意接近零，而随着系统的协同性 C 增大，成功的概率也接近 1。此外，我们还描述了一种具有有利误差缩放的近乎确定性 N 量子比特 Toffoli 门的扩展。这些门可以直接用于量子中继网络中，以促进近乎理想的纠缠交换，从而大大加快纠缠的分发。
