Department of Physics, University of California, Santa Barbara, California 93106, USA.
Phys Rev Lett. 2011 Feb 11;106(6):060401. doi: 10.1103/PhysRevLett.106.060401. Epub 2011 Feb 7.
Quantum entanglement, one of the defining features of quantum mechanics, has been demonstrated in a variety of nonlinear spinlike systems. Quantum entanglement in linear systems has proven significantly more challenging, as the intrinsic energy level degeneracy associated with linearity makes quantum control more difficult. Here we demonstrate the quantum entanglement of photon states in two independent linear microwave resonators, creating N-photon NOON states (entangled states |N0> + |0N>) as a benchmark demonstration. We use a superconducting quantum circuit that includes Josephson qubits to control and measure the two resonators, and we completely characterize the entangled states with bipartite Wigner tomography. These results demonstrate a significant advance in the quantum control of linear resonators in superconducting circuits.
量子纠缠是量子力学的一个基本特征，已在各种非线性自旋系统中得到证实。线性系统中的量子纠缠证明更具挑战性，因为线性相关的固有能级简并使得量子控制更加困难。在这里，我们演示了两个独立的线性微波谐振器中光子态的量子纠缠，创建了 N 光子 NOON 态（纠缠态 |N0> + |0N>）作为基准演示。我们使用包含约瑟夫森量子比特的超导量子电路来控制和测量两个谐振器，并使用双部分威格纳断层摄影术对纠缠态进行完全表征。这些结果表明在超导电路中对线性谐振器的量子控制取得了重大进展。
