Department of Applied Physics and Physics, Yale University, New Haven, CT 06511, USA.
Department of Applied Physics and Physics, Yale University, New Haven, CT 06511, USA. INRIA Paris-Rocquencourt, Domaine de Voluceau, B.P. 105, 78153 Le Chesnay Cedex, France.
Science. 2016 May 27;352(6289):1087-91. doi: 10.1126/science.aaf2941.
Quantum superpositions of distinct coherent states in a single-mode harmonic oscillator, known as "cat states," have been an elegant demonstration of Schrödinger's famous cat paradox. Here, we realize a two-mode cat state of electromagnetic fields in two microwave cavities bridged by a superconducting artificial atom, which can also be viewed as an entangled pair of single-cavity cat states. We present full quantum state tomography of this complex cat state over a Hilbert space exceeding 100 dimensions via quantum nondemolition measurements of the joint photon number parity. The ability to manipulate such multicavity quantum states paves the way for logical operations between redundantly encoded qubits for fault-tolerant quantum computation and communication.
在单模谐振子中，不同相干态的量子叠加被称为“猫态”，这是对薛定谔著名的“猫佯谬”的一种优雅演示。在这里，我们在由超导人工原子桥接的两个微波腔中实现了电磁场的双模猫态，也可以看作是一对纠缠的单腔猫态。我们通过联合光子数奇偶量子非破坏测量，对超过 100 维希尔伯特空间中的这种复杂猫态进行了完整的量子态层析成像。这种多腔量子态的操控能力为容错量子计算和通信中冗余编码量子比特之间的逻辑操作铺平了道路。
