Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026, People's Republic of China.
CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Phys Rev Lett. 2019 Feb 22;122(7):070402. doi: 10.1103/PhysRevLett.122.070402.
The set of all qubit states that can be steered to by measurements on a correlated qubit is predicted to form an ellipsoid-called the quantum steering ellipsoid-in the Bloch ball. This ellipsoid provides a simple visual characterization of the initial two-qubit state, and various aspects of entanglement are reflected in its geometric properties. We experimentally verify these properties via measurements on many different polarization-entangled photonic qubit states. Moreover, for pure three-qubit states, the volumes of the two quantum steering ellipsoids generated by measurements on the first qubit are predicted to satisfy a tight monogamy relation, which is strictly stronger than the well-known monogamy of entanglement for concurrence. We experimentally verify these predictions, using polarization and path entanglement. We also show experimentally that this monogamy relation can be violated by a mixed entangled state, which nevertheless satisfies a weaker monogamy relation.
可通过关联量子比特上的测量来导向的一组量子比特态，预计将在布洛赫球中形成一个椭球——称为量子导向椭球。这个椭球为初始双量子比特态提供了一个简单的可视化描述，并且纠缠的各个方面都反映在其几何性质中。我们通过对许多不同的极化纠缠光子量子比特态进行测量来实验验证这些性质。此外，对于纯三量子比特态，通过对第一个量子比特进行测量生成的两个量子导向椭球的体积预计将满足严格的单配性关系，这比众所周知的纠缠的关联的单配性关系要强。我们使用偏振和路径纠缠实验验证了这些预测。我们还实验证明，这种单配性关系可以被混合纠缠态违反，但它仍然满足较弱的单配性关系。
