Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5 Canada.
Phys Rev Lett. 2013 Jul 19;111(3):030402. doi: 10.1103/PhysRevLett.111.030402. Epub 2013 Jul 15.
The controlled generation of entangled states and their subsequent detection are integral aspects of quantum information science. In this Letter, we implement a simple and precise technique that produces any of the four Bell states in the orbital angular momentum degree of freedom. We then use these states to perform the first experimental demonstration of an accessible nonlinear entanglement witness. Such a witness determines entanglement by using the same measurements as required for a linear witness but can detect, in this case, twice as many states as a single linear witness can. We anticipate that our method of state preparation and nonlinear witnesses will have further uses in areas of quantum science, such as superdense coding and quantum key distribution.
纠缠态的受控产生及其后续检测是量子信息科学的基本方面。在这封信中，我们实现了一种简单而精确的技术，可在轨道角动量自由度中产生四个贝尔态中的任意一个。然后，我们使用这些状态来首次实验演示可访问的非线性纠缠见证。这种见证通过使用与线性见证相同的测量来确定纠缠，但在这种情况下，可以检测到两倍于单个线性见证可以检测到的状态。我们预计，我们的状态制备和非线性见证方法将在量子科学领域有进一步的应用，例如超密集编码和量子密钥分发。
