Clemmen Stéphane, Farsi Alessandro, Ramelow Sven, Gaeta Alexander L
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
Faculty of Physics, Humboldt-University Berlin, Berlin 12489, Germany.
Phys Rev Lett. 2016 Nov 25;117(22):223601. doi: 10.1103/PhysRevLett.117.223601. Epub 2016 Nov 23.
Interferometry using discrete energy levels of nuclear, atomic, or molecular systems is the foundation for a wide range of physical phenomena and enables powerful techniques such as nuclear magnetic resonance, electron spin resonance, Ramsey-based spectroscopy, and laser or maser technology. It also plays a unique role in quantum information processing as qubits may be implemented as energy superposition states of simple quantum systems. Here, we demonstrate quantum interference involving energy states of single quanta of light. In full analogy to the energy levels of atoms or nuclear spins, we implement a Ramsey interferometer with single photons. We experimentally generate energy superposition states of a single photon and manipulate them with unitary transformations to realize arbitrary projective measurements. Our approach opens the path for frequency-encoded photonic qubits in quantum information processing and quantum communication.
利用核、原子或分子系统的离散能级进行干涉测量是众多物理现象的基础，并催生了诸如核磁共振、电子自旋共振、基于拉姆齐的光谱学以及激光或微波激射技术等强大技术。它在量子信息处理中也发挥着独特作用，因为量子比特可被实现为简单量子系统的能量叠加态。在此，我们展示了涉及单个光量子能量态的量子干涉。与原子或核自旋的能级完全类似，我们用单光子实现了一个拉姆齐干涉仪。我们通过实验生成单个光子的能量叠加态，并通过酉变换对其进行操控，以实现任意的投影测量。我们的方法为量子信息处理和量子通信中频率编码的光子量子比特开辟了道路。
