Nondestructive measurement of the energy of optical quanta

V. B. Braginsky, S. P. Viatchanin

Vladimir B. Braginskii, S. P. Vyatchanin

Andreas Reiserer

We propose and analyze an experimental scheme of quantum nondemolition detection of monophotonic and vacuum states in a superconductive toroidal cavity by means of Rydberg atoms. One of the key directions of modern physics is the following challenging problem of understanding the essence of the process of quantum measurement. Of special interest in this respect are experiments with individual quantum objects. Such applications as quantum computing, quantum cryptography and quantum teleportation, which have recently been attracting increasing attention [1], have their roots in this field. Quantum measurements and particularly experiments on the interaction of individual atoms and ions with the quantum field in a cavity are usually associated with the optical domain. With the development of the Rydberg atom technique, however, impressive results have been obtained in the microwave region [2]. This technique allows preparation and nondestructive (quantum non-demolition) repetitive measurements of Fock states with a small number of quanta in a high-Q superconductive cavity [3, 4]. In 1994 V.B.Braginsky and F.Ya.Khalili [5] proposed an elegant scheme employing Rydberg atoms which allowed nondestructive detection of vacuum and monophotonic states. The idea of the experiment is to use a cavity with a geometry such that the flying atom can interact twice with the field.

Axel Schenzle

Colin P. Lualdi, Spencer J. Johnson, Michael Vayninger +4 more

In classical optical interferometry, loss and background complicate achieving fast nanometer-resolution measurements with illumination at low light levels. Conversely, quantum two-photon interference is unaffected by loss and background, but nanometer-scale resolution is physically difficult to realize. As a solution, we enhance two-photon interference with highly nondegenerate energy entanglement featuring photon frequencies separated by 177 THz. We observe measurement resolution at the nanometer (attosecond) scale with only O (10 4 ) photon pairs, despite the presence of background and loss. Our nondestructive thickness measurement of a metallic thin film agrees with atomic force microscopy, which often achieves better resolution via destructive means. With contactless, nondestructive measurements in seconds or faster, our instrument enables metrological studies in optically challenging contexts where background, loss, or photosensitivity are factors.