Beat-note interferometer for direct phase measurement of photonic information

[[abstract]]We describe a simple method of the beat-note interferometer that directly and dynamically measures the phase shift of light pulses induced by highly dispersive samples. Using the method, we show intuitively that the storage and retrieval of light pulses in a medium due to the effect of electromagnetically induced transparency is a coherent process and, quantitatively, that there is no observable phase shift caused by the process. This method is sensitive enough that it can be used to measure the phase of a light pulse with energy on the order of a dozen photons.[[fileno]]2010136010037[[department]]物理

Holographic Mutual Information of Two Disjoint Spheres

We study quantum corrections to holographic mutual information for two disjoint spheres at a large separation by using the operator product expansion of the twist field. In the large separation limit, the holographic mutual information is vanishing at the semiclassical order, but receive quantum corrections from the fluctuations. We show that the leading contributions from the quantum fluctuations take universal forms as suggested from the boundary CFT. We find the universal behavior for the scalar, the vector, the tensor and the fermionic fields by treating these fields as free fields propagating in the fixed background and by using the 1/n prescription. In particular, for the fields with gauge symmetries, including the massless vector boson and massless graviton, we find that the gauge parts in the propagators play indispensable role in reading the leading order corrections to the bulk mutual information.Comment: 37 pages, 1 figure; significant revisions, corrected the discussions on the computations of the mutual information in CFT, conclusions unchange