Efficiency in Multimode Broadband Resonant Quantum Memory

Abstract

We discuss the beam-splitter model of quantum memory for demonstrating the connection between the memory efficiency and the multimode storage of the quantum statistical characteristics of light, such as the Mandel parameter and quadrature squeezing. We demonstrate in what sense the beam-splitter model can be applied to characterize the multimode quantum memory. This subject is considered in terms of the eigenfunctions of the integral transform connecting the initial signal with the restored one. We suggest a pulse of light for remembering its cutoff from a stationary sub-Poissonian laser emission. The mode structure of the laser radiation is interpreted in terms of eigenmodes of a full memory cycle. We find the degree of squeezing and sub-Poissonian statistics for each of the modes. Lastly, we consider a specific regime of the quantum memory operation, when only the first two modes are retained with high efficiency, and these modes can be considered as not overlapping along the time axes. This regime demonstrates the possibility to store the quantum properties of light, even at low efficiency. We discuss such behavior on the example of high-speed resonant quantum memory with a synchronized sub-Poissonian light pulse at the input.