Realization Of Low Threshold Operation Of NOPA With Wedged KTP Crystal

Quantum information as a cross subject of quantum mechanics, computer science and information science is applied for implementing the information transmission and realizing quantum computing by reason of the characteristics of absolute security and fast speed of calculation. Continuous variable entangled state can accomplish non-localized quantum communicating and quantum computing in the research of quantum information. Multipartite entanglement for continuous variables has became the focus of the research field with the development of quantum networks. Multipartite entangled states with more sub-modes are required to complete more complex research of quantum information. In the experiment of multipartite entangled states, a laser need simultaneously pump multiple optical cavity to ensure good coherence between output beams. But, low output power of laser directly limits the generation of multipartite entangled states. Under the condition of without changing the laser output noise characteristics, it is difficult to improve the output power of laser, so we expect to reduce single optical cavity pump power by reducing threshold. Thus we can pump much more NOPAs with only a laser source and obtain the multi-partite entangled states as needed.This article main research content:1. We theoretically calculate the change of quantum correlation noise of output optical fields of non-degenerate optical parametric amplifier (NOPA) with input-output transmissivity, intra-cavity loss, pump power factor.2. We theoretically analyse the three resonance conditions of NOPA. In our experiment, the threshold of the NOPA is reduced from 250mW to 45mW on account of using the wedged three resonance KTP crystal. When the pumping power of is 23mW, the correlation noise of quadrature amplitude and quadrature phase of the EPR entangled optical fields is 5.5dB below the corresponding quantum noise limit.