具有實用價值的糾纏態光源的研制

張寬收 李小英

摘 要：為獲得具有實用價值的糾纏態光源，課題組首先進行了系列高質量全固態連續單頻1064 nm和532 nm激光器的研制。研制完成的全固態連續單頻1 064 nm激光器的性能指標如下：輸出功率達30 W，光光轉換效率達37%，7 h內的輸出功率波動優于±0.3%，光束質量（M2）優于1.1。同時對激光器1 064 nm/532 nm雙波長輸出的激光器的噪聲進行了研究，其強度和位相噪聲均在分析頻率4 MHz處達到散粒噪聲基準。而且非線性晶體還可以作為噪聲抑制裝置，對1 064 nm輸出激光的強度噪聲進行抑制，使其在低頻段的馳豫振蕩噪聲降低40 dB。進行了光通信波段1.55 μm和1.34 μm全固態連續單頻激光器的研制，獲得了680 MW的連續單橫模1.55 μm激光輸出以及400 mW的連續單頻1.55 μm激光輸出，1.5 h內輸出功率波動優于±1.5%，其強度噪聲和位相噪聲在分析頻率5 MHz處均達到散粒噪聲基準；獲得了輸出功率達9 W的連續單頻1.34 μm激光輸出，光光轉換效率達18%。激光器在4小時內的功率穩定性優于±1%，在1 min的頻率漂移為8.5 MHz，輸出激光的光束質量M2因子為1.03。進行了1.55 μm和1.34 μm光通信波段連續變量量子糾纏光源的研制，經過優化實驗系統，獲得了壓縮度為5 dB、波長為1.55 μm的壓縮態光場，壓縮度為6.1 dB、波長為1.3 μm的壓縮態光場；完成了1.08 μm連續變量量子糾纏光源樣機的研制，糾纏源系統的輸出波長為1 080 nm，振幅和位相差起伏方差大于5 dB。設計并研制了雙色可調諧連續變量糾纏態產生裝置，其中，糾纏光束中的一束波長位于堿金屬銣原子的吸收線波段；在實驗室建立起一套基于光纖通信器件的遠程連續變量量子密鑰分發系統平臺，實驗實現了30 km的四態分離調制連續變量量子密鑰分發，有效密鑰速率大于1 kB/s。利用光子晶體光纖，制備了接近單模的E波段單光子，實驗測得其宣布效率可達86%（修正探測效率后），強度關聯函數違背經典光源極限值80倍以上。

關鍵詞：量子信息 連續變量 糾纏源 壓縮態光場 光學參量振蕩器 Kerr非線性效應

Abstract：To build a practical entanglement light source， a series of high quality lasers have been developed. A cw singlefrequency laser at 1 064 μm has been achieved； the maximum output power is 30 W with an optical-to-optical efficiency of 37%. The power fluctuation is better than ±0.3% during 7 hours. The beam quality is less than 1.1. Both the intensity and the phase noise of laser reach the shot noise limit （SNL） at the analysis frequency of 4 MHz. Meanwhile the nonlinear crystal is also used to suppress the extra noise of laser， a 40 dB reduction in the intensity noise at the resonant relaxation oscillation frequency has been observed. Other all-solid-state CW single-frequency lasers at 1.55 μm and 1.34 μm telecom band have been developed and 400 MW CW single frequency laser output has been achieved with the power fluctuation better than ±1.5% during 1.5 hours. Both the intensity and the phase noise of laser reach the SNL at the analysis frequency of 5 MHz. For the 1.34 μm laser， power up to 9 W was realized with an optical-to-optical efficiency of 18%. The power fluctuation is better than ±1% during 4 hours. The frequency drift is 8.5 MHz in 1 minute. The beam quality factor was measured to be less than 1.03. The continuous variable （CV） quantum entangled sources have been investigated in the 1.55 μm and 1.34 μm telecom band. A 5 dB squeezed light at 1.55 μm and a 6.1 dB squeezed light at 1.3 μm have been obtained. The prototype of CV quantum entangled source at 1.08 μm has been manufactured. More than 5dB of amplitude quadrature sum noise spectrum and phase quadrature difference noise spectrum can be observed. The generating device of two-color tunable continuous-variable entanglement has been designed and manufactured. The wavelength of one entangled beam is located at the absorption lines of alkaline atom Rb. The platform of remote continuous variable quantum key distribution system has been established by the fiber-based communication devices. The four-state separation modulation continuous variable quantum key distribution over 30-km fiber has been realized. The effective key rate is greater than 1 kb/s. The single-photon close to the single mode E-band has been prepared by the photonic crystal fiber. The announced efficiency after the experimental measurement is 86%. The intensity correlation function violates the classical light limit of more than 80 times.

Key Words：Quantum Information；Continuous Variables；Entanglement source；Squeezed States of light；Optical Parametric Oscillator；Kerr Nonlinear Effect

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