具有實(shí)用價(jià)值的糾纏態(tài)光源的研制

張寬收 李小英

摘 要：為獲得具有實(shí)用價(jià)值的糾纏態(tài)光源，課題組首先進(jìn)行了系列高質(zhì)量全固態(tài)連續(xù)單頻1064 nm和532 nm激光器的研制。研制完成的全固態(tài)連續(xù)單頻1 064 nm激光器的性能指標(biāo)如下：輸出功率達(dá)30 W，光光轉(zhuǎn)換效率達(dá)37%，7 h內(nèi)的輸出功率波動(dòng)優(yōu)于±0.3%，光束質(zhì)量（M2）優(yōu)于1.1。同時(shí)對(duì)激光器1 064 nm/532 nm雙波長(zhǎng)輸出的激光器的噪聲進(jìn)行了研究，其強(qiáng)度和位相噪聲均在分析頻率4 MHz處達(dá)到散粒噪聲基準(zhǔn)。而且非線性晶體還可以作為噪聲抑制裝置，對(duì)1 064 nm輸出激光的強(qiáng)度噪聲進(jìn)行抑制，使其在低頻段的馳豫振蕩噪聲降低40 dB。進(jìn)行了光通信波段1.55 μm和1.34 μm全固態(tài)連續(xù)單頻激光器的研制，獲得了680 MW的連續(xù)單橫模1.55 μm激光輸出以及400 mW的連續(xù)單頻1.55 μm激光輸出，1.5 h內(nèi)輸出功率波動(dòng)優(yōu)于±1.5%，其強(qiáng)度噪聲和位相噪聲在分析頻率5 MHz處均達(dá)到散粒噪聲基準(zhǔn)；獲得了輸出功率達(dá)9 W的連續(xù)單頻1.34 μm激光輸出，光光轉(zhuǎn)換效率達(dá)18%。激光器在4小時(shí)內(nèi)的功率穩(wěn)定性優(yōu)于±1%，在1 min的頻率漂移為8.5 MHz，輸出激光的光束質(zhì)量M2因子為1.03。進(jìn)行了1.55 μm和1.34 μm光通信波段連續(xù)變量量子糾纏光源的研制，經(jīng)過(guò)優(yōu)化實(shí)驗(yàn)系統(tǒng)，獲得了壓縮度為5 dB、波長(zhǎng)為1.55 μm的壓縮態(tài)光場(chǎng)，壓縮度為6.1 dB、波長(zhǎng)為1.3 μm的壓縮態(tài)光場(chǎng)；完成了1.08 μm連續(xù)變量量子糾纏光源樣機(jī)的研制，糾纏源系統(tǒng)的輸出波長(zhǎng)為1 080 nm，振幅和位相差起伏方差大于5 dB。設(shè)計(jì)并研制了雙色可調(diào)諧連續(xù)變量糾纏態(tài)產(chǎn)生裝置，其中，糾纏光束中的一束波長(zhǎng)位于堿金屬銣原子的吸收線波段；在實(shí)驗(yàn)室建立起一套基于光纖通信器件的遠(yuǎn)程連續(xù)變量量子密鑰分發(fā)系統(tǒng)平臺(tái)，實(shí)驗(yàn)實(shí)現(xiàn)了30 km的四態(tài)分離調(diào)制連續(xù)變量量子密鑰分發(fā)，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(shí)驗(yàn)測(cè)得其宣布效率可達(dá)86%（修正探測(cè)效率后），強(qiáng)度關(guān)聯(lián)函數(shù)違背經(jīng)典光源極限值80倍以上。

關(guān)鍵詞：量子信息 連續(xù)變量 糾纏源 壓縮態(tài)光場(chǎng) 光學(xué)參量振蕩器 Kerr非線性效應(yīng)

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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