抑制熱引發相位編碼失真的O波段分佈回饋式雷射量子密鑰分發

Abstract

首次展示了在O波段（1308.4 nm）的主-從屬雷射的注入鎖定(OIL)系統對使用差分相移(DPS)協定的量子密鑰分發(QKD)傳輸，通過準確控制分佈回饋式雷射(DFBLD)的溫度和電流實現了穩定性。具體來說，長時間的量子密鑰生成中由於自由載流子的過度生成而引起的聲子誘導相位波動是歸因於腔內加熱。通過降低主雷射的偏置電流水平，可以抑制這些波動。接下來，該研究主要探討了主雷射的相位和功率對從屬雷射相位的影響。相位調製器(PM)和強度調製器(IM)被用來精確控制相位和強度，分別。主雷射和從屬雷射的閾值電流分別為5 mA和6 mA，微分阻抗為5歐姆。在絕熱良好的系統中，將增益值設置為100，實現了±0.05%的功率和±0.2 pm的波長擾動。熱電致冷晶片的增益設定為100有效地保持了干涉儀的可見度>96%，dPo/Po, max和dPo/dt測量值在±1%和±1×10-3 mW/s以下。對於主雷射，功率變化150 μW(相當於電流變化0.12 mA)的階梯狀訊號可以產生相位變化。將直流偏置電流從7 Ith (35 mA)降低到2 Ith (10 mA)，可以更穩定地控制從屬雷射的相位。該系統在6 km通信距離處表現出量子誤碼率(QBER)為3.57%和安全金鑰率(SKR)為3524 bit/s。將單個DFBLD由IM和PM調變(M->IM->PM)的參考傳輸系統，在15 km的傳輸中的QBER為3.7%，SKR為178 bit/s，但成本最高。帶有PM調制的OIL系統(M->PM->S)在12 km傳輸中的QBER為3.45%，SKR為4372 bit/s。帶有IM調制的OIL系統(M->IM->S)在9 km傳輸中的QBER為3.45%，SKR為5337 bit/s。對於1024位的DPS-QKD傳輸，QBER分別為M->IM->PM的3.77%，M->PM->S的3.83%，M->IM->S的4.02%和M->S的4.94%。比較這四種系統，顯然M->IM->PM在QBER、SKR和合規傳輸距離方面皆具有最佳的傳輸性能。然而，它的成本最高，約為4984美元。與之相反，M->S的費用最低（266美元），但在QBER、SKR和合規傳輸距離方面的傳輸性能表現最差。

For the first time, a master-to-slave injection-locked DFBLD pair in the O-band at 1308.4 nm is demonstrated for single-photon DPS-QKD with precise stabilization achieved through feedback control of the DFBLDs’ temperature and current. In particular, phonon-induced phase fluctuations are attributed to intra-cavity heating caused by the excessive generation of free carriers during long quantum key generation with a 3-dB bandwidth of 1.5 GHz. These fluctuations can be suppressed by reducing the bias level of the master DFBLD. Next, the study primarily investigates the influence of the phase and power of the master DFBLD on the phase of the slave DFBLD. The PM and IM are used to preciously control the phase and intensity, respectively. The study offers an extensive evaluation of the performance metrics such as key rate, error rate, and transmission distance in both phase and power decoding. Additionally, it investigates temporal stability, coding efficiency, and cost-effectiveness across four DPS-QKD systems based on DFBLD technology. The master and slave DFBLDs had threshold currents of 5 mA and 6 mA, with the differential resistance of 5 ohms. With a Gain value set at 100, we achieved ±0.05% power and ±0.2 pm wavelength fluctuations in the well-insulated system. The set of TE-cooler gain at 100 effectively maintains the DI at visibility >96% with dPo /Po, max and dPo/dt measured below ±1% and±1×10-3 mW/s. For the master DFBLD, the step-like power of 150 μW or an equivalent photocurrent of 0.12 mA can induce the π phase shift. Decreasing the DC bias from 7 Ith (35 mA) to 2 Ith (10 mA), the phase of the slave DFBLD can be more stability. The system demonstrated the QBER of 3.57% and secure key rate of 3524 bit/s at 6 km communication distance. The four QKD systems are discussed in the following The system with the single DFBLD into IM and PM is the reference transmission structure, which has a QBER of 3.7% and an SKR of 178 bit/s in the 15-km transmission, while the cost is the highest. The OIL system with PM modulation has a QBER of 3.45% and an SKR of 4372 bit/s in the 12-km transmission. The OIL system with IM modulation has a QBER of 3.45% and an SKR of 5337 bit/s in the 9-km transmission. In contrast, the OIL system by directly modulated dual lasers has the lowest cost despite the poorest QBER, SKR, and compliant transmission distance performance. For the 1024-bit DPS-QKD transmission, the QBERs are 3.77% of M->IM->PM, 3.83% of M->PM->S, 4.02% of M->IM->S, and 4.94% of M->S. Comparing these four systems, it is evident that M->IM->PM has the best QKD performance in the QBER, SKR, and compliant transmission distance. However, it comes at the highest cost, which is approximately 4984 USD. In contrast, M->S has the lowest expense (266 USD) with the poorest QKD performance in the QBER, SKR, and compliant transmission distance.