As part of the ALLEGRO Horizon Europe project, we are proud to showcase the performance of our silicon nitride photonic integrated receiver by implementing the three-state time-bin BB84 protocol [Boa18].
📡 What we’ve built:
Our experimental setup integrates a full QKD link — from photon generation to detection — using advanced photonic and electronic components:
👩🔬 Alice – The Transmitter
- Ultra-narrow linewidth tuneable laser (<100 kHz)
- High-speed Mach-Zehnder modulator driven by an arbitrary waveform generator (AWG)
- Pulse repetition at 2.2 GHz and 1550 nm wavelength
- Precisely attenuated optical pulses down to the single-photon level
- Time-bin separation of ≈900 ps, matching the AMZI delay in the receiver
👨💻 Bob – The Receiver
- Polarization-controlled input aligned to the silicon nitride PIC
- Integrated tunable couplers (TCs) and asymmetric Mach-Zehnder interferometer (AMZI)
- Free-running InGaAs single-photon detectors for quantum state measurement
⚙️ Key Highlights:
- Demonstrated reconfigurable coupling ratios via thermo-optic phase shifters (TOPS)
- Passive measurement basis selection (Z or X) by output routing
- Full alignment and integration tested over short single-mode fiber links
📊 Performance metrics, such as coupling response and interference visibility, are illustrated in our experimental characterization (see Figure 3-2).
This setup confirms the viability of integrated QKD systems based on silicon nitride platforms—combining low loss, scalability, and protocol flexibility. A big step toward real-world quantum-secure networks.
🔍 This work is carried out as part of ALLEGRO
#QuantumSecurity #QKD #Photonics #QuantumTech #PIC #IntegratedPhotonics #BB84 #Allegro #HorizonEurope #QuantumNetworking #SecureCommunication
