Advances in quantum computing are a rapidly growing threat towards modern cryptography. Quantum key distribution (QKD) provides long-term security without assuming the computational power of an adversary. However, inconsistencies between theory and experiment have raised questions in terms of real-world security, while large and power-hungry commercial systems have slowed wide-scale adoption. Measurement-device-independent QKD (MDI-QKD) provides a method of sharing secret keys that removes all possible detector side-channel attacks which drastically improves security claims. In this Letter, we experimentally demonstrate a key step required to perform MDI-QKD with scalable integrated devices. We show Hong-Ou-Mandel interference between weak coherent states carved from two independent indium phosphide transmitters at 431 MHz with a visibility of 46.5±0.8%. This Letter demonstrates the feasibility of using integrated devices to lower a major barrier towards the adoption of QKD in metropolitan networks.
Advances in quantum computing are a rapidly growing threat towards modern cryptography. Quantum key distribution (QKD) provides long-term security without assuming the computational power of an adversary. However, inconsistencies between theory and experiment have raised questions in terms of real-world security, while large and power-hungry commercial systems have slowed wide-scale adoption. Measurement-device-independent QKD (MDI-QKD) provides a method of sharing secret keys that removes all possible detector side-channel attacks which drastically improves security claims. In this Letter, we experimentally demonstrate a key step required to perform MDI-QKD with scalable integrated devices. We show Hong-Ou-Mandel interference between weak coherent states carved from two independent indium phosphide transmitters at 431 MHz with a visibility of 46.5±0.8%. This Letter demonstrates the feasibility of using integrated devices to lower a major barrier towards the adoption of QKD in metropolitan networks.
As quantum key distribution (QKD) begins to move from laboratories into real-world use cases, some practical aspects need to be addressed before it can be widely adopted. Not least of which is the size and cost of the devices. The semiconductor industry, over the last 50 years, has provided a scalable platform for integrated electronics. Using the same fabrication processes, it is possible to create quantum photonic microchips to entirely replace the optical components needed for QKD. Using both indium phosphide and silicon devices, we can design and fabricate integrated devices to perform QKD with highly competitive speeds and error rates. At the same time, they offer dramatically reduced power requirements, size and costs while offering increased phase stability and inherent scalability. Other recent developments in the field include new protocols to remove the security assumptions about the physical devices used. One such protocol is measurement-device independent QKD (MDI-QKD) which removes all detector side-channels. Combining integrated devices with MDI-QKD, we are working towards developing a practical architecture for metropolitan QKD. Here, we provide a recap of QKD and discuss the current state of integrated QKD devices and their potential applications in metropolitan networks.
The versatility of silicon photonic integrated circuits has led to a widespread usage of this platform for quantum information-based applications, including quantum key distribution (QKD). However, the integration of simple high-repetition-rate photon sources is yet to be achieved. The use of weak-coherent pulses (WCPs) could represent a viable solution. For example, measurement device independent QKD (MDI-QKD) envisions the use of WCPs to distill a secret key immune to detector side channel attacks at large distances. Thus, the integration of III-V lasers on silicon waveguides is an interesting prospect for quantum photonics. Here we report the experimental observation of Hong-Ou-Mandel interference with 46±2% visibility between WCPs generated by two independent III-V on silicon waveguide integrated lasers. This quantum interference effect is at the heart of many applications, including MDI-QKD. This Letter represents a substantial first step towards an implementation of MDI-QKD fully integrated in silicon and could be beneficial for other applications such as standard QKD and novel quantum communication protocols.
The versatility of silicon photonic integrated circuits has led to a widespread usage of this platform for quantum information-based applications, including quantum key distribution (QKD). However, the integration of simple high-repetition-rate photon sources is yet to be achieved. The use of weak-coherent pulses (WCPs) could represent a viable solution. For example, measurement device independent QKD (MDI-QKD) envisions the use of WCPs to distill a secret key immune to detector side channel attacks at large distances. Thus, the integration of III–V lasers on silicon waveguides is an interesting prospect for quantum photonics. Here we report the experimental observation of Hong–Ou–Mandel interference with 46 2% visibility between WCPs generated by two independent III–V on silicon waveguide integrated lasers. This quantum interference effect is at the heart of many applications, including MDI-QKD. This Letter represents a substantial first step towards an implementation of MDI-QKD fully integrated in silicon and could be beneficial for other applications such as standard QKD and novel quantum communication protocols.
Breakthroughs in chip integration technology have accelerated the practical deployment and scalable implementation of quantum key distribution (QKD). On-chip quantum light sources are critical components of fully integrated QKD systems. Measurement-Device-Independent QKD (MDI-QKD) offers significant advantages in network communication by eliminating vulnerabilities to side-channel attacks at the detector side, while relying on high-visibility Hong-Ou-Mandel interference between photons emitted by two independent lasers. Here, we present an innovative design of the silicon-based hybrid integrated self-injection locking (SIL) laser chip that achieves high-frequency-stability operation with the frequency detuning between independent lasers suppressed to within 15 MHz, enabling high-visibility HOM interference in MDI-QKD. Leveraging this design, we experimentally demonstrate a loss-tolerant MDI-QKD system employing the setting-choice-independent correlation security framework explicitly accounting for state-preparation uncertainty. The system achieves a finite-key secret rate of 17 b/s under 34 dB channel loss (or 170-km standard fiber), surpassing previously reported MDI-QKD experiments that incorporated state preparation uncertainty under equivalent transmission loss conditions. Our result makes a promising contribution to practical applications of fully integrated quantum communication networks.
The ideal measurement-device-independent quantum key distribution (MDI-QKD), which is immune to all detector side-channel attacks, is built on the Bell state measurement of two single-photon states. However, in practical MDI-QKD where phase-randomized weak coherent pulses (PR-WCPs) are used, the mismatch between states preparation and measurement in X basis leads to the bit error rate of more than 25%, which poses a challenge to the security of QKD. In this paper, we provide a security analysis of practical MDI-QKD based on polarization coding. We analyze the Hong-Ou-Mandel interference of PR-WCPs and Poisson-distributed photon number states (PNs), and find that these two sources are equivalent in MDI-QKD. The security analysis based on entanglement distillation is carried out on PNs, and the measurement results in Z basis and X basis are averaged to overcome the noncorrelation of the error rates in these two bases. Compared with GLLP scheme, a tighter key rate is obtained in this work, and the key rate deviates from the linear key rate bound in a short distance due to the finite proportion of multiphoton terms.
Measurement-device-independent quantum key distribution (MDI QKD) removes all detector side channels and enables secure QKD with an untrusted relay.It is suitable for building a star-type quantum access network, where the complicated and expensive measurement devices are placed in the central untrusted relay and each user requires only a low-cost transmitter, such as an integrated photonic chip.Here, we experimentally demonstrate a 1.25-GHz silicon photonic chip-based MDI QKD system using polarization encoding.The photonic chip transmitters integrate the necessary encoding components for a standard QKD source.We implement random modulations of polarization states and decoy intensities, and demonstrate a finite-key secret rate of 31 bit=s over 36-dB channel loss (or 180-km standard fiber).This key rate is higher than state-of-the-art MDI QKD experiments.The results show that silicon photonic chipbased MDI QKD, benefiting from miniaturization, low-cost manufacture, and compatibility with CMOS microelectronics, is a promising solution for future quantum secure networks.