Abstract
Measurement-device-independent quantum key distribution (MDI-QKD) is a technique for quantum-secured communication that eliminates all detector side-channels, although is currently limited by implementation complexity and low secure key rates. Here, we introduce a simple and compact MDI-QKD system design at gigahertz clock rates with enhanced resilience to laser fluctuations—thus enabling free-running semiconductor laser sources to be employed without spectral or phase feedback. This is achieved using direct laser modulation, carefully exploiting gain-switching and injection-locking laser dynamics to encode phase-modulated time-bin bits. Our design enables secure key rates that improve upon the state of the art by an order of magnitude, up to 8 bps at 54 dB channel loss and 2 kbps in the finite-size regime for 30 dB channel loss. This greatly simplified MDI-QKD system design and proof-of-principle demonstration shows that MDI-QKD is a practical, high-performance solution for future quantum communication networks.
Highlights
Quantum key distribution (QKD) is a maturing technology that enables distant communication with information-theoretic security[1,2]
In this Letter, we demonstrate a decisive advance in this direction with a compact, simplified, gigahertz-clocked measurement-deviceindependent QKD (MDI-QKD) system that improves upon state-of-the-art secure key rates by up to an order of magnitude
In single-photon time-bin-encoded MDI-QKD, Alice and Bob prepare qubits in one of two bases: Z-basis states with the bit value encoded by the position of a photon in either the early (j0i) or late (j1i) time bin of the clock period; or X-basis states comprising a coherent superposition of a photon across both time bðji0nisþweiiφthj1ibÞ=itpffi2vffi,alwuehereencφodised[0] in or the π for phase between the jþi and jÀi them, states, respectively
Summary
Quantum key distribution (QKD) is a maturing technology that enables distant communication with information-theoretic security[1,2]. The development of such systems is important at present as advances in quantum computation pose a growing threat to current security models based on public-key cryptography. A number of attacks on singlephoton detectors (SPDs) have already been reported, as these are typically the most vulnerable components[3]. To eliminate these side channels, measurement-deviceindependent QKD (MDI-QKD)[4] (see also5) has emerged as a promising new approach. To emphasise this important detail, Charlie is often denoted ‘untrusted’, meaning that no trust has to be put on the intermediate node to guarantee the full security of the MDIQKD protocol
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
