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A direct GHz-clocked phase and intensity modulated transmitter applied to quantum key distribution

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  • G. L. Roberts
  • M. Lucamarini
  • J. F. Dynes
  • S. J. Savory
  • Z. L. Yuan
  • A. J. Shields


Publication details

JournalQuantum Science and Technology
DateAccepted/In press - 13 Aug 2018
DatePublished (current) - 29 Aug 2018
Issue number4
Number of pages7
Original languageEnglish


Quantum key distribution (QKD), a technology that enables perfectly secure communication, has evolved to the stage where many different protocols are being used in real-world implementations. Each protocol has its own advantages, meaning that users can choose the one best-suited to their application, however each often requires different hardware. This complicates multi-user networks, in which users may need multiple transmitters to communicate with one another. Here, we demonstrate a direct-modulation based transmitter that can be used to implement most weak coherent pulse-based QKD protocols with simple changes to the driving signals. This also has the potential to extend to classical communications, providing a low chirp transmitter with simple driving requirements that combines phase shift keying with amplitude shift keying. We perform QKD with concurrent time-bin and phase modulation, alongside phase randomisation. The acquired data is used to evaluate secure key rates for time-bin encoded BB84 with decoy states and a finite key-size analysis, giving megabit per second secure key rates, 1.60 times higher than if purely phase-encoded BB84 was used.

    Research areas

  • quantum communications, quantum cryptography, quantum key distribution

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