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arXiv:1905.09197 · Applied Physics Letters

Demonstration of a 6 state-4 state reference frame independent channel for quantum key distribution

Ramy Tannous, Zhangdong Ye, Jeongwan Jin, Katanya B. Kuntz, Norbert Lütkenhaus, Thomas Jennewein

Published Nov 18, 2019• 24 citations
arXivHTMLPDF

Abstract

We study a reference frame independent (RFI) quantum key distribution (QKD) protocol using six states for Alice and only four states for Bob, while previous RFI protocols require a six state analyzer for Bob. Our protocol can generate a secure key for any possible phase of the entangled state provided the variation is small compared to the measurement rate, as shown by our numerical key rate analysis. We perform a proof-of-principle experiment using polarization entangled photon pairs. In the presence of a varying rotational phase, we obtain a consistently low error rate of less than 4%, indicating the feasibility of this protocol for QKD. Our RFI protocol is hence beneficial but not limited to applications in a satellite or mobile free-space QKD, where a communication node must limit the resources and restrict the number of measured states to four instead of six.

DOI
10.1063/1.5125700

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We study a reference frame independent (RFI) quantum key distribution (QKD) protocol using six states for Alice and only four states for Bob, while previous RFI protocols require a six state analyzer for Bob. Our protocol can generate a secure key for any possible phase of the entangled state provided the variation is small compared to the measurement rate, as shown by our numerical key rate analysis. We perform a proof-of-principle experiment using polarization entangled photon pairs. In the presence of a varying rotational phase, we obtain a consistently low error rate of less than 4%, indicating the feasibility of this protocol for QKD. Our RFI protocol is hence beneficial but not limited to applications in a satellite or mobile free-space QKD, where a communication node must limit the resources and restrict the number of measured states to four instead of six.
Reference-frame-independent quantum key distribution (RFI-QKD) has gained widespread attention due to its unique advantage for practical application, as it circumvents the need for active reference-frame alignment within the system. However, in comparison to the standard BB84 protocol, the original six-state RFI protocol requires a greater number of quantum states to be operated by Alice and Bob, which is an aspect that merits optimization. In this work, we propose a four-state RFI protocol and illustrate that Alice and Bob each require only four quantum states to perform channel estimation that remains independent of reference-frame deviation, which can proficiently reduce the system complexity. Furthermore, through numerical simulations taking the finite-key-size effect into consideration, we show that the four-state RFI protocol can achieve a secure key rate and transmission distance on par with those of the original six-state RFI protocol. Finally, an experiment over 200 km is conducted to evaluate the feasibility of our scheme. We believe that our protocol can streamline the implementation of RFI-QKD and thereby contribute to the practical advancement of RFI-QKD.
Reference frame independent quantum key distribution (RFI-QKD) has gained widespread attention due to the unique advantage for practical application, as it circumvents the need for active reference frame alignment within the system. However, in comparison to the standard BB84 protocol, the original 6-state RFI protocol requires a greater number of quantum states to be operated by Alice and Bob, which is an aspect that merits optimization. In this work, we propose a 4-state RFI protocol and illustrate that Alice and Bob each require only four quantum states to perform channel estimation that remains independent of reference frame deviation, which can proficiently reduce the system complexity. Furthermore, through numerical simulations taking the finite-size key effect into consideration, we show that 4-state RFI protocol can achieve a secure key rate and transmission distance on par with the original 6-state RFI protocol. Finally, a experiment over 200 km is inplemented to conducted the feasibility of our scheme. We believe that our protocol can streamline the implementation of RFI-QKD and thereby contribute to the practical advancement of RFI-QKD.
Reference-frame-independent quantum key distribution (RFI-QKD) provides a practical way to generate secret keys between two remote parties without sharing common reference frames. On the other hand, measurement-device-independent QKD (MDI-QKD) offers a high level of security, as it is immune to all quantum hacking attempts to measurement devices. The combination of these two QKD protocols, i.e., RFI-MDI-QKD, is one of the most fascinating QKD protocols, since it holds advantages of both practicality and security. For further practicality of RFI-MDI-QKD, it is beneficial to reduce the implementation complexity. Here, we show that RFI-MDI-QKD can be implemented using fewer quantum states than those of its original proposal. We find that, in principle, the number of quantum states for one of the parties can be reduced from six to three without compromising security. Compared to conventional RFI-MDI-QKD where both parties transmit six quantum states, it significantly simplifies the implementation of the QKD protocol. We also verify the feasibility of the scheme with a proof-of-principle experiment.
In secure communication, reference-frame calibration is critical to ensuring a secure key rate in quantum key distribution (QKD) systems. This process also increases the complexity of the system, which is not conducive to practical use. Although the reference-frame-independent (RFI) QKD protocol can simplify alignment, it requires three bases to prepare six states. Here the authors present instead a three-state RFI QKD protocol, and verify its security using a recently developed proof based on semidefinite programming. A proof-of-principle experiment is conducted to demonstrate the feasibility of the scheme. This work is sure to boost the practical application of the RFI QKD protocol.
Quantum key distribution (QKD) is moving from research laboratories towards applications. As computing becomes more mobile, cashless as well as cardless payment solutions are introduced. A possible route to increase the security of wireless communications is to incorporate QKD in a mobile device. Handheld devices present a particular challenge as the orientation and the phase of a qubit will depend on device motion. This problem is addressed by the reference frame independent (RFI) QKD scheme. The scheme tolerates an unknown phase between logical states that vary slowly compared to the rate of particle repetition. Here we experimentally demonstrate the feasibility of RFI QKD over a free-space link in a prepare and measure scheme using polarization encoding. We extend the security analysis of the RFI QKD scheme to be able to deal with uncalibrated devices and a finite number of measurements. Together these advances are an important step towards mass production of handheld QKD devices.
Reference-frame-independent (RFI) quantum key distribution (QKD) removes the need to actively align Alice and Bob's bases, but existing security proofs and decoy-state treatments are either numerically heavy or overly pessimistic in realistic scenarios. In this work, we revisit the RFI QKD security proof, demonstrating that the protocol is subject to the same constraints as the standard six-state or BB84 protocol, thereby improving its robustness and performance. We then introduce a one-decoy finite-key analysis based on RFI-invariant correlators and virtual quantum bit error rates. Simulations show that our decoy method restores reference frame independent performance and yields higher secret-key rates than the original RFI analysis with three intensities, while simplifying the experimental setup by requiring only two intensity levels.