Study On Measurement Device Independent Quantum Key Distribution Based On Orbital Angular Momentum

Quantum cryptography is so far the only strictly proved unconditionally secure communication,which based on Heisenberg uncertainty principle and no-cloning principle of quantum mechanics,where secure key can be obtained in the case of an untrusted channel. But in reality, the idealconditions for quantum key distribution protocol are difficult to achieve, and the recently proposedmeasurement device independent quantum key distribution protocol (MDI-QKD) have effectivelysolved the security problem at detectors. However, the polarization encoding MDI-QKD scheme isa basis-dependent scheme, which has impacted the key generation rate. Photon with orbital angularmomentum is a new information carrier, and has high dimensional nature. We study themeasurement device independent quantum key distribution protocol based on orbital angularmomentum (OAM) in this thesis. The details are the following:1. In this thesis, MDI-QKD protocol based on orbital angular momentum states(OAM-MDI-QKD) in two-dimensional space was proposed, the theoretical derivation andimplementation steps of this scheme was given, and the performance of this scheme wasdiscussed when the base selection and measurement methods were differe nt. At the sametime, a novel OAM-MDI-QKD scheme using an efficient OAM separation method wasintroduced. The results showed that, there is no need to align the reference inOAM-MDI-QKD scheme, which avoided the basis-dependent flaw, and increased the keygreneration rate in comparison with the MDI-QKD protocol using polarization states.2. OAM states are easily to extended high dimensionality, an OAM-MDI-QKD inhigh-dimensionality was presented for each quantum state could carry more information.The four-dimensional OAM-MDI-QKD was given as an example to demostrate thehigh-dimensioanlity OAM-MDI-QKD. The results show that high-dimensionalOAM-MDI-QKD increased the bit information tologd2per photon, but the efficiency ofthe photons is not high enough.3. As a ideal single photon source is difficult to achieve in practice, weak coherent pulses areused as a substitute in experment, which introduces the photon splitting attacks. Thedecoyed state method is a good way to overcome this difficulty. In this thesis, theOAM-MDI-QKD using weak coherent pulses and decoy states were given individually. Thekey greneration rate formula was deduced, and the simulations of key greneration rate when using infinite decoy states were given. The results show that under the same conditions, thekey rate in the proposed OAM-MDI-QKD was higher than that in the polarized MDI-QKDscheme. The key rate in OAM-MDI-QKD using two decoy states was very close to infinitedecoy states.