Measurement-device-independent quantum key distribution with source state errors in photon number space

The existing decoy-state MDI-QKD theory assumes the perfect control of the source states which is a an impossible task for any real setup. In this paper, we study the decoy-state MDI-QKD method with source errors without any presumed conditions and we get the final security key rate only with the range of a few parameters in the source state.Comment: Published in PRA in Dec. 2016. We present formula for the MDIQKD with an unstable source, i.e., in the case there are intensity errors. Our general formula applies to almost all types of sources, such as WCS, HSPS, the passive decoy state protocol and so on. arXiv admin note: text overlap with arXiv:1710.0821

Measurement-device-independent quantum key distribution with source state errors and statistical fluctuation

We show how to calculate the secure final key rate in the four-intensity decoy-state MDI-QKD protocol with both source errors and statistical fluctuations with a certain failure probability. Our results rely only on the range of only a few parameters in the source state. All imperfections in this protocol have been taken into consideration without any unverifiable error patterns.Comment: Published in PRA in March 2017. We present general results for MDIQKD with both intensity error of source and statistical fluctuatio

Sending or not sending: twin-field quantum key distribution with large misalignment error

Based on the novel idea of twin-field quantum key distribution, we present a sending-or-not-sending twin-field fault tolerant quantum key distribution protocol. Our protocol can access a secure distance longer than 700 km even though the misalignment error rate is $15\%$. In the case of zero alignment error, our protocol can exceeds a secure distance of 800 km. Thanks to the novel idea of TF-QKD !Comment: 13 pages, 3 figure

Decoy state method for measurement device independent quantum key distribution with different intensities in only one basis

We show that the three-intensity protocol for measurement device independent quantum key distribution (MDI QKD) can be done with different light intensities in {\em only one} basis. Given the fact that the exact values yields of single-photon pairs in the $X$ and $Z$ bases must be the same, if we have lower bound of the value in one basis, we can also use this as the lower bound in another basis. Since in the existing set-up for MDI-QKD, the yield of sources in different bases are normally different, therefore our method can improve the key rate drastically if we choose to only use the lower bound of yield of single-photon pairs in the advantageous basis. Moreover, since our proposal here uses fewer intensities of light, the probability of intensity mismatch will be smaller than the existing protocols do. This will further improve the advantage of our method. The advantage of using Z basis or X basis of our method is studied and significant improvement of key rates are numerically demonstrated.Comment: arXiv admin note: substantial text overlap with arXiv:1308.567

Encoding-side-channel-free and measurement-device-independent quantum key distribution

We present a simple protocol where Alice and Bob only needs sending out a coherent state or not-sending out a coherent state to Charlie. There is no bases switching. We show that this protocol is both encoding-state-side-channel free to the source part and measurement-device-independent. We don't have to control exactly the whole space state of the light pulse, which is an impossible task in practice. The protocol is immune to all adverse due to encoding-state imperfections in side-channel space such as the photon frequency spectrum, emission time, propagation direction, spatial angular moment, and so on. Numerical simulation shows that our scheme can reach a side-channel-free result for quantum key distribution over a distance longer than 200 km given the single-photon-interference misalignment error rate of $20\%$.Comment: 12 pages, 2 figure

Strangeness s = -6 dibaryon

The structure of $(\Omega\Omega)_{0^+}$ dibaryon with strangeness $s=-6$ is studied in the extended chiral SU(3) quark model, in which vector meson exchange dominates the short range interaction. The resonating group method (RGM) is adopted, in which the $\Omega\Omega$ and $CC$ (hidden color) channels are involved. The color screening effect and the effects of mixing of scalar mesons on $(\Omega\Omega)_{0^+}$ are also investigated.Comment: submitted to Physical Review

Effective Eavesdropping to Twin Field Quantum Key Distribution

We present an effective Eavesdropping scheme to attack the twin-field protocol of quantum key distribution [TF-QKD] proposed recently

Unconditional security of sending or not sending twin-field quantum key distribution with finite pulses

The Sending-or-Not-Sending protocol of the twin-field quantum key distribution (TF-QKD) has its advantage of unconditional security proof under any coherent attack and fault tolerance to large misalignment error. So far this is the only coherent-state based TF-QKD protocol that has considered finite-key effect, the statistical fluctuations. Here we consider the complete finite-key effects for the protocol and we show by numerical simulation that the protocol with typical finite number of pulses in practice can produce unconditional secure final key under general attack, including all coherent attacks. It can exceed the secure distance of 500 $km$ in typical finite number of pulses in practice even with a large misalignment error.Comment: Our results with finite number of pulses are secure under general attacks including whatever coherent attac

A Study of P-wave Heavy Meson Interactions in A Chiral Quark Model

The analytical forms of the interaction potentials between one S-wave and one P-wave heavy mesons as well as the potentials between two P-wave heavy mesons are deduced based on a chiral quark model. Our results explicitly show the attractive property between two heavy mesons. Consequently, a series of possible molecular states are obtained. It is expected that our study might shed some light on the popular discussions of the newly observed XYZ states.Comment: arXiv admin note: substantial text overlap with arXiv:1206.052

Sending-or-not twin-field quantum key distribution in practice

We present results of practical sending-or-not quantum key distribution. In real-life implementations, we need consider the following three requirements, a few different intensities rather than infinite number of different intensities, a phase slice of appropriate size rather than infinitely small size and the statistical fluctuations. We first show the decoy-state method with only a few different intensities and a phase slice of appropriate size. We then give a statistical fluctuation analysis for the decoy-state method. Numerical simulation shows that, the performance of our method is comparable to the asymptotic case for which the key size is large enough. Our results show that practical implementations of the sending-or-not quantum key distribution can be both secure and efficient