再谈核磁共振在医学方面的应用

阐述了核磁共振的本质，论述了其在医学领域的应用及前景。     

任意安全的量子保密通讯

利用量子纠缠的非局域性,结合量子纠缠的纯化,以及量子中继器的思想,结合Bell态的测量,我们论证了长距离量子保密通讯可行性.利用保真度与熵的关系,我们给出了量子保密通讯安全性的一般证明.同时,我们指出在‘joint attack'情况下使用‘completely positivemap'作为安全性证明的困难所在.     

Unconditional secure two-way quantum dense key distribution

In this paper, we present a two-way quantum dense key distribution protocol. With double check modes, our scheme is secure regardless of the presence of noises. And with a quantum teleportation process, secret message can be encoded deterministically even if the quantum channel is highly lossy. Therefore, our scheme can be used in a realistic quantum channel regardless of the presence of noises and channel losses.     

生命与熵

 熵是一个古老而又年轻的概念,说它古老,是因为早在100多年前(1854年)就已有人提到了它;说它年轻,是因为它有极强的生命力,正日益广泛地渗透到了许许多多的科技领域及日常生活之中。本文不拟介绍熵在各个领域中的应用,而只想就熵对生命科学中某些方面的影响作些初浅的说明。按照热力学的观点,生命是个开放系统。根据开放系统的热力学理论可以算出,其熵变ΔS=ΔQT-μjΔeNjT-μjΔiNjT(1)式中,ΔQ代表生命系统与外界环境交换的总热量,ΔeNj代表生命系统与外界所交换的第j种组元物质的摩尔数.     

Quantum Key Distribution against Trojan Horse Attacks

Realistic experimental apparatus of quantum cryptography are imperfect, which may be utilized by a potential eavesdropper to eavesdrop on the communication. We show that quantum communication may be improved with quantum teleportation and entanglement swapping, which is robustly secure against the most general Trojan horse attacks. Our scheme is not an improvement of the communication apparatus, but the improvement of quantum communication protocol itself. We show that our modified schemes may be implemented with current technology.     

The Essence of More Nonlocality with Less Entanglement in Bell Tests

In this paper, we will explore the essence of the phenomenon that state with less entanglement may generate greater Bell violation in the two-qubit Bell tests with CH-type inequalities, i.e., more nonlocality with less entanglement. We will show that this interesting but counterintuitive phenomenon is caused by the rotational asymmetry of the nonmaximally entangled state in the measurement plane. This asymmetry allows the both-side detection probabilities and the one-side detection probabilities obtain their maximal values with nonmaximally entangled state. But the maximal Bell violation may not always happen on nonmaximally entangled state, because these probabilities will compete with each other, and the Bell violation behaves differently for various CH-type inequalities.