Quantum secure communication scheme with W state

Recently, Cao et al. proposed a new quantum secure direct communication scheme using W state. In their scheme, the error rate introduced by an eavesdropper who takes intercept-resend attack, is only 8.3%. Actually, their scheme is just a quantum key distribution scheme because the communication parties first create a shared key and then encrypt the secret message using one-time pad. We then present a quantum secure communication scheme using three-qubit W state. In our scheme, the error rate is raised to 25% and it is not necessary for the present scheme to use alternative measurement or Bell basis measurement. We also show our scheme is unconditionally secure.Comment: Comments are welcom

Improved Eavesdropping Detection Strategy in Quantum Direct Communication Protocol Based on Four-particle GHZ State

In order to improve the eavesdropping detection efficiency in two-step quantum direct communication protocol, an improved eavesdropping detection strategy using four-particle GHZ state is proposed, in which four-particle GHZ state is used to detect eavesdroppers. During the security analysis, the method of the entropy theory is introduced, and two detection strategies are compared quantitatively by using the constraint between the information which eavesdropper can obtain and the interference introduced. If the eavesdroppers intend to obtain all information, the eavesdropping detection rate of the original two-step quantum direct communication protocol by using EPR pair block as detection particles is 50%; while the proposed strategy's detection rate is 88%. In the end, the security of the proposed protocol is discussed. The analysis results show that the eavesdropping detection strategy presented is more secure.Comment: 14 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:quant-ph/0308173 by different author

The quantum cryptographic switch

We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.Comment: 7 pages, 4 Figure

Antipsychotic drug use in pregnancy: A multinational study from ten countries

Aim: To compare the prevalence and trends of antipsychotic drug use during pregnancy between countries across four continents. Methods: Individually linked health data in Denmark (2000−2012), Finland (2005–2014), Iceland (2004–2017), Norway (2005–2015), Sweden (2006–2015), Germany (2006–2015), Australia (New South Wales, 2004–2012), Hong Kong (2001–2015), UK (2006–2016), and the US (Medicaid, 2000–2013, and IBM MarketScan, 2012–2015) were used. Using a uniformed approach, we estimated the prevalence of antipsychotic use as the proportion of pregnancies where a woman filled at least one antipsychotic prescription within three months before pregnancy until birth. For the Nordic countries, data were meta-analyzed to investigate maternal characteristics associated with the use of antipsychotics. Results: We included 8,394,343 pregnancies. Typical antipsychotic use was highest in the UK (4.4%) whereas atypical antipsychotic use was highest in the US Medicaid (1.5%). Atypical antipsychotic use increased over time in most populations, reaching 2% in Australia (2012) and US Medicaid (2013). In most countries, prochlorperazine was the most commonly used typical antipsychotic and quetiapine the most commonly used atypical antipsychotic. Use of antipsychotics decreased across the trimesters of pregnancy in all populations except Finland. Antipsychotic use was elevated among smokers and those with parity ≥4 in the Nordic countries. Conclusion: Antipsychotic use during pregnancy varied considerably between populations, partly explained by varying use of the typical antipsychotic prochlorperazine, which is often used for nausea and vomiting in early pregnancy. Increasing usage of atypical antipsychotics among pregnant women reflects the pattern that was previously reported for the general population

Quantum dissonance induced by a thermal field and its dynamics in dissipative systems

In this paper, we study quantum correlation in separable systems termed quantum dissonance [K. Modi, T. Paterek, W. Son, V. Vedral, M. Williamson, Phys. Rev. Lett. 104, 080501 (2010)]. Firstly, we study the emergence of quantum dissonance between two atoms prepared in uncorrelated states and coupled to a single-mode thermal field. We show that even for situations when the thermal field cannot entangle the two atoms, it can nevertheless induce quantum dissonance between them. Then, we investigate the dynamics including the transfer in both Markovian and non-Markovian regimes of quantum dissonance due to dissipation modeled by two independent subsystems each of which consists of a leaky cavity containing a two-level atom and surrounded by a reservoir. The two subsystems possess some amount of atomic quantum dissonance at the beginning but do not interact with each other by any means later on. We show that the quantum dissonance can be transferred among the composite subsystems, but the way it evolves and is transferred may be very different compared to that of entanglement. Finally, we present an efficient method to refrain the unwanted transfer of quantum dissonance from interested systems to reservoirs