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We propose schemes for preparing W and GHZ photonic states entangled in polarization via quantum walks, where the trajectory exchanging of identical photons plus postselection induces the coupling between their polarization degrees of freedom. Being different from the polarization beam splitter-based approach, the indistinguishability of identical photons provides an alternative for coupling photons, which is more phase stable and may induce richer actions than the traditional polarization beam splitter on input photons. Our schemes demonstrate that this new coupling mechanism for photons is originated from the fact that trajectory-exchanging operation plus postselection can extract entangled states from the initially product states, and this new coupling mechanism may find considerable potential applications in both quantum communication and quantum computation.

We present a two-copy-based protocol for directly measuring the concurrence of two-photon polarization entangled mixed states (Collins–Gisin class state and the more complicated bipartite mixed entangled state—Werner class state) without quantum state tomography. The quantum circuit designed for directly measuring concurrence can be realized in an optical system. Our protocol works without the sophisticated controlled-NOT gate, which makes it much simpler than the previous ones. Because all the operations used here are local, the scheme can be used for directly measuring remote mixed entanglement too.

In 1935, Einstein, Podolsky and Rosen claimed that quantum wave function does not provide a complete description of physical reality, which is called EPR paradox1. Based on EPR paradox and hidden variable theory, Bell quantitatively analyzed and put forward the Bell inequality in a seminal paper in 19642. More precisely, the hidden variable theory is expressed in mathematics, which reveals that spatially separated quantum systems can have strong correlations. This kind of correlation is known as nonlocality, and it plays a crucial role in quantum information theory, such as nonlocal computation3. Meanwhile, Bell theory provides a significant criterion for the experimentalists to prove the validity of quantum mechanics, and the corresponding experiments verified the nonlocality property of quantum mechanics4,5,6. From John Bell’s original inequality, John Clauser, Michael Horne, Abner Shimony, and Richard Holt derived a new inequality—CHSH inequality—in a much-cited paper published in 19697. The maximum violation of CHSH inequality can reach in quantum mechanics domain, i.e. the so-called Tsirelson’s bound8, rather than the maximum value 2 in classical domain. Up to now, most of the previous Bell inequality test experiments suffer from the following three loopholes, i.e. the locality loophole (or communication loophole), the freedom-of-choice loophole, and the fair-sampling loophole (or detection loophole). The fact that the measurement choice on one subsystem may influence the outcome of the other (and vice-versa) opens the locality loophole. In a Bell test, the two users must be free to choose random measurement choices that are physically independent of one another and of any property of the particles, otherwise, there comes the freedom-of-choice loophole. The detection efficiency must be independent of the measurement settings, i.e. the sample of detected pairs provides a fair statistical sample of all the pairs. If this is not true, it opens the fair-sampling loophole (or detection loophole). The results of the Bell test experiments with any one of these three loopholes only can be accepted with some assumptions. Very recently, Bell tests that close the most significant two loopholes simultaneously have been reported9,10,11,12. Although loopholes have negative effects on Bell test, they play constructive roles in simulating post-quantum correlations whose violations of Bell inequality surpass the so-called Tsirelson’s bound. The most typical representative of this kind of correlations is the famous Popescu and Rohrlich (PR) correlation. Popescu and Rohrlich showed that it is possible to construct various causality satisfying models, where the violation of CHSH inequality can exceed the quantum mechanical bound and reach the algebraic maximal value 413. The nonlocality revealed by the violation of Bell’s inequality can be described by a correlation box shared between two parties. The boxes with the algebraic maximal violation 4 of CHSH inequality are termed PR boxes. Even though previous researches14,15,16,17 suggested that these post-quantum correlations cannot be implemented by classical or quantum systems, they can be simulated by exploiting the loopholes in a Bell test. Obvious violations of Bell inequality beyond Tsirelson’s bound caused by the fair-sampling loophole (or detection loophole) have been observed in experiments where one of the entangled photons is measured and amplified18 or re-generated18,19, or we have the knowledge of the states being measured20. The loss-induced fair-sampling loophole (or detection loophole) can lead to a violation of Bell inequality beyond Tsirelson’s bound too21,22,23,24,25. Among these studies, the fair-sampling loophole is opened by the selection of states to be measured. Actually, the fair-sampling loophole is still open if we select the results after measurement. In other words, it is still possible to simulate post-quantum correlations via post-select the measurements results. Cabello showed this possibility by simulating bipartite correlations beyond Tsirelson’s bound via appropriately post-selecting two qubits of a three-qubit GHZ state system26, and Chen et al. observed this kind of supercorrelations in optical system experimentally27. But this kind of simulation of post-quantum correlation must make use of tripartite state, which obviously limits its persuasiveness. If this kind of selection is done directly on the two subsystems in a bipartite entangled state, the effect of the result-selection induced fair sampling loophole can be shown more obviously. Marcovitch et al. showed that it can be done within “two-state vector formalism”, namely, a state described by “two-state vector formalism” can exhibit a strong violation of CHSH inequality, which can exceed Tsirelson’s bound and even reach the algebraic maximal value (4)28. Here, the measurement is done on all the samples, and the post-selection is only done after measurement, which is more in line with Bell theory than the case with the selection of the states before measurement. The “two-state vector formalism” is a new concept defined by Yakir Aharonov and Lev Vaidman, which is a complete description of a quantum system at a given time based on the results of experiments performed both before and after this time29. In addition, because the “two-state vector formalism” violates the information causality25,30, it opens the locality loophole too , which makes this kind of result-selection induced loophole a comprehensive loophole (including both locality and fair-sampling loopholes) in Bell test. Besides information causality25,30, the comprehensive loophole opened by the result selection within “two-state vector formalism” is another possible explanation of why post-quantum correlations are incompatible with quantum mechanics and seem not to exist in nature. So, in this paper, we will propose a physical scheme for simulating PR correlations by using the comprehensive loophole opened by the result selection within “two-state vector formalism”. In linear optical system, a PR correlation can be simulated by appropriately pre-selecting photon ensemble to be measured and post-selecting the measurement results. Because all the optical elements used here are very common ones, the physical scheme proposed here is feasible.

Safflower (HH), the dry flower of Carthamus tinctorius L., has long been used to empirically treat neuropsychological disorders such as stroke and major depression in traditional Chinese medicine, and recently been proven effective for regulating levels of dopamine and serotonin in new-born rat brain. The present study assessed whether HH would be bioactive for functionally regulating monoamine transporters using in vitro drug-screening cell lines. Our current results showed that all solvent-extracted HH fractions, in different degrees, markedly increased both dopamine uptake by Chinese hamster ovary (CHO) cells stably expressing dopamine transporter (DAT) and norepinephrine uptake by CHO cells expressing norepinephrine transporter (NET), and also showed that chloroform (HC), ethyl acetate (HE), and n-butyl alcohol extract strikingly depressed serotonin uptake by CHO cells expressing serotonin transporter (SERT); wherein, the potencies of ethanol extract, HC, HE, and aqueous extract to up-regulate dopamine/norepinephrine uptake and potency of HE to inhibit serotonin uptake were relatively stronger. Further investigation revealed that the enhancement of dopamine/norepinephrine uptake by HC and HE was dependent of DAT/NET activity, and the HE-induced inhibition of serotonin uptake was typical of competition. Thus, HH extracts are novel monoamine transporter modulators functioning as DAT/NET activators and/or SERT inhibitors, and would likely improve neuropsychological disorders through regulating monoamine-transporter activity.

The protopine isolated from a Chinese herb Dactylicapnos scandens Hutch was identified as an inhibitor of both serotonin transporter and noradrenaline transporter in vitro assays. 5-hydroxy-DL-tryptophan(5-HTP)-induced head twitch response (HTR) and tail suspension test were adopted to study whether protopine has anti-depression effect in mice using reference antidepressant fluoxetine and desipramine as positive controls. In HTR test, protopine at doses of 5, 10, 20 mg/kg dose dependently increase the number of 5-HTP-induced HTR. Protopine at doses of 3.75 mg/kg, 7.5 mg/kg and 30 mg/kg also produces a dose-dependent reduction in immobility in the tail suspension test. The present results open up new possibilities for the use of protopine in the treatment of mood disorders, such as mild and moderate states of depression.

Single qubit pure state is a fundamental resource in quantum information and quantum computation. Therefore, it is of great importance to protect the coherence of single qubits against decoherence. In this letter, we demonstrate that decoherence caused by spontaneous emission can be effectively suppressed by adding a universal static external field. In order to have an intuitive view to the protection effects and its physical mechanisms, we study the coherence evolution of a single qubit on a Bloch sphere. We can clearly see that different external resonant drivings can rotate the Bloch vector around different axes, and the steady-state solution of the master equation (under protection) are visualized on the Bloch sphere. Furthermore, the frequency detuning between the qubit system and the driving is taken into account, and the results show that our protection scheme still works fine in the detuned cases and the smaller the detuning is, the better the protection effect is. In addition, this protocol can protect the coherence of single qubit states with a wide range of driving parameters, and help people to design simple coherence protection schemes for qubit states. The simplicity and the abundance of the current scheme may warrant its experimental realization.

An optical scheme for simulating nonlocality distillation is proposed in post-quantum regime. The nonlocal boxes are simulated by measurements on appropriately pre- and post-selected polarization entangled photon pairs, i.e. post-quantum nonlocality is simulated by exploiting fair-sampling loophole in a Bell test. Mod 2 addition on the outputs of two nonlocal boxes combined with pre- and post-selection operations constitutes the key operation of simulating nonlocality distillation. This scheme provides a possible tool for the experimental study on the nonlocality in post-quantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones.

Six tigliane-type diterpenoids (1-6) were isolated from the roots of Euphorbia fischeriana. Their structures were elucidated by various spectral analyses. Among them, compounds 1 and 3 were new, and compounds 2, 4, and 5 were naturally obtained for the first time. All compounds were tested against two human cancer cell lines, MDA-MB-231 and HepG2, and one human immortalized cell line, and only compound 6 showed cytotoxicity for MDA-MB-231 cells with an IC(50) value of 6.694 μM.

Four new "cage-like" monoterpene glucosides (1-4) were isolated from Paeonia lactiflora. The structures of these compounds were established by spectroscopic methods, mainly 1D and 2D NMR, and mass spectrometric analysis. Compound 4 exhibited moderate cell-protective activity against hydrogen peroxide-induced PC12 cell damage.

Safflower, the dry flower of Carthamus tinctorius L., has long been applied for empirically treating cerebral ischemia and depression in traditional Chinese medicine. Pathogenesis of major depression involves monoaminergic transmission. The present study assessed whether safflower or its isolate would be effective in functionally regulating monoamine transporter using in vitro screening cell lines. We discovered that safflower insoluble fraction significantly inhibited serotonin uptake in Chinese hamster ovary cells stably expressing serotonin transporter (i.e. S6 cells). This fraction went through an activity-guided isolation and an active ingredient was obtained, which was subsequently elucidated as a novel coumaroylspermidine analog N(1),N(5)-(Z)-N(10)-(E)-tri-p-coumaroylspermidine using NMR techniques. Pharmacologically, this compound potently and selectively inhibited serotonin uptake in S6 cells or in synaptosomes, with IC(50) of 0.74+/-0.15 microM for S6 cells or 1.07+/-0.23 microM for synaptosomes and with a reversible competitive property for the 5HT-uptake inhibition. The potency of it for 5HT uptake was weaker than that of fluoxetine whereas efficacy generally similar for both. Animals treated with this testing compound showed a significant decrease in synaptosomal 5HT uptake capacity. Thus, N(1),N(5)-(Z)-N(10)-(E)-tri-p-coumaroylspermidine is a novel serotonin transporter inhibitor, which could improve neuropsychological disorders through regulating serotoninergic transmission.

Adiponectin is an adipocyte-derived insulin-sensitizing hormone with antidiabetic, antiinflammatory, and antiatherosclerotic properties. A decreased serum level of adiponectin in obesity has been identified as an independent risk factor for diabetes and cardiovascular complications, suggesting that pharmacological intervention aimed at elevating adiponectin production might hold promise for the treatment and/or prevention of these diseases. Here we report the identification of two structurally related natural compounds (astragaloside II and isoastragaloside I) from the medicinal herb Radix Astragali that possess such an activity. Astragaloside II and isoastragaloside I selectively increased adiponectin secretion in primary adipocytes without any obvious effects on a panel of other adipokines. Furthermore, an additive effect on induction of adiponectin production was observed between these two compounds and rosiglitazone, a thiazolidinedione class of insulin-sensitizing drugs. Chronic administration of astragaloside II and isoastragaloside I in both dietary and genetic obese mice significantly elevated serum levels of total adiponectin and selectively increased the composition of its high molecular weight oligomeric complex. These changes were associated with an alleviation of hyperglycemia, glucose intolerance, and insulin resistance. By contrast, the beneficial effects of these two compounds on insulin sensitivity and glucose metabolism were diminished in adiponectin knockout mice. In conclusion, our results suggest that pharmacological elevation of circulating adiponectin alone is sufficient to ameliorate insulin resistance and diabetes and support the use of adiponectin as a biomarker for future drug discovery. The two natural compounds might provide the lead as a novel class of therapeutics for obesity-related diseases. Copyright © 2009 by The Endocrine Society., link_to_OA_fulltext