Efficient and robust estimation of many-qubit Hamiltonians

Characterizing the interactions and dynamics of quantum mechanical systems is an essential task in developing quantum technologies. We propose an efficient protocol based on the estimation of the time-derivatives of few qubit observables using polynomial interpolation for characterizing the underlying Hamiltonian dynamics and Markovian noise of a multi-qubit device. For finite range dynamics, our protocol exponentially relaxes the necessary time-resolution of the measurements and quadratically reduces the overall sample complexity compared to previous approaches. Furthermore, we show that our protocol can characterize the dynamics of systems with algebraically decaying interactions. The implementation of the protocol requires only the preparation of product states and single-qubit measurements. Furthermore, we improve a shadow tomography method for quantum channels that is of independent interest and discuss the robustness of the protocol to various errors. This protocol can be used to parallelize the learning of the Hamiltonian, rendering it applicable for the characterization of both current and future quantum devices.

Efficient Classical Simulation and Benchmarking of Quantum Processes in the Weyl Basis

One of the crucial steps in building a scalable quantum computer is to identify the noise sources which lead to errors in the process of quantum evolution. Different implementations come with multiple hardware-dependent sources of noise and decoherence making the problem of their detection manyfoldly more complex. We develop a randomized benchmarking algorithm which uses Weyl unitaries to efficiently identify and learn a mixture of error models which occur during the computation. We provide an efficiently computable estimate of the overhead required to compute expectation values on outputs of the noisy circuit relying only on the locality of the interactions and no further assumptions on the circuit structure. The overhead decreases with the noise rate and this enables us to compute analytic noise bounds that imply efficient classical simulability. We apply our methods to ansatz circuits that appear in the variational quantum eigensolver and establish an upper bound on classical simulation complexity as a function of noise, identifying regimes when they become classically efficiently simulatable.

SARS-CoV-2 transmission routes from genetic data: A Danish case study

BACKGROUND

The first cases of COVID-19 caused by the SARS-CoV-2 virus were reported in China in December 2019. The disease has since spread globally. Many countries have instated measures to slow the spread of the virus. Information about the spread of the virus in a country can inform the gradual reopening of a country and help to avoid a second wave of infections. Our study focuses on Denmark, which is opening up when this study is performed (end-May 2020) after a lockdown in mid-March.

METHODS

We perform a phylogenetic analysis of 742 publicly available Danish SARS-CoV-2 genome sequences and put them into context using sequences from other countries.

RESULTS

Our findings are consistent with several introductions of the virus to Denmark from independent sources. We identify several chains of mutations that occurred in Denmark. In at least one case we find evidence that the virus spread from Denmark to other countries. A number of the mutations found in Denmark are non-synonymous, and in general there is a considerable variety of strains. The proportions of the most common haplotypes remain stable after lockdown.

CONCLUSION

Employing phylogenetic methods on Danish genome sequences of SARS-CoV-2, we exemplify how genetic data can be used to trace the introduction of a virus to a country. This provides alternative means for verifying existing assumptions. For example, our analysis supports the hypothesis that the virus was brought to Denmark by skiers returning from Ischgl. On the other hand, we identify transmission routes which suggest that Denmark was part of a network of countries among which the virus was being transmitted. This challenges the common narrative that Denmark only got infected from abroad. Our analysis concerning the ratio of haplotypes does not indicate that the major haplotypes appearing in Denmark have a different degree of virality.

Ectoparasitic flies (Diptera, Streblidae) of bats (Chiroptera, Phyllostomidae) in an Atlantic Forest area, southeastern Brazil

We studied infestation rates and parasite-host associations between streblid flies and phyllostomid bats in an Atlantic Forest area of Rio de Janeiro state, southeastern Brazil. We captured 301 individuals from seven Phyllostomidae bat species. Out of that total, 69 bats had been parasitised by nine Streblidae species; the most frequent species were Trichobius joblingi and Trichobius tiptoni. The species Paraeuctenodes longipes, associated with Anoura geoffroyi, was the most frequent species. The highest mean intensity was observed for Paraeuctenodes longipes, associated with A. geoffroyi, and Paratrichobius longicrus associated with Artibeus lituratus, both ectoparasite species with a mean intensity of five individuals per bat. Trichobius joblingi exhibited the highest mean abundance, which was over three on its host species. Streblid richness in the study area was similar to the richness found in other studies carried out in the Atlantic Forest. We observed that streblid richness in this biome depends more on inherent characteristics of each physiognomy and on the host-species than on the sampling effort.

Different mechanisms underlie the analgesic actions of paracetamol and dipyrone in a rat model of inflammatory pain

BACKGROUND AND PURPOSE

The analgesics, paracetamol and dipyrone are weak inhibitors of the cyclooxygenase isoforms 1 or 2 (COX-1, COX-2) but more potent on COX-3. Both are also weak anti-inflammatory agents, relative to their analgesic and antipyretic activities. In a model of inflammatory pain mediated by prostaglandins, both compounds were analgesic. We have analysed this shared effect further in order to elucidate the underlying mechanisms.

EXPERIMENTAL APPROACH

Inflammation was induced in one hind paw of rats by intraplantar injection of 250 microg lambda-carrageenan (CG) and the contralateral paw injected with saline. Nociceptive thresholds to mechanical stimulation were measured immediately before and for 6 h after, injection of CG. The analgesics were s.c. or locally (intraplantar) injected either 30 min before or 2 h after CG. In some groups, naltrexone was injected (s.c. or intraplantar), 1 h before CG.

KEY RESULTS

Pretreatment with paracetamol or dipyrone (60-360 mg kg(-1)) reversed hyperalgesia induced by CG and increased nociceptive threshold in the inflamed paw above the basal level (hypoalgesia). Paracetamol, but not dipyrone, also raised nociceptive thresholds in the non-inflamed paw. Subcutaneous, but not local, administration of naltrexone, a specific opioid antagonist, reversed the hypoalgesia induced by paracetamol, but similar naltrexone treatment had no effect on dipyrone-induced analgesia.

CONCLUSIONS AND IMPLICATIONS

Although both paracetamol and dipyrone are inhibitors of COX isoforms and thus of prostaglandin biosynthesis and were analgesic in our model, their analgesic actions were functionally and mechanistically different. Satisfactory mechanisms of action for these analgesics still remain to be established.

B vitamins induce an antinociceptive effect in the acetic acid and formaldehyde models of nociception in mice

The effect of some B vitamins in chemical and thermal models of nociception in mice was investigated. The association thiamine/pyridoxine/cyanocobalamin (TPC, 20-200 mg/kg, i.p. or per os), thiamine, pyridoxine (50-200 mg/kg, i.p.) or riboflavin (3-100 mg/kg, i.p) induced an antinociceptive effect, not changed by naloxone (10 mg/kg, i.p.), in the acetic acid writhing model. Treatment for 7 days with thiamine/pyridoxine/cyanocobalamin (100 or 200 mg/kg, i.p.), thiamine (50 or 100 mg/kg) or pyridoxine (50 or 100 mg/kg) or acute treatment with riboflavin (6 or 12 mg/kg, i.p) inhibited the nociceptive response induced by formaldehyde. The B vitamins did not inhibit the nociceptive response in the hot-plate model. Both 7-day thiamine/pyridoxine/cyanocobalamin (100 mg/kg, i.p.) or acute riboflavin (25 or 50 mg/kg, i.p.) treatment partially reduced formaldehyde-induced hindpaw oedema. The B vitamins antinociceptive effect may involve inhibition of the synthesis and/or action of inflammatory mediators since it was not observed in the hot-plate model, was not reversed by naloxone, only the second phase of the formaldehyde-induced nociceptive response was inhibited, and formaldehyde-induced hindpaw oedema was reduced.