Exploring large-scale entanglement in quantum simulation

Entanglement is a distinguishing feature of quantum many-body systems, and uncovering the entanglement structure for large particle numbers in quantum simulation experiments is a fundamental challenge in quantum information science1. Here we perform experimental investigations of entanglement on the basis of the entanglement Hamiltonian (EH)2 as an effective description of the reduced density operator for large subsystems. We prepare ground and excited states of a one-dimensional XXZ Heisenberg chain on a 51-ion programmable quantum simulator3 and perform sample-efficient 'learning' of the EH for subsystems of up to 20 lattice sites4. Our experiments provide compelling evidence for a local structure of the EH. To our knowledge, this observation marks the first instance of confirming the fundamental predictions of quantum field theory by Bisognano and Wichmann5,6, adapted to lattice models that represent correlated quantum matter. The reduced state takes the form of a Gibbs ensemble, with a spatially varying temperature profile as a signature of entanglement2. Our results also show the transition from area- to volume-law scaling7 of von Neumann entanglement entropies from ground to excited states. As we venture towards achieving quantum advantage, we anticipate that our findings and methods have wide-ranging applicability to revealing and understanding entanglement in many-body problems with local interactions including higher spatial dimensions.

Quantum-enhanced sensing on optical transitions through finite-range interactions

The control over quantum states in atomic systems has led to the most precise optical atomic clocks so far1-3. Their sensitivity is bounded at present by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated particles, which can-nevertheless-be overcome when operated with entangled particles. Yet demonstrating a quantum advantage in real-world sensors is extremely challenging. Here we illustrate a pathway for harnessing large-scale entanglement in an optical transition using 1D chains of up to 51 ions with interactions that decay as a power-law function of the ion separation. We show that our sensor can emulate many features of the one-axis-twisting (OAT) model, an iconic, fully connected model known to generate scalable squeezing4 and Greenberger-Horne-Zeilinger-like states5-8. The collective nature of the state manifests itself in the preservation of the total transverse magnetization, the reduced growth of the structure factor, that is, spin-wave excitations (SWE), at finite momenta, the generation of spin squeezing comparable with OAT (a Wineland parameter9,10 of -3.9 ± 0.3 dB for only N = 12 ions) and the development of non-Gaussian states in the form of multi-headed cat states in the Q-distribution. We demonstrate the metrological utility of the states in a Ramsey-type interferometer, in which we reduce the measurement uncertainty by -3.2 ± 0.5 dB below the standard quantum limit for N = 51 ions.

Observing emergent hydrodynamics in a long-range quantum magnet

Identifying universal properties of nonequilibrium quantum states is a major challenge in modern physics. A fascinating prediction is that classical hydrodynamics emerges universally in the evolution of any interacting quantum system. We experimentally probed the quantum dynamics of 51 individually controlled ions, realizing a long-range interacting spin chain. By measuring space-time-resolved correlation functions in an infinite temperature state, we observed a whole family of hydrodynamic universality classes, ranging from normal diffusion to anomalous superdiffusion, that are described by Lévy flights. We extracted the transport coefficients of the hydrodynamic theory, reflecting the microscopic properties of the system. Our observations demonstrate the potential for engineered quantum systems to provide key insights into universal properties of nonequilibrium states of quantum matter.

Quantum Information Scrambling in a Trapped-Ion Quantum Simulator with Tunable Range Interactions

In ergodic many-body quantum systems, locally encoded quantum information becomes, in the course of time evolution, inaccessible to local measurements. This concept of "scrambling" is currently of intense research interest, entailing a deep understanding of many-body dynamics such as the processes of chaos and thermalization. Here, we present first experimental demonstrations of quantum information scrambling on a 10-qubit trapped-ion quantum simulator representing a tunable long-range interacting spin system, by estimating out-of-time ordered correlators (OTOCs) through randomized measurements. We also analyze the role of decoherence in our system by comparing our measurements to numerical simulations and by measuring Rényi entanglement entropies.

Cross-Platform Verification of Intermediate Scale Quantum Devices

We describe a protocol for cross-platform verification of quantum simulators and quantum computers. We show how to measure directly the overlap Tr[ρ_{1}ρ_{2}] and the purities Tr[ρ_{1,2}^{2}], and thus a fidelity of two, possibly mixed, quantum states ρ_{1} and ρ_{2} prepared in separate experimental platforms. We require only local measurements in randomized product bases, which are communicated classically. As a proof of principle, we present the measurement of experiment-theory fidelities for entangled 10-qubit quantum states in a trapped ion quantum simulator.

Acceptability and feasibility of mini-clinical evaluation exercise as a formative assessment tool for workplace-based assessment for surgical postgraduate students

Background:

Despite an increasing emphasis on workplace-based assessment (WPBA) during medical training, the existing assessment system largely relies on summative assessment while formative assessment is less valued. Various tools have been described for WPBA, mini-clinical evaluation exercise (mini-CEX) being one of them. Mini-CEX is well accepted in Western countries, however, reports of its use in India are scarce. We conducted this study to assess acceptability and feasibility of mini-CEX as a formative assessment tool for WPBA of surgical postgraduate students in an Indian setting.

Methods:

Faculty members and 2^nd year surgical residents were sensitized toward mini-CEX and requisite numbers of exercises were conducted. The difficulties during conduction of these exercises were identified, recorded, and appropriate measures were taken to address them. At the conclusion, the opinion of residents and faculty members regarding their experience with mini-CEX was taken using a questionnaire. The results were analyzed using simple statistical tools.

Results:

Nine faculty members out of 11 approached participated in the study (81.8%). All 16 2^nd year postgraduate surgical residents participated (100%). Sixty mini-CEX were conducted over 7 months. Each resident underwent 3–5 encounters. The mean time taken by the assessor for observation was 12.3 min (8–30 min) while the mean feedback time was 4.2 min (3–10 min). The faculty reported good overall satisfaction with mini-CEX and found it acceptable as a formative assessment tool. Three faculty members (33.3%) reported mini-CEX as more time-consuming while 2 (22.2%) found it difficult to carry the exercises often. All residents accepted mini-CEX and most of them reported good to high satisfaction with the exercises conducted.

Conclusions:

Mini-CEX is well accepted by residents and faculty as a formative assessment tool. It is feasible to utilize mini-CEX for WPBA of postgraduate students of surgery.

Information literacy competency of post graduate students at Haryana Agricultural University and impact of instruction initiatives

Purpose

Since the education of Master of Science students in the discipline of agriculture is catalectic without libraries, the present paper seeks to assess the information literacy competency (ILC) of post graduate (PG) students at Haryana Agricultural University, Hisar, India, along with the impact of instruction initiatives in this respect.

Design/methodology/approach

Based on the Association of College and Research Libraries (ACRL) Information Literacy Standards for Science and Engineering/Technology, 2006, an instrument was developed with 79 scoring items in the first part of the questionnaire along with non‐scoring items in the second part. Broad headings of the questions asked are shown in detail. Validity and reliability of the instrument are also reported.

Findings

Information literacy competency of PG students has been found satisfactory along with significant difference between the first and second year students. Results of the paper distinguish between the first and second year students in the light of five information literacy (IL) standards along with other considerations. Various instruction initiatives were found to have a positive impact upon the ILC of PG students.

Practical implications

Since the study has been able to establish a positive relationship between instruction initiatives and ILC, such initiatives may be introduced in other academic institutions.

Originality/value

None of the earlier reported research instruments had used science and engineering/technology IL standards, especially upon PG students in agriculture. This study further paved the way for the development of such an nstrument along with assessing the ILC of PG students and impact of instruction initiatives in an agricultural university.

On the kinetics of voltage formation in purple membranes of Halobacterium salinarium

The kinetics of the bacteriorhodopsin photocycle, measured by voltage changes in a closed membrane system using the direct electrometrical method (DEM) of Drachev, L.A., Jasaitus, A.A., Kaulen, A.D., Kondrashin, A.A., Liberman, E.A., Nemecek, I.B., Ostroumov, S.A., Semenov, Yu, A. & Skulachev, V.P. (1974) Nature 249, 321-324 are sixfold slower than the kinetics obtained in optical studies with suspensions of purple membrane patches. In this study, we have investigated the reasons for this discrepancy. In the presence of the uncouplers carbonyl cyanide m-chlorophenylhydrazone or valinomycin, the rates in the DEM system are similar to the rates in suspensions of purple membrane. Two alternative explanations for the effects of uncouplers were evaluated: (a) the 'back-pressure' of the Deltamicro;H+ slows the kinetic steps leading to its formation, and (b) the apparent difference between the two systems is due to slow major electrogenic events that produce little or no change in optical absorbance. In the latter case, the uncouplers would decrease the RC time constant for membrane capacitance leading to a quicker discharge of voltage and concomitant decrease in photocycle turnover time. The experimental results show that the primary cause for the slower kinetics of voltage changes in the DEM system is thermodynamic back-pressure as described by Westerhoff, H.V. & Dancshazy, Z. (1984) Trends Biochem. Sci. 9, 112-117.

Acute rhabdomyolysis and renal failure in HIV-infected patients: risk factors, presentation, and pathophysiology

Rhabdomyolysis is a common cause of acute renal failure and may be related to a variety of predisposing factors. This entity has been increasingly recognized in HIV-infected individuals and is an important cause of morbidity and mortality. We present a series of seven HIV-positive patients admitted with rhabdomyolysis over a 5-year period; three developed acute renal failure. Infections and substance abuse were the most common risk factors identified; an average of three predisposing factors was present in each case. All patients showed resolution of creatinine phosphokinase (CPK) elevation and serum creatinine returned to the normal range in the three patients who developed renal insufficiency; however, all patients required prolonged hospitalization and one patient died of sepsis. The pathophysiological mechanisms of muscle injury in our patients are reviewed and their bearing on prognosis discussed. It is concluded that clinicians should have a high index of suspicion for the development of rhabdomyolysis in HIV-infected patients with a combination of noncompliance with medical therapy and/or substance abuse and acute infection. With comprehensive supportive care, the prognosis of acute rhabdomyolysis in this population may be reasonably good.

Regulation of the bacteriorhodopsin photocycle and proton pumping in whole cells of Halobacterium salinarium

Single-turnover kinetics of the bacteriorhodopsin photocycle and proton-pumping capabilities of whole cells were studied. It was found that the Delta mu (tilde)H+ of the cell had a profound influence on the kinetics and components of the cycle. For example, comparing the photocycle in whole cells to that seen in PM preparations, we found that (1) the single-turnover time of the cycle was increased approximately 10-fold, (2) the mole fraction of M-fast (at high actinic light) decreased from 50 to 20%, and (3) the time constant for M-slow increased significantly. The level of Delta mu(tilde)H+ was dependent on respiration, ATP formation and breakdown, and the magnitude of a pre-existing K+ diffusion gradient. The size of the Delta mu(tilde)H+ could be manipulated by additions of HCN, nigericin, and DCCD (N,N'-dicyclohexylcarbodamide). At higher levels of Delta mu(tilde)H+, further changes in the photocycle were seen. (4) Two slower components of M-decay appeared as major components. (5) The apparent conversion of the M-fast to the O intermediate disappeared. (6) A partial reversal of an early photocycle step occurred. The photocycle of intact cells could be changed to that seen in purple membrane suspensions by the energy-uncoupler CCCP or by lysis of the cells. In fresh whole cells, light-induced proton pumping was not seen until the K+ diffusion potential was dissipated and proton accumulation facilitated by use of a K+-H+ exchanger (nigericin), respiration was inhibited by HCN, and ATP synthesis and breakdown were inhibited by DCCD. In stored cells, the pre-existing K+ diffusion gradient was diminished through slow diffusion, and only DCCD and HCN were required to elicit proton extrusion.

Importance of specific native lipids in controlling the photocycle of bacteriorhodopsin

Brief treatment of purple membrane (PM) with dilute detergent can cause major disruption of the BR photocycle without disrupting the trimer structure of BR [Mukhopadhyay et al. (1996) Biochemistry 35, 9245-9252]. Normal photocyle behavior can be recovered by incubating the damaged membranes with a total extract of the five types of native lipids present in PM. It is shown here that full restoration can also be obtained with combinations of squalene (SQ) and phosphatidyl glycerophosphate (PGP) which act synergistically. The addition of SQ to suboptimal levels of PGP induces complete reconstitution, principally by restoring the characteristics of the fast M intermediate, Mf (as defined in Mukhopadhyay et al. (1996) Biochemistry 35, 9245-9252). The addition of small amounts of PGP to SQ, which alone is ineffective, also induces full reconstituion. At very high levels, full reconstitution can be obtained with PGP alone. These results, in combination with earlier studies which implicate an acidic amino acid residue [Bose et al. (1997) J. Phys. Chem. B 101, 10584-10587], suggest that a crucial interaction between a particular amino acid residue and a SQ-PGP lipid complex may be essential for normal BR photocycle activity.

Picrate Salt of a Cyclic Polyether, 18-Crown-6 (Ca-picrate-18-crown-6), Inhibits the Photosynthetic Electron Transport at the Acceptor Side of Photosystem II

It has been demonstrated that cyclic polyether, K -picrate-18-crown-6 inhibited photosyn­ thetic electron transport (Sabat et al., 1991, Z. Naturforsch. 46c , 87-92) . We further analyzed the alterations induced in the fast chlorophyll a fluorescence and thermoluminescence pattern of pea thylakoids by calcium-18-crown-6 (crown-picrate). The results indicate that the site of action of calcium crown-picrate is at the acceptor side of photosystem II.

Lipoprotein lipase deficiency

A rare case of a 3 month old child with lipoprotein lipase deficiency who presented with bronchopneumonia is reported. After noticing lipaemic serum and lipaemia retinalis, a diagnosis of hyperlipoproteinaemia was considered. Lipoprotein lipase deficiency was confirmed with post heparin lipoprotein lipase enzyme activity estimation.

Inhibition of State Transition and Light-Harvesting Complex II Phosphorylation-Mediated Changes in Excitation Energy Distribution in the Thylakoids of SANDOZ 9785-Treated Plants

Thylakoids isolated from SAN 9785 (4-chloro-5-dimethylamino-2-phenyl-3(2H)-pyridazi-none)-treated pea plants showed an inhibition of “state transition” and the light-harvesting complex II (LHC II) phosphorylation-mediated changes in the energy distribution between photosystem II (PS II) and photosystem I (PS I) as measured by a decrease in PS II and an increase in PS I fluorescence yield. Interestingly, in these thylakoids the extent of phosphorylation-induced migration of light-harvesting complex (LHC II-P) to non-appressed mem­brane regions was only marginally inhibited. We propose that the suppression in the ability for “state transition” by SANDOZ 9785 (SAN 9785) treatment occurs due to a lack of effec­tive coupling of the migrated LHC II-P and PS I. Since we observed a decrease in the antenna size of PS I of the treated plants, the lack of effective coupling is attributed to this decrease in the antenna size of PS I.

Polymorphonuclear leukocyte functions in patients with acute rheumatic fever and rheumatic heart disease

Polymorphonuclear (PMN) cell function was assessed in 30 children with active rheumatic fever (ARF) (Group I), 30 cases with active rheumatic heart disease (RHD) (Group II), 28 cases of ARF and RHD in remission (Group III) and 34 adults with quiescent RHD along with their age matched controls. All the groups showed normal spontaneous and chemotactic movement. Phagocytosis of yeast particles was significantly reduced in groups II (P less than 0.0005), III (P less than 0.025) and IV (P less than 0.005). The opsonic activity of disease sera was low in all 4 groups (P less than 0.0005). The intracellular metabolic activity was moderately elevated in Group III. Phagocytosis and opsonic activity were thus persistently low in all the groups including the remission and quiescent group.

Comparative evaluation of antipyretic activity of ibuprofen and aspirin in children with pyrexia of varied aetiology

The antipyretic activity of ibuprofen and aspirin was compared in sixteen children with pyrexia due to upper respiratory tract infection and in twelve with fever due to other causes. All 28 children received ibuprofen (7 mg/kg of body-weight) and aspirin (15 mg/kg of body-weight) in a single dose on 2 consecutive days in a crossover manner. Rectal temperature was recorded prior to and at regular intervals up to 8 hours after drug administration. Analysis of the results indicate that ibuprofen and aspirin effectively lower temperature and the two drugs are comparable in their antipyretic activity. In conclusion, significant antipyretic activity, good tolerance profile and availability in syrup form make ibuprofen a useful substitute for aspirin in children with fever.