Experimental determination of the Berry phase in a superconducting charge pump

We present the first measurements of the Berry phase in a superconducting Cooper pair pump. A fixed amount of Berry phase is accumulated to the quantum-mechanical ground state in each adiabatic pumping cycle, which is determined by measuring the charge passing through the device. The dynamic and geometric phases are identified and measured quantitatively from their different response when pumping in opposite directions. Our observations, in particular, the dependencies of the dynamic and geometric effects on the superconducting phase bias across the pump, agree with the basic theoretical model of coherent Cooper pair pumping.Comment: 4 pages, 3 figure

Measurement scheme of the Berry phase in superconducting circuits

We present a measurement scheme for observing the Berry phase in a flux assisted Cooper pair pump - the Cooper pair sluice. In contrast to the recent experiments, in which the sluice was employed to generate accurate current through a resistance, we consider a device in a superconducting loop. This arrangement introduces a connection between the pumped current and the Berry phase accumulated during the adiabatic pumping cycles. From the adiabaticity criterion, we derive equations for the maximum pumped current and optimize the sluice accordingly. These results apply also to the high accuracy pumping which results in a potential candidate for a metrological current standard. For measuring the pumped current, an additional Josephson junction is installed into the superconducting loop. We show in detail that the switching of this system from superconducting state into normal state as a consequence of an external current pulse through it may be employed to probe the pumped current. The experimental realization of our scheme would be the first observation of the Berry phase in superconducting circuits.Comment: 19 pages, 5 figure

Nanoampere pumping of Cooper pairs

The authors have employed a tunable Cooper-pair transistor, the sluice, with radio frequency control to pump current over a resistive circuit. They find that the charge transferred per pumping cycle can be controlled with the resolution of a single Cooper pair up to hundreds of pairs. The achieved nanoampere current features more than an order of magnitude improvement over the previously reported results and it is close to the theoretical maximum value for the measured sample.Peer reviewe

Worse health-related quality of life, impaired functioning and psychiatric comorbidities are associated with excess mortality in patients with severe chronic pain

Background Severe chronic pain that interferes with daily activities is associated with an increased risk of mortality. We assessed the overall mortality of tertiary chronic pain patients in comparison with the general population, with a special aim to analyse the association of health-related quality of life (HRQoL) and its dimensions with the risk of death. Methods In this prospective observational follow-up study, patients with non-cancer chronic pain attended an outpatient multidisciplinary pain management (MPM) episode in a tertiary pain clinic in 2004-2012 and were followed until May 2019. Mortality between the patients and the general population was compared with standardized mortality ratios (SMR) in different age groups. Causes of death and comorbidities were compared among the deceased. Association of mortality and HRQoL and its dimensions, measured with the 15D instrument, was studied with Cox proportional hazards model. Results During a mean of 10.4-year follow-up of 1498 patients, 296 died. The SMR in the youngest age group (18-49 years) was significantly higher than that of the general population: 2.6 for males and 2.9 for females. Even elderly females (60-69 years) had elevated mortality (SMR 2.3). Low baseline HRQoL at the time of MPM, as well as poor ratings in the psychosocial dimensions of HRQoL, was associated with an increased risk of death. Conclusions Our results support the role of HRQoL measurement by a validated instrument such as the 15D in capturing both the physical and the psychological symptom burden, and consequently, an elevated risk of death, in patients with chronic pain. Significance Severe chronic pain is associated with elevated mortality. In patients in chronic pain under 50 years old, the mortality was 2.5-3 times higher than in the general population. Psychological distress appears to contribute to the increased mortality. Regular follow-up by health-related quality of life (HRQoL) measurement could be useful in identifying patients in chronic pain who are in need of intensive symptom management and to prevent early death.Peer reviewe

Shot-noise-driven escape in hysteretic Josephson junctions

We have measured the influence of shot noise on hysteretic Josephson junctions initially in macroscopic quantum tunnelling (MQT) regime. Escape threshold current into the resistive state decreases monotonically with increasing average current through the scattering conductor, which is another tunnel junction. Escape is predominantly determined by excitation due to the wide-band shot noise. This process is equivalent to thermal activation (TA) over the barrier at temperatures up to about four times above the critical temperature of the superconductor. The presented TA model is in excellent agreement with the experimental results

Twinfilin is required for actin-dependent developmental processes in Drosophila

The actin cytoskeleton is essential for cellular remodeling and many developmental and morphological processes. Twinfilin is a ubiquitous actin monomer-binding protein whose biological function has remained unclear. We discovered and cloned the Drosophila twinfilin homologue, and show that this protein is ubiquitously expressed in different tissues and developmental stages. A mutation in the twf gene leads to a number of developmental defects, including aberrant bristle morphology. This results from uncontrolled polymerization of actin filaments and misori-entation of actin bundles in developing bristles. In wildtype bristles, twinfilin localizes diffusively to cytoplasm and to the ends of actin bundles, and may therefore be involved in localization of actin monomers in cells. We also show that twinfilin and the ADF/cofilin encoding gene twinstar interact genetically in bristle morphogenesis. These results demonstrate that the accurate regulation of size and dynamics of the actin monomer pool by twinfilin is essential for a number of actin-dependent developmental processes in multicellular eukaryotes

Quantum circuits with uniformly controlled one-qubit gates

Uniformly controlled one-qubit gates are quantum gates which can be represented as direct sums of two-dimensional unitary operators acting on a single qubit. We present a quantum gate array which implements any n-qubit gate of this type using at most 2^{n-1} - 1 controlled-NOT gates, 2^{n-1} one-qubit gates and a single diagonal n-qubit gate. The circuit is based on the so-called quantum multiplexor, for which we provide a modified construction. We illustrate the versatility of these gates by applying them to the decomposition of a general n-qubit gate and a local state preparation procedure. Moreover, we study their implementation using only nearest-neighbor gates. We give upper bounds for the one-qubit and controlled-NOT gate counts for all the aforementioned applications. In all four cases, the proposed circuit topologies either improve on or achieve the previously reported upper bounds for the gate counts. Thus, they provide the most efficient method for general gate decompositions currently known.Comment: 8 pages, 10 figures. v2 has simpler notation and sharpens some result

The three mouse actin-depolymerizing factor/cofilins evolved to fulfill cell-type-specific requirements for actin dynamics

Actin-depolymerizing factor (ADF)/cofilins are essential regulators of actin filament turnover. Several ADF/cofilin isoforms are found in multicellular organisms, but their biological differences have remained unclear. Herein, we show that three ADF/cofilins exist in mouse and most likely in all other mammalian species. Northern blot and in situ hybridization analyses demonstrate that cofilin-1 is expressed in most cell types of embryos and adult mice. Cofilin-2 is expressed in muscle cells and ADF is restricted to epithelia and endothelia. Although the three mouse ADF/cofilins do not show actin isoform specificity, they all depolymerize platelet actin filaments more efficiently than muscle actin. Furthermore, these ADF/cofilins are biochemically different. The epithelial-specific ADF is the most efficient in turning over actin filaments and promotes a stronger pH-dependent actin filament disassembly than the two other isoforms. The muscle-specific cofilin-2 has a weaker actin filament depolymerization activity and displays a 5-10-fold higher affinity for ATP-actin monomers than cofilin-1 and ADF. In steady-state assays, cofilin-2 also promotes filament assembly rather than disassembly. Taken together, these data suggest that the three biochemically distinct mammalian ADF/cofilin isoforms evolved to fulfill specific requirements for actin filament dynamics in different cell types