95 research outputs found
Benchmarking the noise sensitivity of different parametric two-qubit gates in a single superconducting quantum computing platform
The possibility to utilize different types of two-qubit gates on a single
quantum computing platform adds flexibility in the decomposition of quantum
algorithms. A larger hardware-native gate set may decrease the number of
required gates, provided that all gates are realized with high fidelity. Here,
we benchmark both controlled-Z (CZ) and exchange-type (iSWAP) gates using a
parametrically driven tunable coupler that mediates the interaction between two
superconducting qubits. Using randomized benchmarking protocols we estimate an
error per gate of and fidelity for the CZ and the
iSWAP gate, respectively. We argue that spurious -type couplings are the
dominant error source for the iSWAP gate, and that phase stability of all
microwave drives is of utmost importance. Such differences in the achievable
fidelities for different two-qubit gates have to be taken into account when
mapping quantum algorithms to real hardware.Comment: 24 pages, including supplementary informatio
Geometric Phase and Non-Adiabatic Effects in an Electronic Harmonic Oscillator
Steering a quantum harmonic oscillator state along cyclic trajectories leads
to a path-dependent geometric phase. Here we describe an experiment observing
this geometric phase in an electronic harmonic oscillator. We use a
superconducting qubit as a non-linear probe of the phase, otherwise
unobservable due to the linearity of the oscillator. Our results demonstrate
that the geometric phase is, for a variety of cyclic trajectories, proportional
to the area enclosed in the quadrature plane. At the transition to the
non-adiabatic regime, we study corrections to the phase and dephasing of the
qubit caused by qubit-resonator entanglement. The demonstrated controllability
makes our system a versatile tool to study adiabatic and non-adiabatic
geometric phases in open quantum systems and to investigate the potential of
geometric gates for quantum information processing
Microwave-controlled generation of shaped single photons in circuit quantum electrodynamics
Large-scale quantum information processors or quantum communication networks
will require reliable exchange of information between spatially separated
nodes. The links connecting these nodes can be established using traveling
photons that need to be absorbed at the receiving node with high efficiency.
This is achievable by shaping the temporal profile of the photons and absorbing
them at the receiver by time reversing the emission process. Here, we
demonstrate a scheme for creating shaped microwave photons using a
superconducting transmon-type three-level system coupled to a transmission line
resonator. In a second-order process induced by a modulated microwave drive, we
controllably transfer a single excitation from the third level of the transmon
to the resonator and shape the emitted photon. We reconstruct the density
matrices of the created single-photon states and show that the photons are
antibunched. We also create multipeaked photons with a controlled amplitude and
phase. In contrast to similar existing schemes, the one we present here is
based solely on microwave drives, enabling operation with fixed frequency
transmons
Geometric phases in superconducting qubits beyond the two-level-approximation
Geometric phases, which accompany the evolution of a quantum system and
depend only on its trajectory in state space, are commonly studied in two-level
systems. Here, however, we study the adiabatic geometric phase in a weakly
anharmonic and strongly driven multi-level system, realised as a
superconducting transmon-type circuit. We measure the contribution of the
second excited state to the two-level geometric phase and find good agreement
with theory treating higher energy levels perturbatively. By changing the
evolution time, we confirm the independence of the geometric phase of time and
explore the validity of the adiabatic approximation at the transition to the
non-adiabatic regime.Comment: 5 pages, 3 figure
Characterization and tomography of a hidden qubit
In circuit-based quantum computing, the available gate set typically consists
of single-qubit gates acting on each individual qubit and at least one
entangling gate between pairs of qubits. In certain physical architectures,
however, some qubits may be 'hidden' and lacking direct addressability through
dedicated control and readout lines, for instance because of limited on-chip
routing capabilities, or because the number of control lines becomes a limiting
factor for many-qubit systems. In this case, no single-qubit operations can be
applied to the hidden qubits and their state cannot be measured directly.
Instead, they may be controlled and read out only via single-qubit operations
on connected 'control' qubits and a suitable set of two-qubit gates. We first
discuss the impact of such restricted control capabilities on the quantum
volume of specific qubit coupling networks. We then experimentally demonstrate
full control and measurement capabilities in a superconducting two-qubit device
with local single-qubit control and iSWAP and controlled-phase two-qubit
interactions enabled by a tunable coupler. We further introduce an iterative
tune-up process required to completely characterize the gate set used for
quantum process tomography and evaluate the resulting gate fidelities
Temporal and Spatial Impact of Human Cadaver Decomposition on Soil Bacterial and Arthropod Community Structure and Function
As vertebrate carrion decomposes, there is a release of nutrient-rich fluids into theunderlying soil, which can impact associated biological community structure andfunction. How these changes alter soil biogeochemical cycles is relatively unknown and may prove useful in the identification of carrion decomposition islands that have long lasting, focal ecological effects. This study investigated the spatial (0, 1, and 5 m) and temporal (3–732 days) dynamics of human cadaver decomposition on soil bacterial and arthropod community structure and microbial function. We observed strong evidence of a predictable response to cadaver decomposition that varies over space for soil bacterial and arthropod community structure, carbon (C) mineralization and microbial substrate utilization patterns. In the presence of a cadaver (i.e., 0 m samples), the relative abundance of Bacteroidetes and Firmicutes was greater, while the relative abundance of Acidobacteria, Chloroflexi, Gemmatimonadetes, and Verrucomicrobia was lower when compared to samples at 1 and 5 m. Micro-arthropods were more abundant (15 to 17-fold) in soils collected at 0 m compared to either 1 or 5 m, but overall, micro-arthropod community composition was unrelated to either bacterial community composition or function. Bacterial community structure and microbial function also exhibited temporal relationships, whereas arthropod community structure did not. Cumulative precipitation was more effective in predicting temporal variations in bacterial abundance and microbial activity than accumulated degree days. In the presence of the cadaver (i.e., 0 m samples), the relative abundance of Actinobacteria increased significantly with cumulative precipitation. Furthermore, soil bacterial communities and C mineralization were sensitive to the introduction of human cadavers as they diverged from baseline levels and did not recover completely in approximately 2 years. These data are valuable for understanding ecosystem function surrounding carrion decomposition islands and can be applicable to environmental bio-monitoring and forensic sciences
Microbial Biofilm Community Variation in Flowing Habitats: Potential Utility as Bioindicators of Postmortem Submersion Intervals
Biofilms are a ubiquitous formation of microbial communities found on surfaces in aqueous environments. These structures have been investigated as biomonitoring indicators for stream heath, and here were used for the potential use in forensic sciences. Biofilm successional development has been proposed as a method to determine the postmortem submersion interval (PMSI) of remains because there are no standard methods for estimating the PMSI and biofilms are ubiquitous in aquatic habitats. We sought to compare the development of epinecrotic (biofilms on Sus scrofa domesticus carcasses) and epilithic (biofilms on unglazed ceramic tiles) communities in two small streams using bacterial automated ribosomal intergenic spacer analysis. Epinecrotic communities were significantly different from epilithic communities even though environmental factors associated with each stream location also had a significant influence on biofilm structure. All communities at both locations exhibited significant succession suggesting that changing communities throughout time is a general characteristic of stream biofilm communities. The implications resulting from this work are that epinecrotic communities have distinctive shifts at the first and second weeks, and therefore the potential to be used in forensic applications by associating successional changes with submersion time to estimate a PMSI. The influence of environmental factors, however, indicates the lack of a successional pattern with the same organisms and a focus on functional diversity may be more applicable in a forensic context
Total RNA Analysis of Bacterial Community Structural and Functional Shifts Throughout Vertebrate Decomposition
Multiple methods have been proposed to provide accurate time since death estimations, and recently, the discovery of bacterial community turnover during decomposition has shown itself to have predictable patterns that may prove useful. In this study, we demonstrate the use of metatranscriptomics from the postmortem microbiome to simultaneously obtain community structure and functional data across postmortem intervals (PMIs). We found that bacterial succession patterns reveal similar trends as detected through DNA analysis, such as increasing Clostridiaceae as decomposition occurs, strengthening the reliability of total RNA community analyses. We also provide one of the first analyses of RNA transcripts to characterize bacterial metabolic pathways during decomposition. We found distinct pathways, such as amino acid metabolism, to be strongly up‐regulated with increasing PMIs. Elucidating the metabolic activity of postmortem microbial communities provides the first steps to discovering postmortem functional biomarkers since functional redundancy across bacteria may reduce host individual microbiome variability.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152033/1/jfo14083_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152033/2/jfo14083.pd
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