We show that parametric coupling techniques can be used to generate selective entangling interactions for multi-qubit processors. By inducing coherent population exchange between adjacent qubits ...under frequency modulation, we implement a universal gate set for a linear array of four superconducting qubits. An average process fidelity of ℱ = 93% is estimated for three two-qubit gates via quantum process tomography. We establish the suitability of these techniques for computation by preparing a four-qubit maximally entangled state and comparing the estimated state fidelity with the expected performance of the individual entangling gates. In addition, we prepare an eight-qubit register in all possible bitstring permutations and monitor the fidelity of a two-qubit gate across one pair of these qubits. Across all these permutations, an average fidelity of ℱ = 91.6 ± 2.6% is observed. These results thus offer a path to a scalable architecture with high selectivity and low cross-talk.
This thesis begins with an introduction on the theory of general relativity and gravitational waves. Common astrophysical sources are described in Chapter 2. Chapter 3 begins with a description of ...the installed instrument. A discussion on the detector design sensitivity, limiting noise sources, and estimated detection rates is also given. At the end of Chapte 3, the complications of lock acquisition are highlighted. The arm length stabilization system was introduced to Advanced LIGO as a partial way to solve the difficulties of locking. Chapter 4 discusses the motivation for the use of this scheme and explains the methodology. A detailed discussion on the arm length stabilization model is given, along with the noise budget in Chapters 5 and 6 respectively. The full lock sequence is described in Chapter 7. The thesis concludes with the current status of the interferometers. (Abstract shortened by UMI.)
The Advanced LIGO gravitational wave detectors have recently achieved a new milestone. The two detector network is now operational and is being tuned for sensitivity. Currently, the state of the art ...detectors are the most sensitive ground-based interferometers to date and are closer than ever to the reality of a gravitational wave detection.
For many years, there has been a worldwide effort to directly detect gravitational waves, a phenomena that was predicted in Einstein's theory of general relativity. A direct detection would further validate Einstein's theory, but more importantly would provide a novel approach to studying the universe and the elusive physics of gravity beyond Einstein's theory.
However, none of this would be possible without the success of the arm length stabilization scheme. This recently demonstrated technique, which will be the focus of this thesis, is a critical step required to get the LIGO interferometers operational. This scheme is unique to the advanced generations of detectors and is extremely valuable for such a complex instrument. As part of my research, I characterized, modeled, and helped design this important technique. I was also a part of a small team that brought the LIGO Hanford interferometer to its operational point for the first time.
For astrophysical reasons, the goal of Advanced LIGO's design is to measure a gravitational strain as small as 4x10⁻²⁴/rtHz, requiring a length resolution of approximately 10⁻¹⁹ m. This high sensitivity demands multiple optical cavities to enhance the response of the interferometer. The interferometer is a Michelson interferometer geometry consisting of two 4km arm cavities, whose differential length is measured by the phase change of a resonating infrared laser at the gravitational wave readout port. The Michelson interferometer is enhanced by Fabry-Perot arm cavities, a power recycling cavity, and a signal extraction cavity. The Fabry-Perot arm cavities effectively increase the arm lengths by two orders of magnitude. Meanwhile, the power recycling cavity is used to enhance the circulating power within the interferometer, and the signal extraction cavity is used to enhance the optical response at the gravitational-wave readout.
Besides the increased design sensitivity of Advanced LIGO, a crucial requirement for a gravitational wave detection will be a high duty cycle. As an example, a worldwide Advanced LIGO network of five detectors, each with an 80% up-time, would only produce about 30% network up-time. A deterministic, robust, and fast sequence to transition the interferometer from an uncontrolled to a controlled state is mandatory. Advanced LIGO has five longitudinal degrees of freedom which must be controlled in order for the interferometer to be operational. However, all degrees of freedom are strongly coupled making this a traditionally challenging process. The state of the arm cavities can completely alter the state of the dual-recycled Michelson interferometer. Active feedback control is required to operate these instruments and keep the cavities locked on resonance. The optical response is highly non-linear until a good operating point is reached. The linear operating range is between 0.01% and 1% of a fringe for each degree of freedom. The resonance lock has to be achieved in all five degrees of freedom simultaneously, making the acquisition difficult. Furthermore, the cavity linewidth seen by the laser is only ~1Hz which is four orders of magnitude smaller than the linewdith of the free running laser. To mitigate several of these critical problems, a new arm length stabilization technique was introduced to the lock sequence. The arm length stabilization technique utilizes two additional green lasers that are brought into resonance in each arm cavity. This effectively decouples the arm cavities from the rest of the interferometer. While the main infrared beam is kept off resonance from the arm cavity, a modulation technique utilizing third harmonics locks the central dual-recycled Michelson interferometer. In the final step, both arm cavities are slowly tuned onto resonance, nominal sensors are used, and full lock is achieved.
To ensure a high duty cycle for Advanced LIGO and confirm repeatability of the locking sequence, a detailed study and characterization of the arm length stabilization technique was conducted. A model of the scheme and a noise budget was developed. The model was beneficial while designing and implementing the scheme for the first time at the Advanced LIGO observatories. Meanwhile, the noise budget was critical to determine if this scheme would be viable in the lock process. Ultimately, the advent of the arm length stabilization to the lock process has been successful, a decisive milestone for future prospect of collecting meaningful astrophysical data. The technique has been implemented at both detectors and proven reliable and robust. Given the complexity of the interferometers, the success of this scheme to bring the detectors operational was a large accomplishment for the collaboration. With the technique's repeatable performance, efforts can be focused on tuning the interferometers sensitivity and achieving a first direct detection.
This thesis begins with an introduction on the theory of general relativity and gravitational waves. Common astrophysical sources are described in Chapter 2. Chapter 3 begins with a description of the installed instrument. A discussion on the detector design sensitivity, limiting noise sources, and estimated detection rates is also given. At the end of Chapter 3, the complications of lock acquisition are highlighted. The arm length stabilization system was introduced to Advanced LIGO as a partial way to solve the difficulties of locking. Chapter 4 discusses the motivation for the use of this scheme and explains the methodology. A detailed discussion on the arm length stabilization model is given, along with the noise budget in Chapters 5 and 6 respectively. The full lock sequence is described in Chapter 7. The thesis concludes with the current status of the interferometers.
Moving-puncture coordinates are commonly used in numerical simulations of black holes. Their properties for vacuum Schwarzschild black holes have been analyzed in a number of studies. The behavior of ...moving-puncture coordinates in spacetimes containing matter, however, is less well understood. In this paper we explore the behavior of these coordinates for Oppenheimer-Snyder collapse, i.e., the collapse of a uniform density, pressureless sphere of dust initially at rest to a black hole. Oppenheimer-Snyder collapse provides a stringent test of the singularity-avoiding properties of moving-puncture coordinates, since the singularity can form more quickly than it would for matter with pressure. Our results include analytical expressions for the matter density, lapse function, and mean curvature at early times, as well as interesting limits for later times. We also carry out numerical simulations to obtain the full solution and these show that, even in the absence of pressure, moving-puncture coordinates are able to avoid the singularity. At late times the geometry settles down to a trumpet slice of a vacuum black hole.
Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been ...observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress.
Primary bile acids serve important roles in cholesterol metabolism, lipid digestion, host-microbe interactions, and regulatory pathways in the human host. While most bile acids are reabsorbed and ...recycled via enterohepatic cycling, ∼5% serve as substrates for bacterial biotransformation in the colon. Enzymes involved in various transformations have been characterized from cultured gut bacteria and reveal taxa-specific distribution. More recently, bioinformatic approaches have revealed greater diversity in isoforms of these enzymes, and the microbial species in which they are found. Thus, the functional roles played by the bile acid-transforming gut microbiota and the distribution of resulting secondary bile acids, in the bile acid pool, may be profoundly affected by microbial community structure and function. Bile acids and the composition of the bile acid pool have historically been hypothesized to be associated with several disease states, including recurrent
Clostridium difficile
infection, inflammatory bowel diseases, metabolic syndrome, and several cancers. Recently, however, emphasis has been placed on how microbial communities in the dysbiotic gut may alter the bile acid pool to potentially cause or mitigate disease onset. This review highlights the current understanding of the interactions between the gut microbial community, bile acid biotransformation, and disease states, and addresses future directions to better understand these complex associations.
Microbial exposures can define an individual’s basal immune state. Cohousing specific pathogen-free (SPF) mice with pet store mice, which harbor numerous infectious microbes, results in global ...changes to the immune system, including increased circulating phagocytes and elevated inflammatory cytokines. How these differences in the basal immune state influence the acute response to systemic infection is unclear. Cohoused mice exhibit enhanced protection from virulent Listeria monocytogenes (LM) infection, but increased morbidity and mortality to polymicrobial sepsis. Cohoused mice have more TLR2+ and TLR4+ phagocytes, enhancing recognition of microbes through pattern-recognition receptors. However, the response to a TLR2 ligand is muted in cohoused mice, whereas the response to a TLR4 ligand is greatly amplified, suggesting a basis for the distinct response to Listeria monocytogenes and sepsis. Our data illustrate how microbial exposure can enhance the immune response to unrelated challenges but also increase the risk of immunopathology from a severe cytokine storm.
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•Cohousing elevates basal cytokine and chemokine levels•Cohousing alters immune responsiveness to new challenges•Cohoused mice have an altered microbiome composition•TLR4 expression and LPS sensitivity are increased after microbial exposure
Cohousing of laboratory mice with pet store animals changes the immune system and alters responsiveness to future challenges. Huggins et al. demonstrate that microbial exposure results in alterations to immune cells, serum cytokines, and microbiome composition. This study shows that cohousing alters the ability to detect pathogens through pattern-recognition receptors.
Human microbiota-associated (HMA) animal models relying on germ-free recipient mice are being used to study the relationship between intestinal microbiota and human disease. However, transfer of ...microbiota into germ-free animals also triggers global developmental changes in the recipient intestine, which can mask disease-specific attributes of the donor material. Therefore, a simple model of replacing microbiota into a developmentally mature intestinal environment remains highly desirable.
Here we report on the development of a sequential, three-course antibiotic conditioning regimen that allows sustained engraftment of intestinal microorganisms following a single oral gavage with human donor microbiota. SourceTracker, a Bayesian, OTU-based algorithm, indicated that 59.3 ± 3.0% of the fecal bacterial communities in treated mice were attributable to the donor source. This overall degree of microbiota engraftment was similar in mice conditioned with antibiotics and germ-free mice. Limited surveys of systemic and mucosal immune sites did not show evidence of immune activation following introduction of human microbiota.
The antibiotic treatment protocol described here followed by a single gavage of human microbiota may provide a useful, complimentary HMA model to that established in germ-free facilities. The model has the potential for further in-depth translational investigations of microbiota in a variety of human disease states.
Background
Carbohydrate antigen (CA) 19-9 is a biomarker to monitor treatment effect. A threshold to predict prognostic significance remains undefined. We evaluated the impact of CA19-9 on overall ...survival (OS) in patients with early-stage pancreatic cancer (PC) utilizing the National Cancer Database (NCDB).
Methods
The NCDB was queried from 2010 to 2014 to identify patients with clinical stage I–II PC. Patients who had undocumented pretreatment CA19-9 were excluded. Patients were stratified into two cohorts: CA19-9 < 98 U/mL and CA19-9 ≥ 98 U/mL, and further categorized into surgery versus no surgery. Twelve- and 24-month OS rates are reported.
Results
Overall, 32,382 patients (stage I: 12,173; stage II: 20,209) were included. The majority of stage I (52.1%) and II (60%) patients had CA19-9 ≥ 98 U/mL. Stage I–II patients with CA19-9 < 98 U/mL had improved OS rates (stage I: 67.5%, 42.6%; stage II: 59.8%, 32.8%) compared with stage I and II patients with CA19-9 ≥ 98 U/mL (stage I: 50.7%, 26.9%; stage II: 48.1%, 22%). Among resected stage I patients, CA19-9 <98 U/mL was associated with improved OS (< 98: 80.5%, 56%; ≥ 98: 70.2%, 42.8%), and a similar trend was seen in resected stage II patients (< 98: 77.6%, 49.9%; ≥ 98: 71%, 39.2%). Unresected stage I patients with lower CA19-9 had improved OS (< 98: 42.1%, 17.5; ≥ 98: 29.9%, 10%), with similar findings in unresected stage II patients (< 98: 41.1%, 15.3%; ≥ 98: 33.4%, 10.6%).
Conclusions
Our study demonstrated the prognostic value of CA19-9 in patients with clinical stage I–II PC, with a value < 98 U/mL demonstrating improved survival. Surgery significantly improved survival at 12 and 24 months irrespective of CA19-9.
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