67 research outputs found
Preparation and Measurement Uncertainty in Quantum Mechanics
This thesis addresses two forms of quantum uncertainty. In part I, we focus on preparation uncertainty, an expression of the fact that there are sets of observables for which the induced probability distributions are not simultaneously sharp in any state. We exactly characterise the preparation uncertainty regions for several finite dimensional case studies, including a new derivation of the preparation uncertainty region for the Pauli observables of qubits, and two qutrit case studies which have not previously been addressed in the literature. We also consider the variance based preparation uncertainty for position and momentum observables for the well known “particle in a box” system. We see that the appropriate momentum observable is not given by the spectral measure of a self-adjoint operator, although the position observable is. The box system lacks the phase-space symmetry used to determine the free particle and particle on a ring systems so determining the box uncertainty region is rather more difficult than in these cases. We give upper and lower bounds on the boundary of the uncertainty region, and show that our upper bound is exact in an interval.
In part II we turn our attention to measurement uncertainty, exploring the space of compatible joint approximations to incompatible target observables. We prove a general theorem, which shows that, for a broad class of figures of merit, the optimal compatible approximations to covariant targets are themselves covariant. This substantially simplifies the problem of determining measurement uncertainty regions for covariant observables, since the space of covariant compatible approximations is smaller than the space of all compatible approximations. We employ this theorem to derive measurement uncertainty regions for three mutually orthogonal Pauli observables, and for the quantum Fourier pair acting in any finite dimension
Fast estimation of outcome probabilities for quantum circuits
We present two classical algorithms for the simulation of universal quantum
circuits on qubits constructed from instances of Clifford gates and
arbitrary-angle -rotation gates such as gates. Our algorithms complement
each other by performing best in different parameter regimes. The
algorithm produces an additive precision estimate of the Born
rule probability of a chosen measurement outcome with the only source of
run-time inefficiency being a linear dependence on the stabilizer extent (which
scales like for gates). Our algorithm is state-of-the-art
for this task: as an example, in approximately hours (on a standard
desktop computer), we estimated the Born rule probability to within an additive
error of , for a qubit, non-Clifford gate quantum circuit with
more than Clifford gates. Our second algorithm, ,
calculates the probability of a chosen measurement outcome to machine precision
with run-time where is an efficiently computable,
circuit-specific quantity. With high probability, is very close to for random circuits with many Clifford gates, where is the
number of measured qubits. can be effective in surprisingly
challenging parameter regimes, e.g., we can randomly sample Clifford+
circuits with , , and gates, and then compute
the Born rule probability with a run-time consistently less than minutes
using a single core of a standard desktop computer. We provide a C+Python
implementation of our algorithms.Comment: 25+14 pages, 6 figures. Version 2 contains a minor correction to the
scaling of Theorem 3, a small improvement to the scaling of Theorem 2 and
various other improvements. Comments welcom
When the Wealthy Are Poor: Poverty Explanations and Local Perspectives in Southwestern Madagascar
To reduce poverty, one must understand what poverty means in local contexts. We used focus groups to elicit a “folk model” of poverty from Masikoro, Vezo, and Mikea people in rural southwestern Madagascar and then placed this model in dialogue with four social science models: economic growth, substantivism, mode of production, and livelihoods. The folk model emphasizes household continuity, production of people, and exploitative expropriation by the wealthy. Absent from the folk model is scarcity of natural and social resources, the core of economic growth and livelihoods explanations. Consistent with substantivism, poverty and wealth are states one may occupy simultaneously, not maximizable quantities. Compatible with mode of production, the root cause of poverty is the rules regarding control over property. Poverty interventions based on profit, competition, intensification, or devolution of control to traditional social institutions would likely be culturally foreign to rural Malagasy and could further the gap between rich and poor
Proteomics of Buccal Cavity Mucus in Female Tilapia Fish (Oreochromis spp.): A Comparison between Parental and Non-Parental Fish
Mouthbrooding is an elaborate form of parental care displayed by many teleost
species. While the direct benefits of mouthbrooding such as protection and
transportation of offsprings are known, it is unclear if mouthbrooding offers
additional benefits to embryos during incubation. In addition, mouthbrooding
could incur negative costs on parental fish, due to limited feeding
opportunities. Parental tilapia fish (Oreochromis spp.) display
an elaborated form of parental care by incubating newly hatched embryos in oral
buccal cavity until the complete adsorption of yolk sac. In order to understand
the functional aspects of mouthbrooding, we undertake a proteomics approach to
compare oral mucus sampled from mouthbrooders and non-mouthbrooders,
respectively. Majority of the identified proteins have also been previously
identified in other biological fluids or mucus-rich organs in different
organisms. We also showed the upregulation of 22 proteins and down regulation of
3 proteins in mucus collected from mouthbrooders. Anterior gradient protein,
hemoglobin beta-A chain and alpha-2 globin levels were lower in mouthbrooder
samples. Mouthbrooder oral mucus collectively showed increase levels of proteins
related to cytoskeletal properties, glycolytic pathway and mediation of
oxidative stress. Overall the findings suggest cellular stress response,
probably to support production of mucus during mouthbrooding phase
Integrated genomic characterization of pancreatic ductal adenocarcinoma
We performed integrated genomic, transcriptomic, and proteomic profiling of 150 pancreatic ductal adenocarcinoma (PDAC) specimens, including samples with characteristic low neoplastic cellularity. Deep whole-exome sequencing revealed recurrent somatic mutations in KRAS, TP53, CDKN2A, SMAD4, RNF43, ARID1A, TGFβR2, GNAS, RREB1, and PBRM1. KRAS wild-type tumors harbored alterations in other oncogenic drivers, including GNAS, BRAF, CTNNB1, and additional RAS pathway genes. A subset of tumors harbored multiple KRAS mutations, with some showing evidence of biallelic mutations. Protein profiling identified a favorable prognosis subset with low epithelial-mesenchymal transition and high MTOR pathway scores. Associations of non-coding RNAs with tumor-specific mRNA subtypes were also identified. Our integrated multi-platform analysis reveals a complex molecular landscape of PDAC and provides a roadmap for precision medicine
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