2,503 research outputs found
A study to develop neutron activation for measuring bone calcium content
Neutron activation analysis for measuring calcium in monkey bone
Crossover from Kramers to phase-diffusion switching in hysteretic DC-SQUIDs
We have measured and propose a model for switching rates in hysteretic
DC-SQUID in the regime where phase diffusion processes start to occur. We show
that the switching rates in this regime are smaller than the rates given by
Kramers' formula due to retrapping of Josephson phase. The retrapping process,
which is affected by the frequency dependent impedance of the environment of
the DC-SQUID, leads to a peaked second moment of the switching distribution as
a function of temperature. The temperature where the peaks occur are
proportional to the critical current of the DC- SQUID.Comment: 4 pages, 4 figure
A Bayesian analysis of classical shadows
The method of classical shadows heralds unprecedented opportunities for
quantum estimation with limited measurements [H.-Y. Huang, R. Kueng, and J.
Preskill, Nat. Phys. 16, 1050 (2020)]. Yet its relationship to established
quantum tomographic approaches, particularly those based on likelihood models,
remains unclear. In this article, we investigate classical shadows through the
lens of Bayesian mean estimation (BME). In direct tests on numerical data, BME
is found to attain significantly lower error on average, but classical shadows
prove remarkably more accurate in specific situations -- such as high-fidelity
ground truth states -- which are improbable in a fully uniform Hilbert space.
We then introduce an observable-oriented pseudo-likelihood that successfully
emulates the dimension-independence and state-specific optimality of classical
shadows, but within a Bayesian framework that ensures only physical states. Our
research reveals how classical shadows effect important departures from
conventional thinking in quantum state estimation, as well as the utility of
Bayesian methods for uncovering and formalizing statistical assumptions.Comment: 8 pages, 5 figure
Quantum optical microcombs
A key challenge for quantum science and technology is to realize large-scale, precisely controllable, practical systems for non-classical secured communications, metrology and, ultimately, meaningful quantum simulation and computation. Optical frequency combs represent a powerful approach towards this goal, as they provide a very high number of temporal and frequency modes that can result in large-scale quantum systems. The generation and control of quantum optical frequency combs will enable a unique, practical and scalable framework for quantum signal and information processing. Here, we review recent progress on the realization of energy–time entangled optical frequency combs and discuss how photonic integration and the use of fibre-optic telecommunications components can enable quantum state control with new functionalities, yielding unprecedented capability
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