853 research outputs found
Novel duality in disorder driven local quantum criticality
We find that competition between random Kondo and random magnetic
correlations results in a quantum phase transition from a local Fermi liquid to
a spin liquid. The local charge susceptibility turns out to have exactly the
same critical exponent as the local spin susceptibility, suggesting novel
duality between the Kondo singlet phase and the critical local moment state
beyond the Landau-Ginzburg-Wilson symmetry breaking framework. This leads us to
propose an enhanced symmetry at the local quantum critical point, described by
an O(4) vector for spin and charge. The symmetry enhancement serves mechanism
of electron fractionalization in critical impurity dynamics, where such
fractionalized excitations are identified with topological excitations
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Effects of the Big Five Personality Traits on Recreation Types - The Case of Vietnam Tourism
Shadow process tomography of quantum channels
Quantum process tomography is a critical capability for building quantum
computers, enabling quantum networks, and understanding quantum sensors. Like
quantum state tomography, the process tomography of an arbitrary quantum
channel requires a number of measurements that scale exponentially in the
number of quantum bits affected. However, the recent field of shadow
tomography, applied to quantum states, has demonstrated the ability to extract
key information about a state with only polynomially many measurements. In this
work, we apply the concepts of shadow state tomography to the challenge of
characterizing quantum processes. We make use of the Choi isomorphism to
directly apply rigorous bounds from shadow state tomography to shadow process
tomography, and we find additional bounds on the number of measurements that
are unique to process tomography. Our results, which include algorithms for
implementing shadow process tomography enable new techniques including
evaluation of channel concatenation and the application of channels to shadows
of quantum states. This provides a dramatic improvement for understanding
large-scale quantum systems.Comment: 12 pages, 5 figures; Added citation to similar work; Errors
corrected. Previous statements of main result first missed and then
miscalculated an exponential cost in system size; Version accepted for
publicatio
Analyses spectroscopiques du liquide céphalo-rachidien de rat en ex vivo et du noyau du raphé dorsal in vivo
Les propriétés d'absorption et de fluorescence du liquide céphalo-rachidien (LCR) ponctionné au niveau de la cisterna magna du rat, sont analysées puis comparées à l'émission mesurée in situ dans le noyau du raphe dorsal du rat libre de tous mouvements. Les mesures de fluorescence en ex vivo du LCR et in vivo du noyau raphé dorsal, ont été réalisées par la mise en œuvre d'un microcapteur à fibre optique (FOCS). La fluorescence mesurée in vivo sous excitation à 337 nm, présente 2 pics d'émission situés vers 410 et 460 nm. Les spectres d'absorption, d'émission en fluorescence statique et en fluorescence induite par laser sont rapportés. Avec des domaines de longueur d'onde d'excitation de 300-315 nm, 320-355 nm et 360-470 nm, les spectres d'émission du LCR en ex vivo montrent respectivement des pics centrés vers 340 nm, 390 nm et 530 nm. Malgré les limites liées aux différences de localisation anatomique, ces approches ainsi que celles de la littérature permettent de suggérer que le signal de fluorescence mesuré in vivo à 460nm pourrait dépendre pour une grande partie du NADH intracellulaire
Measuring Arbitrary Physical Properties in Analog Quantum Simulation
A central challenge in analog quantum simulation is to characterize desirable
physical properties of quantum states produced in experiments. However, in
conventional approaches, the extraction of arbitrary information requires
performing measurements in many different bases, which necessitates a high
level of control that present-day quantum devices may not have. Here, we
propose and analyze a scalable protocol that leverages the ergodic nature of
generic quantum dynamics, enabling the efficient extraction of many physical
properties. The protocol does not require sophisticated controls and can be
generically implemented in analog quantum simulation platforms today. Our
protocol involves introducing ancillary degrees of freedom in a predetermined
state to a system of interest, quenching the joint system under Hamiltonian
dynamics native to the particular experimental platform, and then measuring
globally in a single, fixed basis. We show that arbitrary information of the
original quantum state is contained within such measurement data, and can be
extracted using a classical data-processing procedure. We numerically
demonstrate our approach with a number of examples, including the measurements
of entanglement entropy, many-body Chern number, and various superconducting
orders in systems of neutral atom arrays, bosonic and fermionic particles on
optical lattices, respectively, only assuming existing technological
capabilities. Our protocol excitingly promises to overcome limited
controllability and, thus, enhance the versatility and utility of near-term
quantum technologies
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