840 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
Error Correction of Quantum Algorithms: Arbitrarily Accurate Recovery Of Noisy Quantum Signal Processing
The intrinsic probabilistic nature of quantum systems makes error correction
or mitigation indispensable for quantum computation. While current
error-correcting strategies focus on correcting errors in quantum states or
quantum gates, these fine-grained error-correction methods can incur
significant overhead for quantum algorithms of increasing complexity. We
present a first step in achieving error correction at the level of quantum
algorithms by combining a unified perspective on modern quantum algorithms via
quantum signal processing (QSP). An error model of under- or over-rotation of
the signal processing operator parameterized by is introduced.
It is shown that while Pauli -errors are not recoverable without additional
resources, Pauli and errors can be arbitrarily suppressed by coherently
appending a noisy `recovery QSP.' Furthermore, it is found that a recovery QSP
of length is sufficient to correct any length- QSP with
unique phases to -order in error . Allowing an additional
assumption, a lower bound of is shown, which is tight for ,
on the length of the recovery sequence. Our algorithmic-level error correction
method is applied to Grover's fixed-point search algorithm as a demonstration
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