It has been known for some years that entanglement entropy obtained from partial trace does not provide the correct entanglement measure when applied to systems of identical particles. Several ...criteria have been proposed that have the drawback of being different according to whether one is dealing with fermions, bosons, or distinguishable particles. In this Letter, we give a precise and mathematically natural answer to this problem. Our approach is based on the use of the more general idea of the restriction of states to subalgebras. It leads to a novel approach to entanglement, which is suitable to be used in general quantum systems and especially in systems of identical particles. This settles some recent controversy regarding entanglement for identical particles. The prospects for applications of our criteria are wide ranging, from spin chains in condensed matter to entropy of black holes.
A multilevel inverter topology feeding a three-phase open-end winding machine is analyzed in this paper. The scheme is based on the use of two insulated DC supplies, each one feeding a standard ...two-level three-phase inverter. The three-phase six-wire winding is connected across the output terminals of the two inverters. A new modulation technique that is able to regulate the sharing of the output power between the two DC sources in each switching cycle is presented. The performance of the whole system has been verified by both numerical and experimental tests.
Abstract
The observables associated with a quantum system
S
form a non-commutative algebra
A
S
. It is assumed that a density matrix
ρ
can be determined from the expectation values of observables. ...But
A
S
admits inner automorphisms
a
↦
u
a
u
−
1
,
a
,
u
∈
A
S
,
u
*
u
=
u
u
*
=
1
, so that its individual elements can be identified only up to unitary transformations. So since Tr
ρ
(
uau
*) = Tr(
u
*
ρu
)
a
, only the spectrum of
ρ
, or its characteristic polynomial, can be determined in quantum mechanics. In local quantum field theory,
ρ
cannot be determined at all, as we shall explain. However, abelian algebras do not have inner automorphisms, so the measurement apparatus can determine mean values of observables in abelian algebras
A
M
⊂
A
S
(
M
for measurement,
S
for system). We study the uncertainties in extending
ρ
|
A
M
to
ρ
|
A
S
(the determination of which means measurement of
A
S
) and devise a protocol to determine
ρ
|
A
S
≡
ρ
by determining
ρ
|
A
M
for different choices of
A
M
. The problem we formulate and study is a generalization of the Kadison–Singer theorem. We give an example where the system
S
is a particle on a circle and the experiment measures the abelian algebra of a magnetic field
B
coupled to
S
. The measurement of
B
gives information about the state
ρ
of the system
S
due to operator mixing. Associated uncertainty principles for von Neumann entropy are discussed in the appendix, adapting the earlier work by Białynicki-Birula and Mycielski (1975
Commun. Math. Phys.
44
129) to the present case.
Emergent gauge symmetries and quantum operations Balachandran, A P; Burbano, I M; Reyes-Lega, A F ...
Journal of physics. A, Mathematical and theoretical,
02/2020, Letnik:
53, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The algebraic approach to quantum physics emphasizes the role played by the structure of the algebra of observables and its relation to the space of states. An important feature of this point of view ...is that subsystems can be described by subalgebras, with partial trace being replaced by the more general notion of restriction to a subalgebra. This, in turn, has recently led to applications to the study of entanglement in systems of identical particles. In the course of those investigations on entanglement and particle identity, an emergent gauge symmetry has been found by Balachandran, de Queiroz and Vaidya. In this letter we establish a novel connection between that gauge symmetry, entropy production and quantum operations. Thus, let A be a system described by a finite dimensional observable algebra and a mixed faithful state. Using the Gelfand-Naimark-Segal (GNS) representation we construct a canonical purification of , allowing us to embed A into a larger system C. Using Tomita-Takesaki theory, we obtain a subsystem decomposition of C into subsystems A and B, without making use of any tensor product structure. We identify a group of transformations that acts as a gauge group on A while at the same time giving rise to entropy increasing quantum operations on C. We provide physical means to simulate this gauge symmetry/quantum operation duality.
Abstract
High-energy, long gamma-ray bursts (GRBs) can be generated by the core collapse of massive stars at the end of their lives. When they happen in the close-by universe they can be ...exceptionally bright, as seen from the Earth in the case of the recent, giant, long-lasting GRB221009A. GRB221009A was produced by a collapsing star with a redshift of 0.152: this event was observed by many gamma-ray space experiments, which also detected an extraordinary long gamma-ray afterglow. The exceptionally large fluence of the prompt emission of about 0.013 erg cm
−2
illuminated a large geographical region centered on India and including Europe and Asia. We report in this paper the observation of sudden electron flux changes correlated with GRB221009A and measured by the HEPP-L charged particle detector on board the China Seismo-Electromagnetic Satellite, which was orbiting over Europe at the time of the GRB event. The time structure of the observed electron flux closely matches the very distinctive time dependence of the photon flux associated with the main part of the emission at around 13:20 UTC on 2022 October 9. To test the origin of these signals, we set up a simplified simulation of one HEPP-L subdetector: the results of this analysis suggest that the signals observed are mostly due to electrons created within the aluminum collimator surrounding the silicon detector, providing real-time monitoring of the very intense photon fluxes. We discuss the implications of this observation for existing and forthcoming particle detectors on low Earth orbits.
SICURA is a two-year project that aims to develop a portable device to be employed in the prevention of illicit trafficking of radioactive material through γ and neutron detection. In order to be ...attractive to industries, efforts were made to fulfill the following characteristics: portability, good photon energy resolution and sensitivity in compliance with relevant international standards, sensitivity to neutrons with energies typical of the most common sources, fast response, low cost, user friendly interface. The SICURA system consists of two photon detectors for photon detection (CsI) and spectrometry (CZT) and a moderated Helium-3 counter for neutron detection. Dedicated analog and digital electronics readout have been developed, ensuring high energy resolution for accurate elements identification, signal digitization, alarm and information transmission to the end user. This paper describes the development of the SICURA device and the first results of its individual detectors characterizations.
Abstract
In this paper we report the detection of five strong gamma-ray bursts (GRBs) by the High-Energy Particle Detector (HEPD-01) mounted on board the China Seismo-Electromagnetic Satellite, ...operational since 2018 on a Sun-synchronous polar orbit at a ∼507 km altitude and 97° inclination. HEPD-01 was designed to detect high-energy electrons in the energy range 3–100 MeV, protons in the range 30–300 MeV, and light nuclei in the range 30–300 MeV n
−1
. Nonetheless, Monte Carlo simulations have shown HEPD-01 is sensitive to gamma-ray photons in the energy range 300 keV–50 MeV, even if with a moderate effective area above ∼5 MeV. A dedicated time correlation analysis between GRBs reported in literature and signals from a set of HEPD-01 trigger configuration masks has confirmed the anticipated detector sensitivity to high-energy photons. A comparison between the simultaneous time profiles of HEPD-01 electron fluxes and photons from GRB190114C, GRB190305A, GRB190928A, GRB200826B, and GRB211211A has shown a remarkable similarity, in spite of the different energy ranges. The high-energy response, with peak sensitivity at about 2 MeV, and moderate effective area of the detector in the actual flight configuration explain why these five GRBs, characterized by a fluence above ∼3 × 10
−5
erg cm
−2
in the energy interval 300 keV–50 MeV, have been detected.
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