243 research outputs found
Off-diagonal geometric phase for mixed states
We extend the off-diagonal geometric phase [Phys. Rev. Lett. {\bf 85}, 3067
(2000)] to mixed quantal states. The nodal structure of this phase in the qubit
(two-level) case is compared with that of the diagonal mixed state geometric
phase [Phys. Rev. Lett. {\bf 85}, 2845 (2000)]. Extension to higher dimensional
Hilbert spaces is delineated. A physical scenario for the off-diagonal mixed
state geometric phase in polarization-entangled two-photon interferometry is
proposed.Comment: small corrections; journal reference adde
Generating random density matrices
We study various methods to generate ensembles of random density matrices of
a fixed size N, obtained by partial trace of pure states on composite systems.
Structured ensembles of random pure states, invariant with respect to local
unitary transformations are introduced. To analyze statistical properties of
quantum entanglement in bi-partite systems we analyze the distribution of
Schmidt coefficients of random pure states. Such a distribution is derived in
the case of a superposition of k random maximally entangled states. For another
ensemble, obtained by performing selective measurements in a maximally
entangled basis on a multi--partite system, we show that this distribution is
given by the Fuss-Catalan law and find the average entanglement entropy. A more
general class of structured ensembles proposed, containing also the case of
Bures, forms an extension of the standard ensemble of structureless random pure
states, described asymptotically, as N \to \infty, by the Marchenko-Pastur
distribution.Comment: 13 pages in latex with 8 figures include
Integrability of Lie systems and some of its applications in physics
The geometric theory of Lie systems will be used to establish integrability
conditions for several systems of differential equations, in particular Riccati
equations and Ermakov systems. Many different integrability criteria in the
literature will be analyzed from this new perspective and some applications in
physics will be given.Comment: 16 page
Fidelity approach to quantum phase transitions
We review briefly the quantum fidelity approach to quantum phase transitions
in a pedagogical manner. We try to relate all established but scattered results
on the leading term of the fidelity into a systematic theoretical framework,
which might provide an alternative paradigm for understanding quantum critical
phenomena. The definition of the fidelity and the scaling behavior of its
leading term, as well as their explicit applications to the one-dimensional
transverse-field Ising model and the Lipkin-Meshkov-Glick model, are introduced
at the graduate-student level. In addition, we survey also other types of
fidelity approach, such as the fidelity per site, reduced fidelity,
thermal-state fidelity, operator fidelity, etc; as well as relevant works on
the fidelity approach to quantum phase transitions occurring in various
many-body systems.Comment: 41 pages, 31 figures. We apologize if we omit acknowledging your
relevant works. Do tell. An updated version with clearer figures can be found
at: http://www.phy.cuhk.edu.hk/~sjgu/fidelitynote.pd
Optimal manipulations with qubits: Universal quantum entanglers
We analyze various scenarios for entangling two initially unentangled qubits.
In particular, we propose an optimal universal entangler which entangles a
qubit in unknown state with a qubit in a reference (known) state
. That is, our entangler generates the output state which is as close as
possible to the pure (symmetrized) state . The most
attractive feature of this entangling machine, is that the fidelity of its
performance (i.e. the distance between the output and the ideally entangled --
symmetrized state) does not depend on the input and takes the constant value
. We also analyze how to optimally generate
from a single qubit initially prepared in an unknown state |\Psi\r a two
qubit entangled system which is as close as possible to a Bell state
, where \l\Psi|\Psi^\perp\r =0.Comment: 11 pages, 3 eps figures, accepted for publication in Phys. Rev.
Hubungan Kelelahan Kerja dan Stress Kerja dengan Kecelakaan Kerja Tertusuk Jarum Jahit pada Pekerja Bagian Garmen di PT. Danliris Sukoharjo
Latar Belakang : Meningkatnya penggunaan teknologi di berbagai sektor usaha
dapat pula mengakibatkan semakin tinggi resiko terjadinya kecelakaan kerja dan
penyakit akibat kerja atau penyakit yang berhubungan dengan pekerjaan yang
mengancam keselamatan, kesehatan dan kesejahteraan tenaga kerja. Dalam tiga tahun
terakhir di PT. Danliris Sukoharjo, terjadi 38 kasus kecelakaan kerja tertusuk jarum
jahit. Tujuan penelitian ini untuk mengetahui apakah kelelahan kerja dan stress kerja
mempunyai hubungan dengan terjadinya kecelakaan kerja tertusuk jarum jahit.
Metode : Penelitian ini menggunakan metode observasional analitik dengan
rancangan cross sectional. Sampel diambil dengan metode simple random sampling
sebanyak 200 pekerja bagian garmen. Pengumpulan data dilakukan dengan pengisian
kuesioner kelelahan kerja dan stress kerja serta kecelakaan kerja tertusuk jarum jahit
dilakukan dengan observasional. Pengolahan dan analisa data menggunakan uji
statistik chi square dengan uji alterrnatif fisher.
Hasil : Hasil penelitian ini menunjukkan tidak ada hubungan antara kelelahan kerja
dengan terjadinya kecelakaan kerja tertusuk jarum jahit (p value 0.619) dan tidak ada
hubungan antara stress kerja dengan kecelakaan kerja tertusuk jarum jahit (p value
0.137).
Kesimpulan : Kelelahan kerja dan stress kerja tidak mempunyai hubungan dengan
terjadinya kecelakaan kerja tertusuk jarum jahit.
Kata Kunci : Kelelahan Kerja, Stress Kerja, Kecelakaan Kerj
Entanglement of a Pair of Quantum Bits
The ``entanglement of formation'' of a mixed state of a bipartite quantum
system can be defined in terms of the number of pure singlets needed to create
the state with no further transfer of quantum information. We find an exact
formula for the entanglement of formation for all mixed states of two qubits
having no more than two non-zero eigenvalues, and we report evidence suggesting
that the formula is valid for all states of this system.Comment: 10 page
INDICATORS OF CLASSICALITY/QUANTUMNESS OF FINITE- DIMENSIONAL SYSTEMS
We discuss measures of classicality/quantumness of states of finite-dimensional quantum systems, which are based on a deviation of quasiprobability distributions from true statistical distributions
- …