2,242 research outputs found
Probabilistic Super Dense Coding
We explore the possibility of performing super dense coding with
non-maximally entangled states as a resource. Using this we find that one can
send two classical bits in a probabilistic manner by sending a qubit. We
generalize our scheme to higher dimensions and show that one can communicate
2log_2 d classical bits by sending a d-dimensional quantum state with a certain
probability of success. The success probability in super dense coding is
related to the success probability of distinguishing non-orthogonal states. The
optimal average success probabilities are explicitly calculated. We consider
the possibility of sending 2 log_2 d classical bits with a shared resource of a
higher dimensional entangled state (D X D, D > d). It is found that more
entanglement does not necessarily lead to higher success probability. This also
answers the question as to why we need log_2 d ebits to send 2 log_2 d
classical bits in a deterministic fashion.Comment: Latex file, no figures, 11 pages, Discussion changed in Section
Gapless Singlet modes in the Kagome strips: A study through DMRG and strong coupling analysis
Recently Azaria et al have studied strips of the Kagome-lattice in the
weak-coupling limit, where they consist of two spin-half chains on the outside
weakly coupled to an array of half-integer spins in the middle. Using a number
of mappings they have arrived at the interesting result that in this system all
spin excitations are gapped but there are gapless spinless modes. Here we study
these Kagome strips in the limit where the interchain couplings are comparable
to the coupling to the middle spins by density matrix renormalization group and
by a strong coupling analysis. In the limit when the coupling to the
middle-spin dominates, the 5-spins of the unit-cell reduce to a single S=3/2
spin, and the overall system has well known gapless spin excitations. We study
the phase transition from this phase to the weak-coupling phase. We also carry
out a strong coupling analysis away from the S=3/2 limit, where the five-spin
blocks have four degenerate ground states with S=1/2, which can be thought of
as two spin and two pseudospin degrees of freedom. A numerical study of this
strong coupling model also suggests a finite spin-gap.Comment: 4 pages, 4 PS figure
Safe abortion – Still a neglected scenario: A study of septic abortions in a tertiary hospital of Rural India
Background and Aims: In spite abortion has been legalized in India over three decades, unsafe abortion continues to be a significant contributor of maternal mortality and morbidity. The aim of the present study is to assess the magnitude of septic abortion in a tertiary care hospital over a period of three years with a special emphasis on maternal mortality and morbidity and various surgical complications. Settings and Design: Retrospective study of patients who were admitted with unsafe abortions over a three year period from 2005 to 2008 in a tertiary teaching Hospital of Rural India. Materials and Methods: Hospital records of the patients who were admitted with unsafe abortion in three years (2005-2008) were reviewed to evaluate the demographic and clinical profile in relation to age, parity, marital status, indication of abortion , the methods of abortion ,qualification of abortion provider complications and maternal mortality. Results: Unsafe abortion constitutes 11.6% ( n=132) of total abortion cases admitted over 3 years. Majority of women (70.45%) were in their thirties, married (89%).Sixty percent wanted abortion for birth spacing. Abortion methods included various primitive methods (30%) but majority by dilatation and evacuation. About 60% of abortionists were unqualified. Majority of women admitted with serious complications like peritonitis (70%), visceral injuries (60%), hemorrhagic and septic shock, renal failure (17.4%), and life threatening conditions like DIC, hepatic failure and encephalopathy. A total of 231 women died of unsafe abortion making it 12.55% of total maternal mortality in our institution. Out of 73 women requiring laparotomy, 22% were done within 24 hours of admission and majority (49%) were performed beyond 24-48 hours. Interestingly no women died when early aggressive surgery was done. Conclusion: The present study confirms that unsafe abortion is a great neglected health care problem leading to a considerable loss of maternal lives. Education and accessibility of contra caption, readily available, quality abortion services by trained abortion providers remain the key to limit mortality and morbidity arising from unsafe abortion
Elementary Particles and Spin Representations
We emphasize that the group-theoretical considerations leading to SO(10)
unification of electro-weak and strong matter field components naturally extend
to space-time components, providing a truly unified description of all
generation degrees of freedoms in terms of a single chiral spin representation
of one of the groups SO(13,1), SO(9,5), SO(7,7) or SO(3,11). The realization of
these groups as higher dimensional space-time symmetries produces unification
of all fundamental fermions is a single space-time spinor.Comment: 4 page
Probing Grand Unification Through Neutrino Oscillations, Leptogenesis, and Proton Decay
Evidence in favor of supersymmetric grand unification including that based on
the observed family multiplet-structure, gauge coupling unification, neutrino
oscillations, baryogenesis, and certain intriguing features of quark-lepton
masses and mixings is noted. It is argued that attempts to understand (a) the
tiny neutrino masses (especially Delta m^2 (nu_2 -nu_3)), (b) the baryon
asymmetry of the universe (which seems to need leptogenesis), and (c) the
observed features of fermion masses such as the ratio m_b/m_tau, the smallness
of V_cb and the maximality of theta_{nu_mu-nu_tau}, seem to select out the
route to higher unification based on an effective string-unified G(224) =
SU(2)_L x SU(2)_R x SU(4)^c or SO(10)-symmetry, operative in 4D, as opposed to
other alternatives.
A predictive framework based on an effective SO(10) or G(224) symmetry
possessing supersymmetry is presented that successfully describes the masses
and mixings of all fermions including neutrinos. It also accounts for the
observed baryon asymmetry of the universe by utilizing the process of
leptogenesis, which is natural to this framework. It is argued that a
conservative upper limit on the proton lifetime within this
SO(10)/G(224)-framework, which is so far most successful, is given by (1/3-2) x
10^34 years. This in turn strongly suggests that an improvement in the current
sensitivity by a factor of five to ten (compared to SuperK) ought to reveal
proton decay. Implications of this prediction for the next-generation nucleon
decay and neutrino-detector are noted.Comment: 40 page, 3 figures. Conference proceedings from Erice School (Sept
2002), Neutrino Conference (Stony Brook, 2002), PASCOS Conference (Mumbai,
2003) Version 2: New references and some clarifications adde
Mediation of Long Range Charge Transfer by Kondo Bound States
We present a theory of non-equilibrium long range charge transfer between
donor and acceptor centers in a model polymer mediated by magnetic exciton
(Kondo) bound states. Our model produces electron tunneling lengths easily
exceeding 10, as observed recently in DNA and organic charge transfer
systems. This long ranged tunneling is effective for weak to intermediate
donor-bridge coupling, and is enhanced both by weak to intermediate strength
Coulomb hole-electron attraction (through the orthogonality catastrophe) and by
coupling to local vibrational modes.Comment: Revised content (broadened scope, vibrations added), submitted to
Phys Rev Lett, added autho
Continuous variable remote state preparation
We extend exact deterministic remote state preparation (RSP) with minimal
classical communication to quantum systems of continuous variables. We show
that, in principle, it is possible to remotely prepare states of an ensemble
that is parameterized by infinitely many real numbers, i.e., by a real
function, while the classical communication cost is one real number only. We
demonstrate continuous variable RSP in three examples using (i) quadrature
measurement and phase space displacement operations, (ii) measurement of the
optical phase and unitaries shifting the same, and (iii) photon counting and
photon number shift.Comment: 7 pages, RevTeX
- …