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$\AA$, 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