Quantum History cannot be Copied

We show that unitarity does not allow cloning of any two points in a ray. This has implication for cloning of the geometric phase information in a quantum state. In particular, the quantum history which is encoded in the geometric phase during cyclic evolution of a quantum system cannot be copied. We also prove that the generalized geometric phase information cannot be copied by a unitary operation. We argue that our result also holds in the consistent history formulation of quantum mechanics.Comment: Latex file, No figures, 9 page

Background Independent Quantum Mechanics, Metric of Quantum States, and Gravity: A Comprehensive Perspective

This paper presents a comprehensive perspective of the metric of quantum states with a focus on the background independent metric structures. We also explore the possibilities of geometrical formulations of quantum mechanics beyond the quantum state space and Kahler manifold. The metric of quantum states in the classical configuration space with the pseudo-Riemannian signature and its possible applications are explored. On contrary to the common perception that a metric for quantum state can yield a natural metric in the configuration space with the limit when Planck constant vanishes, we obtain the metric of quantum states in the configuration space without imposing this limiting condition. Here, Planck constant is absorbed in the quantity like Bohr radii. While exploring the metric structure associated with Hydrogen like atom, we witness another interesting finding that the invariant lengths appear in the multiple of Bohr radii.Comment: 25 Pages;journal reference added:Published in- Int. J. Theor. Phys. 46 (2007) 3216-3229. References revise

Perfect Teleportation and Superdense Coding With W-States

True tripartite entanglement of the state of a system of three qubits can be classified on the basis of stochastic local operations and classical communications (SLOCC). Such states can be classified in two categories: GHZ states and W-states. It is known that GHZ states can be used for teleportation and superdense coding, but the prototype W-state cannot be. However, we show that there is a class of W-states that can be used for perfect teleportation and superdense coding.Comment: 9 pages, no figur

Book Review: The Bhajan: Christian Devotional Music in Indian Diaspora

A review of The Bhajan: Christian Devotional Music in Indian Diaspora by H. Joy Norman

No-Flipping as a consequence of No-Signalling and Non-increase of Entanglement under LOCC

Non existence of Universal NOT gate for arbitrary quantum mechanical states is a fundamental constraint on the allowed operations performed on physical systems. The largest set of states that can be flipped by using a single NOT gate is the set of states lying on a great circle of the Bloch-sphere. In this paper, we show the impossibility of universal exact-flipping operation, first by using the fact that no faster than light communication is possible and then by using the principle of "non-increase of entanglement under LOCC". Interestingly, exact flipping of the states of any great circle does not violate these two principles, as expected.Comment: 8 pages, published versio

Book Review: India and the Indianness of Christianity: Essays on Understanding

A review of India and the Indianness of Christianity: Essays on Understanding edited by Richard Fox Young