29 research outputs found
Local Cloning of Entangled Qubits
We discuss the exact cloning of orthogonal but entangled qubits under local
operations and classical communication. The amount of entanglement necessary in
blank copy is obtained for various cases. Surprisingly this amount is more than
1 ebit for certain set of two nonmaximal but equally entangled states of two
qubits system. To clone any three two qubits Bell states at least log2 3 ebit
is necessary.Comment: 6 pages, 2 figure
Nonlocality without inequality for spin-s system
We analyze Hardy's non-locality argument for two spin-s systems and show that
earlier solution in this regard was restricted due to imposition of some
conditions which have no role in the argument of non-locality. We provide a
compact form of non-locality condition for two spin-s systems and extend it to
n number of spin-s particles. We also apply more general kind of non-locality
argument still without inequality, to higher spin system.Comment: 6 page
Process tomography via sequential measurements on a single quantum system
We utilize a discrete (sequential) measurement protocol to investigate
quantum process tomography of a single two-level quantum system, with an
unknown initial state, undergoing Rabi oscillations. The ignorance of the
dynamical parameters is encoded into a continuous-variable classical system
which is coupled to the two-level quantum system via a generalized Hamiltonian.
This combined estimate of the quantum state and dynamical parameters is updated
by using the information obtained from sequential measurements on the quantum
system and, after a sufficient waiting period, faithful state monitoring and
parameter determination is obtained. Numerical evidence is used to demonstrate
the convergence of the state estimate to the true state of the hybrid system.Comment: 7 pages, 2 figure
Nonlocality without inequality for almost all two-qubit entangled state based on Cabello's nonlocality argument
Here we deal with a nonlocality argument proposed by Cabello which is more
general than Hardy's nonlocality argument but still maximally entangled states
do not respond. However, for most of the other entangled states maximum
probability of success of this argument is more than that of the Hardy's
argument.Comment: 9 pages, 1 figur