4,904 research outputs found
Programmable quantum state discriminator by Nuclear Magnetic Resonance
In this paper a programmable quantum state discriminator is implemented by
using nuclear magnetic resonance. We use a two qubit spin-1/2 system, one for
the data qubit and one for the ancilla (programme) qubit. This device does the
unambiguous (error free) discrimination of pair of states of the data qubit
that are symmetrically located about a fixed state. The device is used to
discriminate both, linearly polarized states and elliptically polarized states.
The maximum probability of the successful discrimination is achieved by
suitably preparing the ancilla qubit. It is also shown that, the probability of
discrimination depends on angle of unitary operator of the protocol and
ellipticity of the data qubit state.Comment: 22 pages and 9 figure
Quantum Information processing by NMR: Implementation of Inversion-on-equality gate, Parity gate and Fanout gate
While quantum information processing by nuclear magnetic resonance (NMR) with
small number of qubits is well established, implementation of lengthy
computations have proved to be difficult due to decoherence/relaxation. In such
circumstances, shallow circuits (circuits using parallel computation) may prove
to be realistic. Parity and fanout gates are essential to create shallow
circuits. In this article we implement inversion-on-equality gate, followed by
parity gate and fanout gate in 3-qubit systems by NMR, using evolution under
indirect exchange coupling Hamiltonian.Comment: 24 pages, 7 figure
Efficient Quantum State Tomography for Quantum Information Processing using a two-dimensional Fourier Transform Technique
A new method of quantum state tomography for quantum information processing
is described. The method based on two-dimensional Fourier transform technique
involves detection of all the off-diagonal elements of the density matrix in a
two-dimensional experiment. All the diagonal elements are detected in another
one-dimensional experiment. The method is efficient and applicable to a wide
range of spin systems. The proposed method is explained using a 2 qubit system
and demonstrated by tomographing arbitrary complex density matrices of 2 and 4
qubit systems using simulations.Comment: 11 pages and 2 figure
Simulation of mirror inversion of quantum states in an XY spin chain using NMR
We report an experimental quantum simulation of unitary dynamics of an XY
spin chain with pre-engineered couplings. Using this simulation, we demonstrate
the mirror inversion of quantum states, proposed by Albanese et al. [Phys. Rev.
Lett. 93, 230502 (2004)]. The experiment is performed with a 5-qubit dipolar
coupled spin system using nuclear magnetic resonance techniques. To perform
quantum simulation we make use of the recently proposed unitary operator
decomposition algorithm of Ajoy et al. [Phys. Rev. A 85, 030303 (2012)] along
with numerical pulse optimization techniques. Further, using mirror inversion,
we demonstrate that entangled states can be transferred from one end of the
chain to the other end. The simulations are implemented with high experimental
fidelity, which implies that these kind of simulations may be possible in
larger systems.Comment: 9 pages, 6 figure
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