598 research outputs found
Experimental implementation of local adiabatic evolution algorithms by an NMR quantum information processor
Quantum adiabatic algorithm is a method of solving computational problems by
evolving the ground state of a slowly varying Hamiltonian. The technique uses
evolution of the ground state of a slowly varying Hamiltonian to reach the
required output state. In some cases, such as the adiabatic versions of
Grover's search algorithm and Deutsch-Jozsa algorithm, applying the global
adiabatic evolution yields a complexity similar to their classical algorithms.
However, using the local adiabatic evolution, the algorithms given by J. Roland
and N. J. Cerf for Grover's search [ Phys. Rev. A. {\bf 65} 042308(2002)] and
by Saurya Das, Randy Kobes and Gabor Kunstatter for the Deutsch-Jozsa algorithm
[Phys. Rev. A. {\bf 65}, 062301 (2002)], yield a complexity of order
(where N=2 and n is the number of qubits). In this paper we report
the experimental implementation of these local adiabatic evolution algorithms
on a two qubit quantum information processor, by Nuclear Magnetic Resonance.Comment: Title changed, Adiabatic Grover's search algorithm added, error
analysis modifie
Nuclear magnetic resonance implementation of the Deutsch-Jozsa algorithm using different initial states
The Deutsch-Jozsa algorithm distinguishes constant functions from balanced
functions with a single evaluation. In the first part of this work, we present
simulations of the nuclear magnetic resonance (NMR) application of the
Deutsch-Jozsa algorithm to a 3-spin system for all possible balanced functions.
Three different kinds of initial states are considered: a thermal state, a
pseudopure state, and a pair (difference) of pseudopure states. Then,
simulations of several balanced functions and the two constant functions of a
5-spin system are described. Finally, corresponding experimental spectra
obtained by using a 16-frequency pulse to create an input equivalent to either
a constant function or a balanced function are presented, and the results are
compared with those obtained from computer simulations.Comment: accepted for publication in the Journal of Chemical Physic
Thermal Equilibrium as an Initial State for Quantum Computation by NMR
We present a method of using a nuclear magnetic resonance computer to solve
the Deutsch-Jozsa problem in which: (1) the number of molecules in the NMR
sample is irrelevant to the number of qubits available to an NMR quantum
computer, and (2) the initial state is chosen to be the state of thermal
equilibrium, thereby avoiding the preparation of pseudopure states and the
resulting exponential loss of signal as the number of qubits increases. The
algorithm is described along with its experimental implementation using four
active qubits. As expected, measured spectra demonstrate a clear distinction
between constant and balanced functions.Comment: including 4 figure
NMR quantum computation with indirectly coupled gates
An NMR realization of a two-qubit quantum gate which processes quantum
information indirectly via couplings to a spectator qubit is presented in the
context of the Deutsch-Jozsa algorithm. This enables a successful comprehensive
NMR implementation of the Deutsch-Jozsa algorithm for functions with three
argument bits and demonstrates a technique essential for multi-qubit quantum
computation.Comment: 9 pages, 2 figures. 10 additional figures illustrating output spectr
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