230 research outputs found
Coherence-protected Quantum Gate by Continuous Dynamical Decoupling in Diamond
To implement reliable quantum information processing, quantum gates have to
be protected together with the qubits from decoherence. Here we demonstrate
experimentally on nitrogen-vacancy system that by using continuous wave
dynamical decoupling method, not only the coherence time is prolonged by about
20 times, but also the quantum gates is protected for the duration of
controlling time. This protocol shares the merits of retaining the superiority
of prolonging the coherence time and at the same time easily combining with
quantum logic tasks. It is expected to be useful in task where duration of
quantum controlling exceeds far beyond the dephasing time.Comment: 5 pages, 4 figure
Quantum Discord for Investigating Quantum Correlations without Entanglement in Solids
Quantum systems unfold diversified correlations which have no classical
counterparts. These quantum correlations have various different facets. Quantum
entanglement, as the most well known measure of quantum correlations, plays
essential roles in quantum information processing. However, it has recently
been pointed out that quantum entanglement cannot describe all the
nonclassicality in the correlations. Thus the study of quantum correlations in
separable states attracts widely attentions. Herein, we experimentally
investigate the quantum correlations of separable thermal states in terms of
quantum discord. The sudden change of quantum discord is observed, which
captures ambiguously the critical point associated with the behavior of
Hamiltonian. Our results display the potential applications of quantum
correlations in studying the fundamental properties of quantum system, such as
quantum criticality of non-zero temperature.Comment: 4 pages, 4 figure
Quantum Factorization of 143 on a Dipolar-Coupling NMR system
Quantum algorithms could be much faster than classical ones in solving the
factoring problem. Adiabatic quantum computation for this is an alternative
approach other than Shor's algorithm. Here we report an improved adiabatic
factoring algorithm and its experimental realization to factor the number 143
on a liquid crystal NMR quantum processor with dipole-dipole couplings. We
believe this to be the largest number factored in quantum-computation
realizations, which shows the practical importance of adiabatic quantum
algorithms.Comment: 5 pages, 3 figure
Simulation of chemical reaction dynamics on an NMR quantum computer
Quantum simulation can beat current classical computers with minimally a few
tens of qubits and will likely become the first practical use of a quantum
computer. One promising application of quantum simulation is to attack
challenging quantum chemistry problems. Here we report an experimental
demonstration that a small nuclear-magnetic-resonance (NMR) quantum computer is
already able to simulate the dynamics of a prototype chemical reaction. The
experimental results agree well with classical simulations. We conclude that
the quantum simulation of chemical reaction dynamics not computable on current
classical computers is feasible in the near future.Comment: 37 pages, 7 figure
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