Experimental detection of nonclassical correlations in mixedstate quantum computation
Abstract
We report on an experiment to detect nonclassical correlations in a highly mixed state. The correlations are characterized by the quantum discord and are observed using four qubits in a liquidstate nuclear magnetic resonance quantum information processor. The state analyzed is the output of a DQC1 computation, whose input is a single quantum bit accompanied by n maximally mixed qubits. This model of computation outperforms the best known classical algorithms and, although it contains vanishing entanglement, it is known to have quantum correlations characterized by the quantum discord. This experiment detects nonvanishing quantum discord, ensuring the existence of nonclassical correlations as measured by the quantum discord.
 Publication:

Physical Review A
 Pub Date:
 October 2011
 DOI:
 10.1103/PhysRevA.84.044302
 arXiv:
 arXiv:1105.2262
 Bibcode:
 2011PhRvA..84d4302P
 Keywords:

 03.67.Lx;
 03.65.Ta;
 03.67.Ac;
 76.60.k;
 Quantum computation;
 Foundations of quantum mechanics;
 measurement theory;
 Quantum algorithms protocols and simulations;
 Nuclear magnetic resonance and relaxation;
 Quantum Physics
 EPrint:
 The second version more closely resembles that of the published manuscript