Quantum discord and the power of one qubit

Abstract

We use quantum discord to characterize the correlations present in the quantum computational model DQC1, introduced by Knill and Laflamme [Phys. Rev. Lett. 81, 5672 (1998)]. The model involves a collection of qubits in the completely mixed state coupled to a single control qubit that has nonzero purity. The initial state, operations, and measurements in the model all point to a natural bipartite split between the control qubit and the mixed ones. Although there is no entanglement between these two parts, we show that the quantum discord across this split is nonzero for typical instances of the DQC1 ciruit. Nonzero values of discord indicate the presence of nonclassical correlations. We propose quantum discord as figure of merit for characterizing the resources present in this computational model.

4 Pages, 1 Figure

References in corpus (2)

• A complete family of separability criteria
• On the role of entanglement and correlations in mixed-state quantum computation

Cited by in corpus (6)

• Experimental quantum computing without entanglement
• Robustness of quantum discord to sudden death
• Classical and quantum correlations under decoherence
• Quantum discord and quantum phase transition in spin chains
• Correlations in local measurements on a quantum state, and complementarity as an explanation of nonclassicality
• Broadcast copies reveal the quantumness of correlations