Shannon and von Neumann entropies of multi-qubit Schrödinger's cat states

Jansen, Nathan; Loucks, Matthew; Gilbert, Scott M.; Fleming-Dittenber, Corbin; Egbert, Julia; Hunt, Katharine Clarke

doi:10.1039/d1cp05255a

Cited by 1 publication

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References 158 publications

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“…The second metric of interest is the one based on the slope of the plot of Shannon entropy versus number of qubits for N -qubit GHZ states proposed by Hunt et al in ref ( 65 ). As can be seen in Figure 4 , we construct a figure of Shannon entropy ( S e ) versus number of qubits ( N ) for each quantum device employed in this study.…”

Section: Resultsmentioning

confidence: 99%

Qubit Condensation for Assessing Efficacy of Molecular Simulation on Quantum Computers

2023

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Quantum computers may demonstrate significant advantages over classical devices, as they are able to exploit a purely quantum-mechanical phenomenon known as entanglement in which a single quantum state simultaneously populates two-or-more classical configurations. However, due to environmental noise and device errors, elaborate quantum entanglement can be difficult to prepare on modern quantum computers. In this paper, we introduce a metric based on the condensation of qubits to assess the ability of a quantum device to simulate many-electron systems. Qubit condensation occurs when the qubits on a quantum computer condense into a single, highly correlated particle-hole state. While conventional metrics like gate errors and quantum volume do not directly target entanglement, the qubit-condensation metric measures the quantum computer's ability to generate an entangled state that achieves nonclassical long-range order across the device. To demonstrate, we prepare qubit condensations on various quantum devices and probe the degree to which qubit condensation is realized via postmeasurement analysis. We show that the predicted ranking of the quantum devices is consistent with the errors obtained from molecular simulations of H 2 using a contracted quantum eigensolver.

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Section: Resultsmentioning

confidence: 99%