Experimental quantum verification in the presence of temporally correlated noise

Growth in the complexity and capabilities of quantum information hardware mandates access to practical techniques for performance verification that function under realistic laboratory conditions. Here we experimentally characterise the impact of common temporally correlated noise processes on both randomised benchmarking (RB) and gate-set tomography (GST). We study these using an analytic toolkit based on a formalism mapping noise to errors for arbitrary sequences of unitary operations. This analysis highlights the role of sequence structure in enhancing or suppressing the sensitivity of quantum verification protocols to either slowly or rapidly varying noise, which we treat in the limiting cases of quasi-DC miscalibration and white noise power spectra. We perform experiments with a single trapped $^{171}$Yb$^{+}$ ion as a qubit and inject engineered noise ($\propto \sigma^z$) to probe protocol performance. Experiments on RB validate predictions that the distribution of measured fidelities over sequences is described by a gamma distribution varying between approximately Gaussian for rapidly varying noise, and a broad, highly skewed distribution for the slowly varying case. Similarly we find a strong gate set dependence of GST in the presence of correlated errors, leading to significant deviations between estimated and calculated diamond distances in the presence of correlated $\sigma^z$ errors. Numerical simulations demonstrate that expansion of the gate set to include negative rotations can suppress these discrepancies and increase reported diamond distances by orders of magnitude for the same error processes. Similar effects do not occur for correlated $\sigma^x$ or $\sigma^y$ errors or rapidly varying noise processes, highlighting the critical interplay of selected gate set and the gauge optimisation process on the meaning of the reported diamond norm in correlated noise environments.Comment: Expanded and updated analysis of GST, including detailed examination of the role of gauge optimization in GST. Full GST data sets and supplementary information available on request from the authors. Related results available from http://www.physics.usyd.edu.au/~mbiercuk/Publications.htm

Control of the conformations of ion Coulomb crystals in a Penning trap

Laser-cooled atomic ions form ordered structures in radiofrequency ion traps and in Penning traps. Here we demonstrate in a Penning trap the creation and manipulation of a wide variety of ion Coulomb crystals formed from small numbers of ions. The configuration can be changed from a linear string, through intermediate geometries, to a planar structure. The transition from a linear string to a zigzag geometry is observed for the first time in a Penning trap. The conformations of the crystals are set by the applied trap potential and the laser parameters, and agree with simulations. These simulations indicate that the rotation frequency of a small crystal is mainly determined by the laser parameters, independent of the number of ions and the axial confinement strength. This system has potential applications for quantum simulation, quantum information processing and tests of fundamental physics models from quantum field theory to cosmology

Optical Coherence Technology Detects Early Signs of Peri-implant Mucositis in the Minipig Model

Background: Peri-implant mucositis defines the inflammation of gingival tissue surrounding osseous integrated implants without destruction of supporting bone. Untreated mucositis may develop into peri-implantitis with irreversible resorption of alveolar bone and implant failure. Mucositis is reversible with early intervention; however, existing clinical approaches have proved inadequate to reveal initial stages of this complication. Optical Coherence Tomography (OCT) is a non-invasive modality that provides real time, cross-sectional optical images of tissue up to 2-3mm in depth from the surface. Here, the minipig model assessed the diagnostic capability of OCT to detect early signs of mucositis by imaging microstructural changes of soft peri-implant tissue based on its correspondent histological analysis. Methods: Implants were placed in edentulous ridges of anesthetized animals. After a 7-8 weeks healing to achieve osseous integration, peri-implant disease was induced by ligature procedures. At endpoints of 3, 7 and 12 days after ligation, implant sites were clinically examined by bleeding on probing, probing depth, clinical attachment loss, suppuration and radiographic changes in bone level. Biopsies were collected for ex vivo optical imaging and histological analysis. Results: As early as 3 to 7 days after ligation, imaging documented the internal disarrangement of peri-implant gingival tissue and the images correlated well with corresponding histological specimens. Clinical signs of inflammation and loss of alveolar bone were absent. Conclusion: Development of clinical applications of OCT imaging for early diagnosis of mucositis could lead to therapeutic interventions to reduce one of the causes of implant failur

Control of the conformations of ion Coulomb crystals in a Penning trap

Ion Coulomb crystals containing small numbers of ions have been created and manipulated in a wide range of configurations in a Penning trap, from a linear string, through various three-dimensional conformations, to a planar crystal. We show that the dynamics of the system simplifies enormously in a frame which rotates at half the cyclotron frequency and we discuss the effect of the radial cooling laser beam in this frame. Simulations show that the crystal conformations can be reproduced by finding the minimum energy configuration in a frame whose radial potential is modified by the rotation of the ion crystal. The rotation frequency of the crystal deduced from the simulations is consistent with the known laser parameters. We also show that even though the number of ions in our system is small (typically less than 20), the system still behaves like a plasma and its static properties can be calculated using the standard model for a single-component plasma in a tra

Control of the conformations of ion Coulomb crystals in a Penning trap

Ion Coulomb crystals containing small numbers of ions have been created and manipulated in a wide range of configurations in a Penning trap, from a linear string, through various three-dimensional conformations, to a planar crystal. We show that the dynamics of the system simplifies enormously in a frame which rotates at half the cyclotron frequency and we discuss the effect of the radial cooling laser beam in this frame. Simulations show that the crystal conformations can be reproduced by finding the minimum energy configuration in a frame whose radial potential is modified by the rotation of the ion crystal. The rotation frequency of the crystal deduced from the simulations is consistent with the known laser parameters. We also show that even though the number of ions in our system is small (typically less than 20), the system still behaves like a plasma and its static properties can be calculated using the standard model for a single-component plasma in a tra