Charge-qubit operation of an isolated double quantum dot

We have investigated coherent time evolution of pseudo-molecular states of an isolated (leadless) silicon double quantum-dot, where operations are carried out via capacitively-coupled elements. Manipulation is performed by short pulses applied to a nearby gate, and measurement is performed by a single-electron transistor. The electrical isolation of this qubit results in a significantly longer coherence time than previous reports for semiconductor charge qubits realized in artificial molecules.Comment: 4 journal pages, 4 figures, Lette

Single shot measurement of a silicon single electron transistor

We have fabricated a custom cryogenic Complementary Metal-Oxide-Semiconductor (CMOS) integrated circuit that has a higher measurement bandwidth compared with conventional room temperature electronics. This allowed implementing single shot operations and observe the real-time evolution of the current of a phosphorous-doped silicon single electron transistor that was irradiated with a microwave pulse. Relaxation times up to 90 us are observed, suggesting the presence of well isolated electron excitations within the device. It is expected that these are associated with long decoherence time and the device may be suitable for quantum information processing

Model for an irreversible bias current in the superconducting qubit measurement process

The superconducting charge-phase "quantronium" qubit is considered in order to develop a model for the measurement process used in the experiment of Vion [Science 296, 886 (2002)]. For this model we propose a method for including the bias current in the readout process in a fundamentally irreversible way, which to first order is approximated by the Josephson junction tilted-washboard potential phenomenology. The decohering bias current is introduced in the form of a Lindblad operator and the Wigner function for the current-biased readout Josephson junction is derived and analyzed. During the readout current pulse used in the quantronium experiment we find that the coherence of the qubit initially prepared in a symmetric superposition state is lost at a time of 0.2 ns after the bias current pulse has been applied, a time scale that is much shorter than the experimental readout time. Additionally we look at the effect of Johnson-Nyquist noise with zero mean from the current source during the qubit manipulation and show that the decoherence due to the irreversible bias current description is an order of magnitude smaller than that found through adding noise to the reversible tilted-washboard potential model. Our irreversible bias current model is also applicable to persistent-current-based qubits where the state is measured according to its flux via a small-inductance direct-current superconducting quantum interference device

Pivotal Advance: Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory response, and apoptosis

In this study, we have investigated the role of the cannabinoid CB2 (CB2) receptor in an in vivo mouse model of hepatic ischemia/reperfusion (I/R) injury. In addition, we have assessed the role of the CB2 receptor in TNF-alpha-induced ICAM-1 and VCAM-1 expression in human liver sinusoidal endothelial cells (HLSECs) and in the adhesion of human neutrophils to HLSECs in vitro. The potent CB2 receptor agonist HU-308, given prior to the induction of I/R, significantly attenuated the extent of liver damage (measured by serum alanine aminotransferase and lactate dehydrogenase) and decreased serum and tissue TNF-alpha, MIP-1alpha, and MIP-2 levels, tissue lipid peroxidation, neutrophil infiltration, DNA fragmentation, and caspase 3 activity. The protective effect of HU-308 against liver damage was also preserved when given right after the ischemic episode. HU-308 also attenuated the TNF-alpha-induced ICAM-1 and VCAM-1 expression in HLSECs, which expressed CB2 receptors, and the adhesion of human neutrophils to HLSECs in vitro. These findings suggest that selective CB2 receptor agonists may represent a novel, protective strategy against I/R injury by attenuating oxidative stress, inflammatory response, and apoptosis

Methylthioadenosine reprograms macrophage activation through adenosine receptor stimulation

Regulation of inflammation is necessary to balance sufficient pathogen clearance with excessive tissue damage. Central to regulating inflammation is the switch from a pro-inflammatory pathway to an anti-inflammatory pathway. Macrophages are well-positioned to initiate this switch, and as such are the target of multiple therapeutics. One such potential therapeutic is methylthioadenosine (MTA), which inhibits TNFα production following LPS stimulation. We found that MTA could block TNFα production by multiple TLR ligands. Further, it prevented surface expression of CD69 and CD86 and reduced NF-KB signaling. We then determined that the mechanism of this action by MTA is signaling through adenosine A2 receptors. A2 receptors and TLR receptors synergized to promote an anti-inflammatory phenotype, as MTA enhanced LPS tolerance. In contrast, IL-1β production and processing was not affected by MTA exposure. Taken together, these data demonstrate that MTA reprograms TLR activation pathways via adenosine receptors to promote resolution of inflammation. © 2014 Keyel et al

Enhanced Quantum Effects in an Ultra-Small Coulomb Blockaded Device Operating at Room-Temperature

An ultra-small Coulomb blockade device can be regarded as a mesoscopic artificial atom system and provides a rich experimental environment for studying quantum transport phenomena[1]. Previously, these quantum effects have been investigated using relatively large devices at ultra-low temperatures, where they give rise to a fine additional structure on the Coulomb oscillations [2-13]. Here, we report transport measurements carried out on a sub-2nm single-electron device; this size is sufficiently small that Coulomb blockade, and other quantum effects, persist up to room temperature (RT). These devices were made by scaling the size of a FinFET structure down to an ultimate limiting form, resulting in the reliable formation of a sub-2nm silicon Coulomb island. Four clear Coulomb diamonds can be observed at RT and the 2nd Coulomb diamond is unusually large, due to quantum confinement. The observed characteristics are successfully modeled on the basis of a very low electron number on the island, combined with Pauli spin exclusion. These effects offer additional functionality for future RT-operating single-electron device applicationsComment: 7 pages, 4 figure

Surface reconstructions and electronic structure of metallic delafossite thin films

Funding: This paper was primarily supported by the U.S. Department of Energy, Office of Basic Sciences, Division of Materials Science and Engineering under Award No. DE-SC0002334. This research was funded in part by the Gordon and Betty Moore Foundation’s EPiQS Initiative (Grant Nos. GBMF3850 and GBMF9073 to Cornell University). This paper made use of the Cornell Center for Materials Research shared facilities, which are supported through the NSF Materials Research Science and Engineering Centers Program (Grant No. DMR-1719875). B.D.F., M.R.B., and B.P. acknowledge support from the National Science Foundation Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM) under Cooperative Agreement No. DMR-2039380. This paper also made use of the Cornell Energy Systems Institute Shared Facilities partly sponsored by the NSF (Grant No. MRI DMR-1338010) and the Kavli Institute at Cornell. Substrate preparation was performed, in part, at the Cornell NanoScale Facility, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the NSF (Grant No. NNCI-2025233). P.K. acknowledges support from the European Research Council (through the QUESTDO project, 714193) and The Leverhulme Trust (grant No. RPG-2023-256).The growing interest in the growth and study of thin films of low-dimensional metallic delafossites, with the general formula ABO2, is driven by their potential to exhibit electronic and magnetic characteristics that are not accessible in bulk systems. The layered structure of these compounds introduces unique surface states as well as electronic and structural reconstructions, making the investigation of their surface behavior pivotal to understanding their intrinsic electronic structure. In this work, we study the surface phenomena of epitaxially grown PtCoO2, PdCoO2, and PdCrO2 films, utilizing a combination of molecular-beam epitaxy and angle-resolved photoemission spectroscopy. Through precise control of surface termination and treatment, we discover a pronounced √3 x √3 surface reconstruction in PtCoO2 films and PdCoO2 films, alongside a 2 × 2 surface reconstruction observed in PdCrO2 films. These reconstructions have not been reported in prior studies of delafossites. Furthermore, our computational investigations demonstrate the BO2 surface’s relative stability compared to the A-terminated surface and the significant reduction in surface energy facilitated by the reconstruction of the A-terminated surface. These experimental and theoretical insights illuminate the complex surface dynamics in metallic delafossites, paving the way for future explorations of their distinctive properties in low-dimensional studies.Peer reviewe