Transport of Spin Qubits with Donor Chains under Realistic Experimental Conditions

The ability to transport quantum information across some distance can facilitate the design and operation of a quantum processor. One-dimensional spin chains provide a compact platform to realize scalable spin transport for a solid-state quantum computer. Here, we model odd-sized donor chains in silicon under a range of experimental non-idealities, including variability of donor position within the chain. We show that the tolerance against donor placement inaccuracies is greatly improved by operating the spin chain in a mode where the electrons are confined at the Si-SiO$_2$ interface. We then estimate the required timescales and exchange couplings, and the level of noise that can be tolerated to achieve high fidelity transport. We also propose a protocol to calibrate and initialize the chain, thereby providing a complete guideline for realizing a functional donor chain and utilizing it for spin transport.Comment: 19 pages, 12 figure

Are CEOs to Blame for Corporate Failure? Evidence from Chapter 11 Filings

This study examines whether chief executive officers (CEOs) are to blame for corporate failures. Using alternative CEO managerial ability measures, we document that high-ability (low-ability) CEOs are less (more) likely to be associated with bankruptcy. We also find that reorganized firms run by high-ability incumbent CEOs experience improved financial performance after filing for Chapter 11. Firms that hire high-ability CEOs with bankruptcy experience also realize improved financial performance. Our evidence indicates that the likelihood of corporate bankruptcy is unrelated to the presence of high-ability managers and that bankruptcy does not adversely affect the post-bankruptcy careers of high-ability CEOs

Electric field driven destabilization of the insulating state in nominally pure LaMnO3

We report an electric field driven destabilization of the insulating state in nominally pure LaMnO3 single crystal with a moderate field which leads to a resistive state transition below 300 K. The transition is between the insulating state in LaMnO3 and a high resistance bad metallic state that has a temperature independent resistivity. The transition occurs at a threshold field (Eth) which shows a steep enhancement on cooling. While at lower temperatures the transition is sharp and involves large change in resistance but it softens on heating and eventually absent above 280K. When the Mn4+ content is increased by Sr substitution up to x=0.1, the observed transition though observable in certain temperature range, softens considerably. The observation has been explained as bias driven percolation type transition between two coexisting phases, where the majority phase is a charge and orbitally ordered polaronic insulating phase and the minority phase is a bad metallic phase. The mobile fraction f of the bad metallic phase deduced from the experimental data follows an activated kinetics with the activation energy nearly equal to 200 meV and the prefactor fo is a strong function of the field that leads to a rapid enhancement of f on application of field leading to the resistive state transition. We suggest likely scenarios for such co-existing phases in nominally pure LaMnO3 that can lead to the bias driven percolation type transition.Comment: Accepted in JPC