Motivated by limitations and capabilities of neutral atom qubits, we examine whether measurement-free error correction can produce practical error thresholds. We show that this can be achieved by extracting redundant syndrome information, giving our procedure extra fault tolerance and eliminating the need for ancilla verification. The procedure is particularly favorable when multi-qubit gates are available for the correction step. Simulations of the bit-flip, Bacon-Shor, and Steane codes indicate that coherent error correction can produce threshold error rates that are on the order of 10 −3 to 10 −4 -comparable with or better than measurement-based values, and much better than previous results for other coherent error correction schemes. This indicates that coherent error correction is worthy of serious consideration for achieving protected logical qubits.

Dephasing decoherence induced by interaction of one qubit with a quantum bath can be simulated classically by random unitary evolution without the need for a bath and this random unitary evolution is equivalent to the quantum case. For a general dephasing model and a single qubit system, we explicitly construct the noise functional and completely specify the random unitary evolution. To demonstrate the technique, we applied our results to three paradigmatic models: spin-boson, central spin, and quantum impurity. For multiple qubits, we identify a class of generalized quantum dephasing models that can be simulated classically. Finally we show that depolarizing quantum models can be simulated classically for all dimensionalities of the principal system.

The performance of quantum error correction schemes depends sensitively on the physical realizations of the qubits and the implementations of various operations. For example, in quantum dot spin qubits, readout is typically much slower than gate operations, and conventional surface code implementations that rely heavily on syndrome measurements could therefore be challenging. However, fast and accurate reset of quantum dot qubits-without readout-can be achieved via tunneling to a reservoir. Here, we propose small-scale surface code implementations for which syndrome measurements are replaced by a combination of Toffoli gates and qubit reset. For quantum dot qubits, this enables much faster error correction than measurement-based schemes, but requires additional ancilla qubits and non-nearest-neighbor interactions. We have performed numerical simulations of two different coding schemes, obtaining error thresholds on the orders of 10 −2 for a 1D architecture that only corrects bit-flip errors, and 10 −4 for a 2D architecture that corrects bit-and phase-flip errors.

This paper will present the experimental results of the evaluation of two high work, transonic, single-stage turbines investigated under the Energy Efficient Engine Program. The objective of the E3 program, a joint P&WA/NASA program (NAS3-20646) is to provide an advanced technology base for a new generation of fuel-conservative turbofan engines. A single-stage turbine required fewer cooled airfoils, a reduced number of leakage paths and no interstage seals. These advanced energy efficient engines require high engine pressure ratios resulting in high expansion ratio, transonic, turbine designs which must have high aerodynamic efficiency. The goal of the turbine program is to develop a high pressure turbine that is compatible with the overall engine design and has an uncooled efficiency of 90.8 percent.

Two of the most prominent evolutionary debunking arguments are Sharon Street's Darwinian Dilemma for Normative Realism and Alvin Plantinga's Evolutionary Argument against Atheism. In the former, Street appeals to evolutionary considerations to debunk normative realism. In the latter, Plantinga appeals to similar considerations to debunk atheism. By a careful comparison of these two arguments, I develop a new strategy to help normative realists resist Street's debunking attempt. In her Darwinian Dilemma, Street makes epistemological commitments that ultimately support Plantinga's structurally similar argument. If Street succeeds in debunking normative realism, I argue, then she also succeeds in debunking atheism. But atheism is a suppressed premise of the Darwinian Dilemma as well as a commitment of almost all normative anti‐realists. If Street's argument entails theism, then the Darwinian Dilemma is internally incoherent and should be abandoned by almost everyone.