A Ticking Evolutionary Clock

How quickly will a gene’s rate of evolution slow to a crawl? …

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Evolution Runs Faster on Short Timescales

Examine evolution over the course of years or centuries, and you’ll find that it progresses much more quickly than it does over geologic time. …

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Solution: ‘Taming Quantum Weirdness’

A simple analogue could offer insights into one of the most astonishing results of quantum mechanics. …

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Estimating the fidelity of T gates using standard interleaved randomized benchmarking

Randomized benchmarking is an important protocol for robustly characterizing the error rates of quantum gates. The technique is typically applied to the Clifford gates since they form a group that satisfies a convenient technical condition of forming a unitary 2-design, in addition to having a tight connection to fault-tolerant quantum computing and an efficient classical simulation. In order to achieve universal quantum computing one must add at least one additional gate such as the T gate (also known as the π /8 gate). Here we propose and analyze a simple variation of the standard interleaved RB protocol that can accurately estimate the average fidelity of the T gate while retaining the many advantages of a unitary 2-design and the fidelity guarantees that such a design delivers, as well as the efficient classical simulation property of the Clifford group. Our work complements prior methods that have succeeded in estimating T gate fidelities, but onl… …

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Why Did Life Move to Land? For the View

The ancient creatures who first crawled onto land may have been lured by the informational benefit that comes from seeing through air. …

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Demonstrating non-Abelian braiding of surface code defects in a five qubit experiment

Currently, the mainstream approach to quantum computing is through surface codes. One way to store and manipulate quantum information with these to create defects in the codes which can be moved and used as if they were particles. Specifically, they simulate the behaviour of exotic particles known as Majoranas, which are a kind of non-Abelian anyon. By exchanging these particles, important gates for quantum computation can be implemented. Here we investigate the simplest possible exchange operation for two surface code Majoranas. This is found to act non-trivially on only five qubits. The system is then truncated to these five qubits, so that the exchange process can be run on the IBM 5Q processor. The results demonstrate the expected effect of the exchange. This paper has been written in a style that should hopefully be accessible to both professional and amateur scientists. …

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Ergodicity in randomly perturbed quantum systems

The theoretical cornerstone of statistical mechanics is the ergodic assumption, i.e. the assumption that the time average of an observable equals its ensemble average. Here, we show how such a property is present when an open quantum system is continuously perturbed by an external environment effectively observing the system at random times while the system dynamics approaches the quantum Zeno regime. In this context, by large deviation theory we analytically show how the most probable value of the probability for the system to be in a given state eventually deviates from the non-stochastic case when the Zeno condition is not satisfied. We experimentally test our results with ultra-cold atoms prepared on an atom chip. …

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‘Digital Alchemist’ Seeks Rules of Emergence

Computational physicist Sharon Glotzer is uncovering the rules by which complex collective phenomena emerge from simple building blocks. …

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