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"With each interaction, Alexa is training to hear better, to interpret more precisely, to trigger actions that map to the user's commands more accurately, and to build a more complete model of their preferences, habits and desires. What is required to make this possible? Put simply: each small moment of convenience - be it answering a question, turning on a light, or playing a song - requires a vast planetary network, fueled by the extraction of non-renewable materials, labor, and data. The scale of resources required is many magnitudes greater than the energy and labor it would take a human to operate a household appliance or flick a switch. A full accounting for these costs is almost impossible, but it is increasingly important that we grasp the scale and scope if we are to understand and govern the technical infrastructures that thread through our lives. III The Salar, the world's largest flat surface, is located in southwest Bolivia at an altitude of 3,656 meters above sea level. It is a high plateau, covered by a few meters of salt crust which are exceptionally rich in lithium, containing 50% to 70% of the world's lithium reserves. 4 The Salar, alongside the neighboring Atacama regions in Chile and Argentina, are major sites for lithium extraction. This soft, silvery metal is currently used to power mobile connected devices, as a crucial material used for the production of lithium-Ion batteries. It is known as 'grey gold.' Smartphone batteries, for example, usually have less than eight grams of this material. 5 Each Tesla car needs approximately seven kilograms of lithium for its battery pack. 6 All these batteries have a limited lifespan, and once consumed they are thrown away as waste. Amazon reminds users that they cannot open up and repair their Echo, because this will void the warranty. The Amazon Echo is wall-powered, and also has a mobile battery base. This also has a limited lifespan and then must be thrown away as waste. According to the Ay

Optimization is a key tool in machine learning, where the goal is to achieve the best possible objective function value in a minimum amount of time. Obtaining any form of global guarantees can usually be done with convex objective functions, or with special cases such as risk minimization with one-hidden over-parameterized layer neural networks (see the June post). In this post, I will consider low-dimensional problems (imagine 10 or 20), with no constraint on running time (thus get ready for some running-times that are exponential in dimension!).

A large team of researchers working with Google Inc. and affiliated with a host of institutions in the U.S., one in Germany and one in the Netherlands has implemented a quantum approximate optimization algorithm (QAOA) on a 53-qubit noisy intermediate-scale quantum (NISQ) device. In their paper published in the journal Nature Physics,, the group describes their method of studying the performance of their QAOA on Google's Sycamore superconducting 53-qubit quantum processor and what they learned from it. Boaz Barak with Harvard University has published a News & Views piece on the work done by the team in the same journal issue.

We study the classical problem of raising capital under asymmetric information. Following Myers and Majluf, we consider firms endowed with assets in place and riskier growth opportunities. When asymmetric information is concentrated on assets in place (rather than growth opportunities), equity-like securities are more likely to be optimal. In contrast, when asymmetric information falls on growth options, debt is optimal. Intuitively, this happens because when the asset with greater volatility is less affected by asymmetric information, issuing a security with greater exposure to upside potential (such as equity) can be less dilutive than issuing a security lacking such exposure (such as debt). Our results suggest that equity is more likely to dominate debt for younger firms with larger investment needs, endowed with riskier, more valuable growth opportunities. Thus, our model can explain why high-growth firms may prefer equity over debt, and then switch to debt financing as they mature.