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Local classical MAX-CUT algorithm outperforms $p=2$ QAOA on high-girth regular graphs

Quantum 5, 437 (2021). https://doi.org/10.22331/q-2021-04-20-437 The $p$-stage Quantum Approximate Optimization Algorithm (QAOA$_p$) is a promising approach for combinatorial optimization on noisy intermediate-scale quantum (NISQ) devices, but its theoretical behavior is not well understood beyond $p=1$. We analyze QAOA$_2$ for the $textit{maximum cut problem}$ (MAX-CUT), deriving a graph-size-independent expression for the expected cut fraction on any $D$-regular graph of girth $> 5$ (i.e. without triangles, squares, or pentagons). We show that for all degrees $D ge 2$ and every $D$-regular graph $G$ of girth $> 5$, QAOA$_2$ has a larger expected cut fraction than QAOA$_1$ on $G$. However, we also show…

Lightweight Detection of a Small Number of Large Errors in a Quantum Circuit

Quantum 5, 436 (2021). https://doi.org/10.22331/q-2021-04-20-436 Suppose we want to implement a unitary $U$, for instance a circuit for some quantum algorithm. Suppose our actual implementation is a unitary $tilde{U}$, which we can only apply as a black-box. In general it is an exponentially-hard task to decide whether $tilde{U}$ equals the intended $U$, or is significantly different in a worst-case norm. In this paper we consider two special cases where relatively efficient and lightweight procedures exist for this task. First, we give an efficient procedure under the assumption that $U$ and $tilde{U}$ (both of which we can now apply as a…

So you’ve watched Seaspiracy — now what?

Boycotting fish may look like a simple answer, but it is too narrow a response to be an effective solution to the issues raised in the film  Audiences across the world have been rightfully shocked by Seaspiracy, Netflix’s new documentary from British director Ali Tabrizi, which highlights gross environmental and human rights abuses — including human trafficking — occurring in the global fishing industry. From the killings of whales, dolphins, and sharks, scores of plastic fishing nets polluting the ocean, illegal fishing, the failure of certification stamps to guarantee protections, and fishermen trafficked onto fishing vessels, there is certainly no shortage of alarming problems facing the world’s fishing industry.   Yet as much as this…

Scientists Grew Human Cells in Monkey Embryos, and Yes, It’s an Ethical Minefield

Scientists Grew Human Cells in Monkey Embryos, and Yes, It’s an Ethical Minefield Few things in science freak people out more than human-animal hybrids. Named chimeras, after the mythical Greek creature that’s an amalgam of different beasts, these part-human, part-animal embryos have come onto the scene to transform our understanding of what makes us “human.” If theoretically grown to term, chimeras would be an endless resource for replacement human organs. They’re a window into the very early stages of human development, allowing scientists to probe the mystery of the first dozen days after sperm-meets-egg. They could help map out how…

Baby bees love carbs, experiments show – here’s why that matters

Baby bees love carbs, experiments show – here’s why that matters Red mason bee just hatched out of its cocoon. Hazet/Wikimedia Commons, CC BY-SA Wild bees are essential for sustaining the landscapes we love. A healthy community of wild pollinators ensures that most flowering plants have an A-team pollinator species and a reserve bench of backups. Honeybees – just one bee species among many – can’t do the job by themselves. Luckily, they don’t have to: there are over 20,000 wild bee species on Earth. The UK is home to around 270 bee species, including 24 species of bumblebee (which,…

Electric cars could make the roads safer – here’s how

Shutterstock/mikolajn Electric cars have the potential to help in our fight against climate disaster. For example, if all cars in the UK were electric, the country’s emissions would drop by 12%. But electric cars might also be able to address another issue that’s affecting people around the world. Traffic-related fatalities are the eighth leading cause of death for people of all ages – ahead of HIV/AIDS and tuberculosis – and the number one cause of deaths for children and young adults. Both because of the way they are driven and the mechanics inside them, electric vehicles could play an important…

Resource theories of multi-time processes: A window into quantum non-Markovianity

Quantum 5, 435 (2021). https://doi.org/10.22331/q-2021-04-20-435 We investigate the conditions under which an uncontrollable background processes may be harnessed by an agent to perform a task that would otherwise be impossible within their operational framework. This situation can be understood from the perspective of resource theory: rather than harnessing 'useful' quantum states to perform tasks, we propose a resource theory of quantum processes across multiple points in time. Uncontrollable background processes fulfil the role of resources, and a new set of objects called $textit{superprocesses}$, corresponding to operationally implementable control of the system undergoing the process, constitute the transformations between them. After…

Non-verbal Adaptation to the Interlocutors' Inner Characteristics: Relevance, Challenges, and Future Directions

Human diversity cannot be denied. In our everyday social interactions, we constantly experience the fact that each individual is a unique combination of characteristics with specific cultural norms, roles, personality, and mood. Efficient social interaction thus requires an adaptation of communication behaviors to each specific interlocutor that one encounters. This is especially true for non-verbal communication that is more unconscious and automatic than verbal communication. Consequently, non-verbal communication needs to be understood as a dynamic and adaptive process in the theoretical modeling and study of social interactions. This perspective paper presents relevance, challenges, and future directions for the study of…

The Interpersonal Neurobiology of Intersubjectivity

In 1975, Colwyn Trevarthen first presented his groundbreaking explorations into the early origins of human intersubjectivity. His influential model dictates that, during intimate and playful spontaneous face-to-face protoconversations, the emotions of both the 2–3-month-old infant and mother are nonverbally communicated, perceived, mutually regulated, and intersubjectively shared. This primordial basic interpersonal interaction is expressed in synchronized rhythmic-turn-taking transactions that promote the intercoordination and awareness of positive brain states in both. In this work, I offer an interpersonal neurobiological model of Trevarthen’s intersubjective protoconversations as rapid, reciprocal, bidirectional visual-facial, auditory-prosodic, and tactile-gestural right brain-to-right brain implicit nonverbal communications between the psychobiologically attuned…

UK Covid live: ministers created confusion by muddling lockdown guidance with law, police watchdog says

Latest updates: HMIC report also highlights ‘frequent frustration’ of police forces over lack of notice about changes to Covid rules 12.15pm BST Downing Street has just released its readout from the meeting that Boris Johnson held this morning with the Football Association, the Premier League and representatives from some supporters’ groups. It says: The prime minister and culture secretary Oliver Dowden met with representatives from the Football Association, the Premier League and football fan groups this morning to discuss action against the proposed European super league. He expressed his solidarity with football fans and agreed they must always be at…

Coronavirus live news: EU to rule on J&J vaccine safety; India records nearly 1.6m cases in a week

EU drug regulator to make ruling on Tuesday; India government says all adults to be eligible for vaccine in May as cases skyrocket; US ships vaccines for all overseas workforce Indian expansion of Covid vaccine drive may further strain supplies What do we know about the Indian coronavirus variant? Greta Thunberg condemns vaccine inequality between rich and poor countries See all our coronavirus coverage 12.07pm BST Some 2.5 million Covid-19 vaccine doses were administered in France last week, the country’s health ministry has announced as its vaccination programme gathers pace. The take-up rate for AstraZeneca stood at 73%, compared to…

Let’s learn about exercise

Exercise might seem like a chore sometimes, especially when we get told so often that we should exercise more. But we need to get up and start moving. Many of us spend too much time sitting and staring at screens. Most teen girls don’t meet the standards for physical activity. Getting scolded about this, though, doesn’t really help. And that’s too bad, because exercise can be both fun and good for the body and the brain. Exercise is good for your muscles, of course. But it’s also good for your bones. Getting exercise (and plenty of sleep) helps tweens and…

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