Infoman

https://cheatography.com/desmovalvo/cheat-sheets/python3-data-structures/

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Flask

https://www.softwaretestinghelp.com/flask-interview-questions-with-answers/

https://mindmajix.com/flask-interview-questions

https://www.knowledgehut.com/interview-questions/flask

Blueprint / init.py

Blueprints help you structure your application by organizing the logic into subdirectories. In addition to that, you can store your templates and static files along with the logic in the same subdirectory. Now you can see that you have clear separation of concerns

FastAPI

https://climbtheladder.com/fastapi-interview-questions/

/blueprint-tutorial

├── /myapp_with_blueprints

│ ├── init.py

│ ├── /admin

│ │ ├── /templates

│ │ ├── /static

│ │ └── routes.py

│ ├── /core

│ │ ├── /templates

│ │ ├── /static

│ │ └── routes.py

│ ├── /products

│ │ ├── /templates

│ │ ├── /static

│ │ └── routes.py

│ └── /profile

| ├── /templates

| ├── /static

| └── routes.py

├── app.py

├── /static

└── /templates

What is init py file?

The init.py files are required to make Python treat directories containing the file as packages. This prevents directories with a common name, such as string , unintentionally hiding valid modules that occur later on the module search path.

Python

Infoman

Job details Salary £34,000 - £36,000 a year Job type Full-time Benefits Pulled from the full job description Company pension Full Job Description Job Purpose and Background in Summary

We are looking for a Python Software Engineer to be responsible for leading and delivering the goals of CDP’s new platform. The successful candidate will work on designing and delivering further automation of CDP’s scoring processes, help to build the azure platform capabilities and will work closely with the scoring methodology team.

This role requires building back-ends for the scoring process to define and handle questionnaire and scoring methodology meta-data, refining the current rules-based system to process automated scoring, and building a back-end to provide interactivity for the manual parts of the scoring process. These back-ends and engines will then be deployed and integrated on Azure. The successful candidate will need to demonstrate capability to work and communicate effectively with others, including stakeholders and thematic teams, to ensure processes are followed, deliverables are aligned to milestones and outputs are built to agreed quality standards.

About CDP

CDP is a not-for-profit charity that runs the global disclosure system for investors, companies, cities, states and regions to manage their environmental impacts. The world’s economy looks to CDP as the gold standard of environmental reporting with the richest and most comprehensive dataset on corporate and city action. In 2021 we launched our new five-year strategy: Accelerating the Rate of Change - find out more here.

Key Responsibilities Include:

Creating back-ends (as part of a developer team) for improving questionnaire and scoring methodology development and resulting data structures driven by business owners Refining the architecture of the rule-based auto-scoring engine (as part of a developer team) for improving the process of dealing with changes in the methodology Creating a back-end (as part of a developer team) for streamlining the processes of interacting with manual scoring and quality assurance by business owners Interacting with an agile scrum team Making use of the Azure stack for development and deployment Required Skills and Experience:

Passion for the environment and clear understanding of the aims of CDP BS/MS in Computer Science or equivalent fields 3+ years of experience as a software engineer 3+ years of experience in Python programming, including building packages Strong understanding of the software design/architecture process 2+ years of experience in services in cloud environments (preferably Azure) Experience with web-frameworks such as FastAPI, Flask, or Django, to create Rest APIs Experience with SQL and ORM with tools like SQLAlchemy or SQLModel Experience in tools such as Git, Docker and shell scripting Experience in unit testing, logging and documentation Experience working in an agile team Experience in communicating with business owners/business side Desired Skills and Experience:

Experience in JavaScript Experience with rule-based engines Experience with complex questionnaire design and data Experience with NoSQL databases, e.g., MongoDB Ambition to enable and coach colleagues as part of an expanding organisation This is a full-time role based at CDP’s London office reporting to the Head of Data Science and Products, based in Berlin.

Salary and Benefits: £34,000 - £36,000 per annum, 30 days’ holiday plus bank holidays, generous non-contributory pension provision, Employee Assistance Programme, life assurance, training and development, flexible working opportunities and other benefits.

Interested applicants must be eligible to work legally in the UK. We cannot sponsor this role.

Before You Apply

We’ll only use the information you provide to process your application. For more details on how we use your information, see our applicant’s privacy notice. By uploading your CV and covering letter, you are permitting CDP to use the information you have provided for recruitment purposes.

How to Apply:

Please upload your CV in the application form along with a covering letter as an additional document setting out how you meet the required skills and experience or key responsibilities, which should be no more than two pages. The deadline is 16th December 2022.

Hiring Insights Job activity Posted 14 days ago

Infoman

https://youtu.be/EO377EwyiuU

Infoman

A 10-minute increase in travel time to London can reduce the average house price significantly. If you’re happy to make that small sacrifice, we’ve rounded up some of the most affordable commuter cities.

Peterborough, Cambridgeshire = £261,594 Purfleet, Essex = £244,021 Wellingborough, Northamptonshire = £257,799 Northampton, Northamptonshire = £298,030 Pitsea, Essex = £287,954 Rugby, Warwickshire = £281,457 Chatham, Kent = £293,664 Bletchley, Buckinghamshire = £297,958 Colchester, Essex = £344,043 Luton, Bedfordshire = £304,925*

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英國置產

6月 21, 2021

https://richardne97.blogspot.com/2021/06/blog-post.html

在英國購買房地產，可能是打算長居英國的台灣人，第一個所需做的重大決策，以下簡單分享在蘇格蘭進行房屋交易的經驗，英格蘭可能會有些不同，下文中如果是以"英國"為主詞說明，表示該經驗應該可以適用整個英國。

尋找標的

英國網路上房地產資訊相當豐富，以全國性的網站而言，資訊較齊全，操作便利性較佳的為 rightmove 以及 zoopla ，因為房地產公司通常會將手上的物件刊登在各大網站上，所以只要找一個自己習慣使用的即可。

房價

英國房地產資訊，不像台灣以每坪多少價格作為主要訴求，也看不這樣的資訊，甚至有些物件在網站還找不到面積資訊，所以也沒有所謂公設比。價格的差異主要反映在地段、房型、樓層，房間數、年份、內裝等，同一地區，甚至同一棟樓的價格差異甚大，以每坪多少價格來評估也沒有意義。

英國所有房屋的交易歷史紀錄，在上述兩個網站上也都查得到，類似台灣的實價登錄，可追溯到數十年以前，就算沒有交易紀錄，上述系統也會根據附近的房價、房型，給予一個預估值。 Home Report

這應該是在看房階段最重要的一份文件了，英國所有房屋在交易時，都會進行房屋鑑定，並且出一份 Home Report，通常至少都50頁以上，詳細說明屋主，鑑定人，鑑定日期，鑑定項目，鑑定包括房屋內外牆、屋頂、公設、管線、電力系統、供暖系統、窗戶、滲水狀況、煙囪等20多項，各項分數分為1 No immediate action or repair is needed. 2 Repair or replacement future attention. 3 Urgent repair or replacement are needed now. 所以通常如果分數都是1的房子，價格會比較好。 Home Report 通常不會放在網站上讓買方直接下載，而是你對這個物件有興趣，打電話給仲介約看房，給他Email，他就會傳到買方信箱裡。

Home report 也會詳述房屋過去的歷史，能源效率，以及目前預估市場價格，能源效率在英國很重要，在冬天時，如果能源效率低於E，表示熱散失很大，會消耗相當多的電或瓦斯，下表是房屋能源效率範例。

看房重點

中古屋 – 歷史建築

蘇格蘭的新成屋，通常和台灣差不多，一切現代化，樓層相對較低，大約在230~250cm左右，以下僅說明有歷史價值的英國傳統建築看房重點。

蘇格蘭很多超過100年以上的中古屋，會被列為Class 2(含)以上的 Listing Building，這類的房屋價差很大，如果裡面已經整修，並且現代化，價格會相對高，如果還是維持原樣，通常價格較低。

100年以上的中古屋，特徵是有八角窗，樓層挑高3米多，甚至到4米的都有，採光佳，天花板多少都有雕刻裝飾，狀況好的中古屋會比同樣房型坪數的物件價格高上20~40%。

Victoria 式的百年建築相當多 Victoria 式的百年建築，在蘇格蘭相當多

公設

公共區域(communal area)，是影響未來房價的重點，很多房屋公設缺乏管理，維運，相當殘破，就算房屋內部還算不錯，房價也不會好，未來要外牆、屋頂出現問題要修復時，會出現大問題，而且常常會有犯罪人口聚集。

格局

因為蘇格蘭早期的建築，是Ground floor到頂樓都是屬於同一戶，但是隨家庭結構改變，需要的房間數較少，所以現在都把過去的建築內部重新改建，變成每1~2層樓一戶，每戶2~3房市主流，若要住獨棟，要往比較郊區的地方找。以樓層來說，Frist floor (台灣的二樓)是最搶手的，因為不會有Ground floor治安的問題，也不用爬太高樓層，因為英國比較沒有台灣的狂風暴雨，所以對防水問題比較不注重，幾乎所有的房屋都會有漏水問題，所以如果住頂樓，要注意Home report的說明，一旦頂樓漏水，其他住戶又不願意分攤處理時，會相當麻煩。經常性費用費用

通常包括每個月房屋稅，物業管理費，停車費等，有些建築共管區域戶數少，沒有請物業管理公司代管，好處是成本低，代價是對公共區域修繕難以達成共識，導致公設殘破，房價下跌，有物業管理，每月會定期收費維護公設，但是有可能價格不斐，從£50/月到數百都有。房屋稅則是依照所購買的房屋區域，房間數，由政府訂定，也是每個月從£100~£900都有，所以購買時也要注意未來房屋的維持費用。房屋仲介角色

蘇格蘭房屋仲介是幫房屋銷售者提供廣告、Home Report製作，帶看房屋等服務，不介入價格談判，房屋成交傭金，則是3~5%左右，所以去看房屋時，如果不是屋主親自接待，詢問帶看房屋的仲介問題，通常僅能的到粗淺的答案。詳細的問題還是要問屋主或透過Solicitor。價格與競標

蘇格蘭房地產交易，有三個價格要注意，第一個是刊登網站或廣告上的價格，如果是新成屋，屋主急於求現，或是房屋久售無法成交，會以 Fix price方式銷售，也就是用標示的價格，就可以購買，但絕大多數是的價格是以 Offers over 方式標示，也就是競標的起標價格。另一個價格是Home report上由房屋鑑價師所評估的市場價值，最後一個是成交價。以競標方式(Offers over方式)銷售的房屋一但公開，買方通常會參考Home report裡的市場價值(market value)，再根據該物件的搶手程度，加上5~15%的溢價出價，好的物件，通常Offers over + 10%，會是market value，然後再加10%是成交價，所以若物件狀況不錯，Offser over是20萬，成交價可能會落在24萬左右。但是也有差的物件，放在網路上很久沒人要，會調降Offser over，甚至變成fix price求售，所以要溢價多少競標，通常需要參考該區附近的歷史成交價。買方若想購買物件，必須透過Solicitor出價，一般來說，不能直接和屋主談價格，而是透握Solicitor出價後，屋主蒐集到夠多的出價者後，會定義Close Date，在那一天就會以最高價者得標，網路上物件狀態會變成 Under offer，此時進入交易談判程序，包括希望屋主保留那些東西，交屋時間等，如果談判成功，物件狀態就會變成Sold STC，如果失敗，可能會找第二順位談，或是又變成Under offer。但也有例外，如果看屋時剛好碰到屋主，相談甚歡，也是有可能直接達成交易條件，接下來就透過Solicitor進行交易程序。好的物件通常上網後，不到一周就會Close，差的掛上幾個月的都有，甚至之前有幾個絕佳物件，才剛上網，我要約看房，仲介說剛剛第一個看房的人已經和屋主達成交易，直接下架，連競標的機會都沒有。英格蘭房地產交易，過程差不多，不過沒有公告Close Date，各買主依照網路上提供的Guide price 或是 Offers in Excess of price 以及 home report 上的 market value 評估價格，透過Solicitor出價，屋主會透過Solicitor告知是否接受你的價格，如果不接受，買家必須再重複出價，重新出價期間有可能會被其他買家用較高的出價取得。 Solicitor

前面提到的Solicitor，中文可翻成事務律師，所有在英國買房的人，都必須要有一位，如果沒有熟識的，可以請房仲介紹，他負責和賣方的Solicitor進行所有法律文件的審核，登記，以及資金檢驗與交易，常常整個交易過程，買賣雙方從來都沒見過面，一切由Solicitor處理。過去在台灣的FB社團，很多人強調Solicitor的服務很重要，但對我來說，在幾次的購屋經驗中，Solicitor就只有幫我投標、交易驗資，所做的事很少，所以我沒有長期配合或找人介紹Solicitor，都是想購屋時找仲介臨時指派。資金檢驗

2019年起，因應洗錢防制，所有交易必須證明資金來源，若是現金，必須在戶頭停留3~6個月，如果是夫妻資助、父母資助、貸款，都必須要有相關關係證明、貸款證明，否則不能交易，2019我第一次買房時，因為是用現金購買，資金分散在台灣各個戶頭，每個戶頭都要資金停留證明，相當麻煩，所以後來是和單一家銀行辦理貸款，提供一張貸款證明，然後隔天再用其他戶頭的錢把貸款還掉，以方便Solicitor驗資，如此資金也不用在英國停留6個月。少部分金額來自夫妻，父母，可以用台灣戶政事務所的英文戶籍謄本證明之間的關係。貸款

以2019~2021年來說，在英國的貸款成本比台灣高出甚多，彈性也差，在台灣貸款利率大約在1.4~1.9%，甚至可隨時借還的理財型房貸，也才約1.8x %，20年期的房貸，要提早還款(Early repayment)，只要不塗銷，沒有罰則，在英國只有前兩年有優惠利率，第三年起大多在3%左右，甚至高貸款成數者還有到4%，Early repayment 一年不能超過還款餘額的10%，否則要罰，所以如果有資金需求，我都是從台灣借款，英國投資划算很多。交屋

和賣方達成買賣協議後，後續整個交易可以很快，也可能長達數月，因為英國人比較少用現金買房，賣家通常也不會搬走才開始賣房，所以要等到買方辦理貸款，賣方把房屋清空，才會進行交屋。結語

以上資訊是我在2019~2021年間，於 Glasgow 看了不下百間房，買來自住及投資的經驗與心得，在England可能在稅負上會有所差異，但交期流程大致上應該是和Scottland差不多的，希望給未來在英國欲置產的台灣人一些幫助。

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Europe’s economyThe Economist (Asia Pacific)

26/11/2022 Frozen out

IF YOU ASK Europe’s friends around the world what they think of the old continent’s prospects they often respond with two emotions. One is admiration. In the struggle to help Ukraine and resist Russian aggression, Europe has displayed unity, grit and a principled willingness to bear enormous costs. But the second is alarm. A brutal economic squeeze will pose a test of Europe’s resilience in 2023 and beyond. There is a growing fear that the recasting of the global energy system, American economic populism and geopolitical rifts threaten the long-run competitiveness of the European Union and non-members, including Britain. It is not just the continent’s prosperity that is at risk, the health of the transatlantic alliance is, too.

Don’t be fooled by the rush of good news from Europe in the past few weeks. Energy prices are down from the summer and a run of good weather means that gas storage is nearly full. But the energy crisis still poses dangers. Gas prices are six times higher than their long-run average. On November 22nd Russia threatened to throttle the last operational pipeline to Europe, even as missile attacks caused emergency power cuts across Ukraine. Europe’s gas storage will need to be refilled once again in 2023, this time without any piped Russian gas whatsoever.

Vladimir Putin’s energy weapon will exact a toll beyond Ukraine. Our modelling suggests that, in a normal winter, a 10% rise in real energy prices is associated with a 0.6% increase in deaths. Hence the energy crunch this year could cause over 100,000 extra deaths of elderly people across Europe (see Graphic detail). If so, Mr Putin’s energy weapon could take more lives outside Ukraine than his artillery, missiles and drones do directly within it. That is one more reason why Ukraine’s resistance to Russia is Europe’s fight, too.

The war is also creating financial vulnerabilities. Energy inflation is spilling over into the rest of Europe’s economy, creating an acute dilemma for the European Central Bank. It needs to raise interest rates to control prices. But if it goes too far it could destabilise the euro zone’s weaker members, not least indebted Italy (see Finance & economics section).

Even as the energy crisis rages, the war has exposed a vulnerability in Europe’s business model. Too many of Europe’s industrial firms, especially German ones, have relied on abundant energy inputs from Russia. Plenty of companies have also become more dependent on another autocracy, China, as an end market (see Business section). The prospect of severed relations with Russia, structurally higher costs and a decoupling of the West and China has meant a reckoning in many boardrooms.

That fear has been amplified by America’s economic nationalism which threatens to draw activity across the Atlantic in a whirlwind of subsidies and protectionism. President Joe Biden’s Inflation Reduction Act involves $400bn of handouts for energy, manufacturing and transport and includes make-in-America provisions. In many ways the scheme resembles the industrial policies that China has pursued for decades. As the other two pillars of the world economy become more interventionist and protectionist, Europe, with its quaint insistence on upholding World Trade Organisation rules on free trade, looks like a sucker.

Already, companies are reacting to the subsidies. Northvolt, a prized Swedish battery startup, has said that it wants to expand production in America. Iberdrola, a Spanish energy company, is investing twice as much in America as in the European Union. Many bosses warn that the combination of expensive energy and American subsidies leaves Europe at risk of mass deindustrialisation. BASF, a German chemicals giant, recently unveiled plans to shrink its European operations “permanently”. It does not help that Europe is ageing faster than America, too.

Losing investment makes Europe poorer and feeds into a sense of declining economic vigour. Compared with its pre-covid gdp trajectory, Europe has done worse than any other economic bloc. Of the world’s 100 most valuable firms, only 14 are European. Politicians will be tempted to chuck out the rule book and respond with subsidies of their own in an escalating arms race of corporate goodies. Germany’s economy minister has accused America of “hoovering up investments”. President Emmanuel Macron of France has called for “a European wake-up”.

Thus the subsidy row is also feeding tensions between America and Europe. America’s financial and military support for Ukraine vastly exceeds Europe’s, and as it pivots to Asia to meet the challenge from China, America resents the eu’s failure to pay for its own security. Most members of nato have failed to meet the goal of spending 2% of gdp on defence. The eu was staggeringly naive about Russian aggression. Although the war caused America and Europe to unite after the ruptures of the Trump years, the danger is that a long conflict and economic tensions will gradually pull them apart again. Mr Putin and China’s president, Xi Jinping, would love that.

To avoid a dangerous rift, America must see the bigger picture. Mr Biden’s protectionism threatens to drain Europe of vitality even as America props up Ukraine’s army, and armadas of tankers cross the Atlantic to supply Europe’s energy. The chief aim of Bidenomics is to stop China dominating key industries: America has no strategic interest in siphoning European investment. It should make European firms eligible for its energy subsidies, and integrate transatlantic energy markets more deeply.

Europe, meanwhile, needs to protect its economy against the energy squeeze. Schemes that rightly aim to subsidise consumers and firms for their basic energy needs should curb demand by charging higher prices at the margin, as in Germany (see Briefing). To lower long-run energy prices Europe should accelerate the renewables revolution, while keeping energy markets open to competition. It also needs to adapt to a new security reality. That means spending more on defence so that it can take up the burden as America shifts its gaze towards Asia.

Besides admiration and alarm, the other emotion governing transatlantic relations is frustration. America is irritated by Europe’s economic torpor and its failure to defend itself; Europe is outraged by America’s economic populism. But just as Europe must not be divided by the war, so it is vital that the most powerful democratic alliance in history adapts—and endures.

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The Universe Is Not Locally Real, and the Physics Nobel Prize Winners Proved It

Admin November 22, 2022 science

One of the more unsettling discoveries in the past half century is that the universe is not locally real. “Real,” meaning that objects have definite properties independent of observation—an apple can be red even when no one is looking; “local” means objects can only be influenced by their surroundings, and that any influence cannot travel faster than light. Investigations at the frontiers of quantum physics have found that these things cannot both be true. Instead, the evidence shows objects are not influenced solely by their surroundings and they may also lack definite properties prior to measurement. As Albert Einstein famously bemoaned to a friend, “Do you really believe the moon is not there when you are not looking at it?”

This is, of course, deeply contrary to our everyday experiences. To paraphrase Douglas Adams, the demise of local realism has made a lot of people very angry and been widely regarded as a bad move.

Blame for this achievement has now been laid squarely on the shoulders of three physicists: John Clauser, Alain Aspect and Anton Zeilinger. They equally split the 2022 Nobel Prize in Physics “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.” (“Bell inequalities” refers to the pioneering work of the Northern Irish physicist John Stewart Bell, who laid the foundations for this year’s Physics Nobel in the early 1960s.) Colleagues agreed that the trio had it coming, deserving this reckoning for overthrowing reality as we know it. “It is fantastic news. It was long overdue,” says Sandu Popescu, a quantum physicist at the University of Bristol. “Without any doubt, the prize is well-deserved.”

“The experiments beginning with the earliest one of Clauser and continuing along, show that this stuff isn’t just philosophical, it’s real—and like other real things, potentially useful,” says Charles Bennett, an eminent quantum researcher at IBM. “Each year I thought, ‘oh, maybe this is the year,’” says David Kaiser, a physicist and historian at the Massachusetts Institute of Technology. “This year, it really was. It was very emotional—and very thrilling.”

Quantum foundations’ journey from fringe to favor was a long one. From about 1940 until as late as 1990, the topic was often treated as philosophy at best and crackpottery at worst. Many scientific journals refused to publish papers in quantum foundations, and academic positions indulging such investigations were nearly impossible to come by. In 1985, Popescu’s advisor warned him against a Ph.D. in the subject. “He said ‘look, if you do that, you will have fun for five years, and then you will be jobless,’” Popescu says.

Today, quantum information science is among the most vibrant and impactful subfields in all of physics. It links Einstein’s general theory of relativity with quantum mechanics via the still-mysterious behavior of black holes. It dictates the design and function of quantum sensors, which are increasingly being used to study everything from earthquakes to dark matter. And it clarifies the often-confusing nature of quantum entanglement, a phenomenon that is pivotal to modern materials science and that lies at the heart of quantum computing.

“What even makes a quantum computer ‘quantum’?” Nicole Yunger Halpern, a National Institute of Standards and Technology physicist, asks rhetorically. “One of the most popular answers is entanglement, and the main reason why we understand entanglement is the grand work participated in by Bell and these Nobel Prize–winners. Without that understanding of entanglement, we probably wouldn’t be able to realize quantum computers.” For Whom the Bell Tolls

The trouble with quantum mechanics was never that it made the wrong predictions—in fact, the theory described the microscopic world splendidly well right from the start when physicists devised it in the opening decades of the 20th century.

What Einstein, Boris Podolsky and Nathan Rosen took issue with, laid out in their iconic 1935 paper, was the theory’s uncomfortable implications for reality. Their analysis, known by their initials EPR, centered on a thought experiment meant to illustrate the absurdity of quantum mechanics; to show how under certain conditions the theory can break—or at least deliver nonsensical results that conflict with everything else we know about reality. A simplified and modernized version of EPR goes something like this: Pairs of particles are sent off in different directions from a common source, targeted for two observers, Alice and Bob, each stationed at opposite ends of the solar system. Quantum mechanics dictates that it is impossible to know the spin, a quantum property of individual particles prior to measurement. When Alice measures one of her particles, she finds its spin to be either up or down. Her results are random, and yet, when she measures up, she instantly knows Bob’s corresponding particle must be down. At first glance, this is not so odd; perhaps the particles are like a pair of socks—if Alice gets the right sock, Bob must have the left.

But under quantum mechanics, particles are not like socks, and only when measured do they settle on a spin of up or down. This is EPR’s key conundrum: If Alice’s particles lack a spin until measurement, how then when they whiz past Neptune do they know what Bob’s particles will do as they fly out of the solar system in the other direction? Each time Alice measures, she effectively quizzes her particle on what Bob will get if he flips a coin: up, or down? The odds of correctly predicting this even 200 times in a row are 1 in 1060—a number greater than all the atoms in the solar system. Yet despite the billions of kilometers that separate the particle pairs, quantum mechanics says Alice’s particles can keep correctly predicting, as though they were telepathically connected to Bob’s particles.

Although intended to reveal the imperfections of quantum mechanics, when real-world versions of the EPR thought experiment are conducted the results instead reinforce the theory’s most mind-boggling tenets. Under quantum mechanics, nature is not locally real—particles lack properties such as spin up or spin down prior to measurement, and seemingly talk to one another no matter the distance.

Physicists skeptical of quantum mechanics proposed that there were “hidden variables,” factors that existed in some imperceptible level of reality beneath the subatomic realm that contained information about a particle’s future state. They hoped in hidden-variable theories, nature could recover the local realism denied to it by quantum mechanics.

“One would have thought that the arguments of Einstein, Podolsky and Rosen would produce a revolution at that moment, and everybody would have started working on hidden variables,” Popescu says.

Einstein’s “attack” on quantum mechanics, however, did not catch on among physicists, who by and large accepted quantum mechanics as is. This was often less a thoughtful embrace of nonlocal reality, and more a desire to not think too hard while doing physics—a head-in-the-sand sentiment later summarized by the physicist David Mermin as a demand to “shut up and calculate.”

The lack of interest was driven in part because John von Neumann, a highly regarded scientist, had in 1932 published a mathematical proof ruling out hidden-variable theories. (Von Neumann’s proof, it must be said, was refuted just three years later by a young female mathematician, Grete Hermann, but at the time no one seemed to notice.)

Quantum mechanics’ problem of nonlocal realism would languish in a complacent stupor for another three decades until being decisively shattered by Bell. From the start of his career, Bell was bothered by the quantum orthodoxy and sympathetic toward hidden variable theories. Inspiration struck him in 1952, when he learned of a viable nonlocal hidden-variable interpretation of quantum mechanics devised by fellow physicist David Bohm—something von Neumann had claimed was impossible. Bell mulled the ideas over for years, as a side project to his main job working as a particle physicist at CERN.

In 1964, Bell rediscovered the same flaws in von Neumann’s argument that Hermann had. And then, in a triumph of rigorous thinking, Bell concocted a theorem that dragged the question of hidden variables from its metaphysical quagmire onto the concrete ground of experiment.

Normally, hidden-variable theories and quantum mechanics predict indistinguishable experimental outcomes. What Bell realized is that under precise circumstances, an empirical discrepancy between the two can emerge. In the eponymous Bell test (an evolution of the EPR thought experiment), Alice and Bob receive the same paired particles, but now they each have two different detector settings—A and a, B and b. These detector settings allow Alice and Bob to ask the particles different questions; an additional trick to throw off their apparent telepathy. In local hidden-variable theories, where their state is preordained and nothing links them, particles cannot outsmart this extra step, and they cannot always achieve the perfect correlation where Alice measures spin down when Bob measures spin up (and vice versa). But in quantum mechanics, particles remain connected and far more correlated than they could ever be in local hidden-variable theories. They are, in a word, entangled.

Measuring the correlation multiple times for many particle pairs, therefore, could prove which theory was correct. If the correlation remained below a limit derived from Bell’s theorem, this would suggest hidden variables were real; if it exceeded Bell’s limit, then the mind-boggling tenets of quantum mechanics would reign supreme. And yet, in spite of its potential to help determine the very nature of reality, after being published in a relatively obscure journal Bell’s theorem languished unnoticed for years.

The Bell Tolls for Thee

In 1967, John Clauser, then a graduate student at Columbia University, accidentally stumbled across a library copy of Bell’s paper and became enthralled by the possibility of proving hidden-variable theories correct. Clauser wrote to Bell two years later, asking if anyone had actually performed the test. Clauser’s letter was among the first feedback Bell had received.

With Bell’s encouragement, five years later Clauser and his graduate student Stuart Freedman performed the first Bell test. Clauser had secured permission from his supervisors, but little in the way of funds, so he became, as he said in a later interview, adept at “dumpster diving” to secure equipment—some of which he and Freedman then duct-taped together. In Clauser’s setup—a kayak-sized apparatus requiring careful tuning by hand—pairs of photons were sent in opposite directions toward detectors that could measure their state, or polarization.

Unfortunately for Clauser and his infatuation with hidden variables, once he and Freedman completed their analysis, they could not help but conclude that they had found strong evidence against them. Still, the result was hardly conclusive, because of various “loopholes” in the experiment that conceivably could allow the influence of hidden variables to slip through undetected. The most concerning of these was the locality loophole: if either the photon source or the detectors could have somehow shared information (a plausible feat within the confines of a kayak-sized object), the resulting measured correlations could still emerge from hidden variables. As Kaiser puts it pithily, if Alice tweets at Bob which detector setting she’s in, that interference makes ruling out hidden variables impossible.

Closing the locality loophole is easier said than done. The detector setting must be quickly changed while photons are on the fly—“quickly” meaning in a matter of mere nanoseconds. In 1976, a young French expert in optics, Alain Aspect, proposed a way for doing this ultra-speedy switch. His group’s experimental results, published in 1982, only bolstered Clauser’s results: local hidden variables looked extremely unlikely. “Perhaps Nature is not so queer as quantum mechanics,” Bell wrote in response to Aspect’s initial results. “But the experimental situation is not very encouraging from this point of view.”

Other loopholes, however, still remained—and, alas, Bell died in 1990 without witnessing their closure. Even Aspect’s experiment had not fully ruled out local effects because it took place over too small a distance. Similarly, as Clauser and others had realized, if Alice and Bob were not ensured to detect an unbiased representative sample of particles, they could reach the wrong conclusions.

No one pounced to close these loopholes with more gusto than Anton Zeilinger, an ambitious, gregarious Austrian physicist. In 1998, he and his team improved on Aspect’s earlier work by conducting a Bell test over a then-unprecedented distance of nearly half a kilometer. The era of divining reality’s nonlocality from kayak-sized experiments had drawn to a close. Finally, in 2013, Zeilinger’s group took the next logical step, tackling multiple loopholes at the same time.

“Before quantum mechanics, I actually was interested in engineering. I like building things with my hands,” says Marissa Giustina, a quantum researcher at Google who worked with Zeilinger. “In retrospect, a loophole-free Bell experiment is a giant systems-engineering project.” One requirement for creating an experiment closing multiple loopholes was finding a perfectly straight, unoccupied 60-meter tunnel with access to fiber optic cables. As it turned out, the dungeon of Vienna’s Hofburg palace was an almost ideal setting—aside from being caked with a century’s worth of dust. Their results, published in 2015, coincided with similar tests from two other groups that also found quantum mechanics as flawless as ever.

Bell’s Test Reaches the Stars

One great final loophole remained to be closed, or at least narrowed. Any prior physical connection between components, no matter how distant in the past, has the possibility of interfering with the validity of a Bell test’s results. If Alice shakes Bob’s hand prior to departing on a spaceship, they share a past. It is seemingly implausible that a local hidden-variable theory would exploit these loopholes, but still possible.

In 2017, a team including Kaiser and Zeilinger performed a cosmic Bell test. Using telescopes in the Canary Islands, the team sourced its random decisions for detector settings from stars sufficiently far apart in the sky that light from one would not reach the other for hundreds of years, ensuring a centuries-spanning gap in their shared cosmic past. Yet even then, quantum mechanics again proved triumphant.

One of the principal difficulties in explaining the importance of Bell tests to the public—as well as to skeptical physicists—is the perception that the veracity of quantum mechanics was a foregone conclusion. After all, researchers have measured many key aspects of quantum mechanics to a precision of greater than 10 parts in a billion. “I actually didn’t want to work on it. I thought, like, ‘Come on; this is old physics. We all know what’s going to happen,’” Giustina says. But the accuracy of quantum mechanics could not rule out the possibility of local hidden variables; only Bell tests could do that.

“What drew each of these Nobel recipients to the topic, and what drew John Bell himself, to the topic was indeed [the question], ‘Can the world work that way?’” Kaiser says. “And how do we really know with confidence?” What Bell tests allow physicists to do is remove the bias of anthropocentric aesthetic judgments from the equation; purging from their work the parts of human cognition that recoil at the possibility of eerily inexplicable entanglement, or that scoff at hidden-variable theories as just more debates over how many angels may dance on the head of a pin. The award honors Clauser, Aspect and Zeilinger, but it is testament to all the researchers who were unsatisfied with superficial explanations about quantum mechanics, and who asked their questions even when doing so was unpopular.

“Bell tests,” Giustina concludes, “are a very useful way of looking at reality.”

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