Quantum mechanics and general relativity don’t fit together, and a big part of the issue comes down to gravity. For decades, the accepted route to an ultimate theory of everything has involved taking our best theory of gravity and squeezing it into the frame of quantum mechanics. Yet, almost a century later, scientists still haven鈥檛 managed to make gravity fit. Ivette Fuentes is a professor of quantum mechanics who conducts experiments at the scales where quantum theory and general relativity interplay. Fuentes sat down with 快猫短视频 features editor Thomas Lewton to discuss the issues and fascinating theories that pop out when we try to fit classical and quantum mechanics together.

Read more: The experiments that could finally explain gravity

In December 2019, a bad tooth almost killed me. A terrible toothache turned into the biggest health crisis of my life, ultimately landing me in an intensive care unit for a week. Once I recovered, I had to make sense of why this happened to me. Personal negligence? Terrible luck? A fault of the US healthcare system? Rattled and unsure of how to feel, I turned to a place where I had long found answers to existential questions 鈥� quantum physics.

Physics is often considered to be humanity鈥檚 oldest science, getting its start with early astronomers. Much of our understanding of the world is built on physics as a solid, rigorous, objective foundation. It is a science that breaks the world into pieces, analyses each of them, then reassembles them all into a whole that we understand better. This process, based on empiricism and mathematics, doesn鈥檛 care about feelings. Physics isn鈥檛 personal: for example, regardless of who you are, you cannot escape a black hole. Yet I have always taken physics extremely personally.

In my book, , I invite the reader to do the same and, by showing how this benefited me, argue that making the objective subjective can be life-changing.

Take my bad tooth. Once the crisis was over, the issue that kept me up at night was essentially one of cause and effect. The effect was that I nearly died in the ICU, that much is clear, but what was the cause? In trying to process the event, I came up with several conflicting options. It was completely my fault because I dislike going to the dentist. It wasn鈥檛 my fault at all because I was a graduate student and couldn鈥檛 afford the dentist anyway. Trying to reconcile these two sequences of cause and effect only disturbed me further.

Relief unexpectedly came to me through chatting with physicists who study causality in the quantum realm. Reporting for 快猫短视频, I learned about the 鈥�quantum switch鈥�, a procedure that allows a system to exhibit indefinite causality, where different sequences of cause and effect could exist at the same time through the quantum phenomenon of superposition. The idea is not without its critics, but experiments with particles of light have added credence to it. Some researchers have taken it as far as suggesting that the quantum switch should be built into emerging quantum technologies like quantum computers and batteries to make them work better.

As a physicist, I understand that I have very little in common with a聽particle of light. Being macroscopic and warm, I am unaffected by the laws of quantum physics, while the photon can鈥檛 escape its quantum nature. Yet, thinking about the photon in the quantum switch, with its behaviour simultaneously dictated by 鈥淎 causes B鈥� and 鈥淏 causes A鈥� in a way that seems forbidden in every other arena, lessened my tooth conundrum.

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Maybe here, too, several conflicting ideas could be true at the same time. This brought me some peace and informed my future decision-making. I go to the dentist more now, and I believe that improving the working conditions of graduate students in the US, for example by providing them with dental insurance, is urgent and crucial.

In Entangled States, I describe a dozen examples like this, instances of quantum physics offering me guidance for something I couldn鈥檛 understand about my life and the world, or at least nudging me into thinking about it differently. I write about reckoning with my queerness, my experience of being a young immigrant, the way I build relationships, the way I used to teach high school students and much more, all in conversation with what I have learned about quantum physics both as a scholar and a reporter.

Being immersed in cutting-edge science, reporting from the border where human knowledge touches the unknown 鈥� which is exactly where quantum physics shines 鈥� undoubtedly changed me. Embracing its influence in an idiosyncratic and emotional way that complements the objective rigour of the science itself has improved my life and made me a better person. I highly recommend it. Instead of thinking about all things quantum as absolutely abstract and odd, do consider sometimes taking them personally.

On Q-Day, your privacy will be at stake. This is the moment when quantum computers break the encryption protecting the modern world, bank transactions become readable, private messages get exposed and even state secrets become vulnerable.

For years it sounded like sci-fi, something that was decades away from happening, if it happened at all. But now, research suggests that we may be hurtling towards Q-Day at a rapid speed.

In this video, 快猫短视频 uncovers why many experts think the countdown to Q-Day may already have begun, and explains how quantum computers work and why these machines could both threaten the security of the modern world and unlock breakthroughs that could change our lives. Special thanks to Quantum Motion for letting us film at its facilities.