Quantum mischief rewrites the laws of cause and effect

Alice and Bob, Many thought test stars, cooking dinner after the accident. Alice accidentally drops a plate; The sound startled Bob, who burns himself in the oven and screams. In another version of the event, Bob burns himself out and screams, causing Alice to drop a plate.

Over the past decade, quantum physicists have searched for patterns of a strange perception: in principle, two versions of the story could happen together. This is because events can occur for indefinite reasons, where “A cause B” and “B cause A” are both true at the same time.

“It sounds terrible,” admitted the physicist-University of Vienna এস Eslav Brookner.

The possibility arises from the quantum phenomenon known as superposition, where the particles hold all possible realities together until the moment of measurement. In labs in Austria, China, Australia, and elsewhere, physicists maintain indefinite efficiency disciplines by placing particles of light (known as photons) in a superposition of two states. They then introduce one branch of the superposition to be processed by process B and the other branch after B under A, in this way, known as the quantum switch, the result of which affects what happens in B and vice versa; Photons sense both functional commands simultaneously.

Over the past five years, a growing community of quantum physicists has been implementing quantum switches in tabletop testing and exploring the benefits of providing indefinite functionality commands for quantum computing and communication. It’s “really something that can be effective in everyday life,” said Jisulia Rubino, a University of Bristol researcher who led The first experimental demonstration Of 2017’s Quantum Switch.

But the practical uses of the event intensify the issues deeply involved.

Physicists have long observed that the natural picture of events is manifested as a sequence of causes and effects that do not contain the basic nature of things. They say that if we sometimes find out the quantum source of gravity, space and time, then perhaps this causal perspective has to go. Until recently, however, there was little idea of ​​how post-work physics could work. “A lot of people around the world think that efficacy is so fundamental to our understanding that if we weaken this idea, we won’t be able to create a coherent, meaningful theory,” says Brookner, one of the leaders in the study as an indefinite cause.

This is changing as physicists consider new quantum switch experiments and related thought experiments so that Alice and Bob, created by the quantum nature of gravity, face functional uncertainties. Accounting for this situation has forced researchers to develop new mathematical formalities and thinking. With the help of the emerging framework, “we can make predictions without properly defined functionality,” Brookner said.

Intercourse, not reason

Progress has accelerated recently, but Lucian Hardy, a British-Canadian theoretical physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, traced the line to attack the quantum gravity problem to work 16 years ago. “In my case, it all started with Lucian Hardy’s paper,” Brookner said.

Hardy was famous by Albert Einstein and was best known at the time for applying the concept to quantum mechanics.

Einstein revolutionized physics not by thinking about what the earth is, but by how individuals measure it. In particular, he envisioned making measurements with rulers and clocks on trains carrying people. Using this “operational” approach he was able to conclude that space and time must be relative.

Lucian Hardy initiated the study of indefinite efficacy as a way to understand the quantum nature of gravity.Photo: Gabriela Sekara / Perimeter Institute for Theoretical Physics

In 2001, Hardy applied this same method to quantum mechanics. He Quantum theory is all restructuring Start with five operational axioms.

He then tried to apply it to even bigger problems: quantum mechanics and general relativity, the 80-year-old problem of how to combine quantum mechanics and general relativity about gravitational space. “Driven by this idea I probably think the method of thinking about quantum theory can be applied to quantum gravity,” Hardy told me about Zoom this winter.

The operational question is: Quantum gravity, what can we observe in principle? Hardy thinks about the fact that quantum mechanics and general relativity each have a key feature. Quantum mechanics is the famous arbiter; Its superpositions allow for simultaneous possibilities. General relativity, meanwhile, suggests space and time massage. In Einstein’s theory, a mass as large as the Earth extends the “metric” of space-time. You are close to a larger object, for example, your watch ticks slow. The metric then defines the “light cone” of an nearby event as the space-time zone that can virtually affect the event.

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