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Since you first started learning about the world, you’ve known that cause leads to effect. Everything that’s ever happened to or near you has reiterated this point, making it seem like a fundamental law of nature. It isn’t.

It is, in fact, possible for an event to occur before its causal factors have manifested or happened. This isn’t how appliances work — you don’t have to worry about will have having left the oven on — but it is how particle physics works. It’s also the key to explaining how time travel, under the laws of quantum physics, could operate.

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If a time traveler went back in time and stopped their own grandparents from meeting, would they prevent their own birth?

That’s the crux of an infamous theory known as the ‘grandfather paradox’, which is often said to mean time travel is impossible — but some researchers think otherwise. A group of scientists have simulated how time-travelling photons might behave, suggesting that, at the quantum level, the grandfather paradox could be resolved.

The research was carried out by a team of researchers at the University of Queensland in Australia and their results are published in the journal Nature Communications. The study used photons — single particles of light — to simulate quantum particles travelling back through time. By studying their behavior, the scientists revealed possible bizarre aspects of modern physics.

In the simulation, the researchers examined two possible outcomes for a time-travelling photon. In the simulation, the researchers examined the behavior of a photon traveling through time and interacting with its older self.

In their experiment they made use of the closely related, fictitious, case where the photon travels through normal space-time and interacts with another photon that is stuck in a time-travelling loop through a wormhole, known as a closed timelike curve (CTC).

Older, but interesting idea—


Warp drive and stargate wormholes could be used for time travel to the past. That’s the surprising conclusion that controversial theoretical physicist and author Dr. Jack Sarfatti has reached from his research into dark energy and dark matter.

Hubble image of dark matter ring in galaxy cluster

Sarfatti, who was the inspiration for “Doc” in the movie “Back To The Future,” will discuss this on the Coast to Coast AM national radio talk show on Sunday, August 26 at 10:30 pm Pacific time.

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Why send a message back in time, but lock it so that no one can ever read the contents? Because it may be the key to solving currently intractable problems. That’s the claim of an international collaboration who have just published a paper in npj Quantum Information.

It turns out that an unopened message can be exceedingly useful. This is true if the experimenter entangles the message with some other system in the laboratory before sending it. Entanglement, a strange effect only possible in the realm of quantum physics, creates correlations between the time-travelling message and the laboratory system. These correlations can fuel a quantum computation.

Around ten years ago researcher Dave Bacon, now at Google, showed that a time-travelling quantum computer could quickly solve a group of problems, known as NP-complete, which mathematicians have lumped together as being hard.

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Why send a message back in time, but lock it so that no one can ever read the contents? Because it may be the key to solving currently intractable problems. That’s the claim of an international collaboration who have just published a paper in npj Quantum Information.

It turns out that an unopened message can be exceedingly useful. This is true if the experimenter entangles the message with some other system in the laboratory before sending it. Entanglement, a strange effect only possible in the realm of , creates correlations between the time-travelling message and the laboratory system. These correlations can fuel a quantum computation.

Around ten years ago researcher Dave Bacon, now at Google, showed that a time-travelling quantum computer could quickly solve a group of problems, known as NP-complete, which mathematicians have lumped together as being hard.

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Scientists from the University of Queensland have used photons (single particles of light) to simulate quantum particles travelling through time. The research is cutting edge and the results could be dramatic!

Their research, entitled “Experimental simulation of closed timelike curves “, is published in the latest issue of Nature Communications. The grandfather paradox states that if a time traveler were to go back in time, he could accidentally prevent his grandparents from meeting, and thus prevent his own birth.

However, if he had never been born, he could never have traveled back in time, in the first place. The paradoxes are largely caused by Einstein’s theory of relativity, and the solution to it, the Gödel metric.

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For the first time, scientists have achieved infinite speeds on a microchip. Although this advance will not enable faster-than-light starships, the light-warping technology behind this innovation could lead to new light-based microchips and help enable powerful quantum computers, researchers said.

Light travels at the speed of about 670 million miles per hour (1.08 billion km/h) in a vacuum, and is theoretically the fastest possible speed at which matter or energy can travel. Exceeding this speed limit should lead to impossible results such as time travel, according to Einstein’s theory of relativity.

However, in a way, researchers have overcome this barrier for decades. [Warped Physics: 10 Effects of Faster-Than-Light Travel].

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In general relativity, closed timelike curves can break causality with remarkable and unsettling consequences. At the classical level, they induce causal paradoxes disturbing enough to motivate conjectures that explicitly prevent their existence. At the quantum level such problems can be resolved through the Deutschian formalism, however this induces radical benefits—from cloning unknown quantum states to solving problems intractable to quantum computers. Instinctively, one expects these benefits to vanish if causality is respected. Here we show that in harnessing entanglement, we can efficiently solve NP-complete problems and clone arbitrary quantum states—even when all time-travelling systems are completely isolated from the past. Thus, the many defining benefits of Deutschian closed timelike curves can still be harnessed, even when causality is preserved. Our results unveil a subtle interplay between entanglement and general relativity, and significantly improve the potential of probing the radical effects that may exist at the interface between relativity and quantum theory.

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In Therefore I Am, the McCoubrey brothers create a compelling time travel mystery in just six minutes. It leaves you with questions, BUT in a good way.

Therefore I Am tracks a conversation a man has with future versions of himself, each one arriving slightly earlier than the last, each one with slightly different instructions for how to get to that point. You can even trace the loops—each one leads to the next. And yet, not a single one seems to have successfully avoided the event they’re trying to stop.

It’s so slickly done, the editing seamlessly moving from one encounter to another. It’s great.

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