Researchers have shown that a quantum computer does not need the arrow of time like a classical computer. In some cases, it’s as if the quantum computer doesn’t need to distinguish between cause and effect at all.
The new work is inspired by an influential discovery made almost ten years ago by complexity scientists James Crutchfield and John Mahoney at the University of California, Davis. They showed that many statistical data sequences will have a built-in arrow of time. An observer who sees the data played from beginning to end, like the frames of a movie, can model what comes next using only a modest amount of memory about what occurred before. An observer who tries to model the system in reverse has a much harder task – potentially needing to track orders of magnitude more information.
This discovery came to be known as ‘causal asymmetry’. It seems intuitive. After all, modelling a system when time is running backwards is like trying to infer a cause from an effect. We are used to finding that more difficult than predicting an effect from a cause. In everyday life, understanding what will happen next is easier if you know what just happened, and what happened before that.
However, researchers are always intrigued to discover asymmetries that are linked to time-ordering. This is because the fundamental laws of physics are ambivalent about whether time moves forwards or in reverse.
“When the physics does not impose any direction on time, where does causal asymmetry – the memory overhead needed to reverse cause and effect – come from?” asks Gu.
The first studies of causal asymmetry used models with classical physics to generate predictions. Crutchfield and Mahoney teamed up with Gu and collaborators Jayne Thompson, Andrew Garner and Vlatko Vedral at CQT to find out whether quantum mechanics changes the situation.
They found that it did. Models that use quantum physics, the team prove, can entirely mitigate the memory overhead. A quantum model forced to emulate the process in reverse-time will always outperform a classical model modelling the process in forward-time.
The work has some profound implications. “The most exciting thing for us is the possible connection with the arrow of time,” says Thompson, first author on the work. “If causal asymmetry is only found in classical models, it suggests our perception of cause and effect, and thus time, can emerge from enforcing a classical explanation on events in a fundamentally quantum world,” she says.
Next the team wants to understand how this connects to other ideas of time. “Every community has their own arrow of time, and everybody wants to explain where they come from,” says Vedral. Crutchfield and Mahoney called causal asymmetry an example of time’s ‘barbed arrow’.
Most iconic is the ‘thermodynamic arrow’. It comes from the idea that disorder, or entropy, will always increase – a little here and there, in everything that happens, until the Universe ends as one big, hot mess. While causal asymmetry is not the same as the thermodynamic arrow, they could be interrelated. Classical models that track more information also generate more disorder. “This hints that causal asymmetry can have entropic consequence,” says Thompson.
The results may also have practical value. Doing away with the classical overhead for reversing cause and effect could help quantum simulation. “Like being played a movie in reverse time, sometimes we may be required to make sense of things that are presented in an order that is intrinsically difficult to model. In such cases, quantum methods could prove vastly more efficient than their classical counterparts,” says Gu.
Causal asymmetry is one of the great surprises in predictive modeling: The memory required to predict the future differs from the memory required to retrodict the past. There is a privileged temporal direction for modeling a stochastic process where memory costs are minimal. Models operating in the other direction incur an unavoidable memory overhead. Here, we show that this overhead can vanish when quantum models are allowed. Quantum models forced to run in the less-natural temporal direction not only surpass their optimal classical counterparts but also any classical model running in reverse time. This holds even when the memory overhead is unbounded, resulting in quantum models with unbounded memory advantage.
Arxiv – Causal Asymmetry in a Quantum World
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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So does this mean the Universe is a simulated quantum computer ?
So does this mean the Universe is a simulated quantum computer ?
Probably means that the universe is like it is because your brain makes it so. But don’t feel special, any macroscopic “observer” (e.g. a rock) would break the beautiful time symmetry of quantum particles and make the tangible macroscopic world and its arrow of time emerge. What it’s funny is that it may make the universe self-justifying: the past was as it was to make sure the present is as it is, and the future as it will be. And not just metaphorically: there will be particle level interactions going on always between all these times, making sure all the others come to pass. With some weirder possibilities: the past could change because something happening in the present, albeit if that is in some observable place (our legit past) or in another universe is up for speculation.
Inference from current effects to previous causes, is, of course, at the heart of mysteries precisely because it is so difficult. Sir Arthur Conan Doyle’s famous quip about what the dog did in the night time is perhaps the best known literary example. Abductive reasoning from current effect to past cause is also standard in the historical sciences. As Charles Lyell argued, the best way to explain what we observe now is to look for causes known to produce the effect in question.
Probably means that the universe is like it is because your brain makes it so.But don’t feel special any macroscopic observer”” (e.g. a rock) would break the beautiful time symmetry of quantum particles and make the tangible macroscopic world and its arrow of time emerge.What it’s funny is that it may make the universe self-justifying: the past was as it was to make sure the present is as it is”” and the future as it will be. And not just metaphorically: there will be particle level interactions going on always between all these times making sure all the others come to pass.With some weirder possibilities: the past could change because something happening in the present”” albeit if that is in some observable place (our legit past) or in another universe is up for speculation.”””
Inference from current effects to previous causes is of course at the heart of mysteries precisely because it is so difficult. Sir Arthur Conan Doyle’s famous quip about what the dog did in the night time is perhaps the best known literary example.Abductive reasoning from current effect to past cause is also standard in the historical sciences. As Charles Lyell argued the best way to explain what we observe now is to look for causes known to produce the effect in question.
No, it means quantum computers are little pieces of the universe.
No it means quantum computers are little pieces of the universe.
Let’s go really out there with this one. It’s a fun one so why not? If all worldlines are actually contiguous this raises an interesting possibility. First, all possible worldlines probably are contiguous, rather than splitting at every potential random event or decision, given that a second observer interacting with an observer opening the box containing Schrodinger’s Cat, but who cannot themselves see into the box, will still exist with their state of awareness encompassing both worldlines simultaneously, while the first observer (the one opening the box) has their state of awareness divided along two different worldlines, and yet the second observer can still communicate with both of the first observer states of awareness, and they with it, providing no information regarding the state of the cat is transferred, causing a division of the second observer’s state of awareness . This requires multiple dimensions of time (probably one for each spatial dimension, given the principle of symmetry and the fact we live in three dimensions of space-time (potentially allowing nine different vectors). This is not unreasonable as our state of awareness tends to run parallel to time, leaving us unable to directly observe it, so that the multiple dimensions of time would generally appear to be one while, at the quantum level, we might refer to our proportionate vectors relative to each as color and, to some degree, spin. This also provides a good reason why something that becomes color unbalanced disappears from our worldline, leaving only energy. But I digress. With a properly designed and coded quantum computer it might be possible to alter the possibilities of our particular state of awareness actually being on a given worldline as we opt for decisions that bring us closer to preferred worldlines, or away from less preferred. This is because a non-causal system could potentially tell us what to do to observe a desired worldline before we actually observe it and have ou
Let’s go really out there with this one. It’s a fun one so why not? If all worldlines are actually contiguous this raises an interesting possibility. First all possible worldlines probably are contiguous rather than splitting at every potential random event or decision given that a second observer interacting with an observer opening the box containing Schrodinger’s Cat but who cannot themselves see into the box will still exist with their state of awareness encompassing both worldlines simultaneously while the first observer (the one opening the box) has their state of awareness divided along two different worldlines and yet the second observer can still communicate with both of the first observer states of awareness and they with it providing no information regarding the state of the cat is transferred causing a division of the second observer’s state of awareness . This requires multiple dimensions of time (probably one for each spatial dimension given the principle of symmetry and the fact we live in three dimensions of space-time (potentially allowing nine different vectors). This is not unreasonable as our state of awareness tends to run parallel to time leaving us unable to directly observe it so that the multiple dimensions of time would generally appear to be one while at the quantum level we might refer to our proportionate vectors relative to each as color and to some degree spin. This also provides a good reason why something that becomes color unbalanced disappears from our worldline leaving only energy.But I digress. With a properly designed and coded quantum computer it might be possible to alter the possibilities of our particular state of awareness actually being on a given worldline as we opt for decisions that bring us closer to preferred worldlines or away from less preferred. This is because a non-causal system could potentially tell us what to do to observe a desired worldline before we actually observe it and have our stat
OK this is out of left field, but I think there maybe a way to use this to effectively create ‘unlimited’ memory, any value your previously computed could be recovered more easily (when you get over a limit of trivial recalls) by quantum back calculation than by classical storage. IE using a quantum computer as storage for an otherwise classical computer but able to access as much memory as its able to compute over a given run time rather than just what it has physical memory for, sort of like using Time as the index for an array. Return the R vector value from X nano seconds ago, rather than storing it in ram. That effecitly infinite memory, more limited by CPU speed than space.
OK this is out of left field but I think there maybe a way to use this to effectively create ‘unlimited’ memory any value your previously computed could be recovered more easily (when you get over a limit of trivial recalls) by quantum back calculation than by classical storage. IE using a quantum computer as storage for an otherwise classical computer but able to access as much memory as its able to compute over a given run time rather than just what it has physical memory for sort of like using Time as the index for an array. Return the R vector value from X nano seconds ago rather than storing it in ram. That effecitly infinite memory more limited by CPU speed than space.
Whoa. Heavy man. I like it 🙂
Whoa. Heavy man. I like it 🙂
Whoa. Heavy man. I like it 🙂
OK this is out of left field, but I think there maybe a way to use this to effectively create ‘unlimited’ memory, any value your previously computed could be recovered more easily (when you get over a limit of trivial recalls) by quantum back calculation than by classical storage. IE using a quantum computer as storage for an otherwise classical computer but able to access as much memory as its able to compute over a given run time rather than just what it has physical memory for, sort of like using Time as the index for an array. Return the R vector value from X nano seconds ago, rather than storing it in ram. That effecitly infinite memory, more limited by CPU speed than space.
Let’s go really out there with this one. It’s a fun one so why not?
If all worldlines are actually contiguous this raises an interesting possibility.
First, all possible worldlines probably are contiguous, rather than splitting at every potential random event or decision, given that a second observer interacting with an observer opening the box containing Schrodinger’s Cat, but who cannot themselves see into the box, will still exist with their state of awareness encompassing both worldlines simultaneously, while the first observer (the one opening the box) has their state of awareness divided along two different worldlines, and yet the second observer can still communicate with both of the first observer states of awareness, and they with it, providing no information regarding the state of the cat is transferred, causing a division of the second observer’s state of awareness .
This requires multiple dimensions of time (probably one for each spatial dimension, given the principle of symmetry and the fact we live in three dimensions of space-time (potentially allowing nine different vectors). This is not unreasonable as our state of awareness tends to run parallel to time, leaving us unable to directly observe it, so that the multiple dimensions of time would generally appear to be one while, at the quantum level, we might refer to our proportionate vectors relative to each as color and, to some degree, spin. This also provides a good reason why something that becomes color unbalanced disappears from our worldline, leaving only energy.
But I digress. With a properly designed and coded quantum computer it might be possible to alter the possibilities of our particular state of awareness actually being on a given worldline as we opt for decisions that bring us closer to preferred worldlines, or away from less preferred. This is because a non-causal system could potentially tell us what to do to observe a desired worldline before we actually observe it and have our state of awareness split..
In practice, although probably much less dramatic and with somewhat fewer really fantastic possibilities (such as the Alice in Wonderland shadow world), this might not be entirely different from what the characters in Roger Zelazny’s Amber series do when they “walk through shadow.”
No, it means quantum computers are little pieces of the universe.
Probably means that the universe is like it is because your brain makes it so.
But don’t feel special, any macroscopic “observer” (e.g. a rock) would break the beautiful time symmetry of quantum particles and make the tangible macroscopic world and its arrow of time emerge.
What it’s funny is that it may make the universe self-justifying: the past was as it was to make sure the present is as it is, and the future as it will be. And not just metaphorically: there will be particle level interactions going on always between all these times, making sure all the others come to pass.
With some weirder possibilities: the past could change because something happening in the present, albeit if that is in some observable place (our legit past) or in another universe is up for speculation.
Inference from current effects to previous causes, is, of course, at the heart of mysteries precisely because it is so difficult. Sir Arthur Conan Doyle’s famous quip about what the dog did in the night time is perhaps the best known literary example.
Abductive reasoning from current effect to past cause is also standard in the historical sciences. As Charles Lyell argued, the best way to explain what we observe now is to look for causes known to produce the effect in question.
So does this mean the Universe is a simulated quantum computer ?