Characterizing the 'arrow of time' in open quantum systems

time
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Even in the strange world of open quantum systems, the arrow of time points steadily forward—most of the time. New experiments conducted at Washington University in St. Louis compare the forward and reverse trajectories of superconducting circuits called qubits, and find that they follow the second law of thermodynamics. The research is published July 9 in the journal Physical Review Letters.

"When you look at a quantum system, the act of measuring usually changes the way it behaves," said Kater Murch, associate professor of physics in Arts & Sciences. "Imagine shining light on a small particle. The photons end up pushing it around and there is a dynamic associated with the measurement process alone.

"We wanted to find out if these dynamics have anything to do with the arrow of time—the fact that entropy tends to increase as time goes on."

In a related video, Murch asks, "Do quantum movies look funny when you play them backwards?" He and his team, including Patrick Harrington, a graduate student in physics and first author of the paper, took that question to the lab—where their work is part of the new Center for Quantum Sensors.

"We looked at microscopic movies of a 's movement during measurement, and asked if the movies looked more likely when played forward or backwards; this comparison can be used to determine if entropy increases or not," Murch said. "We found that even at the microscopic scale, the second law seems to hold: entropy generally increases.

"This increase happens because we look at it—the process of making the movie seemingly creates the arrow of ," he said.

Murch's research group is focused on understanding and controlling open quantum systems. While everyday objects obey the laws of classical mechanics, single particles of light or matter follow instead the laws of quantum physics. But these particles are not easily isolated, and as soon as they interact with the outside world they lose their properties.


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Study sheds light on the role of the entropy in a quantum system

More information: P. M. Harrington et al, Characterizing a Statistical Arrow of Time in Quantum Measurement Dynamics, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.020502
Journal information: Physical Review Letters

Citation: Characterizing the 'arrow of time' in open quantum systems (2019, July 9) retrieved 17 October 2019 from https://phys.org/news/2019-07-characterizing-arrow-quantum.html
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Jul 09, 2019
An "Arrow of Time" - ROFLOL
Humans have, indeed, gone berserk in the 21st century.

There is no such thing as an "arrow of time" except in the imaginations of novella authors. Time is nonexistent except to those who wish it to exist as something that can be quantified and observed, and as something that can not only move forward, but backward also. Backward can't happen.
The one thing that they got right is that it can go forward, but it is EVENTS and ACTIONS that go forward, not Time, and never backward. The English noun "time" is used as a descriptor for the Durations of events and actions that are observable and quantifiable. Time is only a Concept that was thought of in the human Mind and given the title "time" if in English. It's not of a substance, particle, Force, Wave, or derived from anything Quantum. The Concept of Time is merely a product of the Thought Process that has its origin in the Mind/Brain of humans. Even without that Concept, all Events/Actions continue on.

Jul 09, 2019
Perhaps the researchers didn't realise that a 'movie' is the recording of an Event/Action and is only portraying an event or action as a moment in 'time' because it is a movie. In Reality, each Moment has come and gone and cannot reverse, but if it had been recorded, then it is available for posterity.
The movie or video is but a recording that is dependent on a machine to move backward or forward. It is the MACHINE that is causing the video to rewind and go in reverse. The event or action that was first recorded on tape/video/movie did not and could not change in the Real sense.

"...compare the forward and reverse trajectories of superconducting circuits called qubits, and find that they follow the second law of thermodynamics."

Electron and other quantum particles may be jumping back and forth, but they are actually moving forward as an Event or Action. It's analogous to a child playing hopscotch where she jumps backward to the space behind her, then jumps forward.

Jul 09, 2019
"This increase happens because we look at it—the process of making the movie seemingly creates the arrow of time," he said.

In other words the interaction causes the effect in much the same way that observation collapses the wave function and destroys superposition and entanglement.

Observation confers an ordinal property to phenomena where no ordinal property is present.

Jul 10, 2019
An "Arrow of Time" - ROFLOL
Humans have, indeed, gone berserk in the 21st century.

There is no such thing as an "arrow of time" except in the imaginations of novella authors. Time is nonexistent except to those who wish it to exist as something that can be quantified and observed, and as something that can not only move forward, but backward also. Backward can't happen.
The one thing that they got right is that it can go forward, but it is EVENTS and ACTIONS that go forward, not Time, and never backward. The English noun "time" is used as a descriptor for the Durations of events and actions that are observable and quantifiable. Time is only a Concept that was thought of in the human Mind and given the title "time" if in English. It's not of a substance, particle, Force, Wave, or derived from anything Quantum. The Concept of Time is merely a product of the Thought Process that has its origin in the Mind/Brain of humans. Even without that Concept, all Events/Actions continue on.

Jul 10, 2019
Thank you! I have said the same thing about time, although not as elegant as you, in comment sections of "this type" prior. However, others keep insisting - quoting Einstein and other brand names that "The Emporers New Clothes" are real. Another problem is that the ego lives in time as memory. It's almost like an ancient bio-malware. Corporations, traditional religion, and governments love Time and its use as procrastination and fear of the so-called future.

Jul 10, 2019
"This increase happens because we look at it—the process of making the movie seemingly creates the arrow of time,"

It's not gravity but it is electromagnetism. It's like lining up a difficult scene or billiards shot, pi is transcendental, the sphere is transcendental, so the reflections characterizing electromagnetism are transcendental, unpredictable. Gravity has subtle retro-reflective aspects, natural retro-reflection is essentially counter-entropic, retro-reflection angles are predictably 180 degrees.

Jul 10, 2019
I am not knocking Heisenberg on gravity and saying he's all about electromagnetism, but electrons are light, photons are massless, and Heisenberg becomes less relevant the greater the mass observed.

Jul 10, 2019
Just to finish a little thought, Newton's equal-opposite force vectors always had mass behind them, it's very Hebbian in a way, especially if "error-correction" via gravity involves naturally ignoring small-energy fast one-off events.

Jul 10, 2019
not sure what drugs egg unit is on but they're not legal.

You can't argue that time isn't real because it's created in our human perception and then define the physical world as having a cause and effect continuum devoid of that perception.

We have actual situations where time doesn't exist. One example is time doesn't exist in the reference frame of a photon. Everything happens to that photon instantly as far as it's concerned. Regardless to how long it traveled around the universe in an external reference frame. In fact, as far as it's concerned, it doesn't exist and neither does the universe since it will be destroyed the moment it's created within it's reference frame. This would be true of any universe in which time isn't real. If time isn't real, all events and actions would happen instantly in some reference frame.

Since we aren't destroyed instantly upon creation, we know time exists outside of a mental construct and outside of our own reference frame.

Jul 10, 2019
Then there's these things called "clocks."

They seem to predict when the Sun will rise in the East. Maybe @Egg didn't notice.

Jul 17, 2019
And after all that, still nobody KNOWS, without a doubt, what Time is made of.

Jul 17, 2019
Time – Simply Memories of our Windmill of our Minds
SEU> And after all that, still nobody KNOWS, without a doubt, what Time is made of.

Time – If you truly believe, If Your Faith Is True and Strong, foreth of these disciples of time
This undying faith in Time - For fear of our immortal souls as our faith weakens

TIME
For in this cold light of day
Time is just a memory
Of those fleeting moments
That are recorded in the windmills of our minds
For once these memories are remembered
They're never repeated ever again
Foreth
Time - the present is all we know
For the future hath not happened
As the present is this future when it happens
The past does not exist except as memories

Time – Simply, these memories of our windmill of or minds

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