Category: Interpretations of Quantum Mechanics

The Quantum Internet and: Cthulhu Now!, Don’t get your time machine in a twist, and Warped Plotting

Google conducts largest chemical simulation on a quantum computer to date
Google’s Sycamore Quantum Computer

This year’s Philcon is going forward in person, in spite of Covid! It runs from Friday afternoon (11/19/2021) through Sunday afternoon (11/21/2021). Jabs & masks mandatory, but it will be great to see old friends in person. And make a few new as well. My science talk is:

The Quantum Internet: Hype or the next step

What do we mean by the quantum internet? Why do we need more than just quantum computing? What are quantum cryptography, quantum key distribution, quantum sensors? How are these concepts entangled? What are the advantages of the quantum internet? key problems? Who will get to use it? And do we have just a bunch of interesting tech that all have quantum in their name or can the whole be more than the sum of its parts?

This will be 1 pm Saturday November 20th at Philcon 2021

I did this at this year’s Capclave. Went well: some pretty deep questions from the audience at the end, always a good sign. I’ve updated — quantum computing does not stand still! — and looking forward to presenting in a few days. The picture is of Google’s Sycamore Quantum Computer, which recently achieved “Quantum Supremacy”. I will explain what that means!

I’m doing three panels as well:

The Post-Lovecraftian Cthulhu

How have HP Lovecraft’s ideas evolved in the hands of subsequent writers?

At this point, post-Lovecraftian Cthulhu is 99+% of Cthulhu. There are a lot of interesting directions here: from more mythos (Derleth for instance), more grim humor (Stross), high tech reboots (Delta Green), and a deeper (pun intended) take on Lovecraft’s racism (Lovecraft Country, Ballad of Black Tom). And we have uses of Cthulhu in music, film & TV (of course!), theater, and even in real science (the elongated dark region on Pluto nee Yuggoth called Cthulhu Macula!) if we are willing to include songwriters, playwrights, & scientists as part of the dark horde of subsequent writers.

This with Darrell Schweitzer (my co-editor on Tales From the Miskatonic University Library) and Stephanie Burke (writer, cosplayer, and a remarkable presence). I proposed the topic so have been unable to avoid the scourage of moderation.

At 10pm Friday, 11/19/2021

A Beginner’s Guide to Time Travel Paradoxes

You know not to remove a major historical figure, hand Thomas Edison a cell phone, or kill your grandfather. But is it even possible to travel into the past without changing anything?  So you go back to Chicago in 1920, and eat a hamburger in a diner. But, unbeknownst to you, that hamburger was destined to sit for six hours, spoil, and sicken someone else, who misses an important appointment, and… there goes the timestream. Would nature have a way of correcting this?

This with Michael Ventrella, George W. Young, and Russell Handelmann. Michael is currently editing a time travel anthology and is also moderating the panel. Michael’s a lot of fun; the other two I look forward to meeting.

At 2pm Saturday, 11/20/2021

Parsecs, Light Years, and the Speed of Plot

Warp?  Hyperspace?  Ion propulsion?  Improbability drive?  Is it necessary to sacrifice accuracy to maintain pacing?  Our panelists science the heck out of “velocity equals distance divided by time” as used in fiction.

This with Tobias F. Cabral (moderator), Anastasia Klimchynskaya, Tom Purdom. All familiar & valued co-panelists!

At 4pm Saturday, 11/20/2021

Quantum internet at Capclave 2021

Somewhat surprisingly, even tho the Washington DC Science Fiction community is hosting this year’s Worldcon, they are still doing their regular annual convention as well, Capclave 2021. Kudos for courage! And it is inperson as well (proof of vaccination required).

I’m doing a talk on the Quantum Internet this year at Capclave. I moderated a panel on the quantum internet at the most recent Balticon. Panel went well (video of the panel is up on youtube) thanks to my two fellow panelists Kevin Roche and Anne Gray. This is a great subject, so I figured a dedicated talk on this would be fun & helpful to people. Hence:

The Quantum Internet: Hype or the next step

What do we mean by the quantum internet? Why do we need more than just quantum computing? What are quantum cryptography, quantum key distribution, quantum sensors? How are these concepts entangled? What are the advantages of the quantum internet? key problems? Who will get to use it? And do we have just a bunch of interesting tech that all have quantum in their name or can the whole be more than the sum of its parts?

This will be 4pm Saturday October 2nd, 2021 at Capclave

I’m doing two panels as well:

Horrors found in the Editor’s Slush

I’ve copyrighted this story so you cannot steal it and publish it under your name. “And their names were Adam and Eve.” The manuscript written in crayon. Threats if the editor rejects a story. Considering that writers want their stories to be published, they do seem to do everything possible to discourage editors. What are some of the horrors you found in submissions? What should new writers know to avoid?

This with Walt BoyesNeil ClarkeDina Leacock

At 8pm Friday October 1st, 2021 at Capclave

A Century of Robots

The play RUR (Rossum’s Universal Robots) premiered in January 1921. This play was the first to use the word robot for a scientifically created mechanical worker. Why has the concept of robots been so popular? How have robots evolved in fiction?

This with Jennifer PoveyMichael SwanwickJoy Ward

At 11am Sunday October 3rd, 2021 at Capclave

Does the Heisenberg uncertainty principle apply along the time dimension?

Does the Heisenberg uncertainty principle (HUP) apply along the time dimension in the same way it applies along the three space dimensions? Relativity says it should; current practice says no. With recent advances in measurement at the attosecond scale it is now possible to decide this question experimentally. The most direct test is to measure the time-of-arrival of a quantum particle: if the HUP applies in time, then the dispersion in the time-of-arrival will be measurably increased. We develop an appropriate metric of time-of-arrival in the standard case; extend this to include the case where there is uncertainty in time; then compare. There is — as expected — increased uncertainty in the time-of-arrival if the HUP applies along the time axis. The results are fully constrained by Lorentz covariance, therefore uniquely defined, therefore falsifiable. And therefore we have an experimental question on our hands. Any definite resolution would have significant implications with respect to the role of time in quantum mechanics and relativity. A positive result would also have significant practical applications in the areas of quantum communication, attosecond physics (e.g. protein folding), and quantum computing.

Presented as a talk at International Association for Relativistic Dynamics 2020 Conference; currently in submission to the associated Journal of Physics: Conference Series: Proceedings of IARD 2020. 31 pages, 5 figures, 87 references

Time dispersion in time-of-arrival measurements

I will be presenting a paper “Time dispersion in time-of-arrival measurements” at the International Assocation for Relativistic Dynamics this coming Wednesday (6/3/2010). The conference was originally scheduled to be held in Prague but has been moved online because of COVID-19. It may still be held as a physical conference as well, we will see.

My own paper is a follow up to my “Time dispersion in quantum mechanics“, published last year as part of the Institute of Physics Conference Series. That took the hypothesis: the quantum wave function should extend in time as it does in space & worked out the implications. The new paper is about experimental tests of the hypothesis: how would we determine if this hypothesis is true. Since it is real science however I turned the question around & made it “how do we prove that the wave function does not extend in time”.

In the new paper I shift focus to the Heisenberg uncertainty principle (HUP), specifically to the Heisenberg uncertainty principle in time and energy. Einstein & Bohr both held it was true, in fact essential if quantum mechanics was to be consistent with relativity. Bohr’s demonstration that it was was the end of Einstein’s direct attempts to falsify quantum mechanics.

Note that the formulation “the Heisenberg uncertainty principle applies to time/energy as it does to space/momentum” is loosely equivalent to “the wave function extends in time as it does in space”. If the wave function extends in time, then we would get the HUP in time/energy as a side-effect. And the most direct tests of the wave function extending in time are really tests of the HUP in time/energy.

The test I primarily focus on is that if the wave function extends in time all measurements in the time dimension would be just a bit fuzzier. In particular, if you are measuring when a particle is detected, if you are measuring the time-of-arrival, then if the wave function is extended in time you expect to see it both sooner & later than otherwise expected.

The advantage of this as a test is that the additional fuzziness if present at all must be present everywhen. Any time-varying experimental setup can potentially serve as a test.

The main problem — somewhat to my surprise — was that we really don’t know how to predict the time-of-arrival in standard quantum mechanics, let alone quantum mechanics with time in play as well! I’m trying to make a pincer attack on time: left jaw — standard quantum mechanics (SQM), right jaw — quantum mechanics with time (TQM). I was focused on the right jaw, but found that actually it was the left jaw that was weak. So I had to backtrack & deal with this problem. Interesting. And this turned out to be the single trickiest bit in the paper.

After getting the left jaw in better shape, good enough to take a punch anyway, I did a recap of TQM. This was probably the 2nd trickiest bit of the paper: how do you describe a hypothesis that took over a hundred pages and nearly five hundred equations to work out in a just a few pages? I found the core ideas coming a bit clearer in my own head at least. That’s gotta be worth something.

Then the payoff bit, the actual tests, is only the last quarter of the paper. And after working out how the additional fuzziness in time plays out, I got to my favorite test: the single slit in time. This is the single cleanest test of the idea. Not an easy experiment however.

Really the best part of tests of TQM is that if it is proved true, great. But if it proved false it will be taking down one or two of its neighbors with it. TQM is built by applying the quantum rules to relativity (or applying relativity to the quantum rules). If it is false, one (or both) of those two has a problem. And that in turn means there are really no null experiments.

And if I know my experimentalists, there is nothing they like more than proving a bunch of theorists wrong. If I have setup the arguments correctly — we’ll see — then they are sure to break something. As the well-known quantum experimentalist Nicholas Gisin said to me a long time ago (I paraphrase, it was quite a long time ago) “Look, I don’t care what your theory of time is. Just give me something I can prove wrong!”

Is time an observable? or is it a mere parameter?

I’ve just put my long paper “Time dispersion and quantum mechanics” up on the physics archive.   If you are here, it is very possibly because you have at one point or another talked with me about some of the ideas in this paper and asked to see the paper when it was done.  But if you just googled in, welcome!

The central question in the paper is “is time fuzzy? or is it flat?” Or in more technical language, “it time an observable? or is it a mere parameter?”

To recap, in relativity, time and space enter on a basis of formal equivalence. In special relativity, the time and space coordinates rotate into each other under Lorentz transformations. In general relativity, if you fall into a black hole time and the radial coordinate appear to change places on the way in. And in wormholes and other exotic solutions to general relativity, time can even curve back on itself.

For all its temporal shenanigans, in relativity everything has a definite position in time and in space.  But in quantum mechanics, the three space dimensions are fuzzy.  You can never tell where you are exactly along the x or y or z positions.  And as you try to narrow the uncertainty in say the x dimension, you inevitably (“Heisenberg uncertainty principle”) find the corresponding momentum increasing in direct proportion. The more finely you confine the fly, the fiercer it buzzes to escape. But if it were not for this effect, the atoms that make us — and therefore we ourselves in turn — could not exist (more in the paper on this).

So in quantum mechanics space is complex,  but time is boring. It is well-defined, crisp, moves forward at the traditional second per second rate.  It is like the butler Jeeves at a party at Bertie Wooster’s Drone’s Club:  imperturbable, stately, observing all, participating in nothing. 

Given that quantum mechanics and relativity are the two best theories of physics we have, this curious difference about time is at a minimum, how would Jeeves put it to Bertie?, “most disconcerting sir”.

Till recently this has been a mere cocktail party problem: you may argue on one side, you may argue on the other, but it is more an issue for the philosophers in the philosophy department than for the experimenters in the physics department.

But about two years ago, a team led by Ossiander managed to make some experimental measurements of times less than a single attosecond.    As one attosecond is to a second as a second is to the age of the universe, this is a number small beyond small.

But more critically for this discussion, this is roughly about how fuzzy time would be if time were fuzzy.  A reasonable first estimate of the width of an atom in time is the time it would take light to cross the atom — about an attosecond.

And this means that we can — for the first time — put to experimental test the question:  is time fuzzy or flat? is time an observable or a parameter?

To give the experimenters well-defined predictions is a non-trivial problem. But it’s doable. If we have a circle we can make some shrewd estimates about the height of the corresponding sphere.  If we have an atomic wave function with well-defined extensions in the three space dimensions, we can make some very reasonable estimates about its extent in time as well.

The two chief effects are non-locality in time as an essential aspect of every wave function and the complete equivalence of the Heisenberg uncertainty principle for time/energy to the Heisenberg uncertainty principle for space/momentum.

In particular, if we send a particle through a very very fast camera shutter, the uncertainty in time is given by the time the camera shutter is open. 

In standard quantum mechanics, the particle will be clipped in time.  Time-of-arrival measurements at a detector will show correspondingly less dispersion. 

But if time is fuzzy, then the uncertainty principle kicks in.  The wave function will be diffracted by the camera shutter. If the uncertainty in time is small, the uncertainty in energy will be large, the particle will spread out in time, and time-of-arrival measurements will show much greater dispersion. 

Time a parameter — beam narrower in time.  Time an observable — beam much wider in time.

And if we are careful we can get estimates of the size of the effect in a way which is not just testable but falsifiable.  If the experiments do not show the predicted effects at the predicted scale, then time is flat.

Of course, all this takes a bit of working out.  Hence the long paper.

There was a lot to cover:  how to do calculations in time on the same basis as in space, how to define the rules for detection, how to extend the work from single particles to field theory, and so on. 

The requirements were:

  • Manifest covariance between time and space at every step,
  • Complete consistency with established experimental and observational results,
  • And — for the extension to field theory — equivalence of the free propagator for both Schrödinger equation and Feynman diagrams.

I’ve been helped by many people along the way, especially at the Feynman Festivals in Baltimore & Olomouc/2009; at some conferences hosted by QUIST and DARPA; at The Clock and the Quantum/2008 conference at the Perimeter Institute; at the Quantum Time/2014 conference Pittsburgh; at   Time and Quantum Gravity/2015 in San Diego; and most recently at the  Institute for Relativistic Dynamics (IARD) conference this year in Yucatan.  An earlier version of this paper was presented as a talk at this last conference & feedback from the participants was critical in helping to bring the ideas to final form.

Many thanks! 

The paper has been submitted to the IOP Conference Proceedings series.  The copy on the archive is formatted per the IOP requirements so is formatted for A4 paper, and with no running heads or feet.  I have it formatted for US Letter here.



Time Dispersion in Quantum Mechanics

If a quantum wave function goes through a single slit in time is it diffracted or clipped?

I will be speaking at the  2018 meeting of  the IARD — The International Association for Relativistic Dynamics  this afternoon.  Had a nice chat with the organizers & some early arrivals last night over coffee:  my talk clearly a good fit to the conference.

The decisive test is what happens if you send a quantum wave function through a single slit in time, say a very fast camera shutter.  If quantum mechanics does not apply (current generally accepted view), the wave function will be clipped — and the dispersion at a detector arbitrarily small.  If quantum mechanics does apply (proposal here), the wave function will be diffracted — and the dispersion at a detector arbitrarily great.

I’ve uploaded the talk itself  in several formats Time Dispersion in Quantum Mechanics – KeynoteTime Dispersion in Quantum Mechanics – Powerpoint, and Time Dispersion in Quantum Mechanics – PDF.

I’ve incorporated feedback from the IARD conference into the underlying paper Time Dispersion in Quantum Mechanics.  I’ve submitted this to the IOP Conference Proceedings series & have also uploaded it to the physics archive.  I hope it will be a useful contribution to the literature on time and quantum mechanics.

Your comments very welcome!

Time and Quantum Mechanics accepted at IARD conference

The physics paper I’ve been working on for several years, Time & Quantum Mechanics, has been accepted for presentation at a plenary session of the 2018 meeting of  the IARD — The International Association for Relativistic Dynamics. I’m very much looking forward to this:  the paper should be a good fit to the IARD’s program.

Abstract:

In quantum mechanics the time dimension is treated as a parameter, while the three space dimensions are treated as observables.  This assumption is both untested and inconsistent with relativity.

From dimensional analysis, we  expect quantum effects along the time axis to be of order an attosecond.  Such effects are not ruled out by current experiments.  But they are large enough to be detected with current technology, if sufficiently specific predictions can be made.

To supply such we use path integrals.  The only change required is to generalize the usual three dimensional paths to four.  We treat the single particle case first, then extend to quantum electrodynamics.

We predict a large variety of testable effects.  The principal effects are additional dispersion in time and full equivalence of the time/energy uncertainty principle to the space/momentum one.  Additional effects include interference, diffraction, resonance in time, and so on.

Further the usual problems with ultraviolet divergences in QED disappear.  We can recover them by letting the dispersion in time go to zero.  As it does, the uncertainty in energy becomes infinite — and this in turn makes the loop integrals diverge.  It appears it is precisely the assumption that quantum mechanics does not apply along the time dimension that creates the ultraviolet divergences.

The approach here has no free parameters; it is therefore falsifiable.  As it treats time and space with complete symmetry and does not suffer from the ultraviolet divergences, it may provide a useful starting point for attacks on quantum gravity.

Time and Quantum Mechanics

I’ve submitted an extended abstract for my paper “Time and Quantum Mechanics” to the Center for Philosophy of Science’s workshop on Quantum Time. I’m not sure what the odds are of my getting in, but at a minimum prepping the abstract for the center has been a big help getting the paper organized, working out what is essential to the argument, and what can be let go.

Note the abstract is more extended than abstract, about two pages:

CFP-abstract-extended

Quantum Mechanics, Reality, & You at Philcon

Did my Quantum Mechanics, Reality, & You talk at Philcon this last weekend.  Had a very energetic & engaged audience. My thanks to Ed Bishop, Tom Purdom, Ron Bushyager, Ferne Welch, Walt Mankowski, & lots of others for great questions! Did five panels as well.  Full schedule:

Fri 8:00 PM in Plaza III (Three) (1 hour)
LOVECRAFT’S SUCCESSORS (1107)

[Panelists: John Ashmead (mod), Darrell Schweitzer, Marvin Kaye,
A.C. Wise, Neal Levin]

Is anyone writing good cosmic horror today? What new directions has
cosmic horror been taken in
Fri 9:00 PM in Crystal Ballroom Two (1 hour)
COSMOLOGY AND ITS DISCONTENTS (981)

[Panelists: Paul Halpern (mod), John Ashmead, Dr. H. Paul Shuch,
Robert Kauffmann]

The Standard Cosmological Model is the history of the universe as
arrived at over decades of observation and experiment and accepted
by the majority of scientists. It includes the Big Bang, Cosmic
Expansion, Inflation, Dark Matter, Dark Energy, etc. However, there
are real problems with the SM, and real (non-crank) scientists who
disagree with parts of it. What are the issues with Standard
Cosmology, and what alternative ideas are currently being discussed
Sat 12:00 PM in Plaza II (Two) (1 hour)
QUANTUM MECHANICS, REALITY, AND YOU (1319)

[Panelists: John Ashmead (mod)]

Behold the weird! Wigner and his panel of babies! The case of the
highly charged cat! The collapse of the collapse of the wave
function! And quantum chess! What’s new with quantum mechanics &
what does it all mean
Sat 1:00 PM in Plaza III (Three) (1 hour)
TIME TRAVEL FOR THE MILLIONS (1115)

[Panelists: John Ashmead (mod), Andrew C. Murphy, Gail Z. Martin,
Michael F. Flynn, Glenn Hauman]

If everyone could do it, how would this affect daily life? What are
the most frivolous uses of time travel we can think of? What would
be a time traveler’s practical joke
Sat 7:00 PM in Plaza II (Two) (1 hour)
FICTION ABOUT ITSELF: METAFICTION (1200)

[Panelists: John Ashmead (mod), Gregory Frost, April Grey, Neal
Levin, Alexis Gilliland]

Metafiction is when the story and the text becomes interchangeable,
each a part of the other. What are the roots and nature of this kind
of fiction
Sun 1:00 PM in Crystal Ballroom Three (1 hour)
EXOPLANETS AND SCIENCE FICTION (1124)

[Panelists: John Ashmead (mod), Eric Kotani, Inge Heyer, Walter F.
Cuirle]

We now know that planets are as common as stars. Over 500 are known,
nearly 20,000 are suspected.
What impact has this enormous expansion of the known universe had on
science fiction?

 

 

Quantum Mechanics, Reality, & You

I’ll be doing my talk “Quantum Mechanics, Reality, & You” tomorrow at Capclave, the DC SF Convention.  I have the latest slides up on slideshare.

Enjoyed putting the talk together.  I go thru the interpretations of quantum mechanics — some spectacularly silly — and then argue that quantum mechanics is real, you & I — not so much.  🙂

Also doing panels at Capclave on Hot Steamed Punk, Practical Uses of Faster-Than-Light Travel, Choose Your Own Apocalypse, & Great Cthulhu:  Threat or Menace?

 

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