Re: Physicists just build a quantum lie detector. It works

I suspect what you see is what they managed to get working.

Writing stuff up is an exercise in rationalising what you succeeded in getting to work before your least careful graduate student broke it.

I wonder if that one is in the fake half.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

That's exciting, a 24-bit computer attached to a giant helium liquefaction plant.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

That I can believe. My supervision partner was a wizard at making good Josephson junctions back when they were cutting edge.

If two photons were born entangled and are now a light year apart, and their polarizations are measured simultaneously, they will be opposite. Whether you measure up/down or left/right.

Sorry.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The other 183 qubits contradicted Bell, maybe?

Jeroen Belleman

There is no action at a distance. It's just a correlation that appears after you select the subset of measurements that happen to be aligned at both stations. This selection is done by comparing the measurements well after the fact. Nothing goes faster than light.

Jeroen Belleman

Tachyons might do (iff they exist).

Certainly you cannot use it to communicate information (which is the relativistic prohibition required to maintain causality). But in a very real sense the wavefunction collapses to whatever polarisation the first station to measure observes in. This is pretty tricky to explain.

I'm pretty sure eventually some bigger theory that unifies QM and GR will explain it completely but right now just like with gravity in Newton's era you have to accept action at a distance as the least unreasonable way of looking at it from an experimental perspective.

In classical Newtonian mechanics if propagation of gravity from the sun to the Earth was not instantaneous we would spiral into it.

A bit like with the intensity interferometer by Hanbury-Brown and Twiss

- in the 1960's most physicists at the time thought they would never make it work even if theory said that it should. Today there are partially coherent optical interferometers doing full aperture synthesis.

How fast does an electron tunnel through a barrier? It doesn't have to move the distance, because it was on both sides already.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Yes, it's tricky, and quantum mystics wallow in the puddle of nonsense this enables them to put forth. First, the wavefunction is not a physical thing. It's a mathematical tool to express probabilities.

As for the entanglement experiments, if both stations' are aligned, both 'x' or both '+', detections are correlated. Both stations randomly choose their alignment. When at a later time the sequence of alignments is compared, all coincident events where the detectors were not aligned, one 'x' and the other '+', are discarded. The remaining events are correlated, of course. That's what they do in quantum key distribution, for example.

I think we do, but other effects still dominate and cancel that. Closely spaced black holes and neutron stars spiral into each other just fine, allowing us to confirm that gravity *does* propagate as a wave.

I think gravitational wave interactions *are* quantized, but because the interaction times are ~32 orders of magnitude slower, and involve 'particles' with random masses, we just don't readily realize what's going on. Gravitational resonances are readily observable. What are those, if not a quantum phenomenon?

If you think of starlight as a wave instead of as a stream of photons, it should be evident that it's coherent when observed from closely spaced viewpoints. After all, it's close to being an ideal point source. The coherence length is tiny, of course, since it's still blackbody radiation.

Jeroen Belleman

If an object is moving in a straight line through space, does it lose energy from its gravitational radiation? Seems like it should.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It has to accelerate.

Joe

If it passes near another object, it will accelerate that object so must lose energy.

"Near" might be a light year away. The object to be accelerated may not even exist yet.

There's a puzzle in there somewhere.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It's falling, but feels no acceleration. Without acceleration as measured on the moving object, no gravity waves.

Yes.

Yes, and a famous one at that. Einstein created some gedanken experiments precisely on this issue.

.

The falling elevator example is your moving object.

Joe

It wasn't. The matter waveform say that it has a finite probability of being on both sides at the same time, but the electron is always in one place or the other. Continuity says that it has to be half-way through the barrier at some point, but that isn't a useful point of view.

Dirac would probably have said that the electron on the other side of the barrier isn't the same one that started towards the barrier - his positron was a hole in the universal sea of potential electrons - and he is the guy who proved that Schoedinger, Heisenberg and Pauli were all saying the same thing with different notations.

Indeed but that is only in extremis and some of the drag to get them started is due to the insanely strong magnetic fields trapped in the compact stellar remnants (that is what makes pulsars emit polarised radiation) and spew fast particles off the poles.

ISTR the last stable orbit in maximally spinning Kerr metric going with the spin is 3R and going against it is 9R (R = Schwarzchild radius). I'm not so sure about eccentric orbits - never studied them in my course but someone will have done. I'm decades behind cutting edge on this now.

Apparently it was solved in the mid 90's MNRAS article here (heavy math)

The other notable one was whimsically titled "Can a young blue giant find lasting happiness in the arms of a degenerate old dwarf?" - spoiler alert - no they can't. Mass transfer to the dwarf is inevitable as the blue giant expands and you get rather exciting repeat nova that periodically go flash bang called cataclysmic variables. Their spectrum is interesting since the hotspot on the rapidly rotating accretion disk puts a telltale sine wave into the wavelength intensity vs time plot.

Classical mechanical resonance entrainment of oscillators. The same as you can get when playing on a swing or using a parametric amplifier.

Like you I think gravitational waves probably are quantised but until some mathematics comes along that can convincingly unify GR and QM into a single theory that encompasses both and predicts something new. We are about due for a paradigm shift - they happen on average once a century. (since the enlightenment)

The apparently continuous dynamics of the very large sit uncomfortably with the quantised dynamics of the very small. Gravity is the one force of nature that is so different in magnitude from all the others that it has resisted all unification attempts by the best minds on the planet.

Not in GR. The two objects alter the spacetime around them so that each follows a geodesic (which is a posh way of saying a straight line in a curved spacetime). Great circle on a sphere is the easiest to visualise.

Total energy of the whole system is exactly conserved in GR, as is angular momentum and linear momentum (or rather their analogues in the GR treatment are). They are strict invariants of motion.

But some of it may change from being rest mass to photons if the conditions are extreme enough.

No it is a failure of your understanding and lack of imagination. You are trying to apply Newtonian dynamics to a general relativity problem.

Jerk.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The jerk here is John Larkin. He sounds off a lot on subjects where he doesn't know nearly enough, and gets resentful when this is pointed out.

He didn't point anything out. He dumped a lame insult, probably because that's all he has to say on the subject.

I suppose experts are right, a mass moving at uniform velocity in an ideal universe, empty of any other objects, loses no energy from gravitational effects.

Think about that for a minute.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics