The Kalamidas Effect as Fake News
This month marks the 10th anniversary of Quantum Tantra blog for which I will soon be publishing a retrospective. But as I was reviewing dozens of exciting projects reported here, one event shone out in my mind, the day I was standing in my friend Reno's driveway overcome by intellectual ecstasy: I had calculated a way to send signals faster-than-light (FTL).
My thrill lasted only a few hours till a friend found an error in my calculation.
This particular FTL mind high was instigated by Demetrios Kalamidas, a Greek-American physicist, now employed by Raith Nanofabrication, who had recently published in an optics journal a particularly ingenious FTL communication scheme. The quest to refute Kalamidas's proposal was for me a particularly fine adventure: my brief ecstasy in Reno's parking lot was the result of calculating my own refinement of the Kalamidas effect; and it was Demetrios himself who pointed out my math mistake.
I called the Kalamidas proposal KISS (for Kalamidas's Instant Signaling Scheme) and documented the struggle to refute this scheme in six blog posts.
1. KISS: A New Superluminal Communication Scheme
2. Demetrios! The Opera
3. The Kalamidas Experiment
4. FTL Signaling Made Easy
5. Kalamidas Refuted
6. The Kalamidas Experiment -- Easy Pickins
A seventh post: 7. Some Notes on Quantum Entanglement
provides useful background material for understanding FTL proposals of the Kalamidas kind.
When DK put forth his proposal, it attracted the attention of three prominent physicists, GianCarlo Ghiraldi (Trieste), John Howell (Rochester) and Christopher Gerry (CUNY), one of DK's former teachers, who each quickly came up with three different but quite solid refutations.
These three separate refutations should have put an end to the Kalamidas affair, but the feisty Greek came back fighting. Since you know I am wrong, Demetrios replied, it should be "easy pickins" for you to point out my specific mistake. General proofs are fine, but the devil is in the details. Show me that devil, Kalamidas challenged his critics.
The first detailed calculation of the Kalamidas effect was due to Martin Suda at the Technical University of Vienna followed by a similar calculation by Nick Herbert from Boulder Creek. Both of us showed why KISS wouldn't work but the physical meaning of some of the terms in our calculations were difficult for us to understand. But after much conversation, these difficulties were eventually resolved.
And that was the end of the KISS affair. Or was it?
One of the features of the Kalamidas proposal is its extreme cleverness, a feature, that in my opinion, has been insufficiently recognized and appreciated. I intend in this post to briefly explain the Kalamidas effect, and to show off its beauty by placing it in a more familiar context than the physics of photons.
Modern FTL communication schemes conventionally involve two QUANTUM-ENTANGLED photons A and B -- one sent to ALICE and the other to BOB.
Since Bell's Theorem
seems to prove that entangled photons such as A and B are instantly connected, there exists some hope that clever action by BOB on his (B) photon might have some measurable (and instantaneous) action on ALICE's distant (A) photon. However, by using the same quantum math that describes entanglement one can easily prove such instantaneous signaling to be impossible. (To which John Bell was said to have famously remarked that what impossibility proofs show is failure of imagination.)
The KISS scheme begins with a pair of PATH-ENTANGLED photons. This situation is difficult to visualize (because it's a quantum thing) but easy to produce in any modern optics lab. In the manner of Schrödinger's famous Cat, each photon takes two paths at once (path #1 and path #2) as long as you do not observe it. Furthermore, the path of Alice's photon A is perfectly correlated with the path of Bob's photon B: if photon A is observed to be present in its path A1, photon B will be found also in its path B1.
FIG 2 shows a path-entangled photon source S, sending one photon to Alice on the left and a second photon to Bob on the right. Under certain conditions a photon that takes two paths at once can be made to INTERFERE with itself. To prepare for this eventuality, Alice has constructed an INTERFEROMETER by combining her two photon paths at a 50/50 Beam Splitter BS(A) and by placing a variable phase-shifter Q in path A1.
To look for interference, Alice varies the phase Q of path A1. If two waves meet out-of-phase, they cancel one another, and no photons will be observed in Detector A3. In the other detector, waves will meet in-phase and all photons will be observed in detector A4. When the conditions for interference are met, Alice should be able, by varying Q, to vary the percentage of photons in counters A3 and A4 from 0% to 100%.
On the other hand, when the conditions for interference do not exist, the photon counts at Alice's detectors are always 50% each, no matter how she sets phase angle Q. FIG 2 shows such a
no-interference condition (called "the Fock choice", for reasons I won't mention here). Because Bob has chosen to measure which path his photons take, his choice forces Alice's photons to take definite paths as well. Since only a photon that TAKES BOTH PATHS can interfere, Bob's choice of what to look at absolutely precludes any interference on Alice's part.
The gist of any purported FTL signaling scheme is to discover something that Bob can do with his two-path photon that will allow interference to occur at Alice's detectors. Fortunately this is easy to do.
As long as Bob makes any kind of measurement that reveals which path his photon took, he destroys any chance of interference. On the other hand if Bob makes a measurement which ERASES which-path information, then interference at Alice's site becomes possible.
The essence of the Kalamidas proposal is his discovery of a clever scheme that Bob can use for erasing his which-path information.
The simplest way that Bob can erase his which-path information is to create an interferometer just like Alice did. An interferometer combines both paths without prejudice. Once so combined, the question of "which path?" becomes meaningless.
FIG 3 illustrates Bob's choice to measure his photon using an interferometer (called "the Frost choice" for reasons not relevant here). Bob's choice does indeed lead to measurable interference at Alice's detector, but there is a condition on this interference that precludes using this setup for FTL signaling.
Bob's interferometer has two outputs, Detectors B1 and B2. If we just look at the output of B1 and what happens at Alice's detectors we observe a clear interference pattern P1.
Likewise, if we just look at output B2, we see an interference pattern P2 at Alice's interferometer.
However these two interference patterns, P1 and P2 are exact complements of one another, where one has peaks the other has valleys. The sum of P1 and P2 is exactly 50% in each of Alice's detectors, hence no interference pattern at all. This feature seems to be common to all putative FTL schemes of the path-entangled type -- that whatever interference pattern Bob's action creates at Alice's site will be exactly canceled by an equal and opposite anti-interference pattern.
The genius of the Kalamidas scheme was that he had apparently created a way that Bob could erase his which-path information without creating a self-canceling anti-interference partner.
Kalamidas begins with the simple which-path setup of FIG 2, and, rather than erasing or recombining Bob's two separate beams, he "ambiguifies" Bob's path information by randomly adding photons from a synced external source in such a manner that for a certain output (labeled (1,1), it is impossible to say which path the photon took. Furthermore, this process is asymmetric: there is no partner anti-process that might produce at Alice's site a self-canceling anti-interference pattern.
FIG 4 illustrates the "Kalamidas Choice". A mirror with reflectivity "r" is introduced into Bob's path B1. This mirror can add or subtract photons from Bob's beam. The added photons end up at detector B3; the subtracted photons end up at detector B4. The source of added photons is designated U1 which produces a single photon a% of the time; and no photon (100 - a)% of the time.
Using this setup, there are many outcomes where "which path Bob's photon took" can be inferred. But there is one special outcome where we are left in ignorance. This is the outcome [1,1] where both B3 and B5 detect a photon. Did the real photon take the upper path and a "fake photon" take the lower? Or did the opposite occur?
A simple physics calculation shows that this abiguification works. Whenever Bob observes the [1,1] outcome, a corresponding interference pattern appears at Alice's detectors. Furthermore, there seems to exist no obvious Bob outcome that could cancel out this singular effect.
I will return to the resolution of the KISS paradox, but first I would like to pursue an amusing metaphor inspired by Kalamidas's clever and beautiful scheme.
For each photonic event, Bob's two detectors can have several different outcomes but only four are important for this discussion. the outcomes [1,0]. [1,1], [0,1] and [0,0] where the brackets enclose the outcomes of detectors B3 and B5 thus [B3, B5]. Let's look at how each of these 4 outcomes might have been produced by the Kalamidas scheme.
1. The [1,0] outcome ostensibly represents TRUTH: one real photon ended up in detector B3. No "fake photons" were added. No "real photons" subtracted.
2. For the [1,1] outcome, one photon is "real", the other is "fake" (it came from the external U1 source, not the original entangled source S) but there is no way to tell which is which, so "which path" information is totally erased for this outcome.
But the situation rapidly gets more complicated as we can see here:
The [1,0] --> [1,1] is analogous to confusing an issue by deliberately adding "fake news". Suppose someone is claiming that certain towers were taken down by demolition charges rather than by airplanes. Instead of defending the airplane story, one can "muddy the waters" by publicizing a claim that the whole thing was "done by holograms".
One of the features of the Kalamidas effect is that, by virtue of the partially-silvered mirror, a photon can be lost from a beam as well as added. This can lead to the peculiar situation [1,0] --> [0,1] where a photon in the upper beam is incorrectly recorded as though it came from the lower beam. This outcome is produced when the upper mirror deletes the upper photon while the lower mirror adds a "fake photon". This complete reversal of the facts finds many an analogy in mainstream media which also employs both fact suppression and fake news oftentimes simultaneously. A common example is the fabrication of atrocities on the part of the enemy (fake news) while unreporting the atrocities carried out by "the good guys". I call this "switched news", in which the truth is the very opposite of what the media presents. As it turns out, "switched news" is crucial to the resolution of the KISS paradox: what prevents Kalamidas's clever scheme from working?
In the final Kalamidas transformation [1,0] --> [0,0], neither of Bob's primary detectors detects a photon. Whatever channel once held a photon, that photon has been censored, sequestered, quashed, hidden from public view, leaving no evidence of which channel it once occupied. In the media analogy, suppressing the true facts is a not uncommon way of conducting government business as the brave work of Edward Snowden
, Julian Assange
and many others has shown. "What never happened" never needs to be justified.
Make no mistake, fake news, switched news and suppressed news is not confined to obscure photon physics experiments. It constitutes most of what you see and hear on TV. And other media forms are not immune.
Speaking of obscure photon physics experiments, we now return to the resolution of the Kalamidas proposal. As it turns out, all three of these fake processes add enough ambiguity to the question of which path Bob's photon took that they produce interference at Alice's distant site.
But where then is the anti-interference that usually appears to save the day in situations of attempted signaling using quantum entanglement? What exactly intervenes to prevent quantum time travel, humans messing with the past, and general disruption of the space-time continuum?
You might imagine that the [1,1] result is balanced by the [0,0] result, but actually they produce the same kind of interference.
Instead, as calculated first by Martin Suda in Vienna and Nick Herbert somewhere in the redwoods, what cancels out the "fake news" and the "suppressed news", which act in concert, is (surprisingly) the "switched news" which produces equal and opposite interference at Alice's site. No interference. No signaling, FTL or otherwise.
As illustrated by this calculation of interference at Alice's A3 detector as witnessed by my cat.