The
early days of the experimental demonstrations of quantum teleportation, particularly the first three
experiments by Zeilinger, DeMartini, and Kimble, were not without controversy.
This I learned first hand in 1999 when I attended the Sixth International
Conference on Squeezed States and Uncertainty Relations in Naples, Italy. As
the three different experimental group’s publications had just appeared, the conference
decided to have a panel discussion on these three different experiments.
Curiously, the organizers asked me to chair the panel discussion. I was a bit
puzzled by this request, and carefully stated that while I was honored by the
invitation, I was hesitant to accept, since I had never carried out research
(either theoretical or experimental) on quantum teleportation, and was
certainly not an expert on the matter. The organizers looked about the room nervously
and then in hushed tones took me aside and explained their rational — apparently
there was a very contentious debate raging among the three experimental groups
as to who had done the first “true” demonstration of quantum teleportation, and
the organizers expected the panel discussion to be loud and chaotic and they
feared the panelists might become unruly — quantum physicists run amok!
Therefore, they explained to me nervously while averting their eyes from my
gaze, that they needed a moderator who would be able to run the thing with a
strong hand (and a loud voice) in order to keep order. “The organizers are
unanimous in our decision that you, Dr. Dowling, are our only hope.” I had been
in a moment demoted from world’s expert in quantum physics to the quantum
mechanical equivalent of either Obi-Wan Kenobe or a barroom bouncer.
The panel was chaotic from the inception. As I expected, there was one panelist per experimental group, Austrian physicist Gregor Weihs from the Zeilinger group, DeMartini from his own group, and Australian physicist Samuel Braunstein from the Kimble group. (American physicist Marlan Scully once called me the “Bob Hope” of theoretical physics. If that is the case then my good friend and colleague Sam Braunstein is surely the “Woody Allen” of theoretical physics.) Since the debate to be among these three competing groups, I was again puzzled when the organizers, at the last minute, added two additional Italian physicists to the panel, other than DeMartini. I was even more puzzled that these two last minute additions seemed to have even less experience with quantum teleportation than me! I gentle inquired as to why they should be on the panel — my role as bouncer was clear — but their roles were not. Again more hushed tones and averted gazes and the organizers explained that they were both big-shot Italian professors who asked to be on the panel discussion on quantum teleportation, in spite of knowing absolutely nothing about quantum teleportation, but for the simple reason that they were big-shot Italian professors, and thought it would look prestigious to insert themselves onto the panel. I had lived in Italy for a year as a graduate student, and I knew a thing or two about Italian politics in the universities, and conceded to their admittance to the panel in the interest of keeping the peace. Peace, however, was not long kept.
The night before the panel discussion I was in a bit of a panic myself in my hotel room as I wondered how to organize things. I decided that in the hour-long time slot I would give each of the six participants, including myself, five minutes to speak or present a few slides, and then reserve the second half hour for questions from the audience. Now I knew there was this debate between the three experimental groups about whose teleportation experiment was the “best” experiment, where “best is very subjective, but I had not followed this debate at all, and did not really have time to read through all three of the experimental papers and try to figure it all out. Hence I had an experimentalist friend and colleague, German physicist Andreas Sizmann, give me a quick tutorial on the nature of the experimental debate, at the bar, and then went back and carefully reread the original theory proposal by Bennett and colleagues, and with the help of Sizmann constructed a few overhead transparencies on how I thought a quantum teleporter should work and how, if handed such a device, one might be able tell if it was working properly, and if handed three of them, how I might gauge which of the three was “best”. It was then, for the first time, I devised the story of the mythical National Institute of Quantum Standards and Technology (NIQuIST) and the equally mythical quantum teleporter-testing machine NIQuIST had constructed to test the three claimed experimental implementations. In other words I did not compare the three experiments at all, I figured the panelists could do that themselves, but instead I put up a series of tests that each teleporter should pass to get the NIQuIST seal of approval, or more accurately something like a Consumer Reports rating: Recommended, Best Buy, or Not Acceptable. The quantum teleporter-testing machine that I drew up by hand looked like that in figure.
The next part of the tester will be to see how good the teleporter is doing. If an unknown state is sent in by Doug to Alice, we want the state that emerges on Bob’s side of the teleporter to be as close to that state as possible. This is quality control and one measure of the quality of such a state transport is called the quantum fidelity. The fidelity is 100% if the outputted teleported state is identical to the inputted stated to be teleported. The fidelity is 0% if the outputted teleported state is as far from the inputted state as possible, which would be hard to arrange without trying. If the teleporter simply completely scrambles the input state then (on average) the fidelity of the output states, with respect to the input states, will be 50%. That is, if the teleporter sucks, on average the outputted state agrees with the inputted state only half the time. Hence anything better than 50% is considered good; I would call it the bronze standard of teleportation. The gold standard would be 82% fidelity, that is the minimum required for the teleporter to be used to teleport one half of an entangled photon pair and still violate Bell’s inequality. Anything less than 82% can be modeled with a classical local hidden variable and hence does not really test quantum mechanics. A new character in our pantheon, Ellen, on the right (purple), extracts the fidelity; she runs a machine called the “fidellerator” that measures the state of the teleported photon and compares it with the state that was actually teleported. Doug sends the complete information on the states he provided, and Ellen sends the complete information on the states she received, to François (bottom green), who runs a machine called the comparator (which I do not put in quotes because “comparator” is a real word), which compares what Doug sent to what Ellen got and then ranks the teleporter in the test.
So I presented this slide and this spiel in about five minutes at the Naples panel discussion, along with an additional slide and discussion from my partner in crime and sidekick, Andreas Sizmann. Then I allowed each of the remaining five panelists to speak. As expected, the two-big shot Italian professors who were admitted to the panel for political reasons, gave presentations that had nothing to do with quantum teleportation, much to the consternation of the audience, consternation that was on display through audience member protestations consisting of gnarled grimaces (or audible snoring). Then in rapid fire came (in alphabetical order) the three true experimental teleporter panelists, Braunstein, DeMartini, and Wiehs. This took up about a half hour of time, as anticipated. As the other panelists spoke, Sam Braunstein scribbled away furiously on a little notepad and, periodically with great showmanship and dash, he would loudly tear off the note sheet with the scribbles on it, neatly fold it in half, and hand it to me, while he displayed a very serious face to the audience. On the notepad sheets, that I would carefully unfold like a poker hand of two cards (so that nobody else could see them), Braunstein had drawn cartoon caricatures of the various panelists (other then himself), with their name and such artistic embellishments as crossed eyes, drool, maniacal grins, or feathered and bloodied arrows sticking through their craniums from ear to ear.
Each panelist had spoken their piece and then it was time for the grilling from the audience. I did my best to maintain order, timing the questions, cutting people off when sufficient, deafening others (with my ribald vocabulary of Italian curse words) when necessary, but all was lost when a young man (whose name I never got) with a Germanic accent (German, Swiss, or Austrian), grabbed the portable microphone and launched into a diatribe of his own. The young Teuton first assailed the structure and organization of the panel, “This panel discussion was badly organized. I have no idea who these first two Italian guys were or why they were even on the panel, as they had nothing to say about the topic of quantum teleportation!” The Italians looked at the German-accented Wünderkindt in horror as he dared speak the obvious. (I liked this Kindt already.) Then he continued, “Even the presentations from the panelists, who have done work on quantum teleportation, were mostly incomprehensible.” Now all the hackles were raised. “In fact,” continued this spawn of Odin, “The only person on this panel who made any sense was Dr. Jonathan Dowlings (sic)!” (I liked this Kindt even more.) I grinned ear from ear and smiled at all the organizers, but the were not smiling back. Then the blond-haired, German-accented, intemperate audience participant went in for the kill, “And you, DeMartini, your teleportation experiment meets none of Dowlings’ criteria for a success at all!” I stared at this guy in horror as a shudder when down my spine and spread rapidly through the floor and across the audience
That
was it! DeMartini snatched up his transparencies and stormed off the podium,
off the stage, down the steps, and out of the auditorium side door, never to be
seen again (at least at that conference). I, jokingly, announced, “Did anybody
see where DeMartini went? Can somebody check the toilet? No? Okay then I
officially declare the panel discussion to be at an end!”
— The unedited story adapted from Schrödinger's Killer App: Race to Build the World's First Quantum Computer
The panel was chaotic from the inception. As I expected, there was one panelist per experimental group, Austrian physicist Gregor Weihs from the Zeilinger group, DeMartini from his own group, and Australian physicist Samuel Braunstein from the Kimble group. (American physicist Marlan Scully once called me the “Bob Hope” of theoretical physics. If that is the case then my good friend and colleague Sam Braunstein is surely the “Woody Allen” of theoretical physics.) Since the debate to be among these three competing groups, I was again puzzled when the organizers, at the last minute, added two additional Italian physicists to the panel, other than DeMartini. I was even more puzzled that these two last minute additions seemed to have even less experience with quantum teleportation than me! I gentle inquired as to why they should be on the panel — my role as bouncer was clear — but their roles were not. Again more hushed tones and averted gazes and the organizers explained that they were both big-shot Italian professors who asked to be on the panel discussion on quantum teleportation, in spite of knowing absolutely nothing about quantum teleportation, but for the simple reason that they were big-shot Italian professors, and thought it would look prestigious to insert themselves onto the panel. I had lived in Italy for a year as a graduate student, and I knew a thing or two about Italian politics in the universities, and conceded to their admittance to the panel in the interest of keeping the peace. Peace, however, was not long kept.
The night before the panel discussion I was in a bit of a panic myself in my hotel room as I wondered how to organize things. I decided that in the hour-long time slot I would give each of the six participants, including myself, five minutes to speak or present a few slides, and then reserve the second half hour for questions from the audience. Now I knew there was this debate between the three experimental groups about whose teleportation experiment was the “best” experiment, where “best is very subjective, but I had not followed this debate at all, and did not really have time to read through all three of the experimental papers and try to figure it all out. Hence I had an experimentalist friend and colleague, German physicist Andreas Sizmann, give me a quick tutorial on the nature of the experimental debate, at the bar, and then went back and carefully reread the original theory proposal by Bennett and colleagues, and with the help of Sizmann constructed a few overhead transparencies on how I thought a quantum teleporter should work and how, if handed such a device, one might be able tell if it was working properly, and if handed three of them, how I might gauge which of the three was “best”. It was then, for the first time, I devised the story of the mythical National Institute of Quantum Standards and Technology (NIQuIST) and the equally mythical quantum teleporter-testing machine NIQuIST had constructed to test the three claimed experimental implementations. In other words I did not compare the three experiments at all, I figured the panelists could do that themselves, but instead I put up a series of tests that each teleporter should pass to get the NIQuIST seal of approval, or more accurately something like a Consumer Reports rating: Recommended, Best Buy, or Not Acceptable. The quantum teleporter-testing machine that I drew up by hand looked like that in figure.
In the figure we show a
compactified version of the quantum teleporter, being
slowly lowered into the NIQuIST teleportation-testing machine (brownish
orange). As before we have Doug, now a NIQuIST employee (purple, left) who
provides the teleporter with a photon whose quantum polarization state is
unknown to Alice, Bob, or Charlie in the teleporter. Doug produces a large
number of such unknown states using a machine called the “ensembler” that
produces ensembles or collections of single photon polarization states, where the ensembler can be programmed to choose the states at random, or in a pre-selected sequence. There are an infinite
number of states so ensembler
should produce a large number of different states so the test of the teleporter
will be statistically significant. That is if the sample of states
is random enough and sample enough of the possible infinite space in a way that
the teleporter operators cannot anticipate, the more likely that it will be a
fair test and that the teleporter operators cannot somehow cheat by using some
inside knowledge of the states being transmitted.
The
next part of the tester will be to see how good the teleporter is doing. If an
unknown state Y is sent in by Doug to Alice, we want the state
that emerges on Bob’s side of the teleporter to be as close to Y as possible. This is
quality control and one measure of the quality of such a state transport is
called the quantum fidelity. The fidelity is 100% if the outputted teleported
state is identical to the inputted stated to be teleported. The fidelity is 0%
if the outputted teleported state is as far from the inputted state as
possible, which would be hard to arrange without trying. If the teleporter
simply completely scrambles the input state then (on average) the fidelity of
the output states, with respect to the input states, will be 50%. That is, if
the teleporter sucks, on average the outputted state agrees with the inputted
state only half the time. Hence anything better than 50% is considered good; I
would call it the bronze standard of teleportation. The gold standard would be
82% fidelity, that is the minimum required for the teleporter to be used to
teleport one half of an entangled photon pair and still violate Bell’s
inequality. Anything less than 82% can be modeled with a classical local hidden
variable and hence does not really test quantum mechanics. A new character in
our pantheon, Ellen, on the right (purple), extracts the fidelity; she runs a machine
called the “fidellerator” that measures the state of the teleported photon and
compares it with the state that was actually teleported. Doug
sends the complete information on the states he provided, and Ellen sends the
complete information on the states she received, to François (bottom green), who runs a machine
called the comparator (which I do not put in quotes because “comparator” is a
real word), which compares what Doug sent to what Ellen got and then ranks the
teleporter in the test.
The next part of the tester will be to see how good the teleporter is doing. If an unknown state is sent in by Doug to Alice, we want the state that emerges on Bob’s side of the teleporter to be as close to that state as possible. This is quality control and one measure of the quality of such a state transport is called the quantum fidelity. The fidelity is 100% if the outputted teleported state is identical to the inputted stated to be teleported. The fidelity is 0% if the outputted teleported state is as far from the inputted state as possible, which would be hard to arrange without trying. If the teleporter simply completely scrambles the input state then (on average) the fidelity of the output states, with respect to the input states, will be 50%. That is, if the teleporter sucks, on average the outputted state agrees with the inputted state only half the time. Hence anything better than 50% is considered good; I would call it the bronze standard of teleportation. The gold standard would be 82% fidelity, that is the minimum required for the teleporter to be used to teleport one half of an entangled photon pair and still violate Bell’s inequality. Anything less than 82% can be modeled with a classical local hidden variable and hence does not really test quantum mechanics. A new character in our pantheon, Ellen, on the right (purple), extracts the fidelity; she runs a machine called the “fidellerator” that measures the state of the teleported photon and compares it with the state that was actually teleported. Doug sends the complete information on the states he provided, and Ellen sends the complete information on the states she received, to François (bottom green), who runs a machine called the comparator (which I do not put in quotes because “comparator” is a real word), which compares what Doug sent to what Ellen got and then ranks the teleporter in the test.
So I presented this slide and this spiel in about five minutes at the Naples panel discussion, along with an additional slide and discussion from my partner in crime and sidekick, Andreas Sizmann. Then I allowed each of the remaining five panelists to speak. As expected, the two-big shot Italian professors who were admitted to the panel for political reasons, gave presentations that had nothing to do with quantum teleportation, much to the consternation of the audience, consternation that was on display through audience member protestations consisting of gnarled grimaces (or audible snoring). Then in rapid fire came (in alphabetical order) the three true experimental teleporter panelists, Braunstein, DeMartini, and Wiehs. This took up about a half hour of time, as anticipated. As the other panelists spoke, Sam Braunstein scribbled away furiously on a little notepad and, periodically with great showmanship and dash, he would loudly tear off the note sheet with the scribbles on it, neatly fold it in half, and hand it to me, while he displayed a very serious face to the audience. On the notepad sheets, that I would carefully unfold like a poker hand of two cards (so that nobody else could see them), Braunstein had drawn cartoon caricatures of the various panelists (other then himself), with their name and such artistic embellishments as crossed eyes, drool, maniacal grins, or feathered and bloodied arrows sticking through their craniums from ear to ear.
After he would hand these
cartoons to me, he sitting and I standing, with great seriousness and I would peer
intently at them. Astonished, I realized that he was simply trying to get me to
laugh out loud during the panel discussion! Not to be fooled, I would inspect
the crude cartoons carefully, out of eyesight from the other panelists and the
audience, and then fold them neatly, tuck them into my shirt pocket, and
announce, “A very good point, Prof. Braunstein, I will be sure to bring it up
in the discussion session to follow!” All the panelists, the audience, and
Braunstein would then nod in solemn approval of this curious ritual and then
Braunstein would then return madly to his work of furiously scribbling out the
next cartoon caricature on his note pad.
Each panelist had spoken their piece and then it was time for the grilling from the audience. I did my best to maintain order, timing the questions, cutting people off when sufficient, deafening others (with my ribald vocabulary of Italian curse words) when necessary, but all was lost when a young man (whose name I never got) with a Germanic accent (German, Swiss, or Austrian), grabbed the portable microphone and launched into a diatribe of his own. The young Teuton first assailed the structure and organization of the panel, “This panel discussion was badly organized. I have no idea who these first two Italian guys were or why they were even on the panel, as they had nothing to say about the topic of quantum teleportation!” The Italians looked at the German-accented Wünderkindt in horror as he dared speak the obvious. (I liked this Kindt already.) Then he continued, “Even the presentations from the panelists, who have done work on quantum teleportation, were mostly incomprehensible.” Now all the hackles were raised. “In fact,” continued this spawn of Odin, “The only person on this panel who made any sense was Dr. Jonathan Dowlings (sic)!” (I liked this Kindt even more.) I grinned ear from ear and smiled at all the organizers, but the were not smiling back. Then the blond-haired, German-accented, intemperate audience participant went in for the kill, “And you, DeMartini, your teleportation experiment meets none of Dowlings’ criteria for a success at all!” I stared at this guy in horror as a shudder when down my spine and spread rapidly through the floor and across the audience
— The unedited story adapted from Schrödinger's Killer App: Race to Build the World's First Quantum Computer
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