quantum entanglement

Climate change, like quantum physics, will strain language

One of the defining features of quantum mechanics is that it shows up human language, and thought supported by that language, to be insufficient and limited. Many of the most popular languages of the world, including Tamil, Hindi and English, are linear. Their script reads in a line from one end of the page to the other, and their spoken words compile meaning based on a linear sequence and order of words. It is possible to construe these meanings in turn only after word after another, through the passage of time. If time stops, so does language.

Such linearity is incompatible with the possibilities in quantum mechanics for simultaneity, in both space and time. Quantum superposition is not exactly a system in two states at once but in a linear combination of states, but without the specialised knowledge, language can only offer a slew of metaphors, each of which hews asymptotically closer to the actual thing but never captures it in its entirety. Quantum entanglement, similarly, causes one particle to affect another instantaneously, over hundreds of kilometres, defying both the universal information speed limit and the ability of human minds that remain constrained by that limit, as well as a human language that has no place for, and therefore can’t identify, simultaneity. All we have something after another, effect after cause, the first step and then the second, and never both at once.

Indeed, the notion of causality – that cause will always precede effect – is one of the load-bearing pillars of reality as we strive to understand it.

But while quantum mechanics is so kooky, it is also excusably so, considering it represents a paradigm shift of sorts from the truths of classical physics (it plays by different rules, that is). It is almost simply natural that our languages do not encompass the possibilities afforded by a phenomenon we didn’t encounter until the 20th century, and still don’t except through specialised apparatuses and controlled experimental conditions.

However, there is another system of things that plays largely by the rules of classical physics – our interactions with and formalisation of which paralleled the evolution of our languages – and yet increasingly defies the ability of our languages to describe it faithfully: climate change.

True, weather and climate patterns include aspects of chaos theory, which explains how minute differences in initial conditions can lead to vastly different outcomes. But chaos theory still only takes recourse to non-linear effects, which, while harder to conceive of than their linear counterparts, are easier than to grapple with non-locality and non-causality. Of course, climate change doesn’t violate any of these or other similarly foundational principles, yet it complicates interactions in the global weather system and intensifies the interactions between the elements and human culture, technology and biology – both to such a degree that they have consequences both different and new.

For example, to quote from an article The Wire Science published this morning:

Climate change will further exacerbate marine heatwave risks in the [Indian subcontinent] region, according to [Ming] Feng. This could suppress coastal upwelling – the process by which strong winds move surface water in the ocean, permitting water from below to surface – and reduce the amount of oxygen in the water. This in turn could have a “great impact” on fisheries.

A big part of climate change’s (extant as well as impending) devastation is in the form of surprise – that is, of the emergent phenomena that it makes possible. Expounded most famously by the brilliant physicist Philip W. Anderson, especially in his 1972 essay ‘More Is Different’, emergence is the idea that we cannot fully describe a large system only by studying its smallest components. Put another way, larger systems have emergent properties and behaviour that are more than the sum of the ways in which systems’ most fundamental parts interact. Studying climate change is important because the additional complexity it imbues to existing weather systems are ripe with emergent effects, each with new consequences and perhaps more effects of their own.

At the same time, the bulk of these effects, taken together, anticipate such a large volume of possibilities that even though they certainly won’t defy reality’s, and human languages’, assumption that causality is true, they will push it to extreme limits. Two events are still at liberty to happen at the same time, each with a distinct and preceding cause, but even as the ways we communicate wait for cause before composing effect, climate change will confront us with a tsunami of changes – each one reinforcing, screening or ignoring the other, rapidly branching out into a larger, denser forest of changes, until the cause is only relevant as an historical artefact in our grammar of the natural universe.

Disentangling entanglement

There has been considerable speculation if the winners of this year’s Nobel Prize for physics, due to be announced at 2.30 pm IST on October 8, will include Alain Aspect and Anton Zeilinger. They’ve both made significant experimental contributions related to quantum information theory and the fundamental nature of quantum mechanics, including entanglement.

Their work, at least the potentially prize-winning part of it, is centred on a class of experiments called Bell tests. If you perform a Bell test, you’re essentially checking the extent to which the rules of quantum mechanics are compatible with the rules of classical physics.

Whether or not Aspect, Zeilinger and/or others win a Nobel Prize this year, what they did achieve is worth putting in words. Of course, many other writers, authors, scientists, etc. have already performed this activity; I’d like to redo it if only because writing helps commit things to memory and because the various performers of Bell tests are likely to win some prominent prize, given how modern technologies like quantum cryptography are inflating the importance of their work, and at that time I’ll have ready reference material.

(There is yet another reason Aspect and Zeilinger could win a Nobel Prize. As with the medicine prizes, many of whose laureates previously won a Lasker Award, many of the physics laureates have previously won the Wolf Prize. And Aspect and Zeilinger jointly won the Wolf Prize for physics in 2010 along with John Clauser.)

The following elucidation is divided into two parts: principles and tests. My principal sources are Wikipedia, some physics magazines, Quantum Physics for Poets by Leon Lederman and Christopher Hill (2011), and a textbook of quantum mechanics by John L. Powell and Bernd Crasemann (1998).

Principles

From the late 1920s, Albert Einstein began to publicly express his discomfort with the emerging theory of quantum mechanics. He claimed that a quantum mechanical description of reality allowed “spooky” things that the rules of classical mechanics, including his theories of relativity, forbid. He further contended that both classical mechanics and quantum mechanics couldn’t be true at the same time and that there had to be a deeper theory of reality with its own, thus-far hidden variables.

Remember the Schrödinger’s cat thought experiment: place a cat in a box with a bowl of poison and close the lid; until you open the box to make an observation, the cat may be considered to be both alive and dead. Erwin Schrödinger came up with this example to ridicule the implications of Niels Bohr’s and Werner Heisenberg’s idea that the quantum state of a subatomic particle, like an electron, was described by a mathematical object called the wave function.

The wave function has many unique properties. One of these is superposition: the ability of an object to exist in multiple states at once. Another is decoherence (although this isn’t a property as much as a phenomenon common to many quantum systems): when you observed the object. it would probabilistically collapse into one fixed state.

Imagine having a box full of billiard balls, each of which is both blue and green at the same time. But the moment you open the box to look, each ball decides to become either blue or green. This (metaphor) is on the face of it a kooky description of reality. Einstein definitely wasn’t happy with it; he believed that quantum mechanics was just a theory of what we thought we knew and that there was a deeper theory of reality that didn’t offer such absurd explanations.

In 1935, Einstein, Boris Podolsky and Nathan Rosen advanced a thought experiment based on these ideas that seemed to yield ridiculous results, in a deliberate effort to provoke his ‘opponents’ to reconsider their ideas. Say there’s a heavy particle with zero spin – a property of elementary particles – inside a box in Bangalore. At some point, it decays into two smaller particles. One of these ought to have a spin of 1/2 and other of -1/2 to abide by the conservation of spin. You send one of these particles to your friend in Chennai and the other to a friend in Mumbai. Until these people observe their respective particles, the latter are to be considered to be in a mixed state – a superposition. In the final step, your friend in Chennai observes the particle to measure a spin of -1/2. This immediately implies that the particle sent to Mumbai should have a spin of 1/2.

If you’d performed this experiment with two billiard balls instead, one blue and one green, the person in Bangalore would’ve known which ball went to which friend. But in the Einstein-Podolsky-Rosen (EPR) thought experiment, the person in Bangalore couldn’t have known which particle was sent to which city, only that each particle existed in a superposition of two states, spin 1/2 and spin -1/2. This situation was unacceptable to Einstein because it was inimical certain assumptions on which the theories of relativity were founded.

The moment the friend in Chennai observed her particle to have spin -1/2, the one in Mumbai would have known without measuring her particle that it had a spin of 1/2. If it didn’t, the conservation of spin would be violated. If it did, then the wave function of the Mumbai particle would have collapsed to a spin 1/2 state the moment the wave function of the Chennai particle had collapsed to a spin -1/2 state, indicating faster-than-light communication between the particles. Either way, quantum mechanics could not produce a sensible outcome.

Two particles whose wave functions are linked the way they were in the EPR paradox are said to be entangled. Einstein memorably described entanglement as “spooky action at a distance”. He used the EPR paradox to suggest quantum mechanics couldn’t possibly be legit, certainly not without messing with the rules that made classical mechanics legit.

So the question of whether quantum mechanics was a fundamental description of reality or whether there were any hidden variables representing a deeper theory stood for nearly thirty years.

Then, in 1964, an Irish physicist at CERN named John Stewart Bell figured out a way to answer this question using what has since been called Bell’s theorem. He defined a set of inequalities – statements of the form “P is greater than Q” – that were definitely true for classical mechanics. If an experiment conducted with electrons, for example, also concluded that “P is greater than Q“, it would support the idea that quantum mechanics (vis-à-vis electrons) has ‘hidden’ parts that would explain things like entanglement more along the lines of classical mechanics.

But if an experiment couldn’t conclude that “P is greater than Q“, it would support the idea that there are no hidden variables, that quantum mechanics is a complete theory and, finally, that it implicitly supports spooky actions at a distance.

The theorem here was a statement. To quote myself from a 2013 post (emphasis added):

… for quantum mechanics to be a complete theory – applicable everywhere and always – either locality or realism must be untrue. Locality is the idea that instantaneous or [faster-than-light] communication is impossible. Realism is the idea that even if an object cannot be detected at some times, its existence cannot be disputed [like electrons or protons].

Zeilinger and Aspect, among others, are recognised for having performed these experiments, called Bell tests.

Technological advancements through the late 20th and early 21st centuries have produced more and more nuanced editions of different kinds of Bell tests. However, one thing has been clear from the first tests, in 1981, to the last: they have all consistently violated Bell’s inequalities, indicating that quantum mechanics does not have hidden variables and our reality does allow bizarre things like superposition and entanglement to happen.

To quote from Quantum Physics for Poets (p. 214-215):

Bell’s theorem addresses the EPR paradox by establishing that measurements on object a actually do have some kind of instant effect on the measurement at b, even though the two are very far apart. It distinguishes this shocking interpretation from a more commonplace one in which only our knowledge of the state of b changes. This has a direct bearing on the meaning of the wave function and, from the consequences of Bell’s theorem, experimentally establishes that the wave function completely defines the system in that a ‘collapse’ is a real physical happening.

Tests

Though Bell defined his inequalities in such a way that they would lend themselves to study in a single test, experimenters often stumbled upon loopholes in the result as a consequence of the experiment’s design not being robust enough to evade quantum mechanics’s propensity to confound observers. Think of a loophole as a caveat; an experimenter runs a test and comes to you and says, “P is greater than Q but…”, followed by an excuse that makes the result less reliable. For a long time, physicists couldn’t figure out how to get rid of all these excuses and just be able to say – or not say – “P is greater than Q“.

If millions of photons are entangled in an experiment, the detectors used to detect, and observe, the photons may not be good enough to detect all of them or the photons may not survive their journey to the detectors properly. This fair-sampling loophole could give rise to doubts about whether a photon collapsed into a particular state because of entanglement or if it was simply coincidence.

To prevent this, physicists could bring the detectors closer together but this would create the communication loophole. If two entangled photons are separated by 100 km and the second observation is made more than 0.0003 seconds after the first, it’s still possible that optical information could’ve been exchanged between the two particles. To sidestep this possibility, the two observations have to be separated by a distance greater than what light could travel in the time it takes to make the measurements. (Alain Aspect and his team also pointed their two detectors in random directions in one of their tests.)

Third, physicists can tell if two photons received in separate locations were in fact entangled with each other, and not other photons, based on the precise time at which they’re detected. So unless physicists precisely calibrate the detection window for each pair, hidden variables could have time to interfere and induce effects the test isn’t designed to check for, creating a coincidence loophole.

If physicists perform a test such that detectors repeatedly measure the particles involved in, say, two labs in Chennai and Mumbai, it’s not impossible for statistical dependencies to arise between measurements. To work around this memory loophole, the experiment simply has to use different measurement settings for each pair.

Apart from these, experimenters also have to minimise any potential error within the instruments involved in the test. If they can’t eliminate the errors entirely, they will then have to modify the experimental design to compensate for any confounding influence due to the errors.

So the ideal Bell test – the one with no caveats – would be one where the experimenters are able to close all loopholes at the same time. In fact, physicists soon realised that the fair-sampling and communication loopholes were the more important ones.

In 1972, John Clauser and Stuart Freedman performed the first Bell test by entangling photons and measuring their polarisation at two separate detectors. Aspect led the first group that closed the communication loophole, in 1982; he subsequently conducted more tests that improved his first results. Anton Zeilinger and his team made advancements on the fair-sampling loophole.

One particularly important experimental result showed up in August 2015: Robert Hanson and his team at the Technical University of Delft, in the Netherlands, had found a way to close the fair-sampling and communication loopholes at the same time. To quote Zeeya Merali’s report in Nature News at the time (lightly edited for brevity):

The researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 km apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location. There, the two photons were entangled with each other – and this caused both their partner electrons to become entangled, too. … the team managed to generate 245 entangled pairs of electrons over … nine days. The team’s measurements exceeded Bell’s bound, once again supporting the standard quantum view. Moreover, the experiment closed both loopholes at once: because the electrons were easy to monitor, the detection loophole was not an issue, and they were separated far enough apart to close the communication loophole, too.

By December 2015, Anton Zeilinger and co. were able to close the communication and fair-sampling loopholes in a single test with a 1-in-2-octillion chance of error, using a different experimental setup from Hanson’s. In fact, Zeilinger’s team actually closed three loopholes including the freedom-of-choice loophole. According to Merali, this is “the possibility that hidden variables could somehow manipulate the experimenters’ choices of what properties to measure, tricking them into thinking quantum theory is correct”.

But at the time Hanson et al announced their result, Matthew Leifer, a physicist the Perimeter Institute in Canada, told Nature News (in the same report) that because “we can never prove that [the converse of freedom of choice] is not the case, … it’s fair to say that most physicists don’t worry too much about this.”

We haven’t gone into much detail about Bell’s inequalities themselves but if our goal is to understand why Aspect and Zeilinger, and Clauser too, deserve to win a Nobel Prize, it’s because of the ingenious tests they devised to test Bell’s, and Einstein’s, ideas and the implications of what they’ve found in the process.

For example, Bell crafted his test of the EPR paradox in the form of a ‘no-go theorem’: if it satisfied certain conditions, a theory was designated non-local, like quantum mechanics; if it didn’t satisfy all those conditions, the theory be classified as local, like Einstein’s special relativity. So Bell tests are effectively gatekeepers that can attest whether or not a theory – or a system – is behaving in a quantum way and each loophole is like an attempt to hack the attestation process.

In 1991, Artur Ekert, who would later be acknowledged as one of the inventors of quantum cryptography, realised this perspective could have applications in securing communications. Engineers could encode information in entangled particles, send them to remote locations, and allow detectors there to communicate with each other securely by observing these particles and decoding the information. The engineers can then perform Bell tests to determine if anyone might be eavesdropping on these communications using one or some of the loopholes.

Relativity’s kin, the Bose-Einstein condensate, is 90 now

Excerpt:

Over November 2015, physicists and commentators alike the world over marked 100 years since the conception of the theory of relativity, which gave us everything from GPS to blackholes, and described the machinations of the universe at the largest scales. Despite many struggles by the greatest scientists of our times, the theory of relativity remains incompatible with quantum mechanics, the rules that describe the universe at its smallest, to this day. Yet it persists as our best description of the grand opera of the cosmos.

Incidentally, Einstein wasn’t a fan of quantum mechanics because of its occasional tendencies to violate the principles of locality and causality. Such violations resulted in what he called “spooky action at a distance”, where particles behaved as if they could communicate with each other faster than the speed of light would have it. It was weirdness the likes of which his conception of gravitation and space-time didn’t have room for.

As it happens, 2015 also marks another milestone, also involving Einstein’s work – as well as the work of an Indian scientist: Satyendra Nath Bose. It’s been 20 years since physicists realised the first Bose-Einstein condensate, which has proved to be an exceptional as well as quirky testbed for scientists probing the strange implications of a quantum mechanical reality.

Its significance today can be understood in terms of three ‘periods’ of research that contributed to it: 1925 onward, 1975 onward, and 1995 onward.

Read the full piece here.

A closet of hidden phenomena

Science has been rarely counter-intuitive to our understanding of reality, and its elegant rationalism at every step of the way has been reassuring. This is why Bell’s theorem has been one of the strangest concepts of reality scientists have come across: it is hardly intuitive, hardly rational, and hardly reassuring.

To someone interested in the bigger picture, the theorem is the line before which quantum mechanics ends and after which classical mechanics begins. It’s the line in the sand between the Max Planck and the Albert Einstein weltanschauungen.

Einstein, and many others before him, worked with gravity, finding a way to explain the macrocosm and its large-scale dance of birth and destruction. Planck, and many others after him, have helped describe the world of the atom and its innards using extremely small packets of energy called particles, swimming around in a pool of exotic forces.

At the nexus of a crisis

Over time, however, as physicists studied the work of both men and of others, it started to become clear that the the fields were mutually exclusive, never coming together to apply to the same idea. At this tenuous nexus, the Irish physicist John Stuart Bell cleared his throat.

Bell’s theorem states, in simple terms, that for quantum mechanics to be a complete theory – applicable everywhere and always – either locality or realism must be untrue. Locality is the idea that instantaneous or superluminal communication is impossible. Realism is the idea that even if an object cannot be detected at some times, its existence cannot be disputed – like the moon in the morning.

The paradox is obvious. Classical mechanics is applicable everywhere, even with subatomic particles that are billionths of nanometers across. That it’s not is only because its dominant player, the gravitational force, is overshadowed by other stronger forces. Quantum mechanics, on the other hand, is not so straightforward with its offering. It could be applied in the macroscopic world – but its theory has trouble dealing with gravity or the strong nuclear force, which gives mass to matter.

This means if quantum mechanics is to have a smooth transition at some scale into a classical reality… it can’t. At that scale, one of locality or realism must snap back to life. This is why confronting the idea that one of them isn’t true is unsettling. They are both fundamental hypotheses of physics.

The newcomer

A few days ago, I found a paper on arXiv titled Violation of Bell’s inequality in fluid mechanics (May 28, 2013). Its abstract stated that “… a classical fluid mechanical system can violate Bell’s inequality because the fluid motion is correlated over very large distances”. Given that Bell stands between Planck’s individuated notion of quantum mechanics and Einstein’s waltz-like continuum of the cosmos, it was intriguing to see scientists attempting to describe a quantum mechanical phenomenon in a classical system.

The correlation that the paper’s authors talk about implies fluid flow in one region of space-time is somehow correlated with fluid flow in another region of space-time. This is a violation of locality. However, fluid mechanics has been, still is, a purely classical occurrence: its behaviour can be traced to Newton’s ideas from the 17th century. This means all flow events are, rather have to be, decidedly real and local.

To make their point, the authors use mathematical equations modelling fluid flow, conceived by Leonhard Euler in the 18th century, and how they could explain vortices – regions of a fluid where the flow is mostly a spinning motion about an imaginary axis.

Assigning fictitious particles to different parts of the equation, the scientists demonstrate how the particles in one region of flow could continuously and instantaneously affect particles in another region of fluid flow. In quantum mechanics, this phenomenon is called entanglement. It has no classical counterpart because it violates the principle of locality.

Coincidental correlation

However, there is nothing quantum about fluid flow, much less about Euler’s equations. Then again, if the paper is right, would that mean flowing fluids are a quantum mechanical system? Occam’s razor comes to the rescue: Because fluid flow is classical but still shows signs of nonlocality, there is a possibility that purely local interactions could explain quantum mechanical phenomena.

Think about it. A purely classical system also shows signs of quantum mechanical behaviour. This meant that some phenomena in the fluid could be explained by both classical and quantum mechanical models, i.e. the two models correspond.

There is a stumbling block, however. Occam’s razor only provides evidence of a classical solution for nonlocality, not a direct correspondence between micro- and macroscopic physics. In other words, it could easily be a post hoc ergo propter hoc inference: Because nonlocality came after application of local mathematics, local mathematics must have caused nonlocality.

“Not quite,” said Robert Brady, one of the authors on the paper. “Bell’s hypothesis is often said to be about ‘locality’, and so it is common to say that quantum mechanical systems are ‘nonlocal’ because Bell’s hypothesis does not apply to them. If you choose this description, then fluid mechanics is also ‘non-local’, since Bell’s hypothesis does not apply to them either.”

“However, in fluid mechanics it is usual to look at this from a different angle, since Bell’s hypothesis would not be thought reasonable in that field.”

Brady’s clarification brings up an important point: Even though the lines don’t exactly blur between the two domains, knowing more than choosing where to apply which model makes a large difference. If you misstep, classical fluid flow could become quantum fluid flow simply because it displays some pseudo-effects.

In fact, experiments to test Bell’s hypothesis have been riddled with such small yet nagging stumbling blocks. Even if a suitable domain of applicability has been chosen, an efficient experiment has to be designed that fully exploits the domain’s properties to arrive at a conclusion – and this has proved very difficult. Inspired by the purely theoretical EPR paradox put forth in 1935, Bell stated his theorem in 1964. It is now 2013 and no experiment has successfully proved or disproved it.

Three musketeers

The three most prevalent problems such experiments face are called the failure of rotational invariance, the no-communication loophole, and the fair sampling assumption.

In any Bell experiment, two particles are allowed to interact in some way – such as being born from a same source – and separated across a large distance. Scientists then measure the particles’ properties using detectors. This happens again and again until any patterns among paired particles can be found or denied.

Whatever properties the scientists are going to measure, the different values that that property can take must be equally likely. For example, if I have a bag filled with 200 blue balls, 300 red balls and 100 yellow balls, I shouldn’t think something quantum mechanical was at play if one in two balls pulled out was red. That’s just probability at work. And when probability can’t be completely excluded from the results, it’s called a failure of rotational invariance.

For the experiment to measure only the particles’ properties, the detectors must not be allowed to communicate with each other. If they were allowed to communicate, scientists wouldn’t know if a detection arose due to the particles or due to glitches in the detectors. Unfortunately, in a perfect setup, the detectors wouldn’t communicate at all and be decidedly local – putting them in no position to reveal any violation of locality! This problem is called the no-communication loophole.

The final problem – fair sampling – is a statistical issue. If an experiment involves 1,000 pairs of particles, and if only 800 pairs have been picked up by the detector and studied, the experiment cannot be counted as successful. Why? Because results from the other 200 could have distorted the results had they been picked up. There is a chance. Thus, the detectors would have to be 100 per cent efficient in a successful experiment.

In fact, the example was a gross exaggeration: detectors are only 5-30 per cent efficient.

One (step) at a time

Resolution for the no-communication problem came in 1998 by scientists from Austria, who also closed the rotational invariance loophole. The fair sampling assumption was resolved by a team of scientists from the USA in 2001, one of whom was David Wineland, physics Nobel Laureate, 2012. However, they used only two ions to make the measurements. A more thorough experiment’s results were announced just last month.

Researchers from the Institute for Quantum Optics and Quantum Communication, Austria, had used detectors called transition-edge sensors that could pick up individual photons for detection with a 98 per cent efficiency. These sensors were developed by the National Institute for Standards and Technology, Maryland, USA. In keeping with tradition, the experiment admitted the no-communication loophole.

Unfortunately, for an experiment to be a successful Bell-experiment, it must get rid of all three problems at the same time. This hasn’t been possible to date, which is why a conclusive Bell’s test, and the key to quantum mechanics’ closet of hidden phenomena, eludes us. It is as if nature uses one loophole or the other to deceive the experimenters.*

The silver lining is that the photon has become the first particle for which all three loopholes have been closed, albeit in different experiments. We’re probably getting there, loopholes relenting. The reward, of course, could be the greatest of all: We will finally know if nature is described by quantum mechanics, with its deceptive trove of exotic phenomena, or by classical mechanics and general relativity, with its reassuring embrace of locality and realism.

(*In 1974, John Clauser and Michael Horne found a curious workaround for the fair-sampling problem that they realised could be used to look for new physics. They called this the no-enhancement problem. They had calculated that if some method was found to amplify the photons’ signals in the experiment and circumvent the low detection efficiency, the method would also become a part of the result. Therefore, if the result came out that quantum mechanics was nonlocal, then the method would be a nonlocal entity. So, using different methods, scientists distinguish between previously unknown local and nonlocal processes.)

—

This article, as written by me, originally appeared in The Hindu’s The Copernican science blog on June 15, 2013.

A closet of hidden phenomena

An apparatus to study quantum entanglement, with superconducting channels placed millimeters apart. Photo: Softpedia

At the nexus of a crisis

The paradox is obvious. Classical mechanics is applicable everywhere, even with subatomic particles that are billionths of nanometers across. That it’s not is only because its dominant player, the gravitational force, is overshadowed by other stronger forces. Quantum mechanics, on the other hand, is not so straightforward with its offering. It could be applied in the macroscopic world – but its theory has trouble dealing with gravity and the strong nuclear force, both of which have something to do with mass.

The newcomer

This is a vortex. Hurt your eyes yet?

Coincidental correlation

However, there is nothing quantum about fluid flow, much less about Euler’s equations. Then again, if the paper is right, would that mean flowing fluids are a quantum mechanical system? Occam’s razorcomes to the rescue: Because fluid flow is classical but still shows signs of nonlocality, there is a possibility that purely local interactions could explain quantum mechanical phenomena.

There is a stumbling block, however. Occam’s razor only provides evidence of a classical solution for nonlocality, not a direct correspondence between micro- and macroscopic physics. In other words, it could easily be a post hoc ergo propter hoc inference: Because nonlocality came after application of local mathematics, local mathematics must have caused nonlocality.

“However, in fluid mechanics it is usual to look at this from a different angle, since Bell’s hypothesis would not be thought reasonable in that field.”

Three musketeers

The three most prevalent problems such experiments face are called the failure of rotational invariance, the no-communication loophole, and the fair sampling assumption.

The final problem – fair sampling – is a statistical issue. If an experiment involves 1,000 pairs of particles, and if only 800 pairs have been picked up by the detector and studied, the experiment cannot be counted as successful. Why? Because results from the other 200 could have distorted the results had they been picked up. There is a chance. Thus, the detectors would have to be 100 per cent efficient in a successful experiment.

In fact, the example was a gross exaggeration: detectors are only 5-30 per cent efficient.

One (step) at a time

(This blog post first appeared at The Copernican on June 15, 2013.)

The travails of science communication

There’s an interesting phenomenon in the world of science communication, at least so far as I’ve noticed. Every once in a while, there comes along a concept that is gaining in research traction worldwide but is quite tricky to explain in simple terms to the layman.

Earlier this year, one such concept was the Higgs mechanism. Between December 13, 2011, when the first spotting of the Higgs boson was announced, and July 4, 2012, when the spotting was confirmed as being the piquingly-named “God particle”, the use of the phrase “cosmic molasses” was prevalent enough to prompt an annoyed (and struggling-to-make-sense) Daniel Sarewitz to hit back on Nature. While the article had a lot to say, and a lot more waiting there to just to be rebutted, it did include this remark:

If you find the idea of a cosmic molasses that imparts mass to invisible elementary particles more convincing than a sea of milk that imparts immortality to the Hindu gods, then surely it’s not because one image is inherently more credible and more ‘scientific’ than the other. Both images sound a bit ridiculous. But people raised to believe that physicists are more reliable than Hindu priests will prefer molasses to milk. For those who cannot follow the mathematics, belief in the Higgs is an act of faith, not of rationality.

Sarewitz is not wrong in remarking of the problem as such, but in attempting to use it to define the case of religion’s existence. Anyway: In bridging the gap between advanced physics, which is well-poised to “unlock the future”, and public understanding, which is well-poised to fund the future, there is good journalism. But does it have to come with the twisting and turning of complex theory, maintaining only a tenuous relationship between what the metaphor implies and what reality is?

The notion of a “cosmic molasses” isn’t that bad; it does get close to the original idea of a pervading field of energy whose forces are encapsulated under certain circumstances to impart mass to trespassing particles in the form of the Higgs boson. Even this is a “corruption”, I’m sure. But what I choose to include or leave out makes all the difference.

The significance of experimental physicists having probably found the Higgs boson is best conveyed in terms of what it means to the layman in terms of his daily life and such activities more so than trying continuously to get him interested in the Large Hadron Collider. Common, underlying curiosities will suffice to to get one thinking about the nature of God, or the origins of the universe, and where the mass came from that bounced off Sir Isaac’s head. Shrouding it in a cloud of unrelated concepts is only bound to make the physicists themselves sound defensive, as if they’re struggling to explain something that only they will ever understand.

In the process, if the communicator has left out things such as electroweak symmetry-breaking and Nambu-Goldstone bosons, it’s OK. They’re not part of what makes the find significant for the layman. If, however, you feel that you need to explain everything, then change the question that your post is answering, or merge it with your original idea, etc. Do not indulge in the subject, and make sure to explain your concepts as a proper fiction-story: Your knowledge of the plot shouldn’t interfere with the reader’s process of discovery.

Another complex theory that’s doing the rounds these days is that of quantum entanglement. Those publications that cover news in the field regularly, such as R&D mag, don’t even do as much justice as did SciAm to the Higgs mechanism (through the “cosmic molasses” metaphor). Consider, for instance, this explanation from a story that appeared on November 16.

Electrons have a property called “spin”: Just as a bar magnet can point up or down, so too can the spin of an electron. When electrons become entangled, their spins mirror each other.

The causal link has been omitted! If the story has set out to explain an application of quantum entanglement, which I think it has, then it has done a fairly good job. But what about entanglement-the-concept itself? Yes, it does stand to lose a lot because many communicators seem to be divesting of its intricacies and spending more time explaining why it’s increasing in relevance in modern electronics and computation. If relevance is to mean anything, then debate has to exist – even if it seems antithetical to the deployment of the technology as in the case of nuclear power.

Without understanding what entanglement means, there can be no informed recognition of its wonderful capabilities, there can be no public dialog as to its optimum use to further public interests. When when scientific research stops contributing to the latter, it will definitely face collapse, and that’s the function, rather the purpose, that sensible science communication serves.