A Quantum Christmas

Jim Al-Khalili explains in a TED talk: robins may fly south in winter due to a process called 'quantum entanglement.' Image Source: Digital Photographer / Michael Williams.

Destiny and faith should be foreign concepts in the realm of science. But perhaps quantum physics will devise a formula for them. This possibility started in the 1930s, with Albert Einstein (1879-1955) and Niels Bohr (1885-1962) arguing whether or how objective reality could be measured, because observing something changes its nature into what we would call a subjective reality. Of course, the distinction between objective reality - which religious people sometimes associate with God - and subjective awareness - the world limited by our individual perceptions - is a very old problem. The 16th century French philosopher Michel de Montaigne (1533-1592) wrote: "We are, I know not how, double in ourselves, so that what we believe we disbelieve, and cannot rid ourselves of what we condemn." The central question of religion asks: how are we flawed and animal humans connected to the larger order of the universe? Science asks the same question.

Image Source: Archillect.

To determine if it was possible to measure objective reality, Einstein and Bohr proposed a thought experiment to measure one particle of light, or photon, without affecting it. To do this, they proposed to measure a second particle that was related to the first one, and infer the nature of the related, but unmeasured, first particle. Then they encountered a curious problem. Their measurement of the second particle affected the nature of the first one, but they could not determine how the impact of their actions had been transferred to the first particle, especially because that information traveled instantaneously, that is, faster than the speed of light, which violated Einstein's Theory of Relativity. The distance between the photons did not matter either. They could be close together or on opposite sides of the universe. Einstein did not like this. Wiki:

[I]f a pair of particles is generated in such a way that their total spin is known to be zero, and one particle is found to have clockwise spin on a certain axis, then the spin of the other particle, measured on the same axis, will be found to be counterclockwise; because of the nature of quantum measurement. However, this behavior gives rise to paradoxical effects: any measurement of a property of a particle can be seen as acting on that particle (e.g. by collapsing a number of superposed states); and in the case of entangled particles, such action must be on the entangled system as a whole. It thus appears that one particle of an entangled pair "knows" what measurement has been performed on the other, and with what outcome, even though there is no known means for such information to be communicated between the particles, which at the time of measurement may be separated by arbitrarily large distances. ...

The counterintuitive predictions of quantum mechanics about strongly correlated systems were first discussed by Albert Einstein in 1935, in a joint paper with Boris Podolsky and Nathan Rosen. ... They wrote: "We are thus forced to conclude that the quantum-mechanical description of physical reality given by wave functions is not complete." ... 

Following the EPR paper, Erwin Schrödinger wrote a letter (in German) to Einstein in which he used the word Verschränkung (translated by himself as entanglement) "to describe the correlations between two particles that interact and then separate, as in the EPR experiment." He shortly thereafter published a seminal paper defining and discussing the notion, and terming it "entanglement." In the paper he recognized the importance of the concept, and stated: "I would not call [entanglement] one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought."

Like Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information implicit in the theory of relativity. Einstein later famously derided entanglement as "spukhafte Fernwirkung" or "spooky action at a distance."

In 2013, Chinese physicists clocked the speed of 'spooky action at a distance.' They proved the speed of information as it moves through quantum entangled states is more than four times the speed of light, or three trillion metres per second. Their research paper was published in Physical Review Letters, vol. 110, listed here.

Quantum entanglement. Image Source: Glitch.

Quantum Entanglement documentary. Video Source: Youtube.

Caption for the above video: "A historical account from 1985 of the long standing debate between Niels Bohr and Albert Einstein regarding the validity of the quantum mechanical description of atomic phenomena and observation of quantum states with respect to the uncertainty principle and quantum entanglement . Starring some famous physicists, John Archibald Wheeler, John Stewart Bell, Alain Aspect, David Bohm and others. ... © 1985 Jorlunde Film Denmark with sound editing ... by Muon Ray."

This means that on the quantum level, we are physical systems connected by energy, not solid entities, and everyone and everything is connected to everyone and everything else. In a talk explaining quantum entanglement, Chris Fields remarks: "Entanglement or non-separability is the core idea of quantum theory. It is a simple idea: the universe is not a bunch of independent parts, but is rather one entity that evolves through time as one entity." An entangled universe inspires pseudo-scientific theories and strange hypotheses, such as quantum telepathy and consciousness (see Michio Kaku comment on that notion here), or a quantum Internet, or quantum 3-D printing.

One theory posits that time itself is a by-product of entanglement, that is, that time emerges from a process of interactions between entangled particles. Physicist Seth Lloyd maintains that this is why we perceive time flowing in one direction: "The arrow of time is an arrow of increasing correlations." Therefore, understanding entanglement in relation to how time works may explain how the universe works as a connected whole. In 2013 and 2014, scientists claimed to have proved the theory that time emerges from quantum entanglement. It is not surprising that these problems are coming up in the field of quantum computing and nanotechnology, where machines are being reduced to molecular sizes and the speed of communication between particles is of paramount concern. A good example is a report from October 2015 from Cambridge University, on how instantaneous quantum entanglement reactions can aid in the development of solar energy cells.

After quantum entanglement was related to the Arrow of Time, scientists asked if that arrow could be turned around. Before the so-called 'God Particle' was discovered in 2012 (see my related posts here), Time reported in 2009 that two physicists, Bech Nielsen of the Niels Bohr Institute in Copenhagen and Masao Ninomiya of the Yukawa Institute for Theoretical Physics in Kyoto, Japan, declared that efforts to find the particle were deliberately being hampered or slowed by scientists (or a concerned universe, or agents thereof) sending obstructions from the future. Nielsen and Ninomiya devised something called 'reverse chronological causation,' meaning that actions in the future can be taken to change events in the past:

In a series of audacious papers, Nielsen and Ninomiya have suggested that setbacks to the LHC occur because of "reverse chronological causation," which is to say, sabotage from the future. The papers suggest that the Higgs boson may be "abhorrent to nature" and the LHC's creation of the Higgs sometime in the future sends ripples backward through time to scupper its own creation. Each time scientists are on the verge of capturing the Higgs, the theory holds, the future intercedes. The theory as to why the universe rejects the creation of Higgs bosons is based on complex mathematics, but, Nielsen tells TIME, "you could explain it [simply] by saying that God, in inverted commas, or nature, hates the Higgs and tries to avoid them."

Nielsen counters that nature might allow a small number of Higgs to be produced by the Tevatron, but would prevent the production of the large number of particles the LHC is anticipated to produce. He also acknowledges that Higgs particles are probably produced in cosmic collisions, but says it's impossible to know whether nature has stopped a great deal of these collisions from happening. "It's possible that God avoids Higgs [particles] only when there are very many of them, but if there are a few, maybe He let's them go," he says.

Nielsen and Ninomiya's theory represents one side of an intellectual divide between particle physicists today. Contemporary physicists tend to fall into one of two camps: the theorists, who posit ideas about the origins and workings of the universe; and experimentalists, who design telescopes and particle accelerators to test these theories, or provide new data from which novel theories can emerge.

Most experimentalists believe that the theorists, due to a lack of new data in recent years, have reached a roadblock — the Standard Model, which is the closest thing the theorists have to an evidence-backed "theory of everything," provides only an incomplete explanation of the universe. Until theorists get further data and evidence to move forward, the experimentalists believe, they end up simply making wild guesses — like those concerning time-traveling saboteurs — about how the universe works. "Nielsen and Ninomiya's theories are clearly crazy theories," says Dmitri Denisov, a physicist and Higgs-hunter at the DZero experiment at Fermilab. "In recent years theorists have been starving for experimental input and as a result, theories of second type are propagating widely. The majority of them have nothing to do with world we live in." Perhaps the better question to ask would be - do they have anything to do with the world we will live in?

On 9 December 2015, the Daily Galaxy asked, "Can We Receive Messages from the Future?" in a report on researchers who argued that quantum particles moving on open timelike curves could allow messages to be sent back from the future, because the message had no relationship to whatever it encountered in the past, thus avoiding problems such as the grandfather paradox and causality in space-time. Even with closed timelike curves (on which the particle visits an earlier version of itself), an earlier experiment from 2014 had further concluded that paradoxes and causality could be by-passed. Theoretically, the future can change the past, not just as historians would normally understand it in terms of reinterpretation and meaning, but in real terms of physical agency. When this research asks if we can change the flow of causality, it transforms all understanding of cause and effect, and from that, of human morality; although of course, physicists would not see it that way. A key experiment in 1999, the 'delayed choice quantum eraser,' concluded that changing the past from the future through retrocausality was impossible, but other physicists still refute these findings.

Open timelike curves at the quantum level. Image Source: Daily Galaxy.

To add another extra-dimensional layer to how time relates to entanglement, in May 2013, researchers at the Hebrew University of Jerusalem further dismantled our whole understanding of time. They found that two photons could be entangled and not co-exist in the same time; that is, they were entangled after one was destroyed. This implies that our present can be connected to different futures, or to spacetimes that are separated from us, as well as the fact that quantum entanglement exists beyond what we regard as the physical world. You can see a 2014 paper which attempts to explain how these quantum connections work here. Extreme Tech:

Ready for a mind-bending news story that will forever change your perception of life? Quantum physicists in Israel have successfully entangled two photons that don’t exist at the same time. They create one photon and measure its polarization, destroying it — they then create another photon, and though it never coexisted with the first, it always has the exact opposite polarization, proving they’re entangled. ...

Quantum mechanics, almost by definition, is completely different from our own perceptions and experiences, which are governed by classical mechanics. Believe it or not, quantum mechanics actually has no problem with the behavior demonstrated by the Israeli physicists — entanglement was never a tangible, physical property, and this experiment is a perfect example of why it’s sometimes very naive to boil quantum ideas into classical analogies.

Entanglement is a state where the state of two quantum particles (photons, for example) are intrinsically and absolutely linked. Quantum particles, due a principle called quantum superposition, exist in every theoretically possible state at the same time. A photon, for example, spins horizontally and vertically (different polarizations) at the same time. When you measure a quantum particle, though, it fixes on a single state. With entanglement, when you measure one half of the entangled pair, the other half instantly assumes the exact opposite state. If you measure one photon and it’s vertically polarized, its entangled sibling will be horizontally polarized. ... [E]ntanglement seems to occur instantly, even if the particles are on opposite ends of the universe. This experiment shows how entanglement exists through time, as well as space — or, in scientific terms, the non-locality of quantum mechanics in spacetime.

The article, in Physical Review Letters, vol. 110.210403, is here and listed here. In 2014, a series of papers from Erik Verlinde at the University of Amsterdam related entanglement to entropy and the creation of gravity, along with dark energy and dark matter. In October 2015, another article posited that dark matter is also quantum entangled.

See my posts related to the Arrow of Time.