Observers are powerful players in the quantum world. According to the theory, particles can be in several places or states at once — this is called a superposition. But oddly, this is only the case when they aren’t observed. The second you observe a quantum system, it picks a specific location or state — breaking the superposition. The fact that nature behaves this way has been proven multiple times in the lab — for example, in the famous double slit experiment.
QBism or Quantum Bayesianism is an interpretation that takes an agent’s actions and experiences as the central concerns of the theory. The principal thesis of QBism is simply this: quantum probabilities are numerical measures of personal degrees of beliefs.
The problem of Wigner’s friend
The “paradox” of Wigner’s friend involves (i) Wigner’s friend measuring the spin of an electron and updating his wave function accordingly and (ii) Wigner, who turns his back to the experiment and so describes his friend as being in an entangled superposition. Wigner and his friend therefore have distinct wave functions.
The paradox is then stated as follows:
“So, who’s right? Has the qubit collapsed, or is it still a superposition? As long as the wave function is regarded as a real thing or as a description of a real process, the question is no more easily resolved than Bishop Berkeley’s infamous question about the tree in the forest: When a tree falls in the forest and nobody hears it, does it make a sound?”
But this statement seems incorrect. Theories which admit the reality of the wave function yield straightforward answers to this question. For example, it is a trivial implication of collapse theories that Wigner is wrong, his friend is right.
According to QBism, there is no unique wave function. Wave functions are not tethered to electrons […] they are assigned by an agent and depend on the total information available to the agent. They are malleable and subjective. In short, wave functions and quantum probabilities are Bayesian
Therefore, a measurement does not reveal a per-existing value. In-stead, that value is created in the interaction between the quantum system and the agent […] the same kind of fact creation occurs when any two quantum systems happen to come together.
Thousands of years ago, a very powerful line was said in the ‘Vedas’, that is, “Yatha Drishti, tatha Srishti!”. It means — As the Vision, So the World.
Why is the Sun able to produce so much energy over such a long period of time? Physicists tend to answer this question with an explanation that goes something like this:
The sun is composed of many little parts, including hydrogen atoms. If hydrogen atoms fuse together they yield helium. The difference in mass between the products and reactants is manifested as the release of large amounts of energy.
According to quantum theory, hydrogen atoms are able to get close enough together to fuse because they undergo quantum tunneling.
It is not open to the QBist to describe atoms as tunneling, since for QBists tunneling is a psychological phenomenon regarding our degrees of belief. Then what of the explanation? Could the QBist reconstruct the explanation in their own terms? I’m not sure if QBists believe in hydrogen atoms or fusion (as opposed to just the experiences induced by our measurements of them). But assuming they do, QBist explanations will inevitably look something like this:
The sun is composed of many little parts, including hydrogen atoms. If hydrogen atoms fuse together, they yield helium. The difference in mass between the products and reactants is manifested as the release of large amounts of energy. According to QBism, hydrogen atoms are able to get close enough together to fuse, because we expect them to — indeed we are willing to place bets on it.
The worry with the latter “explanation” is that it is tautologous: something should be expected to happen because we should expect it to happen. But what we want to know is why we should expect it to happen?
Srimadh Bhagavad Gita tries to answer this question:
annād bhavanti bhūtāni parjanyād anna-sambhavaḥ
yajñād bhavati parjanyo yajñaḥ karma-samudbhavaḥ
karma brahmodbhavaṁ viddhi brahmākṣhara-samudbhavam
tasmāt sarva-gataṁ brahma nityaṁ yajñe pratiṣhṭhitam
From food come forth beings; from rain food is produced; from yajna arises rain
And Yajna is born out of action (karma).
Know that action comes from the creator and the creator come from Imperishable Reality.
Therefore, the all-pervading Reality ever rests in Yajna.
These verses from the Bhagavad Gita narrates the cosmic wheel of cooperative action (yajna). The above verses make it clear that the innate nature of Reality is Yajna (co-operative action), and that the Absolute Reality rests in Yajna. What does it mean?
It is evident if we look at nature, the living creatures are born out of food, and they are sustained by food. The mineral-wealth of the world becomes assimilable food only by the action of rain upon it. There will be no rain if sun doesn’t shine upon the waters of the ocean — evaporating them and forming clouds. This cosmic-wheel of co-operative action is termed (Yajna) and is symbolized as the various Vedic rituals where oblations are poured over fire. The symbolism behind them is that all actions (karma) are being sustained by the universal energy which vedantins call ‘prana’.
Yajna is therefore the wheel that sets everything in its trajectory of action according to its own innate nature, which makes it unique. The word ‘Dharma’ in sanskrit means “That which makes a thing what it is”, for example the ‘Dharma’ of the sun is to shine or illumine. The energy of the sun sets the environment in the planet earth conducive for life. Thus, Yajna and Dharma are co-related. It is the active participation of a part in the whole system which makes it complete and perfect.
Therefore, as Individuals in the world, what is our role in this cosmic-wheel?
It is being said in the following verse:
evaṁ pravartitaṁ chakraṁ nānuvartayatīha yaḥ
aghāyur indriyārāmo moghaṁ pārtha sa jīvati
He who does not follow here the wheel thus set revolving, is of a sinful life, rejoicing in selfish endeavors — he lives in vain, O son of Pritha.
Every member in the entire kingdom of minerals, the vegetables and the animals instinctively follow this principle of Yajna and contributes thereby to the smooth running of the Universal wheel of action. The thinking human can alone have the freedom of action to contribute to the harmony, or to bring about discord in the smooth running of this cosmic mechanism. Man can make or mar his life. What should be the path for humans then? The message of Gita ends with the following verse:
yatra yogeshvarah krishno yatra partho dhanur-dharah
tatra shrir vijayo bhutir dhruva nitir matir mama
Wherever is Krishna, the Lord of Yoga, wherever is Partha, the archer,
There are prosperity, victory, happiness and firm policy
Shrimad Bhagavad Gita uses Krishna as a literary device to impart the Science of Absolute and unitive living to the warrior prince Arjuna. In this specific verse, Krishna is said to be the Lord of Yoga (unitive living). Unitive living can only remain a false hope until one imbibes noble spiritual values to one’s own life. This is not enough. Noble values and the readiness to act (symbolized by Arjuna — the archer) is necessary to bring forth prosperity, victory, happiness etc — not just in one’s personal life but also to the community or the world as a whole.
Living by these values is taking part in the cosmic wheel of co-operative action (yajna) — which makes us not only as a part of the whole system, but by uplifting us to the status of true masters of Nature.