Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum QUOTES

1 " The full story of the invention of the matrix form of quantum mechanics is far more complex than I can tell here, as it reveals a very dynamic, collective effort of a diverse community of theorists, in close interaction. Still, diverse as they were, the matrix mechanicians were by 1927 all framing the new theory in terms of the radically anti-realist philosophy that Bohr preached. The only holdouts were those who had come to quantum mechanics through the wave-particle duality, Einstein, de Broglie, and Schrödinger, who stubbornly remained realists. But once it was proved that Schrödinger’s wave mechanics was equivalent to Heisenberg’s matrix mechanics, the realists could be dismissed as stubbornly grasping on to old metaphysical fantasies, and ignored. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

2 " One quantum theory of the atom is great, but two are a problem, especially since they both reproduced the right spectrum of hydrogen. The two theories could not have differed more, as reflects the philosophies of their discoverers. Einstein, de Broglie, and Schrödinger were realists. Even if there were mysteries, they believed an electron was real and somehow existed as both wave and particle. Bohr and Heisenberg were enthusiastic anti-realists who believed we have no access to reality, only to tables of numbers which represent the interactions with the atom, but not the atom directly. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

3 " Several of the new proposals have at their core the concept that the world is made of information. This can be summarized in John Wheeler’s slogan “it from bit,” modernized as “it from qubit,” where a qubit is a minimal unit of quantum information, i.e., a quantum binary choice, as in our story about pet preference. In practical terms, this program imagines that all physical quantities are reducible to a finite number of quantum yes/no questions, and also that evolution in time under Rule 1 can be understood as processing this quantum information as a quantum computer would. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

4 " A quantum state is a useful tool because it can do just that. This is our next principle: Given the quantum state of an isolated system at one time, there is a law that will predict the precise quantum state of that system at any other time. This law is called Rule 1. It is also sometimes called the Schrödinger equation. The principle that there is such a law is called unitarity. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

5 " One of the hardest lessons to learn in academic life—and for me one of the most disconcerting—is the speed with which a radical insurgency can become orthodoxy. In just a few years a generation of students championing a dangerous new idea are elevated by an initial success into professorships. From these positions of influence they form a powerful network of academic power brokers, which they use to ensure the continuation of the revolution. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

6 " When we make a measurement on a system, we disturb it, typically by forcing it to interact with a measuring instrument. So Rule 1 does not apply to measurements. This is true not only of measurements, but of any interaction between the system and outside forces. So is there anything special about measurements? Measurements are special because they are where probabilities enter quantum theory. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

7 " Quantum mechanics asserts that the relationship between the quantum state and the outcome of a measurement is probabilistic. Generally, there is a range of possible outcomes of a given measurement. These will each occur with some probability, and these probabilities depend on the quantum state. In the case where we measure the position of a particle, this dependence is particularly simple: The probability of finding the particle at a particular location in space is proportional to the square of the height of the "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

8 " Rule 1, by dictating how a quantum system changes in time, plays the same essential role in the theory that Newton’s laws of motion played in pre-quantum physics. Like Newton’s laws, Rule 1 is deterministic. It takes an input state and evolves it to a definite output state at a later time. This means it takes input states which are constructed as superpositions to output states which are similarly constructed from superpositions. Probability plays no role. But measurements, as described by Rule 2, do not evolve superpositions to other superpositions. When you measure some quantity, like pet "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

9 " Rule 1, by dictating how a quantum system changes in time, plays the same essential role in the theory that Newton’s laws of motion played in pre-quantum physics. Like Newton’s laws, Rule 1 is deterministic. It takes an input state and evolves it to a definite output state at a later time. This means it takes input states which are constructed as superpositions to output states which are similarly constructed from superpositions. Probability plays no role. But measurements, as described by Rule 2, do not evolve superpositions to other superpositions. When you measure some quantity, like pet preference or position, you get a definite value. And afterward the state is the one corresponding to that definite value. So even if the input state is a superposition of states with definite values of some observable quantity, the output state is not, as it corresponds to just one value. Rule 2 does not tell you what the definite value is; it only predicts probabilities for the different possible outcomes to occur. But these probabilities are not spurious; they are part of what quantum mechanics predicts. Rule 2 is essential, because that is how probabilities enter quantum mechanics. And probabilities are essential in many cases; they are what experimentalists measure. However, quantum mechanics requires that Rule 1 and Rule 2 never be applied to the same process, because the two rules contradict each other. This means we must always distinguish measurements from other processes in nature. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

10 " These last few points are key to how quantum mechanics works, so let me summarize them: The wave represents the quantum state. When we leave the system alone, it changes in time deterministically, according to Rule 1. But the quantum state is only indirectly related to what we observe when we make a measurement, and that relation is not deterministic. The relation between the quantum state "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

11 " The pilot wave theory predicts everything quantum mechanics does, but explains a good deal more. The mysterious way in which the ensemble seems to influence the individual is cleared up and explained straightforwardly as the influence of the wave on the particle. Both are real, and both exist for every individual atom. Everything that was puzzling and mysterious about quantum mechanics is revealed to be a consequence of that theory leaving out half of every story. Despite "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

12 " These last few points are key to how quantum mechanics works, so let me summarize them: The wave represents the quantum state. When we leave the system alone, it changes in time deterministically, according to Rule 1. But the quantum state is only indirectly related to what we observe when we make a measurement, and that relation is not deterministic. The relation between the quantum state and what we observe is probabilistic. Randomness enters in a "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

13 " Within the realist approaches, I believe there is a case to be made that Everett’s hypothesis is the least progressive—although there are arguments on both sides. An enormous effort has gone into developing Everett quantum mechanics, much of it technical and extremely clever, but most of that work has gone to addressing problems that arise only in the Many Worlds Interpretation, but do not trouble the other approaches. I might suggest that the Everett program is, of the realist approaches, the least open to the possibility that future discoveries will lead us to modify the principles and the mathematical formalism of quantum mechanics. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

14 " It is also very legitimate to criticize the scientists and philosophers who drew unnecessarily pessimistic conclusions based on an incomplete picture that neglected the positive effects of self-organization in far-from-equilibrium systems. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

15 " But, even if the quantum state gives us only probabilities for what we observe, once we get a result, there is something that is definite, because afterward you know exactly what the state is. It is the state corresponding to the result obtained by the measurement. Suppose we measure an electron’s momentum, and get the result that the electron is moving north with momentum 17 (in some units). Then, just after the measurement we know that the "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

16 " The existence of all these copies of ourselves would then seem to me to present a moral and ethical quandary. If no matter what choices I make in life, there will be a version of me that will take the opposite choice, then why does it matter what I choose? There will be a branch in the multiverse for every option I might have chosen. There are branches in which I become as evil as Stalin and Hitler and there are branches where I am loved as a successor to Gandhi. I might as well be selfish and make the choices that benefit me. Irrespective of what I choose, the kind and generous choice will be made by an infinite number of copies living in an infinite number of other branches. This seems to me to be an ethical problem because simply believing in the existence of all these copies lessens my own sense of moral responsibility. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

17 " 17. This is enshrined in a second rule,fn2 which we call Rule 2: The outcome of a measurement can only be predicted probabilistically. But afterward, the measurement changes the quantum state of the system being measured, by putting it in the state corresponding to the result of the measurement. This is called collapse of the wave function. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

18 " Rule 2 raises a whole bunch of questions. Does the wave function collapse abruptly or does it take some time? Does the collapse take place as soon as the system interacts with the detector? Or only later, when a record is made? Or perhaps later still, when it is perceived by a conscious mind? Is the collapse a physical change, which means that the quantum state is real? Or is it just a change in our knowledge of the system, which means the "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

19 " quantum state is only a representation of that knowledge? How does a system know a particular interaction has taken place with a detector, so that it should then, and only then, obey Rule 2? What happens if we combine the original system and the detector into a larger system? Does Rule 1 then apply to the whole system? These questions "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum

20 " The full story of the invention of the matrix form of quantum mechanics is far more complex than I can tell here, as it reveals a very dynamic, collective effort of a diverse community of theorists, in close interaction. Still, diverse as they were, the matrix mechanicians were by 1927 all framing the new theory in terms of the radically anti-realist philosophy that Bohr preached. The only holdouts were those who had come to quantum mechanics through the wave-particle duality, Einstein, de Broglie, and Schrödinger, who stubbornly remained realists. "

― Lee Smolin , Einstein's Unfinished Revolution: The Search for What Lies Beyond the Quantum