The Observer Effect of Quantum Physics : Physics Concepts

Transcript

hello my name is Walter and glob and this is the observer effect of quantum physics so in quantum physics we have discrete systems we have a few particles that we typically consider or maybe a system with many particles but certainly not continuous systems in all cases and the dynamics of the wave function that describes the set of particles or particle in the physical system is described by the Schrodinger equation so here this is an expression of the time independent Schrodinger equation which if I write this in direct notation I have an observable here the Hamiltonian which is an expression of the energy in the system and when it is applied to a state vector sy then I have the energy which is the eigenvalue for the matrix representation or eigenvalues for the matrix representation of the Hamiltonian times the same state vector sy so this is a vector this is this can be represented by a matrix and this is a scalar or a set of scalars and what's going on when you make an observation this is known as a measurement so when you make a measurement what you're doing is ultimately you're recording the value that you measure of this eigen value we don't necessarily have to apply this Hamiltonian operator it can be there are many other operators which represent these physical observables but these observables aren't actually the numbers that we measure we measure the eigen value so in quantum mechanics it is a probabilistic theory and if I have a different set of possible values that I can measure there will be some probability distribution associated with these different possible outcomes when I measure a physical system when I perform a particular type of measurement what happens is that this probability distribution ceases to exist there is just one value that I measure because in one experiment you cannot measure a distribution you just measure one number and this is known as the wavefunction collapse if you work back from the probability which is defined in terms of the wave vector the wave function so this represents a probability distribution and when you make a measurement you're just looking at one value of the state and this raises a lot of interesting questions in quantum mechanics regarding the interpretation of the measurement process because once you've made this measurement if you continue to make measurements on this physical system the system is stuck in this eigenstate of your observable this is known as the quantum Zeno effect in many quantum systems and you can essentially keep a two-level system like an atom from decaying by constantly measuring it and there are ways to interpret this in classical settings but the question of what actually occurs during this highly nonlinear process is still open and up for grabs so the two most common interpretations are that of the Copenhagen interpretation which essentially states that you can have a superposition of quantum states and when you make a measurement you are actually creating that particular state that you measure or Everett's many-worlds theorem which has been gaining some popularity in the recent past and this interpretation states that when you make a measurement of a quantum system the universe branches out to all the different possible measurements of the system and we find ourselves in the one in which we measured that particular value so what work and continued research is being done on attempting to learn more about what this highly nonlinear process entails for entangled systems and other exotic quantum states of matter my name is Walter new globe and this is the observer effect of quantum physics you