I'd like this to be an open discussion about ideas. I'm posting my thoughts here because this has to do with the nature of time. These thoughts don't seem to answer any questions. They have helped me come to grips with the tough topics and maybe could generate some fun discourse (maybe not).
Understanding the Irreversibility of Time Using Gates.
I'm a graduate student attempting to make sense of a complicated situation. Unfortunately, there may not be a lot of highly novel ideas with this post, yet I consider the following argument to be the clearest idea I've had about perceiving reality with a preferentially directed time.
In my Quantum Mechanics course this semester an emphasis is being placed on quantum computing. This has required an extended introduction to the world of quantum circuits. I have spent almost a year understanding Feynman Diagrams with the help of my advisor, so the circuit approach to quantum computing is certainly enjoyable to see.
This past Monday (2/11/2019) Professor Tzu-Chieh Wei from Stony Brook University gave a colloquium giving a practical theoretical approach to quantum computing. During the talk I asked him about the physical restriction of time ordering gates, given the necessity to have discretized time for processing time-dependent Hamiltonians. He admitted that is posed a minor problem, but that optimization was already a priority.
I concluded that this idea of discretized time was a form of time that existed without the need of measurement. Where does that leave measurement? The necessity to define time as a measurable process has left. Instead we get two forms of time. One that belongs to the system (e.g. a quantum circuit that has no measurement) and one that belongs to a quantum system that closes with a measurement.
This is important for two reasons. Firstly, the quantum gates are required to be reversable processes. This is to say that any devised quantum gate used for quantum computation must be reversible in time. Also, if there exists any form of entanglement, there must be this notion of discretized time, since a bit of information cannot pass through multiple quantum gates at once (this is concluded from my questions and professor Wei's remarks). Secondly, measurement gates are a portal from quantum into classical and are no longer required to be reversable.
Precariously, there is nothing stopping the information leaving the measurement gate to slip right back into a reversable quantum circuit (I would argue in many cases this is done on purpose). Does this quantum computing system not apply to the universe?
Reality seems merely a series of measurement gates one after the other in this perceived direction of time. If any process takes place that is not reversible, would that not give a preferential direction to the following measurement gates? It is certainly believed there are non-reversible classical measurements in the form of collapsed wave functions. With all these remarks there is still no indication that information between measurements cannot behave with the reversible quantum motion (maybe infinitely passing through gates between each measurement).
This leads me to conclude that there are two versions of time one restricted to reversible processes and one that is not restricted. We have mathematics to understand both separately. This imagery is the first thought I have combining the two concepts into a coherent process. I am open to this idea being flat out incorrect and I am under no obligation to believe this is reality. Perhaps, this is nothing more than a trivial situation poorly connected to a complicated system. I am open to any thoughts.
Thanks for reading,