Recent content by RobikShrestha

The proof in the wiki link seems to be proof by contradiction. Like, first it assumes existence of a cloning device and then, it figures out that such a device would only work when a=b or <a|b>=0 (orthogonal). Our task is to describe how a cloning device would work when non-orthogonal states can...

Re-thinking about it now, seems like, my solution also needs to preserve states |a> and |b>. So, step #1, "detection mechanism" is really a supposition.

@naima @atyy I was hoping that we would only make assumption the author asks us to make i.e. about a non-orthogonal states being distinguishable. I mean, if input control state is observed, then can we really guarantee it remains unchanged? I mean, if we had some mechanism to do that, wouldn't...

Ah ok. Re-thinking about the solution about cloning it multiple times and measuring them, it really is for determining exact state. But may be there is some other way in which we don't have measure the entire state to just "distinguish" the two states. I mean, the question only asks to...

@naima Thank you for your answer. A couple questions though: Here, we are doing an "observation" to determine target output. Once we observe, the state might be lost right? So, what mechanism will ensure that output control state will be same as input control state? To verify, we also need to...

@atty Make measurements as well as momentum? Do you mean measure position and momentum, violating Heisenberg's principle?

No idea what "non-commuting observables" means. But if we had a cloning device, we could clone it multiple times right? Then measure them.

Yes the author does not specify if it can be repeated. The author also does not specify what "detecting" means? I mean it could be that the device outputs 1 for state a and 0 for state b, or it could output entire description to fully define the state. That's why I was confused. One way I was...

Ok. I haven't got that far into the book, but I think the answer has to be more "thorough" than just saying prepare the state which you have detected.

Ok then that means Alice knows exactly what states a and b are. If we know the exact state, then we can prepare the state in principle right? So the answer to how to build cloning device would be: 1. Detect the state 2. Prepare the detected state ? Or is the answer trickier than that? And what...

I am a little confused about exercise 1.2 in the book "Quantum Computation And Quantum Information" By Michael Nielson. The question is: Explain how a device which, upon input of one of two non-orthogonal quantum states |a> or |b> correctly identified the state, could be used to build a device...

So, the state is just a superposition of all states with each state assigned a probability? That does make some sense.

I thought we were trying to detect "previous state" with measurement. Like, trying to figure out what state electron was under 45-degree preparation field by measuring it with 90-degree field. I mean isn't that the whole point of measuring? Trying to figure out state of electron? Seems like the...

Is it possible that energy lost by electron does not depend on the angle it makes with the field?

I am referring to an experiment mentioned in Quantum Entanglement lecture: (Starting from: 14:20) In that lecture, as far as I understand, the description of the experiment is as follows: Assume: "up state" means north pole is vertically upwards 1. Preparing the state: Prepare...