Renato renner phd thesis


  1. The Quanta Newsletter
  2. Decoupling with unitary approximate two-designs
  3. Frédéric Dupuis: Publications
  4. Acknowledgements

She is now a Professor at Heriot-Watt University. He received his Bachelor of Technology B.

His research interests include investigating fundamental quantum limits on optics-based information processing with applications to communications, imaging and computation, with specific attention to structured realizations of optical systems that can approach those performance limits. He is also interested in network science and network communication theory, and is particularly fascinated by percolation theory. Institute for Quantum Computing, University of Waterloo. He moved to the computer industry in early where he worked on various projects. During this fellowship he investigated multiparticle tests of quantum mechanics and developed an interest in entanglement, methods to characterize it and its practical use in QIP.

He currently runs the theoretical quantum physics research group. He has performed pioneering experiments in atomic and molecular physics, quantum optics and quantum information processing.

The Quanta Newsletter

You have opened the box. And it will collapse even if you never look at the detector. It just being there is enough to open the box. Essentially all one has to do to preserve realism and causality is to go back to the Lorentz ether interpretation of relativity. It has a preferred frame, which can be used to make faster than light causal influences compatible with classical causality.

The generalization of the Lorentz ether to gravity is simple: Consider the Einstein equations of GR or the equations of whatever covariant metric theory of gravity you prefer in harmonic coordinates, and interpret the harmonic condition as continuity and Euler equations for the Lorentz ether. Instead, superdeterminism is much worse.

There, the superdeterminism loophole does not even exist: Once we have no information about, say, how a dice is faked, we have to assume equal probability to all outcomes. This is sufficient to rule out superdeterminism by the way too.


Not as a hypothesis about reality real dices may be faked but as a consequence of the fact that we have no information about this big conspiracy we cannot take it into account in plausible reasoning. But does that depend on your interpretation of what a measurement is? Careless of me. It seems to me that Scott raises a valid question.

This is missed in the paper. It is the consideration of only a part of the experiment, namely she knows the initial state she gives to Bob, and then considers the final experiment W. This reduction is quite explicit:. Fine, indeed, it is. But given that the reduced picture omits the experiment A, which changes the state of F2, the reduced scenario is simply not applicable to the full experiment. Yes, this change of the state of F2 by the measurement of F1 by A is that spooky action at a distance which is related with entanglement, and the Bohmian trajectory of both laboratories will be surrealistic ones, but this does not make them inconsistent.

The same logical error I see in the derivation is sufficient to prove a classical analog.

Sean Sketch - PhD Thesis Defense

Alice tells Bob she is communist. Bob will tell Diana what he knows about Alice political views. Knowing that Bob is a honest guy, Alice will surely think that Diana thinks she is communist. Everything fine, no contradiction, given that Alice at that time is communist. In the classical world, somebody who is once communist remains communist forever. Now we add the analogon of quantum theory where Charlie can give Alice Solshenizyn for reading, looking at her reaction to measure if she is communist. With some probability for tunneling, that she becomes anti-communist and so Charlie thinks she is anti-communist.

Alice does not talk to Bob after this, so the prediction remains, Alice will surely think that Diana thinks she is communist.

Decoupling with unitary approximate two-designs

So, there may be multiple outcomes about what people think about Alice being communist or not. And we have, again, a world without different people having different views about what Alice believes.

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Now, apply your argument to this Bohmian internet theory. This is a consistent story, you can apply it. Once there is no Solshenizyn reading in this story, Alice remains communist, and Bob will tell Diana that Alice is communist even if he checks the Bohmian internet. But this reduction gives a different result than the full story. Does it follow that the theory is somehow inconsistent? So Charlie, Diane even know that they are each just part of an entangled, superposed state which will soon be collapsed in a different basis.

It is only when they neglect this in their collective reasoning that the paradox survives. Instead, they know that they are uncertain about what Bob and Alice will measure.

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A Many-worlds does not have a problem if agents properly understand what the branching structure of the universe will be when decoherence occurs. B Other approaches have a big problem, because not even conscious and certain measurement by Turing-Class intelligences justifies a movement from the quantum-superposition to the classical-probabilities level of analysis. We know that by placing a particle detector at one slit the interference pattern disappears. It does not matter if you actual notice the detector, or if you look at its output.

It is the presence of the detector that changes the behavior of the incoming particles, not your knowledge. In the case of a cat in the box I can always place a detector outside the box to determine if the cat is alive or not by detecting its gravitational field with a very sensitive accelerometer for example. We are still limited by the uncertainty principle, but for a macroscopic object such as a cat it is irrelevant. So, the box is useless.

There is no way to place a cat in superposition by placing it in a box. The measurements are done on the superposition or sum of the three components, not separately on each component. There are many viewpoints with interesting insights. Quick question — what is the functional difference if any between infinite hidden variables and infinite parallel universes? I will show that it is not reasonable to ascribe equal probability to all outcomes for a fake dice. I will show that the argument presented in your paper against superdeterminism is question-begging, so it fails. I will use classical electromagnetism as an example.

It is possible that if all those microstates are correctly counted the statistically independence would be restored, but there is no reason to ascribe a high probability for it to happen. That pretty much follows from the definition of the words. Without any information, we have no reason to prefer one of the two answers. This is all nice but the same line of reasoning can be used to reject non-local connections as well.

Not only we do not know if a measurement at one location has an instantaneous effect at another, distant location, but everything we know about physics seems to preclude such a behavior. Your argument is question-begging because it ascribes a very low probability for superdeterminism and I agree with that but does not provide us with any reason to ascribe a higher probability for non-local connections. In fact, the situation is exactly opposite.

When confronted with a new type of correlation for which the cause is not known the most reasonable assumption is that we are in the presence of a past, even if unknown cause, not in the presence of a non-local cause. This is the standard way to approach new phenomena in science. Specifically, the Newcomb Box certificates, that were originally deposited by agents F and agents F-bar, are subsequently altered by the Lindbladian dynamical processes that generate the projective measurement processes of agents W and W-bar.

In a nutshell, by the usual rules of prediction games, agents W and W-bar are cheating. Good you are mentioning the de Broglie-Bohm theory dBB. It serves as an excellent example to illustrate how our thought experiment is different from the simplified version that Scott proposed. As you are writing, one can indeed apply dBB to our thought experiment and trace in detail what happens. In contrast, in our thought experiment, all measurement outcomes by all agents are obtained in one single run and hence, in dBB, represented by the corresponding Bohmian particle positions in that single run.

One can therefore reason about them without referring to counterfactuals. Next to my random number generator that determines which blogs I should comment see 48 I have an even more elaborate device that tells me which ones I should not even read.

Frédéric Dupuis: Publications

But OK first of all the cat interacts with a qubit. It does not matter if the cat is dead or alive when it does so. In order for that interaction to affect observers outside the box it has to be outside the box and that is exactly what the box is intended to prevent. The cat is constantly interacting with qubits inside the box.

After all the whole point is to have the cat interact with an unstable particle qubit in order to place itself into superposition. And wave collapse is not universal. We view the cat as being in superposition. In order for us and the cat to agree there must be information flow across the walls of the box. Think of wave collapse as a very bad social disease.

Any contact at all and you spread the cooties. The box protects the cat from our cooties.


The Born rule is then applied to this state. But this is taken into account in the chain of reasoning; see in particular the second row of Table 3, i. Thank you for awesome exposition! If they develop large scale quantum computers that give exponential speed up over classical computers would that disprove super-determinism?