Recent content by Strilanc

I come from quantum computing, where measurement is *extremely* well delineated. In your circuit diagrams, it's the box that has an M in it :biggrin:. It's sometimes defined as specifically the operation that reports whether the qubit was ON or OFF (instead of something more general). More...

But measurement *is* the leaking of information into the larger environment...? You're saying it's not caused by measurement it's caused by measurement. Anyways, I would consider this experiment to be equivalent to a straightforward application of the deferred measurement principle and its...

Ah, it's not a description of a solution it's a description of a problem. When you have a register x that contains a uniform superposition and you measure f(x), where f is a periodic function period p, you are left with a superposition where every p'th state is present... with some...

You have computational basis states ##|0\rangle##, ##|1\rangle##, ##|2\rangle##, etc. Instead of writing ##|2\rangle## you could write ##|1+1\rangle## because ##1+1=2##. Instead of writing ##|2\rangle## you could write ##|3+7 \pmod{8}\rangle## because ##(3+7) \bmod 8 = 2##. Get the idea? From...

I liked the video. A lot. One question, though. The video claims that you wouldn't see the same "interference across different arm lengths" for photons that come from spontaneous emission. Is that actually true? What is it about spontaneous emission that breaks it? The video says something like...

This is a follow-up video I made to a previous one on common misconceptions about the experiment. I'm interested in people's opinions here about how close the simulated experiment is to the real thing (e.g. there have to be some compromises due to the simulator not having free space propagation...

I just wanted to point out a resource useful for dealing with claims of violating Bell's theorems. You can point the claimant at https://algassert.com/quantum/2015/10/11/Bell-Tests-vs-No-Communication.html and say "I won't believe you unless you can make the 'Write Your Own Classical CHSH...

To make things simple, you'll want to know which entangled state you're checking for. For example, maybe the relevant entangled state is ##|00\rangle + |11\rangle##. The stabilizer generators of that state are ##X_1 X_2## and ##Z_1 Z_2##. No other state has those generators. Therefore we can...

In the classical analogue, Bob and Charles' initial estimates of the boxes contents are also maximally uncertain. I understand that entangled states are different from probabilistic states. They are observably distinguishable using e.g. Bell inequality tests. But the DCQE doesn't do anything...

This was my attempt at making an explanatory video discussing some of the misconceptions about the experiment. I'm looking for feedback on how it could have been better. In particular, based on some of the confusions in the comments on the video, it's clear to me that I should have e.g. gone...

You can try all of these in a simulator and see what it says: https://lab.quantumflytrap.com/ For example, here's my quick attempt at your setup #1: I think this simulator negates the amplitude of one of the polarizations when the light bounces off a mirror or beam splitter. You might have...

If you look at figure 3, you can see where the "magic" is. They're discarding runs where the ancilla qubit is true, and analyzing the leftover data as if they weren't doing that. The result is postselected dynamics that aren't unitary. Note that e.g. P_111 is not present in the readout column...

Individual photons don't have a phase in the way you're thinking. Instead, in a two photon system, each possible way of arranging the two photons has a phase (an amplitude to be more specific). If you line two photons up on top of each other, there's amplitude in the state "two photons here" and...

There's nothing fundamental that prevents you from making a quantum CPU with a quantum program counter, a quantum instruction decoder (for reversible instructions), a quantum RAM, etc. Nothing prevents you from then loading a superposition of programs and inputs, ticking the CPU some number of...

Why do you think quantum computers can't have the same types of loops? Just put a loop in the quantum circuit conditioned on a measurement result. Quantum computers can do everything classical computers can do, so of course they can loop.