This isn't just a result about Gaussian boson sampling/GKP/LOQC/whatever - it is really quite general. For most flavours of quantum photonics, using and understanding these results will let you model your quantum optics experiments better + faster!
According to our reviewers, the original version of the manuscript "failed to articulate the broader impact these powerful results" [quote is paraphrased]. In light of this I'll say...
our results on simulating realistic quantum photonics experiments has just been published in Advanced Photonics t.co/xj8TInLLGD 🥳🎉🍾
Like @craiggidney.bsky.social points out, what they are doing in this paper is really pretty much the same as that: post selecting a weakly entangled state into a subspace where there is lots of entanglement.
This is the kind of post selected entanglement that has been used in the SPDC based demonstrations of loop hole free bell tests.
Before their measurement, they have 2 such states. So when you e.g. post select on seeing a photon pair across the two states, some of this entanglement persists.
There is definitely still entanglement left, even if they don't admit it. The entanglement here can be seen when you don't post select. SPDC makes states roughly, in the fock basis, like: a|0,0> + b|1,1> + c|2,2> +... For some a,b,c where typically |a|^2>>|b|^2>>|c|^2. This state is entangled.
They pass the photons through filters such that if you post select on measuring a photon pair, both photon's frequencies are well defined and so there is no longer this kind of entanglement (approximately, a small amount would still remain in practice).
If you post select on measuring a photon pair and you resolve this mode information e.g. time and/or frequency resolving measurement, you can witness entanglement in this DoF.
It can often happen in SPDC (how they create the photon pairs) that the photons created are not always in the same "mode" i.e. the same time/frequency wavepacket
In this rev. mod. phys. hal.sorbonne-universite.fr/hal-03016379... they call it "modal unitary". I also see people call it the "linear optical unitary" representation.
There are lots of different terms out there. For something more physics-y I'd say you could also call it the "transfer matrix representation" which comes from what people in classical optics call the same thing. You could add "electric field" or "single photon" as a prefix to be more specific.
What's going on? The hump of balls that naturally forms here is a special mathematical shape called a bell curve-also sometimes known as a normal distribution. This pattern appears in an astounding variety of places, from test scores to height charts. Bell curves also arise from large numbers of random events-as in this exhibit, where hundreds of metals ball encounter a series of random left- or right-forking paths as they fall. Place a single ball at the center and watch its path down. Can you predict where it will land? Bell curve-shaped wear patterns on this old stairway were slowly carved by centuries of footfalls
Ah sorry, it's a bit blurry even in the footage on my phone. Here's a zoom in of the screenshot. Although the jist of my post only requires observing that it is an example of a crudge analogue randomness generator.
Public service announcement, this is not a generative AI and will not help solve the AI power consumption issues.
If the balls were replaced with photons... then...
very much still not
So I'd perhaps suggest splitting up theory for experiments and experiments into different categories. Protocols could go with theory for experiments? Algorithms and applications could be merged?
I wonder is this stems from Scirate. If you follow the voting there, it is easy to be misled that most work posted to quant-ph is theory work. But I think this is due to scirate users seemingly being mostly theorists. There's also lots of cool experimental work being posted on quant-ph too.
Splitting things up seems like a nice idea. Although I think having most categories focused on subdividing theory work, giving experiments only 1 category out of the 7, which is also shared with theory for experiments seems too lopsided.
another example
Whenever I see massive equations written out like this, I wonder who it's actually for. Is ever helpful to the reader? Perhaps a better way to communicate such expressions would be to stick whatever mathematica/sympy notebook that created the expression up on github...?
DARPA has selected PsiQuantum for the final phase of the Utility-Scale Quantum Computing program evaluation. www.psiquantum.com/featured-news/darpa-final-phase
