mkorobko.bsky.social
Quantum physicist: quantum optics, gravitational-wave detectors and foundations of quantum mechanics | staff scientist @ Uni Hamburg | member of LIGO
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That's a good point! My thinking was that the set of 3 detectors is synchronized "two-way" with light, but then detects GWs arriving uniformly from various directions, and then any anisotropy would appear as deviations from this "average" two-way value. But I'm really out of my depth here...
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That's a good point, I've also been reading up on it since, but it's not so clear in the case of a different carrier (GWs)...I mean, the clock synchronization in this case is directional (the detectors are in different places), but the GW is not. Thus we kind of show the isotropy already.
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...alternative theories with direction-dependent speed of light, but that's a curious application of GWs, I think. Unless the logic is flawed, of course :)
[1] journals.aps.org/prd/abstract...
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we have two independent measurements: the speed of gravity is equal to c, and the one-way speed of light is equal to the speed of gravity. Thus, one-way speed of light is equal to c! To within ~1% or so, whatever the current statistics would be. Not sure if that's enough to exclude...
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From statistics of GW events, as it's shown in [1], we can independently estimate the speed of gravity to be equal to the speed of light to within ~1-2%. That is based on the first 50 detections. Now we have seen over 200 events, and I'm sure new statistics will pin this down well below a %.
So...
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...found that the speed of gravitational waves equals the speed of light up to the ~8th decimal digit. But that in itself doesn't tell anything about the speed of light!
Luckily, we have another way to measre the speed of gravity: using the delay in arrival of a GW to different detectors.
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...I think :)
Curiously, I haven't found this argument anywhere in the literature. So I want to argue that we actually have measured the one-way speed of light. Using...gravitational waves!
In 2017, we saw GWs and light coming from the neutron star merger GW170817. From this measurement, we...
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Well, the quantum computing stocks went up 15% with this press release, so there's that...
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Here is a short thread about the review itself:
bsky.app/profile/mkor...
And the journal issue is here, some interesting papers there (including a few on future gravitational-wave detectors).
www.mdpi.com/2075-4434/13/1
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...new detectors, Einstein Telescope and Cosmic Explorer, will only reach teir potential if we use the most advanced quantum technology.
In my review, I look at its challenges and promises. It is (I hope) quite accessible, and there's a ton of interesting literature!
www.mdpi.com/2075-4434/13...
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It never ceases to amaze me, even though I'm using quantum squeezed light every day in the labs (well, mostly my students these days, I miss the lab!).
We litterally add a few correlated photons into the detector, and this allows us to look many megaparsec deeper into the Universe!
In future,...↓
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Thank you!
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@physgal.bsky.social I work on quantum optics & gravitational-wave detection. Would be happy to be on the physics list :) My scholar: scholar.google.com/citations?us...
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Great, thanks a lot!
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I see, thanks for the explanation! Out of curiousity, do you happen to know how the relation between the "official" and "community" catalogs works in other branches of astrophysics? Do they coexist, or get merged eventually is some way...
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Hi Manuel, I'd like to contribute to the physics/quantum feeds. I work in quantum optics & gravitational wave detection. Excited to join, thanks for doing this! My scholar: scholar.google.com/citations?us...
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Nice work! I haven't quite understood if these events have not been identified by LVK at all, or if they remained as "sub-threshold" events, which become more significant in another analysis. If it's the former, do you know why LVK pipelines missed them?
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Fair enough! Still fun to think about. Thanks for clarification!
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I see! So difference is that when we look for the emergent time, we can have a boundary condition "fixing" the reality (e.g. the big bang). But we don't have it when arguing that the stationary wavefunction (far in the future) secretely has some time-dependent branches with crazy stuff happening.
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Very nice episode! I was puzzled that you criticized the decoherent histories rebuttal of the Universe's stationary state for its infinite possible configurations, but was open towards the idea of emergent time in quantum gravity, which seems to face the same issue. Is there a conceptual difference?
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Of course, this is a very theoretical proposal, practically this would be rather complicated, at least for the large-scale detectors. But it's fun to think about these things and also creates better understanding of what's possible there.
Link to arxiv: arxiv.org/abs/2403.03758
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But it turned out that there's even more useful feature there: this additional cavity could be tailored to optimize quantum noise in the detector. In particular, we could make the system more compact or enhance the sensitivity in particular frequency range.
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Then I thought: we tune the cavities to have the resonance at high frequency and generate a lot of quantum correlated light there. What if we add another cavity, that would be resonant at low frequency and would allow to generated quantum correlations there? That's what we did, and it worked!
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Initially I had the idea of "quantum expander", where we proposed to generate quantum correlated states inside the detector. Then one can signficantly suppress quantum noise and increase the sensitivity to high-frequency gravitational waves. (a popular summary: mkorobko.craft.me/quantum_expa...)
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The idea of the paper is that quantum response of a sensor can be significantly modified using simply an additional mirror and special tuning of the optical cavities.
It may seem obvious, but the way it works turned out to be rather non-trivial.
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Thanks!