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Craig Ewing's avatar

Thanks for the deep dive into US military research. As I was reading this, I kept thinking, "How would the Ukrainians do it?"

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Hans Torvatn's avatar

I am not sure they need to do that. What they need to do is upgrade their drones.

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H Desmo's avatar

One problem here is “With a thinner civil service, the US will have to rely more on trusted defense firms, universities, and NATO partners for shared R&D” and the current administration is treating 2 of those 3 as adversaries to be subdued.

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David McDonald's avatar

They're not doing defence firms any favours either when they go about pissing on allies and repeatedly threatening to abandon aliances

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Gwilym's avatar

If and when it gets into the field, will they be able to maintain it? It is one thing to build it, whole other thing to keep it running. Top down hierarchies tend to be more interested in possessing things than the mundane task of maintaining them. Small, replacement parts don’t have near the graft opportunities of whole system purchases.

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Stephen Fossey's avatar

If you’re in a technological arms race, you need to spend the funds if you want to keep up and it starts with the most basic research. Thanks for the analysis.

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Hans Torvatn's avatar

Claims are cheap…

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David McDonald's avatar

Ummm... Wouldn't the Austrian Institute of Science and Technology be in Austria (not Australia)?

I had a quick look at the webpage of the Australian Institute of Science and Technology and the contact telephone is a mobile phone, there are factual errors there (e.g. making reference to Wollongong on a page about a campus in Melbourne, stating that Wollongong is the largest city in New South Wales - it certainly isn't, has a photo of a grand sandstone edifice that is in no way associated with a minor institution).

I'm suspicious that the original announcement is a bit of poorly written propaganda

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Bahrainiac's avatar

Clickbait!!!!!

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Michael's avatar

The physics of quantum radar fall apart in real world scenarios

It just won’t work

Quantum illumination has only been shown to give a 6dB advantage, and that is in lab conditions without a messy atmosphere.

Fancy single photon detectors may improve the detection limits of classical radar, but for a quantum radar they don’t help if your photons decohere in a messy atmosphere after a fraction of their round trip.

But I guess we should be glad that a potential adversary is wasting time and money on a unworkable technology?

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Ponti Min's avatar

> Military radar has remained largely unchanged since its development well over 100 years ago.

Military radar dates from the late 1930s, though there were experiments before then.

> However, because modern stealth aircraft are optimized for stealth against radio waves, quantum radar, which uses photons, would make stealth aircraft much more susceptible to detection.

Er, photons and radio waves are the same thing. (Though there are of course photons at frequencies other than those categorised as radio frequencies.)

>In addition, traditional radars are “loud” in that they typically give away their position on the ground (or in the air in the case of the AWACS) by blasting out a high-energy radio signal. [...] But quantum radar is nearly undetectable as it emits very little energy.

Radars have to be loud because only a very small fraction of the transmitted energy is received back to the radar system. If this is not true for quantum radar, then that would be a big advantage.

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Kent Smith's avatar

It was inevitable and will get worse as China relentlessly invests in improved technological capabilities while we rip up our scientific and technological prowess.

Venezuelan fishing boats are easy. The Chinese will not be.

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Hans Torvatn's avatar

Thank you for the analysis. I am afraid you are underestimating the damage done to US research at the moment. Trump is replacing people who can do science, buy science, lead science etc with his loyal goons. Going deeper and deeper into all organizations that are part of the research ecosystem, be they universities, DArpa, whatever military institutions… this will really hurt the innovation ability. At the same time Trump is alienating all allies so that strategy will not work. But he wouldn’t try to fight China anyhow. Poor Taiwan.

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steak's avatar

You're very good to be focusing on this tech. But you are underestimating the capability. China has put their quantum focus on photons because they can be integrated into existing infrastructure with the right routers. These boxes are part of an integrated network that allows them collectively to act as a natural "sense" that can "sniff" F22s. Also, this is snarky I know, but radio waves are photons too.

https://www.nature.com/articles/s42254-021-00348-9

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sz's avatar

Quantum radar requires the detected photon to be send from the same detector, so the only networking you'll be doing with that information is of the ordinary kind.

The Nature article you refer to is about quantum computing, which has nothing to with this. Quantum computing, encryption/communication and radar/detection are different techniques which are only related by the fact they rely on quantum entanglement to work.

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steak's avatar

Astute! The raw data is self-contained with the measuring device and the communicated data will be classical in this example. My mentioning of optical quantum routing was a bit of a non-sequeter in this context though it is a huge differentiator with how China is approaching the tech vs the west.

The Nature article is the foundation for the current generation of quantum sensors anywhere. It is incorpored into every single one. The method improves the quality of measurements dramatically which is necessary for any high noise environment.

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sz's avatar
Oct 23Edited

Quote from the summary of that paper with the title "Variational quantum algorithms":

"Current quantum devices have serious constraints, including limited numbers of qubits and noise processes that limit circuit depth. Variational quantum algorithms (VQAs), which use a classical optimizer to train a parameterized quantum circuit, have emerged as a leading strategy to address these constraints. "

Again, this has nothing to do with quantum sensing.

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steak's avatar

The paper I shared was the foundational paper for the method which has since been applied to almost all quantum sensors being utilized in real-world applications today. Below is a paper talking about using a VQA approach for photonic quantum computing including photonic quantum sensors.

“Our experimental results showcase significant improvements in estimation accuracy and noise robustness, highlighting the potential of variational techniques for practical applications in quantum sensing and more generally in quantum information processing using photonic circuits.”

https://www.nature.com/articles/s41534-024-00821-0

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sz's avatar

Thanks for providing a more relevant paper.

I still think you are jumbling things together which are conceptually different. On the other hand, your focus seem to be on VQA's and the general advancement & future of quantum tech, so my distinction may seem wrong or irrelevant to you.

This paper has 'nothing' to do with quantum computation. Here they use a VQA to tune/optimize a quantum sensor, which would merely be a component of an photonic quantum computer.

VQA is not one particular method, but a class, and it's a tool rather than being something fundamental to any quantum tech. Now, practically it could very well be the breakthrough needed to make quantum tech usuable in the real world, but it does not make the distinction between computation and sensing disappear.

Here a paper on photonic quantum metrology I found following citations:

https://pubs.aip.org/avs/aqs/article/2/2/024703/997285/Photonic-quantum-metrology

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Brent James's avatar

Did you mention bolstering inside spying in China? That seems pretty critical.

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