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#quantum

32 posts23 participants10 posts today
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Bharath Krishnan

In a magazine article [1] on problems and progress in quantum field theory, Wood writes of Feynman path integrals, “No known mathematical procedure can meaningfully average an infinite number of objects covering an infinite expanse of space in general. The path integral is more of a physics philosophy than an exact mathematical recipe.”

This article [2] provides a method for averaging an arbitrary collection of objects; however, the average can be any number in the extension of the range of these objects. (Note, an arbitrary collection of these objects is a function.)

Question: Suppose anything meaningful has applications in quantum field theory. Is there a way to meaningfully choose a unique, finite average of a function whose graph matches the description in Wood's quote?

For more info, see this post [3].

[1]: quantamagazine.org/mathematici

[2]: arxiv.org/pdf/2004.09103

[3]: math.stackexchange.com/q/50520

Quanta Magazine · Mathematicians Prove 2D Version of Quantum Gravity Really Works | Quanta MagazineIn three towering papers, a team of mathematicians has worked out the details of Liouville quantum field theory, a two-dimensional model of quantum gravity.
#PathIntegral#quantum#FeynmanPathIntegral
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Hacker News

CERN scientists find evidence of quantum entanglement in sheep

home.cern/news/news/physics/ce

CERNCERN scientists find evidence of quantum entanglement in sheepThe CERN flock of sheep on site in 2017. (Image: CERN) Quantum entanglement is a fascinating phenomenon where two particles’ states are tied to each other, no matter how far apart the particles are. In 2022, the Nobel Prize in Physics was awarded to Alain Aspect, John F. Clauser and Anton Zeilinger for groundbreaking experiments involving entangled photons. These experiments confirmed the predictions for the manifestation of entanglement that had been made by the late CERN theorist John Bell. This phenomenon has so far been observed in a wide variety of systems, such as in top quarks at CERN’s Large Hadron Collider (LHC) in 2024. Entanglement has also found several important societal applications, such as quantum cryptography and quantum computing. Now, it also explains the famous herd mentality of sheep. A flock of sheep (ovis aries) has roamed the CERN site during the spring and summer months for over 40 years. Along with the CERN shepherd, they help to maintain the vast expanses of grassland around the LHC and are part of the Organization’s long-standing efforts to protect the site’s biodiversity. In addition, their flocking behaviour has been of great interest to CERN's physicists. It is well known that sheep behave like particles: their stochastic behaviour has been studied by zoologists and physicists alike, who noticed that a flock’s ability to quickly change phase is similar to that of atoms in a solid and a liquid. Known as the Lamb Shift, this can cause them to get themselves into bizarre situations, such as walking in a circle for days on end. Now, new research has shed light on the reason for these extraordinary abilities. Scientists at CERN have found evidence of quantum entanglement in sheep. Using sophisticated modelling techniques and specialised trackers, the findings show that the brains of individual sheep in a flock are quantum-entangled in such a way that the sheep can move and vocalise simultaneously, no matter how far apart they are. The evidence has several ramifications for ovine research and has set the baa for a new branch of quantum physics. “The fact that we were having our lunch next to the flock was a shear coincidence,” says Mary Little, leader of the HERD collaboration, describing how the project came about. “When we saw and herd their behaviour, we wanted to investigate the movement of the flock using the technology at our disposal at the Laboratory.” Observing the sheep’s ability to simultaneously move and vocalise together caused one main question to aries: since the sheep behave like subatomic particles, could quantum effects be the reason for their behaviour? “Obviously, we couldn’t put them all in a box and see if they were dead or alive,” said Beau Peep, a researcher on the project. “However, by assuming that the sheep were spherical, we were able to model their behaviour in almost the exact same way as we model subatomic particles.” Using sophisticated trackers, akin to those in the LHC experiments, the physicists were able to locate the precise particles in the sheep’s brains that might be the cause of this entanglement. Dubbed “moutons” and represented by the Greek letter lambda, l, these particles are leptons and are close relatives of the muon, but fluffier. The statistical significance of the findings is 4 sigma, which is enough to show evidence of the phenomenon. However, it does not quite pass the baa to be classed as an observation. “More research is needed to fully confirm that this was indeed an observation of ovine entanglement or a statistical fluctuation,” says Ewen Woolly, spokesperson for the HERD collaboration. “This may be difficult, as we have found that the research makes physicists become inexplicably drowsy.” “While entanglement is now the leading theory for this phenomenon, we have to take everything into account,” adds Dolly Shepherd, a CERN theorist. “Who knows, maybe further variables are hidden beneath their fleeces. Wolves, for example.” Theoretical physicist John Ellis, pioneer of the penguin diagram, with its updated sheep version. Scientists at CERN find evidence of quantum entanglement in sheep in 2025, the year declared by the United Nations as the International Year of Quantum Science and Technology. (Image: CERN)
#HackerNews#CERN#quantum
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Université de Liège

Quantum leap! Researchers have developed a method to generate NOON states—key quantum superpositions—10,000 times faster using ultracold atoms.

By combining geometric optimization with counterdiabatic driving, the team reduced preparation time from several minutes to just 0.1 seconds, with 99% fidelity. This breakthrough opens new doors in quantum metrology and quantum information technologies.

cesam.uliege.be/cms/c_13458141

A NOON state is a superposed quantum state where N particles are in one state "at the same time" and in another "at the same time". Here, the particles are trapped in two wells, within a trap formed by lasers. The superimposed state therefore consists of a state in which all the particles are in the left-hand well, and a state in which they are trapped in the right-hand well. The particles interact with each other and 'stick' together when they are in the same site, preventing an isolated particle from leaving the trap.
The proposed protocol (blue, GCD) makes it possible to widen the energy bottleneck (compared with the usual protocol in red, G) and therefore to have to brake less when approaching it. The image can be understood in the context of a motorbike race: the red motorbike will have to brake much more than the blue motorbike because the turn is less "smooth". The blue bike will therefore arrive at its destination before its opponent. Here, the change in the system's energies (and therefore its states) is less abrupt, allowing the process to be accelerated drastically.
#quantum#science#research
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Marek Gluza

A year ago I published at @quantumjournal a single-author manuscript which opens with: "Studying many-body systems is an area where quantum computing may lead to practical advances outside the scope of what we can compute numerically."

I attempted to optimally state the potential of quantum computers:
1. It is my assumption that quantum computing applications for material science will be the first to sustainably matter. I'll miss out if I'm wrong but for now I assume I'm right. (Paraphrasing a lecture by M. Troyer which has been formative for me: "We don't have *the* app for quantum computers. We don't. What will you make it be?")

2. May lead to practical advances says "may" not because I'm manifesting something unrealistic but because we are yet to develop a useful protocol guaranteed to be very fast. (Paraphrasing Troyer: "Shor's algorithm is useful to break RSA and becomes not useful once we migrate to a different code").

3. To me the essence of what the area of basic science research called quantum computing should be delivering is: Learn what happens when processing information using quantum operations and find the problems which these phenomena solve. Don't compete with smartphones. (Paraphrasing Troyer: "We can invert large matrices using regular computers rather well.")

Meaningful quantum computing needs doable, challenging and important problems. Material science allows qualitative answers ("Which phase?", "Is the response function high?") which is convenient but requires quantitative parameters ("Should the Hubbard model have 10% next-nearest-neighbor couplings?", "Does the impurity here change conductance there?") which is difficult.

Link: arxiv.org/abs/2206.11772

This basket in Nagano is called Kagomé
There exist magnets where each spin is placed on a node of the kagomé lattice and the triangles around the hexagons easily lead to something physicists call frustration
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KilleansRow 🇺🇲 🇺🇦🍀

@ThreeSigma Remember those fundamental pre string theory issues in #Quantum foundations ? Feynman famously stated that the two slit experiment encompassed all the mysteries. Wave and particle duality are fundamental observables so stubborn that we ended up telling people to just shut up and calculate…because for the standalone calculations we need to do QM is king. #StringTheory is one result of the can continually kicked down the road. It gives us tools we *need* to get to what’s next

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