QUINTO projectMay 13

We just submitted the first QUINTO draft of paper to a journal. Let's see what the editors and reviewers think.

The paper is about fractional quantum Hall states in atomic arrays. Here is the popular summary we submitted alongside:

"When atoms are arranged in a regular, dense array, their response to light can change drastically. The photons can bounce between the atoms, getting absorbed and re-emitted again and interfering with themselves. This field of quantum optics with atomic arrays is of active interest. Due to interactions, the limit of many absorbed photons generally remains hard to model, but at the same time may result in new, counterintuitive physical phenomena. In the search for ways to understand such systems, we can look for analogies in condensed matter physics, where the behavior of many interacting particles (electrons in this case) has been studied for decades. Here, we report on finding such an analogy between the behavior of few photons absorbed by an array and peculiar many-electron quantum states known as fractional quantum Hall (FQH) states. FQH states display many counterintuitive properties -- for example the electrons behave like they decomposed into pieces (e.g. "one third of an electron"), even though we know that in reality they are indivisible. Now we know that photons in arrays can behave similarly."

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#physics #science #CondensedMatterPhysics #CondensedMatter #condMat #QuantumOptics #Quantum @physics

MatMatMay 6

New preprint from our team: https://arxiv.org/abs/2409.04372

A new algorithm for computing #material properties in #densityfunctionaltheory (#dft) based on inexact #krylov methods: we safe 40% computational cost by an adaptive selection of convergence tolerances inspired from #mathematical analysis.

#condensedmatter #planewave #dfpt #response #physics #simulation #computation

Kohn-Sham inversion with mathematical guarantees

We use an exact Moreau-Yosida regularized formulation to obtain the exchange-correlation potential for periodic systems. We reveal a profound connection between rigorous mathematical principles and efficient numerical implementation, which marks the first computation of a Moreau-Yosida-based inversion for physical systems. We develop a mathematically rigorous inversion algorithm which is demonstrated for representative bulk materials, specifically bulk silicon, gallium arsenide, and potassium chloride. Our inversion algorithm allows the construction of rigorous error bounds that we are able to verify numerically. This unlocks a new pathway to analyze Kohn-Sham inversion methods, which we expect in turn to foster mathematical approaches for developing approximate functionals.

arXiv.org
QUINTO projectApr 30

We just came back from the "Light-Matter Interactions and Collective Effects" workshop in Paris. We heard some interesting talks on how quantum emitters (not only atoms, but also e.g. molecules and quantum dots) interact with each other and how people try to arrange them into arrays (like, putting chains of molecules inside a carbon nanotube). Darrick (my boss and supervisor of the project) gave a talk on spin liquids, while I presented a poster on fractional quantum Hall states in atom arrays.

#physics #quantum #science #QuantumOptics #CondensedMatter #CondMat

ℵ₀ 🏳️‍⚧️🏴‍☠️Apr 11

https://youtu.be/qqjlcuEHUlg

#Quantum #computation from #spacetime defect #networks | #MargaritaDavydova (#Caltech)

“Recorded as part of the Generalized Symmetries: #HighEnergy, #CondensedMatter and #Mathematics KITP conference from Apr 7, 2025 - Apr 10, 2025 at the Kavli Institute for #TheoreticalPhysics on the #UCSantaBarbara campus.”

#UCSB
#physics #computing #qubits #topologicaldefects #lagrangian

more at: https://www.kitp.ucsb.edu/activities/gensym-c25

Quantum computation from spacetime defect networks | Margarita Davydova (Caltech)

YouTube
José - Luis Gutiérrez VillanueApr 7

Superconductivity = zero resistance ⚡

New research digs into Cooper pair density and how it drives the superconducting state.

Big implications for quantum tech + energy.

🔗 https://phys.org/news/2025-03-superconducting-state-cooper-pair-density.html

#Superconductivity #QuantumPhysics #CondensedMatter #Physics

New superconducting state discovered: Cooper-pair density modulation

Superconductivity is a quantum physical state in which a metal is able to conduct electricity perfectly without any resistance. In its most familiar application, it enables powerful magnets in MRI machines to create the magnetic fields that allow doctors to see inside our bodies. Thus far, materials can only achieve superconductivity at extremely low temperatures, near absolute zero (a few tens of Kelvin or colder).

Phys.org
QUINTO projectMar 31

Fractional quantum Hall states in atom arrays

Our second approach to create a topological order in atom arrays is to focus on a different kind of topological order: fractional quantum Hall (FQH) states. These were first discovered in condensed matter. It is possible to confine electrons to move in two-dimensions only (such as in the 2D material graphene or in so-called metal-oxide-semiconductor transistors) and then put them in a strong perpendicular magnetic fields. The electrons then move in circles (so-called “cyclotron motion”), but since they are quantum objects, only some values of radius are allowed. Thus, the energy can only take certain fixed values (we call them “Landau levels”). There are however different possibilities of an electron having the same energy, because the center of the orbit can be located in different places – we say that Landau levels are “degenerate”. And when there is degeneracy, the interaction between electrons becomes very important. Without interactions, there are many possible ways of arranging electrons within a Landau level, all with the same energy. In the presence of interactions, some arrangements become preferred – and it turns out those correspond to topological orders known as the FQH states. Such systems host anyons which look like fractions of an electron – like somehow the electron split into several parts.

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#Physics #science #TopologicalOrder #Quantum #QuantumOptics #CondensedMatter #CondMat #cond_mat #QuantumHall

Beilstein-InstitutMar 14

📢 Meet our Managing Editor Dr. BarbaraHissa @BarbaraHissa visits the DPG Spring Meeting of the Condensed Matter Section (SKM) in Regensburg next week from 📅 March 17 to 19, 2025.

➡️ https://www.beilstein-journals.org/bjnano/news/QRB4PYY6ROZZMP6GW5XLW627JQ?M=y

#CondensedMatter #DPGR25 #EDITOURS #BJNANO 💎 🔓

BJNANO - Dr. Barbara Hissa attends the DPG Spring Meeting of the Condensed Matter Section (SKM)

Dr. Barbara Hissa attends the DPG Spring Meeting of the Condensed Matter Section (SKM)

QUINTO projectMar 10

Spin liquids in Rydberg atom arrays in cavities

What is our proposal for the realization of spin liquid?

We consider an atom array held by optical tweezers and placed in an optical cavity. The cavity consists of two mirrors placed on the opposite sides of the system. The photons which normally would escape the system (at least some of them) will bounce back and forth between the mirrors. In such a configuration, the distance between atoms becomes irrelevant and the probability of an excitation hopping between any two atoms becomes the same.

The second ingredient is that the excited state of the atoms would be a Rydberg state – a very high-energy state where the electron is far away from the nucleus. The atoms in Rydberg states interact strongly by van der Waals forces. In our case it would mean that two excitations will have much higher energy when they are at nearest-neighboring atoms than if they are far away.

This setting seems much different from usual crystals. In the typical material, the electrons are much more likely to hop between nearest-neighboring atoms than far-away ones, while in our case they would be able hop arbitrarily far with the same probability. But it turns out that there is in equivalence between such “infinite-range hopping + Rydberg” model and the Heisenberg model, commonly used to describe magnets, including the frustrated ones.
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#Physics #Quantum #TopologicalOrder #CondMat #CondensedMatter #QuantumOptics #Science

Beilstein-InstitutMar 5

📢 Our Managing Editor Dr. BarbaraHissa @BarbaraHissa visits the DPG Spring Meeting of the Condensed Matter Section (SKM). Meet her in Regensburg, Germany, from 📅 March 17 to 19, 2025.

➡️ https://www.beilstein-journals.org/bjnano/news/QRB4PYY6ROZZMP6GW5XLW627JQ?M=y

#CondensedMatter #DPGR25 #EDITOURS #BJNANO 💎 🔓

BJNANO - Dr. Barbara Hissa attends the DPG Spring Meeting of the Condensed Matter Section (SKM)

Dr. Barbara Hissa attends the DPG Spring Meeting of the Condensed Matter Section (SKM)

Paul HouleMar 1

🐐 Breaking the pattern: How disorder toughens materials

https://techxplore.com/news/2025-02-pattern-disorder-toughens-materials.html

#materials #metamaterials #research #condensedmatter #disorder

Breaking the pattern: How disorder toughens materials

Cut open a bone and you'll see a subtly disordered structure. Tiny beams, called trabeculae, connect to one another in irregular patterns, distributing stress and lending bones an impressive toughness. What if human-made materials could exhibit similar properties?

Tech Xplore
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QUINTO projectMar 31

Fractional quantum Hall states in atom arrays

Our second approach to create a topological order in atom arrays is to focus on a different kind of topological order: fractional quantum Hall (FQH) states. These were first discovered in condensed matter. It is possible to confine electrons to move in two-dimensions only (such as in the 2D material graphene or in so-called metal-oxide-semiconductor transistors) and then put them in a strong perpendicular magnetic fields. The electrons then move in circles (so-called “cyclotron motion”), but since they are quantum objects, only some values of radius are allowed. Thus, the energy can only take certain fixed values (we call them “Landau levels”). There are however different possibilities of an electron having the same energy, because the center of the orbit can be located in different places – we say that Landau levels are “degenerate”. And when there is degeneracy, the interaction between electrons becomes very important. Without interactions, there are many possible ways of arranging electrons within a Landau level, all with the same energy. In the presence of interactions, some arrangements become preferred – and it turns out those correspond to topological orders known as the FQH states. Such systems host anyons which look like fractions of an electron – like somehow the electron split into several parts.

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#Physics #science #TopologicalOrder #Quantum #QuantumOptics #CondensedMatter #CondMat #cond_mat #QuantumHall

Show threadQUINTO projectMar 31

Magnetic field acts completely differently on atom arrays than on electrons, as photons, unlike electrons, don’t have electric charge. But it turns out that in some circumstances (atoms with two excited states instead of one, responding to the light that is circularly polarized, i.e its electric field vector traces out a circle instead of oscillating along a line), they give rise to something similar to a Landau level – a topological energy band, a range of allowed energies which also corresponds to cyclotron motion. If this range is sufficiently narrow (a “nearly-flat band”), there is an approximate degeneracy and FQH states may occur.

We are currently working on a draft of article showing that for small enough number of atoms and excitations, the topological band becomes sufficiently flat that it can host FQH states of few excitations. For a minimal case of two excitations, we propose how these states can be created and measured. We plan to build on these ideas to increase the system size and the number of particles, to build a genuinely many-body quantum-optical version of the fractional quantum Hall effect.
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