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Wednesday, Sep 18, 2024
Kazuki Ikeda (UMass Boston) 

Toward Realization of Quantum Turing Patterns 

Turing patterns are a concept introduced by the computing pioneer Alan Turing. In simple terms, Turing patterns describe how the interaction of two or more chemicals (reactants), which diffuse at different rates, can result in patterns that are stable in space. This concept helps to explain various natural phenomena, from the stripes on zebras to spots on leopards, as well as many other patterns found in biology and chemistry. 

While Turing patterns have been studied in a framework of classical statistical mechanics, in this talk, we discuss its quantum extension. Unlike the conventional diffusion process, quantum Turing patterns would appear as a result of interplay between a unitary time-evolution and thermalization. As a concrete setup, we consider two-flavor Dirac fermions, where different couplings and masses of different quarks give the condition of the patterns. We perform both quantum and classical simulations using 100 qubits using quantum circuits and tensor network (MPS).

This work is ongoing with Dr. Sebastian Grieninger at Stony Brook University. 

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Wednesday, Sep 25, 2024
Johannes Hofmann (University of Gothenburg)

Hydrodynamics transport in two-dimensional Fermi liquids

There is currently much experimental interest in studying transport in ultraclean two-dimensional materials, which is dominated by electron interactions as opposed to the conventional phonon or impurity scattering. This gives rise to an effective hydrodynamic description of electron flow, with transport coefficients (like the shear viscosity) that can be predicted from an underlying Fermi-liquid description. While one could think that this framework should be extremely well understood, it turns out that there are still fundamental aspects that remain unexplored. In this talk, I will give an introduction to Fermi liquids and hydrodynamic transport in 2D materials, and discuss how Pauli blocking gives rise to excitations with lifetimes that are much longer than conventionally expected in Fermi liquid theory. I will then discuss how such long-lived modes will change the conventional hydrodynamic description of the electron fluid.

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Friday, Sep 27, 2024
Please note the unusual date and time
Ralph Dum (GLUON Foundation, President)

Innovation at the Nexus of Science, Technology and the Arts

Already during the Renaissance, Florence flourished from a mix of artists, scientists, and (not the least) financiers like the Medicis. Today, the arts have again become a catalyst of human-centered innovation and contribute to tackle pertinent urgent issues that are a consequence of (digital) progress, including e.g. social media and artificial intelligence. Equally important, artists have long been in the vanguard of raising awareness of the fragility of nature. The arts have become a gauge and a sensor of human impact on nature.

Continuing a long tradition of historic movement, like Bauhaus, the European S+T+ARTS program funds collaborations between science, technology and the arts to trigger synergies between artistic and engineering approaches that help  address the urgent issues of today.

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Wednesday, Oct 2, 2024
Byung-Jun Yoon (Texas A&M)

Objective-Driven Optimal Experimental Design: Quantifying the Uncertainties that Matter and Reducing Them Efficiently & Effectively

Modeling complex real-world systems involve immense uncertainties due to a wide variety of factors, including inherent stochasticity of the system, limited availability of data for modeling the system, presence of unobservable hidden variables, and measurement noise. In practice, these uncertainties may not be completely eliminated and difficult to reduce, requiring one to focus on the uncertainties that actually matter for achieving the modeling goal(s). In this talk, we present how one may quantify the model uncertainty in an objective-driven manner and develop optimal experimental design (OED) techniques that can reduce the uncertainty that critically affects the operational goal(s) of the model. Furthermore, we discuss how one may leverage machine learning (ML) approaches to accelerate uncertainty quantification (UQ), and ultimately, OED. To demonstrate the advantages and potentials of these approaches, we will consider examples in systems biology, drug discovery, and material design.

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Wednesday, Oct 9, 2024
Joanna B. Dahl

Measuring the Mechanical Behavior of Small, Squishy Bio-Things Using Microfluidics

Understanding of the mechanical behavior of microscale biological bodies such as cells, cell clusters, and vesicles are important for fundamental cell biology research and for disease diagnostics and therapeutics in clinical settings. Microfluidic devices are ideally suited for studying small, soft objects due to their well-defined laminar flows, transparent material for direct observation, and high-throughput capabilities. With accompanying mechanical modeling, we can perform detailed mechanical analysis of biological soft bodies trapped at the stagnation point or passing through the extensional flow region. This presentation focuses on our current projects performing miniaturized creep tests on biomimetic hydrogel microparticles, exploring how the stiffnesses of large extracellular vesicles from cancer cells vary with lipid-altering mutations, and investigating the continuum of cell spheroid biomechanical behavior with spheroid size.

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Wednesday, Oct 16, 2024
Jonathan Milette (Lathrop GPM LLP)

Patent prosecution: how to protect your invention and the importance of written description

Patents are key assets for bringing inventions from the bench to the marketplace. They allow inventors to not only prevent others from making and using their invention but also for maintaining their right to sell their invention exclusively. While owning a patent presents many advantages, obtaining a patent involves many steps that can be challenging for inventors to navigate. In this talk, we will present an overview of the process of obtaining a patent. We will also closely look at how the written description in patent applications plays an important role in obtaining a patent based on a recent decision from the U.S. Supreme Court.

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Wednesday, Oct 23, 2024
Sara Hashmi (Northeastern University)

Clogging and intermittent dynamics in complex fluid flows through confined spaces 

Intermittency and clogging of complex fluids flowing through small spaces can occur nearly anywhere: in the porous media of the earth, in industrial flows through hoppers, in water filters, 3D printing nozzles, and in some of the worst instances, in our blood vessels.  These examples include flows of colloidal particles, granular material, crosslinking polymers, and multicomponent systems.  Despite the differences in the type of complex fluid involved, some aspects of clogging are universal, like its stochastic nature and the importance of the constituent material properties.  Understanding the nature of clogging is key to controlling or preventing it, and facilitates improved design of filters, hoppers, and diagnostic tools.  This talk explores intermittency and clogging in pores from the centimeter scale to the micron scale, investigating granular hopper flows and microfluidic polymer flows.  Despite salient differences between these two systems, we find the material properties of the complex fluid to govern flow behavior.  On the macro-scale, a quasi-2D rotating hopper is used to investigate both jamming and avalanche flows in small-system mixtures of soft and rigid particles.  Increasing the fraction of soft particles in the mixture can alleviate jamming while simultaneously causing more avalanches.  On the micro-scale, polymers crosslinking in situ in flow through microchannels exhibit intermittent dynamics, in which gelation, deposition, and ablation occur repeatedly and persistently.  This model system might represent situations encountered in polymer flows in 3D printing applications, or, in a greatly simplified way, two of the final steps in the coagulation cascade.  We map the intermittent behavior as a function of crosslinking density and gel concentration.  Inverting the “flow phase diagram” generates a map that is reminiscent of colloidal jamming.  We can describe the dynamics using an analytical transport model of diffusive-driven deposition in a boundary layer.  The results suggest that gels formed in lower component concentrations or at slower flow rates are those that occlude the channel to a greater degree before ablation.  Increasing the stiffness of the gel reduces the degree of occlusion.  Intriguingly, despite the low-Reynolds number nature of the flow, we find signatures of chaotic behavior as system conditions approach regions of complete failure. 

Bio: Sara M. Hashmi is an Assistant Professor of Chemical Engineering at Northeastern University, with affiliated appointments in Mechanical & Industrial Engineering and Chemistry & Chemical Biology.  Prof. Hashmi obtained her AB in Physics & Philosophy at Harvard.  After spending one year as a research assistant, she obtained MS and PhD degrees in Chemical & Environmental Engineering from Yale University.  Following postdoctoral research studying colloidal phenomena in petroleum fluids, Prof. Hashmi founded and directed a highly collaborative, campus-wide instrument facility at Yale, the Facility for Light Scattering.  At Northeastern, she leads the Hashmi Complex Fluids lab, where her research focuses on “flowing soft materials through small spaces.”  The Complex Fluids Labs studies flows of complex fluids, soft and active materials through confined geometries on both the micro- and macro-scale.  The research both reveals fundamental fluid dynamic principles and applies them to real world applications.  The highly visual and engaging nature of the research lends itself nicely to educational outreach efforts as well.  Prof. Hashmi has been awarded both a CAREER Award from the NSF, and Northeastern University’s Dr. R.H. Sioui Award for Excellence in Teaching.

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Wednesday, Oct 30, 2024
Juven Wang (Harvard University CMSA and LIMS Royal Institution)

Ultra Quantum Matter to Unification Beyond the Standard Model Physics

The eclectic cross-disciplinary fertilization of ideas between quantum condensed matter and geometry and topology in math may help solve these big open phenological problems in high-energy physics. Historically, from the 1950s to 1960s, the development of superconductivity from BCS to Anderson inspired the later Nambu-Goldstone-Anderson-Higgs mechanism applied to the Standard Model of particle physics. In this colloquium, we will explore the developments in topological quantum matter (from the 1980s to 2020s and up to date) that may guide us to overcome problems in the high-energy physics frontier. We will find that a new anomaly cancellation scenario suggests that the Standard Model coexists with a missing sector of topological order with a low-energy topological field theory. Such that in the new scenario, in addition to strong, electroweak, and gravity, there is an extra 5th topological force (mediated by discrete Baryon minus Lepton B-L gauge field) joining in an Ultra Unification; while the topological quantum matter becomes part of the dark matter. There are fractionalized anyon-like extended excitations above the topological order energy gap sharing the same 4-dimensional spacetime with us, while there could also be a 16-fold-class B-L-symmetry-protected topological superconductor in the 5th dimension attached to our 4-dimensional Standard Model world. Along the way, we may eventually understand: why neutrinos obtain tiny mass and oscillate between electron, muon, and tauon types of three flavors? What consists of dark matter? What causes leptogenesis and baryogenesis? Why are there three families/generations of quarks and leptons?

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Wednesday, Nov 6, 2024
Elena Cambria (MIT)

Mechanisms of Tumor Cell Mechanical Memory: Implications for Cancer Metastasis and Therapeutic Targeting

The majority of cancer-related deaths are due to metastasis. The failure to develop efficient anti-metastatic drugs has been attributed to an incomplete understanding of the biological mechanisms that drive metastasis. However, mechanical cues have recently emerged as contributors to tumor development and progression. One of the main physical hallmarks of cancer is elevated extracellular matrix stiffness, which alters tumor cell proliferation, survival, contractility, deformability, and migration. Moreover, recent evidence shows that human cells that change their behavior in response to a certain physical microenvironment have the ability to maintain this behavior even after withdrawal of the original physical stimulus and exposure to a new microenvironment, a concept called “cell mechanical memory”. Bringing these ideas together, we hypothesize that the stiffness-induced biophysical adaptations that are imprinted on tumor cells in the primary tumor microenvironment are retained throughout the metastatic process via mechanical memory, and enhance tumor cell extravasation, survival, and colonization in the metastatic organ. This talk will cover our ongoing investigation of the role of cell mechanical memory in cancer metastasis using microfluidic models of human microvasculature and mouse models. We will also discuss how deciphering mechanisms of mechanical memory formation and retention, including persistent epigenetic changes, can power the discovery of a new class of anti-metastatic drugs.

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Wednesday, Nov 13, 2024
Laurent Loinard (UNAM, Harvard)

Why do the EHT images all look the way they do?

The Event Horizon Telescope (EHT) has now published images of M87 and Sgr A* at angular resolutions comparable with their horizon scales. Both images show the overall same structure: a bright ring (with some azimuthal variations) surrounding a darker region. In this talk, I will show that this overall structure reflects fundamental properties of spacetime around Kerr black holes. The darker region is the expected shadow of the black hole and the bright ring is largely dominated by emission from the so-called photon shell. These two universal black hole features define almost entirely the observed images. The physics of the plasma around the black hole, on the other hand, can be accessed through the polarimetric properties of the images that I will also discuss in some detail.
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Wednesday, Nov 20, 2024
Arthur Parzygnat (MIT)

Time-reversal symmetry for quantum measurements

The state of a quantum system at any point in time is encoded in an operator called the density matrix, which is uniquely determined by its expectation values upon measuring a basis of observables. For example, a multi-qubit state is characterized by the measurement of all Pauli observables on each qubit. Meanwhile, for a state that evolves in time within some environment and interacts with a measuring device, the operator that provides the expectation values for sequential measurements is called a “state over time”. Moreover, a quantum generalization of Bayes’ rule predicts time-symmetric joint expectation values for two-time sequential measurement outcomes. I will provide an introduction to these ideas, while focusing on the example of a qubit undergoing amplitude-damping noise.

This talk is based primarily on the following reference:

Parzygnat, Fullwood "Time-symmetric correlations for open quantum systems" https://arxiv.org/abs/2407.11123

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Wednesday, Nov 27, 2024
No colloquium -- Thanksgiving

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Wednesday, Dec 4, 2024
Irmgard Bischofberger (MIT)

Under Pressure: Suspensions Pushed Too Far  

Particle suspensions can fracture into intricate patterns as they are pushed out of equilibrium. We probe the fracture and relaxation characteristics of dense aqueous cornstarch suspensions that exhibit discontinuous shear-thickening behavior. Air injection into three-dimensional bulk suspensions can lead to smooth bubbles that rise upwards under the action of buoyancy or to sharp fractures that remain attached to the injection nozzle. We link the shape and the relaxation dynamics of the air cavity to the suspension rheology. In a second example, we report the crack dynamics and morphology occurring as drops of aqueous nanoparticle suspensions evaporate on a glass surface and leave behind a solid particle deposit. We show that in the final stage of drying, the stresses in the deposit can be released in two distinct ways: by bending out of plane or by forming a second generation of cracks.

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Wednesday, Dec 11, 2024
Siddarth Ramachandran (BU)

Long-lived Photons in Forbidden States

the influence of light’s topology on its propagation characteristics

The internet, connectivity in data centres, networks of quantum compute nodes, high-power lasers as well as biomedical endoscopy, to name just a few applications, owe their success to seminal demonstrations by Colladon, Babinet and Tyndal, over 150 years ago, of the principle of total internal reflection (TIR) of light. Waveguides operating on this principle yield bound states of light in discrete momentum states, with losses so low that signal transportation over 1000s of km is now possible today. In analogy with bound states of electrons in quantum wells, though, there are only a limited number of such modes of light, and the aforementioned revolution of data transport notwithstanding, we now face an upper limit on the amount of information that can be sent down optical fiber waveguides today.

Here we describe the recent discovery of an alternative form of light transport, where the photon is conventionally unbound, i.e. it violates the principles of TIR, and yet is long-lived due to a centrifugal barrier the photon’s topological charge creates for itself. The effect is similar to that of the centrifugal barrier that prevents the collapse of binary stars in orbits. We show how this distinctive effect can fuel a new march towards increasing the information capacity of photons in optical fibers, for classical as well as quantum networks.

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