2024 Open House Poster Presentation Abstracts

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Shruti Puri Group

Harshvardhaan K Babla, Graduate Student

Fault-Tolerant Fusion-Based Quantum Computing with the 4-Legged Cat Code

With its ability to correct for single-photon loss, the 4-legged cat code stands out as a promising bosonic quantum memory, becoming the first code to surpass the QEC breakeven point [1]. We extend its capabilities with a universal set of operations composed of destructive Bell measurements and entangled resource state generation. These operations are efficiently implemented using standard cQED tools: inter-cavity beam-splitter coupling, cavity displacements, cavity-transmon dispersive coupling, and transmon drives. Notably, the Bell measurements are not limited by undesired non-linearities in the cavities, particularly cavity self-Kerr. Additionally, analytics and pulse-level simulations demonstrate that these operations are, at worst, second-order sensitive to both photon loss in the storage cavity and decoherence in the transmons. The proposed universal set of operations is particularly suited for fusion-based fault-tolerant quantum computation with the XZZX cluster state. The inherent first-order robustness promises a suppression of physical qubit error rates beyond what is expected from unencoded physical qubits.
[1] Ofek et. al. Nature 536, 441–445 (2016)

Yu He Group

Maria Bambrick-Santoyo, Graduate Student

Tuning superconductivity by rare-earth element doping in Bi-based high TC cuprate superconductors

Motivated by over three decades of studies on elemental doping of high temperature cuprate superconductors, we explore the superconducting mechanism by studying its enemies. By understanding how superconductivity can be “killed” with elemental substitution, we hope to glean insights into the factors critical to enabling it. We identify cerium and praseodymium as the two elements most effective at suppressing superconductivity in Bi2Sr2CaCu2O8 (Bi-2212) without directly substituting copper, and incorporate them into the crystal lattice at varying concentrations. Making use of angle-resolved photoemission spectroscopy (ARPES) and single-crystal x-ray diffraction, we investigate the electronic and structural properties of the doped and undoped systems, including charge doping, modulations in the superstructure, substitution site of the Ce/Pr atoms, and changes to the low-energy electronic structures. In doing this, we extract factors that negatively impact superconductivity. This knowledge can not only inform future studies exploring ways to mitigate these negative factors, but also provide insight into microscopic engineering principles to boost superconductivity towards higher temperatures.

Jack Harris Group

Igor Brandão, Graduate Student

Magnetically Levitated mm-sized Helium-3 Spheres as an Optomechanical Platform for Free Quantum Rotations

Ground state cooling has been achieved in a plethora of optomechanical systems in
recent years. Most prominently, setups using optically levitated nanoparticles made
rapid progress on this front given their unprecedented isolation. However, the high
optical power needed to trap and manipulate the particles leads to photon recoil rates
which limit the achievable mean phonon number and mechanical coherence times.
Combined with the relatively small single photon coupling rates realized in these
systems, subsequent state preparation has been limited to the linearized regime and
Gaussian states. Magnetic levitation of liquid helium is an attractive alternative since
it removes this decoherence channel. The choice to levitate mm-sized liquid helium
drops instead of silica (SiO2) solid spheres, allows us to use the levitated object itself
as the optical cavity. This can be achieved using the optical whispering gallery
modes (WGM) which couple directly to the drop's surface waves and rotational
modes. Surface waves may achieve the single-photon strong-coupling regime, and
have been the subject of preliminary experimental studies in superfluid helium-4
drops at temperature ~ 300 mK. Rotational coupling can be achieved in helium-3,
which undergoes rigid-body rotation at similar temperatures. This coupling is
predicted to be dominated by the centrifugal force experienced by the drop, which
would induce a shape deformation. This detunes the optical WGM by an amount
proportional to the square of the drop's angular momentum, adding a new form of
interaction to the toolbox of levitodynamics. Here, we report the first magnetic
levitation of helium-3 drops, and describe our ongoing efforts to study their
optomechanical and optorotational behavior.

Shruti Puri Group

Katie Chang, Graduate Student

Surface Code with Imperfect Erasure Checks

Due to the possibility of hardware-efficient error correction, recently a lot of effort has been devoted towards designing erasure-biased qubit architectures with the ability to detect dominant errors after every gate operation converting them to erasures. Inevitably however, the experimental implementation of erasure detection will have a finite accuracy. We consider a practical noise model in which an erasure check may return a false negative result, but the subsequent check registers the previously missed erasure. Such delayed erasure detection is not accounted for in existing performance analysis of error correction with erasure qubits. Consequently, in this work we examine the impact of our delayed erasure noise model on the performance of fault-tolerant surface code quantum memory. We assume that an erasure check is applied after every noisy gate in the syndrome extraction circuit. Missed erasures can give rise to correlated errors and moreover, the precise location of these correlations become unknown. We investigate how these effects influence the subthreshold scaling of the logical error rate. Furthermore, we find that when all erasure detections are delayed by a timestep, the threshold decreases to 2.6%, which is nearly half the threshold for perfect erasure detection. Crucially, this threshold of 2.6% is twice the threshold for Pauli errors, implying that erasure qubits are an attractive candidate for easing the requirements of fault-tolerance even when detection is unreliable.

Corey O'Hern Group

Gautham Gopinath, Graduate Student

Wetting of deformable particles on soft substrates

Cell aggregates on soft gels are a model system to study tissue migration. Notably, the gel stiffness can be tuned to make aggregates change from spreading to non spreading behaviour. This is analogous to how some liquid droplets will spread on a surface while others will not. We use a deformable particle model to study the wetting transition of cell aggregates on a soft substrate. We model the substrate as a bed of springs and observe interesting elastocapillary effects when the substrate is soft.

Damon Clark Group

Tong Gou, Graduate Student

Adaptation to stimulus sparsity recruits broad responses to infrequent stimuli

Sensory systems adapt their response properties to the statistics of their inputs. For instance, visual systems adapt to low-order statistics like mean and variance to encode the stimulus efficiently or to facilitate specific downstream computations. However, it remains unclear how other statistical features affect sensory adaptation. Here, we explore how Drosophila’s visual motion circuits adapt to stimulus sparsity, a measure of the signal’s intermittency not captured by low-order statistics alone. Early visual neurons in both ON and OFF pathways alter their responses dramatically with stimulus sparsity, responding positively to both light and dark sparse stimuli but linearly to dense stimuli. These changes extend to downstream ON and OFF direction-selective neurons, which are activated by sparse stimuli of both polarities, but respond with opposite signs to light and dark regions of dense stimuli. Thus, sparse stimuli activate both ON and OFF pathways, recruiting a larger fraction of the circuit and potentially enhancing the salience of infrequent stimuli. Overall, our results reveal visual response properties that increase the fraction of the circuit responding to sparse, infrequent stimuli.

Ben Machta Group

Isabella Graf, Postdoctoral Associate

Milli-Kelvin thermal sensitivity in the snake pit organ via proximity to a saddle-node bifurcation

In various biological systems, information from many noisy molecular receptors must be integrated into a collective response. A striking example is the thermal imaging organ of pit vipers. Single nerve fibers in the organ reliably respond to milli-Kelvin (mK) temperature increases, a thousand times more sensitive than their molecular sensors, thermo-transient receptor potential (TRP) ion channels. Here, we propose a mechanism for the integration of this molecular information. In our model, amplification arises due to proximity to a dynamical bifurcation, separating a regime with frequent and regular action potentials (APs), from a regime where APs are irregular and infrequent. Near the transition, AP frequency can have an extremely sharp dependence on temperature, naturally accounting for the thousand-fold amplification. Furthermore, close to the bifurcation, most of the information about temperature available in the TRP channels’ kinetics can be read out from the times between consecutive APs even in the presence of readout noise. A key model prediction is that the coefficient of variation in the distribution of interspike times decreases with AP frequency, and quantitative comparison with experiments indeed suggests that nerve fibers of snakes are located very close to the bifurcation. While proximity to such bifurcation points typically requires fine-tuning of parameters, we propose that having feedback act from the order parameter (AP frequency) onto the control parameter robustly maintains the system in the vicinity of the bifurcation. This robustness suggests that similar feedback mechanisms might be found in other sensory systems which also need to detect tiny signals in a varying environment.

Chiara Mingarelli Group

Bjorn Larsen, Graduate Student

The NANOGrav 15-year dataset: a Study of Chromatic Gaussian Process Noise Models in Six Pulsars

Pulsar timing arrays (PTAs) are a promising technique for detecting low-frequency gravitational waves. However, the accuracy of PTA measurements of gravitational waves is limited by noise, including radio-frequency dependent "chromatic" noise due to propagation effects such as dispersion measure (DM) and scattering delay variations. In this work, we use Gaussian processes (GPs) to model chromatic noise in six pulsars from the NANOGrav 15-year dataset. We showcase how the noise properties of these pulsars vary as a function of the noise model and also compare our noise results with the European PTA DR2 noise results. We find the GP models closely reproduce the DM time series as estimated from timing model analyses, but that GPs provide flexibility to detect additional chromatic noise consistent with scattering delay variations. Furthermore, we find the choice of chromatic noise model noticeably affects the achromatic noise properties of several pulsars and is likely to impact the spectral characterization of the nHz gravitational wave background. These results highlight the potential for custom GP noise models to improve the sensitivity of NANOGrav datasets to gravitational waves.

Jack Harris Group

Yilin Li, Graduate Student

"Prospects for a superfluid whispering gallery mode
optomechanical resonator"

In this poster we discuss a whispering-gallery-mode (WGM) optomechanical resonator system in superfluid Helium. The detection of phonon annihilation/creation has been successfully demonstrated utilizing filter Fabry-Perot cavities and single photon detectors. The WGM system aims to overcome the limitation of our current fiber-based Fabry-Perot cavities, which has a phonon lifetime of around 50micoseconds.

Hui Cao Group

Rohin McIntosh, Graduate Student

Delivering Broadband Light Deep Inside Diffusive Media

Wavefront shaping enables targeted delivery of coherent light into random-scattering media, such as biological tissue, by constructive interference of scattered waves. However, broadband waves have short coherence times, weakening the interference effect. Here, we introduce a broadband deposition matrix that identifies a single input wavefront that maximizes the broadband energy delivered to an extended target deep inside a diffusive system. We experimentally demonstrate that long-range spatial and spectral correlations result in a six-fold energy enhancement for targets containing 1700 speckle grains and located at a depth of up to ten transport mean free paths, even when the coherence time is an order of magnitude shorter than the diffusion dwell time of light in the scattering sample. In the broadband (fast decoherence) limit, enhancement of energy delivery to extended targets becomes nearly independent of the target depth and dissipation. Our experiments, numerical simulations, and analytic theory establish the fundamental limit for broadband energy delivery deep into a diffusive system, which has important consequences for practical applications.

Karsten Heeger and Reina Maruyama Groups

Maya Moore, Graduate Student

CUORE/CUPID: Capacious Cryogenics with Cubic Crystals

Located at the Gran Sasso National Laboratory in Italy, the Cryogenic Underground Observatory for Rare Events (CUORE) is an experiment searching for neutrinoless double beta decay, a theorized process in which a candidate isotope undergoes beta decay by emitting only two electrons. Observing this process would prove that neutrinos are Majorana particles– they are their own antiparticle. CUORE will stop taking data in 2026 and development is already in place for its next-generation experiment, the CUORE Upgrade with Particle Identification (CUPID). CUPID will use the same infrastructure as CUORE with increased sensitivity to probe the full inverted hierarchy region for neutrino masses. Here we discuss the ongoing R&D and analysis efforts by the Heeger-Maruyama group for CUORE and CUPID.

Charles Brown Group

Andrew O. Neely, Graduate Student

Building an Optical Quasicrystal of Ultracold Lithium

Experiments with quantum degenerate atomic gasses (i.e., “ultracold” atoms) have proven to be useful tools for exploring the physics of condensed matter, largely owing to their unique combination of flexibility, tunability, and purity. This combination allows for the precise study of phenomena that are sometimes difficult, or even impossible, to access in a solid-state system. Experiments with model systems that are built with ultracold atoms provide access to phenomena that appear in the often-exotic physics of quantum materials and strongly correlated materials. Such experiments may provide unique insight into the emergent exotic properties of solid materials that are generated by the interplay of quantum coherence, strong interactions, topology, and entanglement. In particular, solid quasicrystals, which exhibit long-range order in spite of their total lack of translational symmetry, have proven somewhat difficult to study with conventional solid-state techniques. At the same time, quasicrystals are gaining increasingly more interest, since their unique combination of symmetries imbues them with interesting mathematical properties that are associated with rich new physics. To explore the physics of quasicrystals, our team is building an experiment that will create a quasicrystalline potential energy landscape using laser light and populate this potential with a quantum degenerate gas of lithium. We plan to use the tools of atomic, molecular, and optical physics to study this quasicrystalline system in great detail, with the goal of understanding the interplay of geometry, topology and many-body quantum mechanics in the properties of quasicrystals.

Jack Harris Group

Yogesh Patil, Associate Research Scientist

Measuring the geometric phase in the evolution of a non-Hermitian system

"When the Hamiltonian of a linear system is slowly tuned around a closed circuit in parameter space, the adiabatic theorem guarantees that an eigenstate of the system returns to itself up to an overall phase. This phase has two dominant components: a dynamical component that depends on the time taken to traverse the circuit, and a geometric component that depends only on the shape of the circuit. For non-Hermitian systems it has been predicted that, for circuits in which the adiabatic theorem is applicable, the geometric phase may be complex, i.e. it may contain both a real phase and a gain/loss component. We measure the fully complex geometric phase accumulated by a set of coupled oscillators, whose non-Hermitian Hamiltonian is parametrically tuned in real time via optomechanical dynamical back-action. We show that this phase is well predicted by only the circuit geometry for a variety of circuits.

This work is supported by the MURI program under AFOSR grant No. FA9550-21-1-0202 and by the DoD Vannevar Bush Faculty Fellowship."

Jack Harris Group

Akshai Jayakumar Pillai, Graduate Student

Cavity Optomechanics in Solid Helium and Solid Neon

Cavity optomechanical systems have been used to realize highly sensitive metrological devices and are also proposed as a tool for studying questions in fundamental physics. We have previously demonstrated an optomechanical system using an optical fiber cavity filled with superfluid He in which an optical mode (wavelength = 1550 nm) couples to an acoustic mode of the superfluid with precisely half the wavelength. This acoustic mode has a resonance frequency of 320 MHz, and so is cooled to a mean phonon number ~ 1 in a conventional dilution refrigerator. Here we look at the feasibility of using solid He and Ne crystals as the medium in such cavities, as their greater sound velocity will result in 1550 nm light coupling to acoustic modes at 600 MHz and 1.4 GHz respectively. As the crystals are acoustically anisotropic, we use the Christoffel equation and finite element simulations to find the acoustic eigenmodes of the cavity. The spatial profiles of these eigenmodes depend on the angle between the crystal axis with the cavity axis. We find that for a range of crystal orientations, there exist eigenmodes whose spatial profiles closely resemble a Gaussian. These acoustic eigenmodes are predicted to have a high degree of overlap with the optical Gaussian mode, and thus are good candidates to realize a large optomechanical coupling.

Leonid Glazman Group

Benjamin Remez, Postdoctoral Associate

Schmid Transition in DC-Biased Transmons Shunted by High-Impedance Waveguides

Current passage through a Josephson junction must overcome a Coulomb blockade, hence a small junction will behave like an insulator. According to the Schmid transition paradigm, shunting the junction restores superconductivity, appearing as a sharp transition at vanishing current and voltage. Motivated by recent experiments with high-impedance waveguides, we extend the theory to large direct current bias. Focusing on resistively shunted transmon qubits, we derive the voltage-current relation and the spectrum of radiated photons, and find the crossover fingerprints of the superconductor-insulator transition. We compute how a finite waveguide length induces resonant peaks in these observables.

David Poland Group

Gordon Rogelberg, “primary author” of Theory Graduate Students

Yale Theory Department

Members of the high energy theory group at Yale are engaged in many exciting research programs which make contact with particle, condensed matter, and gravitational physics. Here, we highlight the research of some of the graduate students in the group. We discuss energy correlators and their applications to particle phenomenology. We also discuss light ray operators, which are often studied formally as objects in a conformal field theory, but can also be interpreted as the theoretical description of detectors within a collider experiment. Also within the realm of conformal field theories, we discuss the conformal bootstrap, a program to derive CFT observables from symmetry and self-consistency constraints.

Ben Machta Group

Mason N. Rouches, Graduate Student

Prewetting & Surface Phases in Critical Membranes & Collapsible Polymers

Nuclear proteins such as transcription factors demix into liquid-like droplets at high concentrations in vitro, and they phase separate onto DNA and RNA polymers at somewhat lower concentrations in vivo. Separately, long polymers in vitro can undergo extended to collapsed transitions as solvent conditions change. In vivo, spatial rearrangements of the chromosome in three dimensions regulate transcrip- tion, and are thought to be enhanced or established by the presence of specific DNA binding proteins. Here we explore a model where coupling to proteins with a propensity to phase separate in three dimensions modulates a collapse transition of long polymers. We draw parallels to a recent model we proposed for clusters of cytoplasmic signaling molecules that phase separate exclusively at the surface of the plasma membrane, itself poised near a 2D liquid-liquid critical point, below which it phase separates into coexisting liquid phases. Here we use approaches from statistical physics to understand the coupling between liquid-liquid phase separation of a ‘‘bulk’’ protein solution and phase transitions of a lower dimen- sional surface. Our analysis reveals that the surface of a long polymer is best viewed as a compressible ‘‘scaffold’’ onto which a bulk fluid can phase separate. This transition coincides with the polymer collapse transition, and the presence of a scaffold dramatically widens the regime of demixing-like transitions in the bulk. In the case of membranes we show that proximity to the membrane critical point simi- larly enhances the range of prewetting phase transitions, where bulk fluids phase separate exclusively on the surface. Systems with polymers or membranes lacking their respective transitions or fluidity do not see a similar degree of enhancement.

Charles Ahn Group

Kidae Shin, Graduate Student

Molecular Beam Epitaxy-grown Transition Metal Oxides for Rare Earth Ion Qubits

Rare earth ions (REIs) in solids are attractive for quantum information processing due to long coherence time and scalability. To identify suitable host crystals for Er3+ ions and demonstrate REI qubits in thin films, we grow Er-doped anatase TiO2 using molecular beam epitaxy (MBE) and characterize them with x-ray diffraction, atomic force microscopy and optical measurements.

Helen Caines and Laura Havener Groups

Youqi Song, Graduate Student

Colliding protons and heavy ions to study the perfect superfluid

"The Relativistic Heavy Ion Group (RHIG) at Yale studies proton-proton and heavy ion collisions at the Large Hadron Collider (LHC) at CERN and Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab to probe the strong nuclear force. While colliding protons allows us to probe Quantum Chromodynamic (QCD), the underlying theory of the strong force, colliding heavy ions takes us one step further by testing this theory in matter.
Heavy ion collisions (such as Pb-Pb) that occur at 99.9% the speed of light give rise to a hot, dense state of nuclear matter called the Quark Gluon Plasma (QGP). The QGP behaves like a strongly correlated fluid of quarks and gluons and additionally, is the most perfect superfluid to ever exist! Investigating its properties requires the convergence of many sub fields within physics such as statistical mechanics, quantum hydrodynamics and quantum field theory.
The RHIG group studies QCD both in vacuum and in matter to probe the many unanswered questions about the strong nuclear force. Studying both collision systems (p-p and Pb-Pb), allows us to compare QCD in vacuum to QCD in matter. Furthermore, conducting experiments at RHIC and the LHC gives access to a wide range of energies for exploring collider physics.

Members of the group investigate a wide variety of questions by using quantum hydrodynamic observables, jet physics, and machine learning. Some topics of current interest include hadronization mechanisms, energy loss in the QGP, jet quenching mechanisms, jet substructure in p-p and heavy ions, and strangeness enhancement in the QGP etc."

Joerg Bewersdorf Group

Sylvi Stoller, Graduate Student

Developing FLASH-PAINT Probes for Highly Multiplexed Tissue Imaging

Single-molecule super-resolution microscopy overcomes the diffraction limit of light and
resolves structures down to 1-10nm but is limited by imaging speed and color
separation of fluorescent dyes which only permits the visualization of four targets at once.
FLASH-PAINT, a variant of DNA-PAINT, has a modular design using Transient Adapters
which provides advantages such as spectrally unlimited multiplexing and gentle and
efficient signal elimination. We demonstrate FLASH-PAINT’s compatibility with FISH
with telomeres in mammalian cells. Next, we present the development of more Transient
Adapters to expand FLASH-PAINT to 100+ multiplexing.

Michael Murrell Group

Zachary Gao Sun, Graduate Student

F-actin architecture governs self-organized criticality in the cytoskeleton

Self-Organized criticality (SOC) is observed across diverse natural phenomena, including earthquakes, avalanches, and landslides. These critical phenomena are often accompanied by cascading dissipative events. Recent work has suggested that living systems are poised close to critical points. During complex behaviors of the cell such as migration and division, the F-actin cytoskeleton undergoes dramatic changes in structure, organization, and dynamics. To drive these changes, the non-equilibrium activity of molecular motors imparts mechanical stresses, which are continuously accumulated and relaxed. To explore criticality in the dynamics of the cytoskeleton, we reconstruct an experimental model of the cytoskeleton in vitro, composed of purified protein polymers (F-actin) and motors (myosin II), in which the organization and activity of the proteins are controlled precisely. We find that without regard to organization, the accumulation is stress is slow, but relaxation is dramatic, as marked by high dissipative events. However, in bundled networks, the distribution of dissipative events follows a double exponential, while in branched networks they are Levy-a distributed and exhibit 1/f noise – a key signature of criticality. By computation simulation, we demonstrate that myosin activity depends on the isostaticity of adjacent F-actin, demonstrating that simple, local geometry determines the nature of cascading dissipative events within a living system.

Corey O'Hern Group

Andrew Ton, Graduate Student

Deformable particle simulations of wound healing and embryo development

We are developing novel simulation methods to model biomechanical processes such as wound healing and embryo development. Using the deformable particle model, we demonstrate how mechanical differences in the cell membrane lead to distinct wound closure phenotypes seen in wounds of embryonic and larval drosophila. In particular, the embryonic ectoderm is best described by cell membranes with an elasto-plastic response, whereas larval wing discs are best described by cell membranes with a purely elastic response. Additionally, we extend the deformable particle model to describe tissue solidification within the developing zebrafish embryo. Here, we investigate the role of intra-tissue and inter-tissue adhesion mechanisms in supporting healthy body axis development.

Emma Carley, director of PEB


PEB poster