CQRT Seminars
The Atomic, Molecular and Optical (AMO) and Condensed Matter (CM) physics groups are hosting a joint seminar as part of the Center for Quantum Research and Technology (CQRT). This endowed seminar series brings in experts from across the country as well as across campus to discuss the latest in research advances in quantum science.
Seminars are scheduled for 2:00-3:00 pm on Tuesdays and/or Fridays, and are held in-person in Lin Hall 105, depending upon speaker availability and preference. Please check this web page or the email announcements for the current week's talks. By attending the seminar, either in person or on Zoom, you are agreeing to abide by our departmental code of conduct.
To get on the seminar mailing list, please contact one of the seminar organizers, Profs. Bihui Zhu and Kieran Mullen
Spring 2025
Title: In the nanoworld, noise helps! Observation of stochastic resonance in a cold atom optical lattice
Samir Bali, Miami University
Friday, February 14, 2025
10:00-11:00am, 105 Lin Hall
Abstract: Scientists making sensitive measurements usually think of noise as undesirable energy that inevitably spills from the environment into the system, degrading system performance. For example, in the case of atoms arranged in a periodic array by light (also known as an optical lattice), the principal obstacle to achieving controlled nanoscale atomic transport is that the directed motion of the atoms (i.e., the system performance) is overwhelmed by randomly directed recoils due to photon scattering (i.e., the noise). Current efforts to build efficient artificial nanomachines center on the counter-intuitive phenomenon of “stochastic resonance”, which refers to a peak in system response as the strength of the random noise increases. Scientists suspect that naturally occurring bio-molecular motors rely on stochastic resonance to efficiently power the processes of life, outperforming state-of-the-art human-made nanomachines by many orders of magnitude.
Here, we report on the observation of a resonant enhancement in the directed propagation of atoms in an optical lattice, as the rate of randomly directed recoils due to photon scattering is increased. Optical lattices are widely considered to be an architectural paradigm for developing new nanotechnology tools. The notion that the controlled addition of random noise fluctuations helps rather than hinders system performance is critical for the development of nano devices that can operate efficiently in noisy environments.
Title: Nano-optics at the extreme
Artur Davoyan, University of California, Los Angeles
Friday, February 21, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: Nanoscale structures offer an unprecedented potential f or shaping optical fields at the fraction of a wavelength and for enhancing light-materials interaction. As light gets confined to nanometer dimensions strong enhancement of optical fields allows accessing novel regimes of light-matter interaction. In this talk I will present two manifestations of nanostructure-mediated light-materials interaction. First, I will show that layered van der Waals materials exhibiting strong material resonances allow for extreme confinement of light at the nanoscale, enabling ultra-small-footprint photonic structures and boosting second order nonlinear light generation. Second, I will show that nanostructures provide allow new ways of controlling lasers of extreme intensity. I will demonstrate that plasmonic nanostructures are ideally suited for creating structured solid-density plasmas to tame ultra-high intensity femtosecond beams. For high energy nanosecond pulses light-materials interaction is even more complex and involves materials heating and phase transitions. In particular, I will show that resonant nanostructures allow controlling time-resolved dynamics of photo-thermal interaction, as well as controlling phase transitions.
Title: Taming quantum chaos with measurements and feedback
Thomas Iadecola, Iowa State University
Friday, February 28, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: Generic isolated quantum systems rapidly lose memory of their initial conditions as they evolve in time. It is a problem of both fundamental and practical interest to devise mechanisms to avert this quantum chaos. Taking inspiration from quantum error correction, we ask whether chaos can be suppressed by an external observer capable of measuring the quantum system and performing feedback operations conditioned on the measurement outcomes. Fortuitously, a classical version of this problem was solved three decades ago with an approach dubbed "probabilistic control of chaos." Probabilistic control randomly intervenes in the chaotic dynamics and attempts to steer the system onto a desired dynamical trajectory with measurement and feedback. As a function of how often the control is applied, a transition occurs between a chaotic phase and a controlled phase where the target trajectory is a global attractor. We generalize this approach to the quantum many-body setting and find that, in addition to the control transition that appears classically, a new entanglement phase transition appears. We discuss the interplay of the two transitions and comment on the possible implications for near-term quantum computers.
Title: Quantum Melting of Spin 'Solids' in Two Dimensions
Andriy Nevidomskyy, Rice University
Tuesday March 4, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: For several decades, the attention of both theoretical and experimental physicists has focused on finding examples of quantum spin liquids — exotic phases of matter characterized by the spin fractionalization, whereby the energy and momentum are carried not by spin waves, but by emergent elementary excitations. By contrast, defining a quantum spin ‘solid’ as a state that spontaneously breaks the lattice translation symmetry, I shall pose the following question — how do quantum solids ‘melt’ and how does entanglement establish itself in a quantum spin liquids ? To answer this question, I shall present our recent work on several 2D systems, from the familiar spin-1/2 on frustrated lattices, to the perhaps less familiar models of spin-1 and SU(3) objects. We study these models using the density matrix renormalization group (DMRG) and infinite projected entangled-pair states (iPEPS) techniques, supplemented by the analytical mean-field and linear flavor wave theory calculations. I shall also discuss another mechanism of quantum ‘melting’, induced by a strong magnetic field — the conventional picture is that this process can be understood as a Bose-Einstein condensation of the auxiliary bosons. Here we show that a more exotic, non-BEC transition occurs when magnetic frustration drives the system across the Lifshitz point, and we find an exotic bosonic liquid that avoids the BEC altogether — so-called Bose metal with algebraic correlations.
Title: Transport in Kicked Quantum Matter
Subhadeep Gupta, University of Washington
Friday, March 14, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: Understanding the interplay of interactions and disorder in quantum transport poses long-standing fundamental challenges for both theory and experiment. We have utilized a synthetic momentum lattice platform using ultracold quantum gases kicked by pulsed optical lattices, to investigate this problem. Using periodic as well as quasi-periodic kick protocols, we have experimentally simulated the Anderson transport model in 1D and 3D and observed the interaction-driven emergence of dynamical delocalization, many-body quantum chaos, and shift of the metal-insulator transition [1, 2]. The observed dynamics feature sub-diffusive energy growth and sheds light on the evolution of dynamically localized states in the presence of many-body interactions, which has long remained an open question. The kicking protocol can also open new opportunities for investigating pairing in strongly interacting fermionic systems. Our results shed light on interaction-driven transport phenomena in quantum many-body systems, in a regime where theoretical approaches are extremely challenging.
[1] J. See Toh et al., Nature Physics 18, 1297 (2022).
[2] J. See Toh et al., Phys. Rev. Lett. 133, 076301 (2024).
Title: "Epsilon near zero materials - so what?"
Nathaniel Kinsey, Virginia Commonwealth University
Friday, April 11, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: The epsilon-near-zero regime has received attention in the last decade for enabling unique optical phenomena and enhancing interactions. Among them, the ability to improve nonlinear optical interactions has been one of the most praised features. In this talk i will summarize the work of my team to measure, model and analyze nonlinear interactions in the epsilon-near-zero regime, focusing primarily on permittivity modulation. We will critically examine what features ENZ actually provides to improve nonlinear interactions and why, as well as explore avenues to push its strengths. Finally, we will conclude with some examples where my team has explored potential use cases for nonlinear refraction in ENZ such as frequency control and ultrafast pulse measurement.
Title: Quantum Abacus: Anyons in One Dimension
Nathan Harshman, American University
Friday, April 11, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: Recent experimental advances with ultracold atoms in one-dimensional optical traps allows exploration of non-standard particle statistics. In this talk, I use the possibility of a quantum abacus to explain and explore the ideas of topological quantum computing with anyons in one dimension. Most proposals for topological quantum computers rely on the properties of braiding anyons in two dimensions. But is it possible to make a topological quantum computer in one dimension? Are anyons even possible in one dimension? The answer, recently confirmed by experiments, is yes: topological exchange statistics are possible in one dimension.
Title: Developing two-dimensional materials for quantum technologies
Nicholas Borys, Montana State University
Friday, April 25, 2025
2:00-3:00pm, 105 Lin Hall
Abstract: ability to engineer materials at the levels of single atomic layers. Material systems based on 2D materials have been exploited to realize new states of matter, and many are appealing for applications, spanning from modern electronics to the development of new quantum technologies. At the atomic level, the unifying characteristic of these materials is their layered structure that enables individual sheets of atoms to be mechanically peeled – or exfoliated – from a bulk crystal and isolated in a true 2D form. Depending on the material, the resulting atomic sheets can be metals, semiconductors, ferromagnets, superconductors, etc. These layers can be further picked up and transferred onto one another, providing seemingly endless opportunities for layer-by-layer assembly of sophisticated 2D heterostructures with distinct physical properties.
A major challenge to capitalizing on the unprecedented versatility of 2D materials is that assembling such 2D heterostructures is typically performed manually, making the process painstakingly tedious and plagued with low yields. I will overview our efforts within the MonArk NSF Quantum Foundry to develop robotic instrumentation to overcome these challenges and demonstrate how automation advancements from the semiconductor industry along with artificial intelligence can expedite 2D quantum materials research. In addition, I will highlight our work to develop on-demand single-photon light sources based on 2D semiconductors for quantum photonic technologies. These studies include the exploration of new architectures and the use of nano-optical techniques to unravel the interplay between strain, electronic structure, and excited state dynamics in the quantum light emission processes. The research efforts here contribute to the development of 2D semiconductors for integrated quantum photonics and illustrate how the right fabrication and characterization tools can accelerate the pace of exploration of the technological and scientific opportunities presented by 2D materials.
Fall 2024
Title: Electron Transport in Nanodevices: Quantum dragons; tatty devices; order-amidst-disorder; universal scaling
Mark Novotny, Mississippi State University
Tuesday, Septmember 10th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: The standard short-ranged single-orbital tight binding model, analyzed using standard NEGF (Non-Equilibrium Green’s Function) methods, is used to study electron transport in unconventional 2D, 3D, and 2D+3D nanodevices. Quantum dragon nanodevices, and nanodevices that are almost quantum dragons, are studied. A quantum dragon nanodevice [1] has the coherent electron transport transmission probability T(E)=1 for all injected electron energies E that propagate through attached thin leads, even though the device may have strong disorder in the tight binding parameters. Starting from a thin 2D nano-ribbon and using allowed operations of cutting, twisting, sewing, and braiding can give very tatty quantum dragon nanodevices. Quantum dragon nanodevices may exhibit order-amidst-disorder [2], where the Hamiltonian is strongly disordered but commonly measured quantities such as bond currents and the projected local density of states (LDOS) are ordered. We derive and demonstrate two different regimes of universal scaling for all nanodevices that are almost quantum dragon nanodevices.
[1] M.A. Novotny, Phys. Rev B 90, 165103 (2014).
[2] M.A. Novotny, G. Inkoom, and T. Novotný, EuroPhysics Lett. 143, 26005 (2023).
Title: Integrated Photonics for Sensing and Computing with Artificial Intelligence and Machine Learning Applications
Ray Chen, Univerity of Texas, Austin
Friday, Septmember 27th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: The advancement of sensing, interconnects and computing in the last one hundred years is mainly from the R&D works on electrons and photons, which carry drastically different characteristics defining different technology roadmaps. Due to the saturation of the Moore’s law, the advantages of photon-based devices provide solutions with the unprecedented performance. In this talk, we will present the integrated photonic devices covering near and mid-IR wavelengths for biosensing, SERS and spectroscopy sensing for Methane, Nitrogen Dioxide, CO, Ethanol, Ammonia, and TEP. Mid-IR Lidar Chip centered at 4.6 micron will also presented. Silicon photonics for both digital and analog computing will be introduced with low latency, high bandwidth and multi-wavelength operations for AI and ML applications.
Title: Quantum chemistry on a quantum computer
October 1st, 2024: Susanne Yelin, Harvard University.
Tuesday, October 1st, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: Simulations of quantum chemistry and quantum materials are believed to be among the most important potential applications of quantum information processors, but realizing practical quantum advantage for such problems is challenging. In this talk, I will introduce a simulation framework for strongly correlated quantum systems modeled by spin Hamiltonians, focusing on practical applications in quantum chemistry and materials. Our approach uses reconfigurable qubit architectures to simulate real-time dynamics and employs an algorithm for extracting chemically relevant spectral properties through classical co-processing. We develop a digital-analog simulation toolbox, utilizing digital Floquet engineering and hardware-optimized multi-qubit operations to realize complex spin-spin interactions, demonstrated via a proposal based on Rydberg atom arrays. This method allows for extracting detailed spectral information, such as excitation energies and finite-temperature susceptibilities, from a single dataset. I will also highlight how this framework can be applied to compute key properties of polynuclear transition-metal catalysts and 2D magnetic materials.
Title: High-efficiency, superconducting single-photon detectors from ultraviolet to long-wavelength infrared wavelengths
Richard Mirin, Quantum Nanophotonics Group, NIST
Tuesday, October 15th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: The development of high performance superconducting single-photon detectors has been a key development in the advancement of photonic quantum information science. Both transition edge sensors (TESs) and superconducting nanowire single-photon detectors (SNSPDs) have demonstrated system detection efficiencies approaching 100% at wavelengths around 1550 nm. In 2015, both of these detectors were used in landmark demonstrations of loophole-free Bell experiments that conclusively showed that quantum entanglement cannot be explained by hidden local variables. Both of these detectors have been used for demonstrations of photonic quantum computing. There are many applications beyond quantum information science, such as medical imaging, semiconductor characterization, laboratory astrophysics, and exoplanet detection that are enabled by these detectors. I will describe some of the latest innovations in these superconducting single-photon detectors, including the development of SNSPD arrays with 400,000 pixels, from the Quantum Nanophotonics Group/Faint Photonics Group in the Applied Physics Division of NIST.
Title: Tunneling and Interlayer Coherence in Twist-Controlled van der Waals Heterostructures
Emanuel Tutuc, University of Texas, Austin
Friday, October 25th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: Van der Waals (vdW) heterostructures of two-dimensional materials offer an unprecedented playground to combine materials with different electronic properties, without the constraints of lattice matching associated with epitaxial growth. Recent years have witnessed the emergence of interlayer twist as a new parameter that controls the electronic properties of vdW heterostructures, and allows the realization of flat energy bands. This presentation will provide an overview of experimental techniques to control interlayer twist, with an emphasis on twist-controlled double layers. We show that interlayer tunnelling serves as unique tool to probe interlayer coherence in twist-aligned, closely spaced double layers where interaction leads to a coherent superposition of electronic states in individual layers, with Josephson junction-like tunnelling characteristics robust to temperature, and layer density detuning. We describe a novel tunneling spectroscopy technique in twist-aligned double layers, where momentum-conserving tunneling between different energy bands serves as an energy filter for the tunneling carriers, and allows a measurement of the quasi-particle state broadening at well-defined energies with respect to the Fermi level.
Title: Strain engineering of epitaxial BiFeO3 film under biaxial tensile strain
In-Tae Bae, The Aerospace Corporation
Friday, November 1st, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: BiFeO3 (BFO) has been known as the only multiferroic material that exhibits ferroelectricity and antiferromagnetism simultaneously well above room temperature since 1970s. The resurgence of BFO as a multiferroic material was triggered by the revelation of its true bulk ferroelectricity (= ~90 mC/cm2) in the mid-2000s.1 Subsequently, with the availability of high quality single crystal oxide substrates, BFO films are grown epitaxially on a variety of single crystal substrates in an attempt to further improve its physical properties by imparting epitaxial strains.[1],[2] Since the crystal symmetry and microstructural characteristics caused by the epitaxial strains dominate the multiferroic property changes in BiFeO3, substantial efforts have been devoted to understand the relationship between the crystal symmetry and ferroelectric domain structure in epitaxially strained BFO films. As a result, a number of strain-induced new crystal structures were proposed by experiments and theoretical calculations. However, details about strain-induced structural modifications remain elusive owing to: (1) the remarkably complex nature of BiFeO3, (2) its willingness to adapt unusually high lattice strain of over ~6 %,[3] and (3) the use of pseudocubic notation to describe the equilibrium BFO phase of rhombohedral (space group: R3c). In this talk, I discuss: (1) how the use of hexagonal notation (that represents the true symmetry in equilibrium BFO phase) helps unambiguously identify the crystal symmetry and subsequent quantitative strain measurement in epitaxially strained BiFeO3,[4]-[7](2) the relationship between spontaneous polarization and the crystallographic orientations in ferroelectric domains.[8] In addition, how electron probe used within scanning transmission electron microscope affects the spontaneous polarization orientation measurement is discussed as well.[9]
References
[1] J. Wang et al., Science 299, 1719 (2003)
[2] R. J. Zech et al., Science 326, 977 (2009)
[3] D. Sando, B. Xu, B. Bellaiche and V. Nagarajan, Appl. Phys. Rev. 3, 011106 (2016)
[4] I.-T. Bae, H. Naganuma, T. Ichinose, K. Sato, Phys. Rev. B, 93, 064115 (2016)
[5] I.-T. Bae et al. Sci. Rep. 7, 46498 (2017)
[6] I.-T. Bae et al. Sci. Rep. 8, 893 (2018)
[7] I.-T. Bae et al. Sci. Rep. 9, 6715 (2019)
[8] I.-T. Bae, Z. R. Lingley, B. J. Foran, and H. Paik, Sci. Rep. 13, 19018 (2023)
[9] I.-T. Bae, B. J. Foran, and H. Paik, Sci. Rep. 14, 15513 (2024)
Title: Doing more with the same: using metastable states of trapped ions
Tuesday, November 5th, 2024: Jameson O'Reilly, University of Oregon
Tuesday, November 5th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: Today’s most advanced ion trap quantum computers have at most one qubit per ion, each defined within the ground state manifold. Additional non-qubit ions provide sympathetic cooling to keep the computational ions cold enough to perform many rounds of high-fidelity coherent operations. Typically, the two subsets of ions must be different species to prevent cooling light from disturbing the computation. To bypass this added system complexity, we can instead promote our computational ions to a long-lived excited state that is isolated from the ground-state cooling transitions. This promotion also enables new features including erasure conversion and projective state preparation. We will discuss two recent efforts to develop this architecture: entangling gates between metastable qubits and sympathetic cooling of a metastable ion by a ground-state ion. Finally, we will take advantage of the larger metastable manifold to explore high-fidelity qudit control.
Title: Control of Spontaneous Emission with Semiconductor Metasurfaces: from Single Photons to Ultrafast Beam Steering
Igal Brener, Sandia National Lab
Friday, November 15th, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: Metamaterials and their 2D implementation – metasurfaces - have been used extensively for wavefront manipulation since their inception nearly two decades ago. This has led to a revolution in optics due to the ability to design optical components with functionality and form factor that was unthinkable not long ago. Another use of metasurfaces relies on the ability to tailor distributions and intensities of local electromagnetic fields to study a variety of fundamental phenomena in light-matter interaction, 1 create novel tunable and active devices 2 and enhance optical nonlinearities.3-5 In particular, metasurfaces made from III-V semiconductors 6 offer an excellent platform for enhancing optical nonlinearities and controlling spontaneous emission, as single and ensembles of quantum emitters can be embedded inside the meta-atoms. 7
In this talk I will focus on two topics: single-photon emission from local-droplet etching (LDE) quantum-dots embedded in III-V metasurfaces 8 and spontaneous parametric down-conversion (SPDC) from metasurfaces containing high-Q resonances. 5For single photon emission from LDE quantum dots embedded in GaAs metasurfaces, we use Huygens metasurfaces to enhance collection efficiency by more than 20-fold, and show how this platform enables measurements of g(2) at excitation power densities that are much lower than what has been used previously. For the second part, the SPDC work follows from years of research inharmonic generation and other optical nonlinearities from III-V metasurfaces 3, 6. We recently showed SPDC from GaAs metasurfaces containing quasi bound-states-in-the-continuum (q-BIC) resonances 5. The q-BIC resonances enhance the optical density of states at either the signal or idler wavelength and greatly enhance the SPDC rates for both the degenerate and non-degenerate case. Finally, I’ll present recent results for further enhancing the SPDC rates beyond what was published in [5] as well as polarization tomography of the emitted photon pairs.
1. R. Sarma, N. Nookala, K. J. Reilly, et al., “Strong Coupling in All-Dielectric Intersubband Polaritonic Metasurfaces”, Nano Lett 21, 367-374 (2021).
2. A. Benz, I. Montano, J. F. Klem, et al., “Tunable metamaterials based on voltage controlled strong coupling”, Applied Physics Letters 103, 263116 (2013).
3. R. Sarma, J. Xu, D. de Ceglia, et al., “An All-Dielectric Polaritonic Metasurface with a Giant Nonlinear Optical Response”, Nano Letters 22, 896-903 (2022).
4. S. Liu, P. P. Vabishchevich, A. Vaskin, et al., “An all-dielectric metasurface as a broadband optical frequency mixer”, Nature Communications, 1 - 6 (2018).
5. T. Santiago-Cruz, S. D. Gennaro, O. Mitrofanov, et al., “Resonant metasurfaces for generating complex quantum states”, Science 377, 991-995 (2022).
6. S. Liu, G. A. Keeler, J. L. Reno, et al., “III–V Semiconductor Nanoresonators—A New Strategy for Passive, Active, and Nonlinear All‐Dielectric Metamaterials”, Advanced Optical Materials 4, 1457-1462 (2016).
7. S. Liu, A. Vaskin, S. Addamane, et al., “Light-Emitting Metasurfaces: Simultaneous Control of Spontaneous Emission and Far-Field Radiation”, Nano Lett 18, 6906-6914 (2018).
8. P. P. Iyer, S. Prescott, S. Addamane, et al., “Control of Quantized Spontaneous Emission from Single GaAs Quantum Dots Embedded in Huygens’ Metasurfaces”, Nano Letters (2024).
Title: TBA
Martin Scheutz, Amazon Web Services
Friday, November 22nd, 2024
2:00-3:00pm, 105 Lin Hall
Abstract: TBA
