Spring 2024
January 26, 2024 (Friday) 4:00-5:00p.m.
Speaker: Christopher Monahan, W&M Physics
Hosts: M. Sher
Title: Exploring the Quantum Universe: Report of the 2023 Particle Physics Project Prioritization Panel
Abstract: Particle physics studies the smallest constituents of our vast and complex universe. At such small scales, the fundamental principles of quantum physics prevail. Remarkably, the entire observable universe, now billions of light years across, was once so small as to be quantum in nature. This quantum history of the universe is imprinted on its large-scale structure.
The 2023 P5 (Particle Physics Project Prioritization Panel), building on the community-driven Snowmass process, recently released the P5 report, which recommends funding priorities for the Department of Energy and the Natonial Science Foundation over the next decade. Our recommended program describes particle physics in three science themes. Within each of these themes, we identify two focus areas, or science drivers, that represent the most promising avenues of investigation for the next 10 to 20 years. I will introduce P5 and the P5 report and highlight the key recommendations and their implications for particle physics in the US and beyond in the near future."
Febrary 7, 2024 (Wednesday) 4:00-5:00p.m.
Speaker: Stuart Masson, Columbia University New York
Hosts: E. Mikhailov
Title: Collective decay in ordered arrays of quantum emitters
Abstract: Collective phenomena are found in every branch of science; the behavior of the whole differs strongly from the behavior of the individual elements. In quantum optics, a hallmark example is Dicke superradiance. Here, a fully inverted ensemble of quantum emitters emits a short and bright light pulse, known as a superradiant burst, that initially grows in intensity. This is in stark contrast to independent atoms which decay exponentially, emitting a pulse that monotonically decreases in time. Experiments in dense disordered systems have observed the superradiant burst, but there, inhomogeneous broadening plays a large role, making the systems hard to model or control. In contrast, ordered arrays have much lower inhomogeneity - emitters in the bulk all see the same set of neighbors - making them an ideal platform to study dissipative many-body physics. Here, we show the conditions under which such systems produce a superradiant burst. We go beyond two-level approximations, and demonstrate that long-wavelength transitions from ytterbium and strontium atoms can be used to observe such physics. Using the insight gained, we then show how to use such systems as generators of non-classical light.
Febrary 8, 2024 (Thursday) 4:00-5:00p.m.
Speaker: Jose D'Incao, Associate Fellow JILA
Hosts: E. Mikhailov
Title: The complex nature of few-atom interactions: the physics of forbidden molecules
Abstract: In the past few decades, the progress made by the field of ultracold quantum gases has increasingly been translated into promising prospects for controlling atomic and molecular behavior. The present-day experimental ability to manipulate interactions and to precisely prepare the system in a well-defined quantum state enables ultracold quantum gases to access a variety of complex few-body phenomena at an unprecedented level of detail. This progress has, for instance, allowed for the exploration of the strongly interacting regime in which unique and counterintuitive molecular states, such as Feshbach and Efimov, exist. In this talk, I will discuss how the microscopic control of the underlying interactions responsible for such states have revolutionized the research in both fields of few-body physics and ultracold quantum gases, ultimately allowing for the exploration of novel phases of the matter. I will also highlight the prospects of using such molecular states as a source of entangled atomic states to create new classes of matter-wave interferometers, with applications in both fundamental science and technology.
Febrary 14, 2024 (Wednesday) 4:00-5:00p.m.
Speaker: Izabella Lovas, Kavli Institute for Theoretical Physics
Hosts: E. Mikhailov
Title: Information spreading in quantum many-body systems
Abstract: The rapid development of quantum simulators in the past decades has opened unprecedented possibilities to study quantum many-body systems. A wide range of Hamiltonians has been directly engineered in analog simulators, and provided crucial insights into quantum phases of matter, as well as into dynamical phenomena. This progress was accompanied by recent breakthroughs in digital quantum devices, promising to grant computational capacities far beyond the reach of classical architectures. This talk illustrates the opportunities and outstanding challenges presented by this rapidly developing field. In the first part, we demonstrate the power of combining theoretical approaches with experiments in a trapped ion quantum simulator, allowing us to identify and observe signatures of universal transport in a long-range interacting quantum magnet. We then turn to the challenges of protecting quantum coherence against environmental noise. In contrast to the general expectation that in an open system coherent information is quickly lost to the dissipative environment, we construct a regime of open quantum dynamics, functioning as a quantum error-correcting code which is dynamically protected against generic boundary noise. We comment on the implications of these results for designing robust quantum devices.
Febrary 16, 2024 (Friday) 4:00-5:00p.m.
Speaker: Ahana Chakraborty, Rutgers University
Hosts: E. Mikhailov
Title: Open Quantum Systems: A new frontier of many-body physics
Abstract: The open quantum system (OQS) represents a novel platform of many-body physics, allowing a quantum system to interact with an external observer or exchange energy and particles with its environment. Understanding the non-unitary dynamics of OQS is crucial for addressing fundamental questions in statistical physics, such as thermalization, the approach to non-thermal steady states, and the generation of quantum entanglement.
An interesting realization of OQS is the ubiquitous interaction between quantum material with external electromagnetic field. In this talk, I will explore how light, whether in the form of a classical laser field or quantum light in cavities, can be employed to manipulate the properties of a quantum material, leading to the emergence of novel phases that are inaccessible in closed systems.
Furthermore, OQS offers promising applications in quantum information processing devices. By navigating the interplay between entangling unitary dynamics and disentangling measurements, we can induce novel entanglement phase transitions. I will discuss our recent findings on unique critical properties associated with entanglement phase transitions in monitored quantum circuits, along with the potential for their realization in quantum devices.
Febrary 21, 2024 (Wednesday) 4:00-5:00p.m.
Speaker: Gregory Bentsen, Minerva University
Hosts: E. Mikhailov
Title: Harnessing entanglement with cold atoms
Abstract: Quantum entanglement is one of the most salient, bizarre, and powerful features of quantum mechanics. Simple forms of entanglement can be used to teleport quantum information between distantly separated points; more complicated patterns of entanglement can be employed to facilitate universal quantum computation, or to simulate intractable problems in many-body physics. At present, the full range of complex entanglement accessible to a many-body quantum system constitutes a vast, largely unexplored frontier. One of the most exciting challenges for near-term experimental platforms is to engineer and exploit these complex patterns of entanglement for applications including precision metrology, many-body quantum simulation, and quantum information processing. In this talk I will introduce many-body quantum entanglement and discuss a few of its applications in an ensemble of neutral 87Rb atoms coupled to an optical resonator. The long-range, all-to-all interactions of this experimental platform provide unique capabilities for generating entanglement efficiently, by rapidly spreading quantum information throughout the system. I will demonstrate how the resulting patterns of entanglement can be harnessed to implement Heisenberg-limited precision metrology, to study quantum chaos, and to simulate aspects of gravitational physics such as black holes and holographic duality.
Febrary 23, 2024 (Friday) 4:00-5:00p.m.
Speaker: Yanzhu Chen, Virginia Tech
Hosts: E. Mikhailov
Title: Moving the barrier to practical quantum computing on two fronts
Abstract: Quantum computing has long promised to speed up certain tasks that are intractable on classical computers. However, quantum devices are inherently noisy, with coherence times limited by unwanted interactions between the quantum processor and its environment. Overcoming this limitation requires new techniques for recovering useful information from quantum computations despite the noise, as well as new algorithms with enhanced speed and resource efficiency. In this talk, I will describe recent advances on both these fronts. First, I will present a new class of adaptive, quantum-classical hybrid algorithms that outperform previous quantum simulation algorithms in terms of both speed and resources, bringing practical quantum computing on near-term devices closer to reality. Then I will present a new method for characterizing and mitigating correlated noise, a ubiquitous and especially challenging type of noise that evades most existing error mitigation strategies.
Febrary 28, 2024 (Wednesday) 4:00-5:00p.m.
Speaker: Ebubechukwu ILO-OKEKE, Shanghai New York University
Hosts: E. Mikhailov
Title: Quantum information with neutral atoms: From Time transfer to finding ground state of many-body atoms
Abstract: Neutral atoms are at the heart of many successes in quantum physics in the last few decades, ranging from Bose-Einstein condensation and high-precision magnetometers to lattice atomic clocks. The level of control at the single particle and repeated measurement of the same atom samples while preserving the quantum features like superposition coherence and entanglement makes neutral atoms prime candidates for quantum devices.
An example is atom clocks, used in many technologies like GPS and national labs for timekeeping. However, due to drifts, it becomes necessary to synchronize two or more distant clocks to reliably keep accurate time. A method proposed to synchronize such distant clocks uses quantum entanglement, called quantum clock synchronization (QCS), to transfer time between the clocks. However, John Preskill identified that defining quantum states between parties without consistent phase definitions can lead to unknown systematic errors. I will discuss how the introduction of quantum state purification filters off the unknown phase definitions by the parties and channels noise, which allows for the implementation of QCS.
Furthermore, finding the ground state of Hamiltonians is essential in quantum information science and optimization problems. An imaginary time evolution finds the ground state of a given Hamiltonian after long evolution times by amplifying the ground state of a given system. I will discuss my recent work on using a sequence of measurements and conditional unitary rotations to realize deterministic imaginary time evolution and provide an example application.
March 22, 2024 (Friday) 4:00-5:00p.m.
Speaker: Jeremy Wolcott, Tufts University
Hosts: M. Kordosky
Title: Multifaceted Nu Insights: Harnessing MCMC to Inspect Neutrino Oscillations From Every Angle
Abstract: Neutrinos are among the most unusual of the fundamental particles known in modern physics. Besides interacting with ordinary matter so rarely that supermassive detectors or extremely intense sources are required to even observe them, and being separated from the other fundamental fermions by at least six orders of magnitude in mass, neutrinos' “flavor oscillations” exhibit a rich phenomenology that may at last give us hints as to where we should look beyond current theory for new fundamental insights. The discovery of an underlying symmetry in the way the neutrino states interact with one another or the way the neutrinos' masses are arranged, for instance, or the violation of symmetries between neutrinos and their antimatter counterparts, could have profound consequences for both particle physics and cosmology.
However, contemporary experiments attempting to access this phenomenology must grapple with its numerous degeneracies and multiple degrees of freedom. In this talk, I will discuss how Bayesian Markov Chain Monte Carlo (MCMC) is being used to simultaneously examine many different aspects of neutrino oscillation measurements with an efficient computing approach. I will review its applications to current data from the NOvA experiment at Fermilab, and show how we obtain insights into both the underlying physical system and our instrumental setup. I will conclude with some thoughts about MCMC's promise for future neutrino oscillation measurements.
March 29, 2024 (Friday) 4:00-5:00p.m.
Speaker: Frank N. von Hippel, Senior Research Physicist and Professor of Public and International Affairs emeritus, Program on Science and Global Security, Princeton University
Hosts: M. Sher
Title: Danger of nuclear war: Physicists can help!
Unfortunately, that has not been the case. Indeed, the danger of accidental nuclear war may be increasing. US and Russian strategic missiles remain in a launch-on-warning posture in an era when hackers have penetrated some of our supposedly most secure computer systems. China appears to be moving toward a similar posture.
Both Russia and the United States have committed to hugely costly programs to replace their nuclear weapons with new systems designed to maintain that status quo for the remainder of the century. Meanwhile, an offense-defense nuclear arms race is developing between the US and China, which is building up the number of its nuclear weapons that can reach the US as the US increases the number of its ballistic missile interceptors – nominally to defend against North Korea.
In the past, independent physicists have played leading roles in informing Congress and the world about the dangers and offering ideas for how to reduce them – both unilaterally and through agreements with our adversaries. The American Physical Society sponsored the Physicists Coalition for Nuclear Threat Reduction, https://physicistscoalition.org, during its first two years to help renew the engagement of physicists and other physical scientists and engineers with Congress and the public on nuclear-weapons issues.
For those interested, the speaker will be happy to discuss opportunities to work with the Physicists Coalition, including its Next Generation Fellowships, before the colloquium. Interested students can come to Small 122 at noon or can meet individually in the afternoon. Email Marc Sher (mtsher@wm.edu) if you want to set up an individual meeting.
April 1, 2024 (Monday) 4:00-5:00p.m.
Speaker: Javad Shabani, New York University
Hosts: E. Rossi
Title: Progress in Realizing Topological Superconductivity in Planar Josephson Junctions
Abstract: A central goal in condensed matter physics is to understand and control the order parameter characterizing the collective state of electrons in quantum heterostructures. For example, new physical behaviors can emerge that are absent in the isolated constituent materials. With regards to superconductivity this has opened a whole new area of investigation in the form of topological superconductivity. This type of superconductivity is expected to host exotic quasi-particle excitations including Majorana bound states. In this talk, we first discuss the important role of epitaxial superconductor-semiconductor hybrid systems as an enabling materials platform. We discuss the role of disorder and spin orbit coupling and how they may impact observation of topological phases in Josephson junctions. We present microwave measurements that exhibit unprecedented values of transparency for individual Andreev bound states and their extension in presence of magnetic field. These findings reveal a versatile two-dimensional platform to explore mesoscopic and topological superconductivity
April 12, 2024 (Friday) 4:00-5:00p.m.
Speaker: Elana Urbach, Harvard University
Hosts: S. Aubin
Title: Nanoscale and Gigascale: Quantum Sensing of Condensed Matter Systems and a Cosmological Survey
Abstract: Nanoscale magnetic sensing can provide a wealth of information about the properties of biological and condensed matter systems, but few techniques have the sensitivity and spatial resolution necessary to act as truly local probes of these materials. Recently, the nitrogen vacancy (NV) center in diamond has emerged as a powerful tool capable of detecting single electron and nuclear spins. In this colloquium, I will present several experiments that utilize the NV center to gain insight into the structure and dynamics of 2D systems at the nanoscale.
Switching to the gigascale, the Vera C. Rubin Observatory is nearing completion and will soon embark on the Legacy Survey of Space and Time (LSST), a ten year survey of the southern sky. I will talk about the goals of the survey and the work that we're doing now to ensure the survey's success.
April 19, 2024 (Friday) 4:00-5:00p.m.
Speaker: Katherine Freese, University of Texas
Hosts: M. Sher
Title: Dark Matter in the Universe
Abstract: The nature of the dark matter in the Universe is among the longest and most important outstanding problems in all of modern physics. The ordinary atoms that make up the known universe, from our bodies and the air we breathe to the planets and stars, constitute only 5% of all matter and energy in the cosmos. The remaining 95% is made up of a recipe of 25% dark matter and 70% dark energy, both nonluminous components whose nature remains a mystery. I’ll begin by discussing the evidence that dark matter is the bulk of the mass in the Universe, and then turn to the hunt to understand its nature. Leading candidates are fundamental particles including Weakly Interacting Massive Particles (WIMPs), axions, sterile neutrinos, light dark matter, as well as primordial black holes. I will discuss multiple experimental searches: at CERN in Geneva; in underground laboratories; with space telescopes; with gravitational wave detectors; and with ancient rocks. I’ll tell you about our novel idea of Dark Stars, early stars powered by dark matter heating, and the possibility that the James Webb Space Telescope has already discovered them. At the end of the talk, I'll turn to dark energy and its effect on the future of the Universe.
