NYU Arts & Science

All Scheduled Events

April 18, 2024 Thursday 11:00 AM  +
726 Broadway, Room 1067
Center for Quantum Information Physics Seminars (cqip)


Eliot Kapit
Colorado School of Mines

On the approximability of random-hypergraph MAX-3-XORSAT problems with quantum algorithms

Constraint satisfaction problems are an important area of computer science. Many of these problems are in the complexity class NP which is exponentially hard for all known methods, both for worst cases and often typical. Fundamentally, the lack of any guided local minimum escape method ensures the hardness of both exact and approximate optimization classically, but the intuitive mechanism for approximation hardness in quantum algorithms based on Hamiltonian time evolution is poorly understood. We explore this question using the prototypically hard MAX-3-XORSAT problem class. We conclude that the mechanisms for quantum exact and approximation hardness are fundamentally distinct. We qualitatively identify why traditional methods such as quantum adiabatic optimization are not good approximation algorithms. We propose a new spectral folding optimization method that does not suffer from these issues and study it analytically and numerically. We consider random rank-3 hypergraphs including extremal planted solution instances, where the ground state satisfies an anomalously high fraction of constraints compared to truly random problems. We show that, if we define the energy to be E=Nunsat−Nsat, then spectrally folded quantum optimization will return states with energy E≤AEGS (where EGS is the ground state energy) in polynomial time, where conservatively, A≃0.6. We thoroughly benchmark variations of spectrally folded quantum optimization for random classically approximation-hard (planted solution) instances in simulation, and find performance consistent with this prediction. We do not claim that this approximation guarantee holds for all possible hypergraphs, though our algorithm's mechanism can likely generalize widely. These results suggest that quantum computers are more powerful for approximate optimization than had been previously assumed.


April 18, 2024 Thursday 1:45 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

Informal HEP Talk
Thomas Faulkner
UIUC

Quantum Error Correction at large N for von Neumann algebras and quantum gravity

I will discuss a new framework for constructing quantum error correcting codes out of large N limits. The code subspace can accommodate quantum field theory with an associated local algebraic description. Using several examples I will demonstrate that these codes give a natural framework for studying the emergence of spacetime and locality in AdS/CFT.


April 18, 2024 Thursday 4:00 PM  +
Hybrid: 726 Broadway, 940 and Zoom
Physics Colloquia (colloquia)


John Eiler
Caltech

Body Temperatures of Dinosaurs

The study of life’s origin, evolution and distribution in the universe involves many questions that seem unsolvable on first inspection; a familiar example concerns the body temperatures of the dinosaurs: Should we look at their fossilized skeletons and imagine vigorous, warm-blooded, bird-like animals, or plodding, sedentary reptiles like modern alligators? This question has often been approached through qualitative arguments based on phylogeny, histology, ecology and other loose correlatives with metabolism — disappointing if you want the kind of direct and quantitative data a veterinarian might gather with a well-aimed thermometer.
Recent advances in studies of the chemical physics of isotopes has provided surprisingly nuanced and precise answers to this question. Well-preserved tooth enamel and egg shells of dinosaurs and other ancient vertebrates contain carbonate groups (CO3-2) that were drawn from their host’s blood stream and represent fossil remnants of their metabolic chemistry. The heavy rare isotopes, 13C and 18O, are present as trace substitutions in these carbonate groups, in amounts that reflect a variety of factors, such as diet and local climate. But the state of organization of those rare isotopes — their propensity to ‘stick’ to one another with a shared chemical bond as opposed to being randomly scattered across a population of molecules — is controlled by the temperature dependent changes in vibrational energy caused by isotopic substitution. I will present the latest discoveries revealed by exceptionally sensitive and precise measurements of isotopic ordering in fossils of ancient vertebrates, revealing their body temperatures and informing inferences regarding their metabolism, physiology, lifestyle and ecology.


April 19, 2024 Friday 11:00 AM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

Informal HEP Talk
Edward Mazenc
ETH Zurich

Strings From Feynman Diagrams

How are bulk strings related to boundary Feynman diagrams? I will give an overview of my work with Rajesh Gopakumar on deriving the closed string dual to the simplest possible gauge theory, a Hermitian matrix integral. Working in the conventional ‘t Hooft limit, we extract topological string theories which replace the minimal string away from the double-scaling limit. We show how to exactly reconstruct both the closed string worldsheet and its embedding into the emergent target space, purely from the matrix Feynman diagrams. Along the way, we will encounter the notion of open-closed-open triality which allows us to establish this dictionary, and predicts multiple open string descriptions of the same bulk physics. I’ll close by embedding our results in the broader context of AdS/CFT.


April 19, 2024 Friday 3:30 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

Special Seminar
John Eiler
Caltech

The new science of life's origins and distribution in the universe

The study of the origins of life and its possible existence beyond the earth has long lived in the liminal space between science, quasi-scientific speculation, and nonsense. Nevertheless, the questions that motivate this field are among the greatest unanswered problems in the natural sciences and human thought more broadly. The modern era of this subject began in the 1990’s with a wave of top-down funding agency investments and several highly visible and equally ludicrous false starts. But recently this subject has transformed its scope, methods and opportunities, and has radically expanded and re-organized its connections to more established, rigorous fields, including astronomy, synthetic chemistry, geology, geochemistry, and the biological ‘omics’ disciplines. The last decade has seen dramatic progress on several interconnected fronts, yet the field remains ravenous for its first truly transformative discovery. The central questions remain: What will constitute definitive evidence of life’s origins on earth and existence in the wider universe; and, how should we best seek that evidence?


April 22, 2024 Monday 12:30 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

CCPP Brown Bag
David Hogg
New York University

Applied special relativity: Velocities of stars measured at the cm/s level

Planets are being discovered and measured using radial-velocity (Doppler shift) measurements. Current precision, even for the best spectrographs, is currently limited at 1 m/s, in part because it is non-trivial to even *define* a Doppler shift at better precision. We (Megan Bedell, Lily Zhao, DWH, and others) have new ideas for improving precisions by a factor of 10 or 30. The discovery and measurement of true Earth analogs require a factor of 10 at least.


April 22, 2024 Monday 3:30 PM  +
Hybrid: 726 Broadway, 871 and Zoom
Soft Condensed Matter Seminars (csmr)


CSMR Monday Morning Seminar

Shivang Rawat and Matt Gronert Presenting
https://nyu.zoom.us/j/96532204069



April 23, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Alicia Kollar
University of Maryland

"Quantum Simulation with Coplanar-Waveguide Lattices"

Lattices of coplanar waveguide (CPW) resonators realize artificial photonic materials in the tight-binding limit [1] capable of realizing non-Euclidean geometries [2] and unconventional unit cells [3]. Combined with strong qubit-photon interactions, these systems can be used to study dynamical phase transitions, many-body phenomena, and spin models in driven-dissipative systems. These lattices permit the creation of unique devices which host photons in curved spaces, gapped flat bands, and novel forms of qubit-qubit interaction. Here I will present measurements from a next-generation CPW lattice device featuring multiple transmon qubits coupled to a quasi-1D lattice which features not only conventional quadratic band edges, but also flat and linearly-dispersing bands. I will show that presence of the transmon qubits allows enhanced characterization of the distribution of lattice modes and observation of interacting photon effects in the flat bands of the lattice. Alternatively, the lattice modes endow the qubits with an extended interaction, which has different spatial profiles depending on the type of band mediating the interaction. Flux tunability of the qubits allows them to be brought into proximity with all of the different types of bands present in the device.
[1] D. Underwood et al., Phys. Rev. A 86, 023837 (2012)
[2] A. J. Koll ́ar et al., Nature 571, 45 (2019)
[3] A. J. Koll ́ar et al., Comm. Math. Phys. 376,1909 (2019)


April 23, 2024 Tuesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
Astrophysics and Relativity Seminars (astro)


Nikhil Padmanabhan
Yale

Mapping the Expansion History with DESI Y1 data

I will present the recently released distance measurements from the first year of DESI data using the baryon acoustic oscillation technique. I will review the improvements made in this analysis, highlight our blinded analysis and will emphasize the robustness of the BAO technique. I will then explore the cosmological implications of these results, including a tantalizing hint of time variations in dark energy.


April 24, 2024 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


T Daniel Brennan
UCSD



April 25, 2024 Thursday 1:00 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

Oral Defense
Nick Faucher

TBA



April 25, 2024 Thursday 4:00 PM  +
Hybrid: 726 Broadway, 940 and Zoom
Physics Colloquia (colloquia)


David Awschalom
University of Chicago

The Quantum Revolution: Emerging Technologies at the Atomic Scale

Traditional electronics are rapidly approaching the length scale of atoms and molecules. In this regime, a single atom out of place can have outsized negative consequences and so scaling down classical technologies requires ever-more perfect control of materials. Surprisingly, one of the most promising pathways out of this conundrum may emerge from current efforts to embrace these atomic ‘defects’ to construct devices that enable new information processing, communication, and sensing technologies based on the quantum nature of electrons and atomic nuclei. In addition to their charge, individual defects in semiconductors and molecules possess an electronic spin state that can be employed as a quantum bit. These qubits can be manipulated and read using a simple combination of light and microwaves with a built-in optical interface and retain their quantum properties over millisecond to second timescales. With these foundations in hand, we discuss emerging opportunities and the importance of collaborating with industry to atomically-engineer qubits for nuclear memories, entangled registers, sensors and networks for science and technology.
Note: this talk will not be taped nor put on YouTube


April 29, 2024 Monday 10:00 AM  +
726 Broadway, Room 1067
Center for Quantum Information Physics Seminars (cqip)


Berk Diler Kovos
Quantum Machines

Unlocking the potential of quantum-classical processing.

In recent years, it has become increasingly clear that realizing the potential of quantum technologies require tight quantum-classical integration to overcome shortcomings of quantum systems. We will start by explaining the framework, benchmark, and metrics we, as Quantum Machines, think about regarding quantum-classical integration. We then will provide some examples from various qubit platforms on sensing, communication, and computation on the benefits of such a tight quantum-classical integration, enabled by Quantum Machines. We will then conclude with discussing the newest developments at Quantum Machines, including the OPX1000 platform, Photonic Control Unit built in collaboration with QuEra Computing and DGX-Quantum built in collaboration with Nvidia. The attendees will hear about the state-of-the-art developments in quantum technologies and will learn how Quantum Machines is powering this acceleration.


April 29, 2024 Monday 12:30 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

CCPP Brown Bag
Giovanni Verza
New York University

The universal multiplicity function: counting halos and voids



April 30, 2024 Tuesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
Astrophysics and Relativity Seminars (astro)


Anna Suliga
U. C. Berkeley

Core-collapse supernovae as probes of (not only) non-standard neutrino physics

Core-collapse supernovae are one of the most complex phenomena in the Universe. Not only are they one of the production sites of the heavy elements that enable the existence of life, but their cores are also one of the densest environments we can probe, albeit indirectly. Core-collapse supernovae are also among the most spectacular and efficient neutrino factories. Detecting these neutrinos can allow us to probe physics in extreme conditions inaccessible on Earth. In this talk, I will discuss how we can prepare for the next nearby supernova neutrino detection to extract as much information as possible from the neutrino signal. I will also talk about how observing neutrinos from all the past collapses in our Universe – the diffuse supernova neutrino background - can help us better understand the supernova population and may provide hints about physics beyond the Standard Model.


April 30, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Taketo Handa
Columbia University

Excitons or not Excitons in Transition Metal Dichalcogenides Monolayers

Two-dimensional (2D) semiconductors, especially transition metal dichalcogenides (TMDCs), and their van der Waals interfaces can host intriguing properties including rich quantum phases. Since the seminal work on MoS2 monolayers, photoexcitation in atomically-thin TMDCs has been considered to result in excitons due to their large binding energies (~200 to 500 meV). Because the exciton binding energies are an order-of-magnitude larger than thermal energy at room temperature, it is also puzzling that efficient photocurrent and photovoltage generation have been observed in TMDC-based devices. In this talk, I will discuss our recent results on time-resolved far-field THz spectroscopy on large-area, single-crystal WS2, WSe2, and MoSe2 monolayers. In contrast to conventional belief of the dominance of charge-neutral excitons, we find that ~10% of excitons can spontaneously dissociate into charge carriers with lifetimes exceeding 0.2 ns. Scanning tunneling microscopy reveals that free photo-carrier generation is intimately related to mid-gap defect states. Only in state-of-the-art quality monolayers with record low defect density does intrinsic exciton physics dominate the THz response. Our results clarify the fate of excitons in TMDCs depending on the defect density, whose role is amplified by the Coulomb interaction inherent to their 2D nature.


May 1, 2024 Wednesday 12:30 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

ArXiv Discussion
HEP/Pheno Journal Club



May 1, 2024 Wednesday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
High Energy Physics Seminars (hep)


Michael Toomey
MIT

TBA

TBA


May 2, 2024 Thursday 2:00 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

Oral Defense
Conghuan Luo

TBA



May 2, 2024 Thursday 4:00 PM  +
Hybrid: 726 Broadway, 940 and Zoom
Physics Colloquia (colloquia)


Kathleen Stebe
University of Pennsylvania

Defect Propelled Swimming of Nematic Colloids

Nematic liquid crystals (NLCs) are highly non-linear fluids that have elastic responses that resist nematogen rearrangement and high-energy defect sites at which nematogen order is lost. Generally, the field of nematic colloids seeks to develop control over these elastic responses and defect structures to tailor colloidal interactions. We have been studying ferromagnetic disk colloids rotated by an in-plane magnetic field in nematic liquid crystals. The disk diameter and rotation rate are sufficiently slow that colloid inertia is negligible. In Newtonian fluids, these colloids rotate without translation. However, in NLC, the colloids’ anisotropic defect structure and the NLC’s elastic response generate broken symmetries that propel colloid translation. For patchy, rough colloids, a defect loop which forms on the disk undergoes periodic defect pinning, release, and contraction. This periodic defect motion generates a swim stroke that powers colloidal swimming. Changes in defect configuration with rotation rate provide a steering mechanism. In addition to this swimming motion, colloid shape and surface chemistry generate long-ranged emergent interactions with neighboring passive colloids in quasi-static settings. Furthermore, the non-linear response of the nematic fluid host allows pair interactions among rotating disks that differ strikingly in range and form from their static counterparts. These interactions provide a rich toolkit for reconfigurable materials assembly and open important fundamental questions regarding swimming at low Reynolds number in NLC.


May 6, 2024 Monday 12:30 PM  +
726 Broadway, 940, CCPP Seminar
Other Center for Cosmology and Particle Physics Events (ccpp)

CCPP Brown Bag
Jiarong Zhu and Connor Hainje
New York University

Adventures in Dark Matter-Baryon Interactions



May 7, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Tian-Xing Zheng
University of Chicago

Towards Entanglement-Enhanced Sensing in Dipolar-Interacting Spin Systems

Spin systems are an attractive candidate for quantum-enhanced metrology. In this presentation, I will introduce a variational method to generate metrological states in small dipolar-interacting spin ensembles with limited qubit control, as present in nanoscale quantum sensing applications. The simulation results show that for both regular and disordered spatial spin configurations the generated states enable sensing beyond the standard quantum limit (SQL) and, for small spin numbers, approach the Heisenberg limit (HL). Depending on the circuit depth and the level of readout noise, the resulting states resemble Greenberger-Horne-Zeilinger (GHZ) states or Spin Squeezed States (SSS). Sensing beyond the SQL holds in the presence of finite spin initialization and a non-Markovian noise environment. Potential experimental platforms include dipolar-interacting ensembles of NV centers, nitrogen defects in diamond (P1), rare-earth-doped crystals, and ultra-cold molecules. I will also discuss our recent experimental progress towards realizing the entanglement-enhanced sensing on a millikelvin confocal microscope platform.


May 14, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Albert Liu
Brookhaven National Lab

2-D Terahertz Spectroscopy of Cuprate Superconductors

Quantum materials, systems in which quantum effects lead to unique macroscopic phenomena with tremendous technological potential, comprise the forefront of condensed matter physics research. In particular, collective excitations associated with broken-symmetry phases have attracted tremendous attention as powerful windows into their microscopic physics and dynamics. However, spectroscopy of these collective excitations has been hindered by the so-called ‘terahertz gap’, which refers to difficulties in generation and detection of radiation in the terahertz frequency range, where many relevant modes of quantum materials are found.

In response to this challenge, we translate a technique known as 2-D spectroscopy, an optical analogue of multi-dimensional NMR spectroscopy, into the terahertz frequency range. We implement, for the first time to our knowledge, 2-D Terahertz Spectroscopy in a non-collinear, reflection geometry, enabling study of opaque materials and isolation of their constituent terahertz nonlinearities. We apply this technique to the Josephson plasma resonance in La2-xSrxCuO4, a layered high-temperature superconductor, to distill the underlying plasmon correlations and reveal a disordered superconducting state [1]. Measurements of the superconducting transition then reveal evidence of finite-momentum superconducting fluctuations that we directly probe with our technique [2]. I will conclude with an outlook for light-induced phase transitions.

[1] A. Liu et al., arXiV:2308.14849
[2] A. G. Salvador et al., arXiV:2401.05503


May 16, 2024 Thursday 11:00 AM  +
726 Broadway, Room 1067
Center for Quantum Information Physics Seminars (cqip)


Shashank Misra
Sandia National Laboratories

TBA



May 16, 2024 Thursday 2:00 PM  +
726 Broadway, Room 1067
Center for Quantum Information Physics Seminars (cqip)


Joel IJ Wang
Massachusetts Institute of Technology

TBA



May 17, 2024 Friday 10:00 AM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Shashank Misra
Sandia National Laboratories

TBA



May 23, 2024 Thursday 11:00 AM  +
726 Broadway, Room 1067
Center for Quantum Information Physics Seminars (cqip)


Jia Leo Li
Brown University

TBA



September 17, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Jeremy Johnson
Brigham Young University

TBA



October 15, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Kenneth Burch
Boston College

TBA



October 22, 2024 Tuesday 2:00 PM  +
726 Broadway, 1067, CQP Seminar
Center for Quantum Phenomena Seminars (cqp)


Richard Averitt
UC San Diego

TBA