Please join us on Wednesday, February 1, 2016, as Stefan Ballmer of Syracuse University gives his talk:
"Gravitational-Wave Astronomy in the Next Decades"
One year ago the Advanced LIGO detectors provided the first observation of gravitational waves from merging black holes. They just started to observe again last December. I will discuss what we learned from the initial discovery, and where the detector sensitivity stands for the current observation run. Then I will look into the future, describing the technology we need for the next sensitivity upgrades and future gravitational-wave observatories. Such observatories will enable us to observe compact binary mergers from an era when the first stars just started to formed, allowing us a completely new perspective at the history of star formation.
Recent years have witnessed the surprising emergence of solid state mechanical resonators as practical subjects for quantum measurement and control. Many of the enabling advances came in the field of optomechanics, where techniques have been developed to strongly couple nanomechanical resonators to electromagnetic cavities. Landmark demonstrations include observation of quantum measurement back-action (radiation pressure shot noise), cooling of a nanomechanical resonator mode to its ground state, and ponderomotive squeezing of light. I'll take up this story in our lab at EPFL, where we've been exploring nano-optomechanics as a platform for measurement-based quantum control. Using a microcavity-based interferometer, we've recently been able to resolve the vibration of a glass nanostring with an imprecision 46 dB smaller than its zero-point fluctuations and an imprecision-back-action product 5 times the uncertainty limit. This highly effcient measurementallows us to actively cool the string mode from 4 K to near its ground state, in the process canceling ~1000 back-action quanta - a rudimentary example of `quantum feedback'. I'll discuss how non-classical correlations in the light field emitted from the cavity can be used to absolutely calibrate the string's phonon occupancy, and how we've used the same correlations - manifesting as squeezed light - to realize a quantum-enhanced force sensor. I'll also describe our effort to develop a new class of ultra-coherent nanomechanical resonators based on micro-patterned thin films. These devices may enable optomechanics experiments deep in the quantum regime, even at room temperature.
An overview will be given of recently discovered connection between asymptotic symmetries in general relativity and soft theorems in quantum field theory together with their implications for the black hole information paradox.
The detection of high energy extra-terrestrial neutrinos by IceCube opens a new window for observations of the Universe. I will discuss the origin of these neutrinos, the clues that their detection provide towards the solution of the long standing question of the origin of cosmic-rays, and the prospects for identifying the cosmic-ray sources and for studying open questions in astro- and particle- physics using combined electromagnetic and neutrino observations.
About the speaker
Professor Eli Waxman earned his Ph.D. in Physics in 1994 from The Hebrew University of Jerusalem and is currently a Professor at The Weizmann Institute of Science in Rehovot, Israel.
Eli’s research involves various topics in Theoretical Astrophysics, with a focus on High-Energy and Particle Astrophysics. A significant fraction of his time is devoted to leading the Israeli side of the Israeli/US UV satellite mission ULTRASAT, which is aiming at revolutionizing the study of astronomical transients.
For information on the WIS Astrophysics group and on its activity, check the astro web-page.
Trapped atomic ions are a versatile platform with pristine qubits and excellent control, which enables many quantum engineering tasks involving interacting spin and bosonic Hamiltonians. Entangling gates are generated with laser-induced optical dipole potentials and Coulomb mediated couplings, which can be used for applications ranging from quantum metrology to quantum simulations of condensed matter systems. Here we realize a long-range antiferromagnetic Ising Hamiltonian, with individually controlled transverse fields. Such a controlled quantum system exhibits extremely rich phenomena, including frustrated ground states in equilibrium; as well as excited state dynamics probed by many-body spectroscopy.
Extending to out-of-equilibrium scenarios the physics is even richer, signatured by the existence of dynamical phases such as Prethermalization and many-body localization (MBL). In this talk I will focus on these highly non-equilibrium quantum dynamics, centered on Discrete Time-crystals (DTC): the spontaneous time-translation symmetry breaking in a Floquet (periodically driven) system. Experimental observations of a DTC open the door for studies of novel driven phases of quantum matter such as Floquet topological structures. I will also discuss the unique insights provided by long-range interactions, which brings interesting physics down to one dimension. This will be illustrated with the observation of dynamical phase transitions that only exist in the presence of long-range forces. I will conclude with an outlook on how to apply quantum information techniques to precisely tailor open quantum systems.
I will describe two experimental platforms --- optical tweezer trapping of single atoms and quantum gas microscopy --- and how we have used them to realize experiments with low-entropy systems of neutral atoms. While these platforms share a common goal of creating and microscopically manipulating quantum states of neutral atoms, they employ opposite strategies. The optical tweezer approach aims to assemble quantum systems from single atoms in a bottom-up fashion; quantum gas microscopes employ a top-down strategy, where smaller many-body systems are distilled from larger samples. In describing these ideas, I will focus on two experiments we performed that utilize the capabilities of these platforms. In one experiment with optical tweezers, we realized atomic Hong-Ou-Mandel interference with independently prepared atoms. In a second experiment with a quantum gas microscope, we performed studies of quantum thermalization, which leverage this atomic Hong-Ou-Mandel interference to probe the role of entanglement in thermalization of closed systems. Lastly, I will discuss future avenues that draw on the capabilities of these platforms and build on these experimental studies.
Fundamentally, nuclear physics arises from the Standard Model, however calculation of even the simplest properties of nuclei from this underlying theory is an extremely challenging task. With advances in high performance computing this situation is changing; and the numerical techniques of lattice Quantum Chromodynamics (LQCD), applied successfully in particle physics, is now allowing us to study the intricate dynamics of light nuclei from first principles. In this talk, I will discuss recent progress in LQCD calculations of the electroweak interactions and structure of nuclei, including the determination of the pp fusion cross-section and the second-order weak transition nn --> pp relevant for double beta decay.
How can you learn about the early moments of the universe? How can you discover evidence for new sub-atomic particles? We usually think of ever-more exotic telescopes, or of ever-larger particle accelerators. I will talk about the third leg of the stool: precision measurement. We will see that the humble two-atom molecule should be thought of as an ultrahigh electric-field laboratory.
About the speaker
Dr. Eric Cornell is a Professor Adjoint at the University of Colorado Boulder and Nobel Laureate. He received his PhD. in Physics from the Massachusetts Institute of Technology in 1990. He was named a fellow at the Joint Institute for Laboratory Astrophysics (JILA) in 1995. JILA is a joint physics institute of the University of Colorado at Boulder and the National Institute of Standards and Technology (NIST). They support an eclectic and innovative research program that fosters creative collaborations among their scientists. He received the Nobel Prize in 2001 for the creation of the first atomic Bose-Einstein condensate.
Dr.Cornell is interested in precision measurements and Bose-Einstein condensation and related topics in ultracold atoms. His experiments are in Bose-Einstein condensation and related topics in ultracold atoms. More recently, he has been involved with an experiment to put an improved limit on the electron electric dipole moment. He has also started a project to develop technology for extracting electricity from waste heat.
Light-matter interactions lie at the heart of a very broad range of fundamental physics and applications. At a single particle level, such interactions enable all-optical quantum control of qubits which is of great interest for quantum information. At a more macroscopic level, strong light-matter interactions are a key to collective phenomena such as condensation of exciton-polaritons in microcavities. In this talk I will present my previous and current research which is unified under the broad field of light-matter interactions in semiconductors. In particular, I will briefly introduce polariton condensates along with the typical experimental methods used for their study and will cover a few exciting experiments ranging from the observation of pinned singly-charged vortices to the demonstration of a polaritonic Josephson junction. Moving from such collective quasi-particle phenomena to the investigation of more discreet quantum emitter systems, I will then address experimental efforts on the coherent control of scalable quantum emitter platforms. More specifically, I will present recent work on site-controlled quantum dots and silicon vacancies in diamond, and will conclude with an overview of my vision for future research.
In recent years, there has been a surge of activities in proposing exactly solvable quantum spin chains with the surprisingly high amount of ground state entanglement entropies--beyond what one expects from critical systems described by conformal field theories (i.e., super-logarithmic violations of the area law). We will introduce entanglement and discuss these models. We prove that the ground state entanglement entropy is \sqrt(n) and in some cases even extensive (i.e., ~n). These models have rich connections with combinatorics, random walks, and universality of Brownian excursions. Lastly, we develop techniques that enable proving the gap of these models. As a consequence, the gap scaling rules out the possibility of these models having a relativistic conformal field theory description.
Movassagh, Farhi, Goldstone, Nagaj, Osborne, Shor, PRA (2010)
Bravyi, Caha, Movassagh, Nagaj and Shor, PRL (2012)
Movassagh and Shor, PNAS, doi:10.1073/pnas.1605716113 (2016)
The discovery of coalescing binary black holes by Advanced LIGO heralds the birth of a new field of research: gravitational wave (GW) astronomy. Coalescing neutron star (NS) binaries are among the new GW sources expected over the next few years. Maximizing the knowledge gained from this discovery will require identifying a coincident electromagnetic counterpart. One promising counterpart is an optical/IR flare, powered by the radioactive decay of neutron-rich elements synthesized in the merger ejecta (a so-called `kilonova'). Beyond providing a beacon to the GW chirp, kilonovae probe one of the dominant astrophysics sites for creating the heaviest elements in the Universe via rapid neutron capture (r-process) nucleosynthesis. I will describe how the lifetime of the hypermassive NS created during a NS-NS merger impacts the light curves and color of kilonovae. The decay of free neutrons in the fastest outermost layers of the ejecta may power a bright 'precursor' to the main kilonova, enhancing its prospects for detection. A small fraction of short gamma-ray bursts are accompanied by long-lived X-ray emission, which may suggest that some mergers result in the formation of long-lived - or even indefinitely stable - NS remnants. If this association is confirmed, this would place stringent constraints on the equation of state of nuclear density matter.
About the speaker
Dr. Brian Metzger is a theoretical astrophysicist and an Assistant Professor in the Department of Physics at Columbia University. He received his Ph.D. from the University of California Berkeley in 2009. His main interests are topics in high energy astrophysics and time domain astronomy, including supernovae, gamma-ray bursts, accretion disks, compact objects, electromagnetic counterparts to gravitational wave sources, and nucleosynthesis (astrophysical origin of the elements).
Dr. Metzger is interested in a broad range of topics in theoretical astrophysics, with a focus on high energy and stellar astrophysics. A unifying theme of his current research is a connection to transient (or 'time domain') phenomenon. This is motivated by many sensitive, wide-field telescopes coming online in the next decade across the electromagnetic spectrum. He is also excited by the scientific potential of the upcoming generation of gravitational wave interferometers, such as Advanced LIGO, and the promise for a future era of "gravitational wave astronomy".
Bouncing cosmologies propose that the structure of our observable universe is generated during a period of contraction that precedes the current expanding phase. In this talk, I will review no-go theorems that were thought to be major roadblocks for bouncing cosmologies to explain the large-scale structure of the universe and show how to evade them.
Many of the most unusual - and useful – materials properties arise from the spin and charge dynamics of the electrons moving through the solid. Thus, understanding these dynamics is of fundamental importance. The technique of inelastic x-ray scattering provides one of the very few experimental measurements of these dynamics in regimes that are relevant to some of the most important problems today. In this talk, I discuss the technique and the advances made in recent years, illustrating the synergy between work at synchrotrons and Free Electron Lasers (FELs) in this area. I will present very recent time-resolved inelastic x-ray scattering results that show how magnetic systems evolve following an ultrafast injection of energy. Such experiments may ultimately lead to ultrafast photo-control of the materials properties themselves. I conclude with a brief discussion of the next generation facilities that will be coming online in the next few years at both synchrotrons and FELS.
About the speaker
Dr. John Hill serves as the Director of the National Synchrotron Light Source II and as the Deputy Associate Laboratory Director for Energy Sciences. He is responsible for all aspects of Facility operations for NSLS-II. He assists in strategic issues for the Energy Sciences Directorate with particular focus on synergies with the NSLS-II.
Dr. Hill obtained a Bachelor of Science degree in Physics in 1986 from Imperial College. He then earned a Ph.D. in Physics from the Massachusetts Institute of Technology (MIT) in 1992. He then joined Brookhaven Lab’s Physics Department as a postdoc. He was promoted through the ranks, received tenure in 1999, and was appointed group leader of the X-ray Scattering Group in 2001. Dr. Hill was awarded the Presidential Early Career Award and the DOE Young Independent Scientist Award in 1996, was elected a fellow of the APS in 2002, and received a Brookhaven Science and Technology Award in 2012.
Dr. Hill has focused on using resonant elastic scattering to study magnetic and electronic order in a range of materials. More recently, he has extended these studies by pioneering the use of inelastic x-ray scattering techniques to study electron dynamics in similar systems. His research is presently focused on understanding the novel electronic ground states and excitations in strongly correlated electron systems.