The maximum refractive index of optical materials: from quantum optics to quantum chemistry
Abstract: It is interesting to observe that all known optical materials have a refractive index that is of order unity at visible/telecom wavelengths. However, it is not easy to reconcile this with the fact that the individual atoms making up the material are well-known to have a huge optical response near resonance, when isolated, as characterized by a scattering cross section that is much larger than the physical size of the atom.
Broadband spin-wave quantum memories in cold and ultracold atomic systems
Abstract: Quantum memories using cold and ultracold atoms are a promising platform for storing and manipulating photonic signals, and will be a key component in quantum communications systems, especially in realizing critical quantum repeater infrastructure. Cold atoms have significant potential as high performance spin-wave quantum memories, due to the long storage times associated with low temperature and slow thermal diffusion. Broadband, low-noise performance in such memories is also required, but these two principles are often at odds with each other.
Replica symmetry breaking in a cavity QED spin glass
Abstract: Spin glasses are canonical examples of complex matter. Although much about their structure remains uncertain, they inform the description of a wide array of complex phenomena, ranging from magnetic ordering in metals with impurities to aspects of evolution, protein folding, climate models, and artificial intelligence, where spin glass theory forms a mathematical basis for neuromorphic computing.
Quantum in the Army and Rydberg Receivers
Abstract: Why does the Army care about quantum mechanics? In this JQI Seminar, Dr. Kevin Cox will discuss what it's like to be a physicist at the Army Research Laboratory and talk about how his group is using Rydberg atoms to create radio-frequency receivers that can sense the entire spectrum.
*You will need to bring your cell phone, so you can sign in. For Zoom, please submit a chat saying hello with your first and last name, so you can receive lunch. Lunch will be served after the seminar only to the individuals that have attended.*
Novel Quantum Speed Limits Tackle Messy Reality of Disorder
Researchers studying quantum technologies are exploring uncharted territory. Sometimes, theorists can streamline progress by spotting roadblocks in the distance or identifying the rules of the road. For instance, researchers have found several quantum speed limits and developed protocols for quantum computers that achieve the best possible speeds for specific cases. To make calculating the limits easier, physicists have mostly neglected the influence of disorder. Now, JQI researchers are facing down the impact disorder has on speed limits.
Qubit-Oscillator Concatenated Codes: Decoding Formalism and Code Comparison
Concatenating bosonic error-correcting codes with qubit codes can substantially boost the error-correcting power of the original qubit codes. It is not clear how to concatenate optimally, given that there are several bosonic codes and concatenation schemes to choose from, including the recently discovered Gottesman-Kitaev-Preskill (GKP) – stabilizer codes [Phys. Rev. Lett. 125, 080503 (2020)] that allow protection of a logical bosonic mode from fluctuations of the conjugate variables of the mode.
Analysis of SoS Relaxations for the Quantum Rotor Model
The noncommutative sum-of-squares (ncSoS) hierarchy was introduced by Navascues--Pironio--Acin as a sequence of semidefinite programming relaxations for approximating values of "noncommutative polynomial optimization problems," which were originally intended to generalize quantum values of nonlocal games. Recent work has started to analyze the hierarchy for approximating ground energies of local Hamiltonians, initially through rounding algorithms which output product states for degree-2 ncSoS.
Putting On a Particle Play
Back in the 1950s, theoretical physicists postulated that the kinds of particles we actually see in nature are just the tip of the iceberg. Many other types of particles with weird properties, which they termed paraparticles, were popping out of the math as theoretical possibilities. But as physicists discovered more about the fundamental particles seen in nature, they found no evidence for paraparticles.
In 2016 Cinthia Alderete, then a graduate student in theoretical physics, discovered a way to simulate paraparticles in which ions and light come together to put on a paraparticle play. To direct this dramatic reenactment, Alderete made the switch from theory to experiment and moved from Mexico to the United States, collaborating with the group of Norbert Linke, a member of the NSF Quantum Leap Challenge Institute for Robust Quantum Simulation and a former Fellow of the Joint Quantum Institute. Together, they brought to life an obscure theoretical curiosity from the past.
Full counting statistics as a probe of chaotic and integrable dynamics
Abstract: Experiments with ultracold gases and digital quantum simulators can take simultaneous snapshots of all the particles in a system. Unlike conventional response experiments, these snapshots encode arbitrarily high-order correlation functions. It is natural to ask what new information these high-order correlations contain. I will present solvable models, as well as experimental data, showing how these new probes can elucidate (and disprove) certain proposed mechanisms for many-body dynamics.
It ain’t just a detector: A new class of optical sensors based on Optoelectronic Chromatic Dispersion in photodiodes
Abstract: Light is essential for life as we know it, and the ubiquitous PN-junction is the pervasive light sensor, whether for optical detection or for energy harvesting. Since its inception over 70 years ago, the physics behind the photodiode is now well understood, including its dependence on the illumination wavelength. However, there is a further prominent feature of photodiodes that has been largely overlooked. These devices can exhibit significant and tunable chromatic dispersion, which we call Optoelectronic Chromatic Dispersion (OED).