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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 will bring in experts from across the country as well as across campus to discuss the latest in research advances in quantum science.

Seminars in Fall 2020 will be conducted over Zoom and will usually be held on Tuesdays from 1:15-2:15pm. or Fridays from 12:00-1:00pm, depending upon speaker availability.  If you wish to attend a seminar and are not on our mailing list, please contact either Kieran Mullen (kieran@ou.edu)  or Doerte Blume (Doerte.Blume-1@ou.edu) to obtain a link.

Fall 2019

Mid-IR to Thz nanophotonics: materials-based approaches to quantum photonics
Joshua Caldwell, Vanderbilt University

Friday, August 23, 2019
11:30am-12:30pm
Lin Hall, 105

The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. Up until recently, research in this field has been primarily focused on the use of plasmonic metals. However, the high optical losses inherent in such metal-based materials has led to an ever-expanding effort to identify, low-loss alternative materials capable of supporting sub-diffractional confinement. One highly promising alternative is to implement polar dielectric crystals, whereby sub-diffraction confinement of light can be achieved through the stimulation of surface phonon polaritons within an all-dielectric, and thus low loss material system. Due to the wide array of high quality crystalline species and varied crystal structures, a wealth of unanticipated optical properties have recently been reported. Specifically, the recent demonstration of hyperbolic behavior within natural polar crystals provides exciting opportunities in on-chip, sub-diffractional refractive optics and a dramatically expanded density of states that can provide avenues for strong light matter interactions and control of emission rates. This talk will discuss recent advancements from our group including the realization of localized phonon polariton modes, the observation and exploitation of the natural hyperbolic behaviors in strongly anisotropic crystals, the detection of dark hyperbolic modes and polaritonic ultrastrong coupling phenomena.

Infrared Optical Circuitry for Quantum Technologies
 Joseph Tischler, Naval Research Lab

Wednesday, September 11, 2019
1:15-2:15pm
Lin Hall, 105

Analogously to plasmon polaritons, phonon polaritons in ionic crystals provide unparalleled optical confinement and therefore high local field intensity. Because phonon lifetimes are several orders of magnitude longer than lifetimes of photoexcited free carriers in metals, phonon polariton losses are significantly smaller resulting in sharp resonances that allow observation of physical effects otherwise obscured by the lack of spectral resolution. Also, the symmetry of the ionic crystal allows the observation of surface phonon polaritons and volume phonon polaritons. While isotropic crystals result in purely metallic spectral bands and therefore surface phonon polaritons, anisotropic crystal can generate hyperbolic spectral bands and therefore volume phonon polaritons. In this work we present new physics of nanostructured ionic crystals that illustrate our current understanding of both volume and surface phonon polaritons. Furthermore, I will show some of our most recent work and ideas towards the exploitation of surface phonon polaritons to create optical circuitry based on collective behavior of surface phonon polariton molecules and/or solids.

Cool quantum optics with hot atoms
Irina Novikova, College of William and Mary 

Friday, September 20, 2019
11:30am-12:30pm
Lin Hall, 105

Efficient and reliable quantum communication will require the control of the quantum state of both photons and atoms. In this talk I will discuss a possible realization of strong coupling between quantum optical field and collective spin excitation in atomic vapor via electromagnetically induced transparency, as well as possible applications of the effect for precision metrology, generation of non-classical light and quantum imaging.

Towards the production and braiding of anyons with Rydberg Atoms in Optical Cavities
Eric Mueller, Cornell University 

Tuesday, September 24, 2019
1:15pm-2:15pm
Lin Hall, 105

Researchers are trying to find ways of engineering states of matter with interesting (and hopefully useful) entanglement properties.  I will discuss ways in which atoms in optical cavities can be used to achieve this goal.  In particular, after describing the big-picture, and giving some background information about the properties of atoms and optical cavities, I will present a situation where we predict that light will behave like a highly unusual quantum fluid, similar to the one formed by electrons in the fractional quantum Hall effect.  This fluid has excitations which act like particles which are neither bosons nor fermions.  I will explain how these anyonic statistics can be directly probed in an experiment.

Excitations and dynamics in inversion symmetry-broken phases
Jonathan Spanier, Drexel University

Friday, September 27, 2019
11:30am-12:30pm
Lin Hall, 105

Emergent phenomena in solids, whether they involve lattice, charge, spin, orbital, or other degrees of freedom, are attractive for creating, stabilizing and/or controlling novel states of matter.  New paradigms based on these phenomena are attractive candidates for capturing, converting, and carrying energy more efficiently.  I will discuss two intriguing electromagnetic wave-matter interaction phenomena that can emerge in non-centrosymmetric solids. The first involves visible-light generation of two types of photovoltaic currents, one of which transforms, remarkably, a band insulator into a high-mobility conductor.  In the second, we reimagine the energy landscape associated with a two-dimensional crystal defect that has traditionally been viewed as an impediment to the flow of radio-frequency microwave energy.  Under special conditions a resonant behavior emerges, enabling the material to exhibit dielectric properties that can exceed intrinsic limits.

Physics of the hybrid perovskite semiconductors
Alexander Zhakhidov, Texas University San Marcos

Friday, October 04, 2019
11:30am-12:30pm
Lin Hall, 105

Organic lead halide hybrid perovskites (HPs) is a novel promising class of materials for the low-cost printed solar cells (record power conversion efficiency - 23.7%), photodetectors, LEDs, sensors and other optoelectronic devices. Yet, the nature of light-matter interaction in HPs is still debated. Benchmark CH3NH3PbI3 perovskite is reported to have a structure with inversion symmetry. Yet, Bulk Photovoltaic Effect (BPVE) [1] and Second Harmonic Generation (SHG)[2] non-linear optical effects recently reported for this material require the inversion symmetry breaking. 

In our recent work we presented the Density Functional Theory (DFT) with +U Hubbard correction computational model that predicts the existence of polarons in HPs.[3] We argue that breaking of bulk inversion symmetry in these experiments can be caused by light-induced polarons, which lead to the collective distortion of the crystal lattice. In fact, the presence or absence of polarons in the MAPI films may explain the controversial reports on MAPI polarity. The reported effects may enable third generation perovskite solar cells with efficiency that exceed the Shockley–Queisser limit. Our observations also open new venues for perovskite spintronics and tunable THz sources. 

[1]. P.A. Obraztsov, et al., Comm. Physics 1, 14 (2018). 

[2]. A.A. Popkova, et al., OSA Technical Digest JW3A.49 (2018). [3]. E. Welch, et al., AIP Advances 6, 125037 (2016).

Rydberg physics in the single and few atom regime

Mark Saffman, University of Wisconsin 

Friday, November 15, 2019
11:30am-12:30pm
Lin Hall, 105

 

Rydberg interactions have emerged as a leading approach for implementing quantum computation and simulation with atomic qubits. The Rydberg blockade mechanism is the underlying effect leading to entanglement, with the potential for fidelity that is high enough to reach thresholds for quantum error correction. 

I will go “under the hood” in a neutral atom quantum computer and present approaches for achieving long coherence times and high fidelity entanglement using optimized pulse sequences. Fully scalable quantum computation will require error correction, which brings with it additional experimental requirements including crosstalk free qubit measurements. I will show how interspecies Rydberg interactions can be used to solve this challenge.      

Note special date, time and venue


Machine-Learning-Assisted Photonics: 
From Optimized Design to Quantum Measurements 

Alexandra Boltasseva, School of Electrical & Computer Engineering and Birck Nanotechnology Center, Purdue University

Monday, November 18, 2019
3:30pm-4:30pm
Nielsen Hall, 170

 

Emerging photonic concepts such as optical metamaterials, metasurfaces, novel lasers, single-photon sources and other quantum photonic devices together with novel optical material platforms promise to bring revolutionary advances to information processing and storage, communication systems, energy conversion, imaging, sensing and quantum information technology. In pursuit of the next generation of photonic technologies, machine learning approaches have emerged as a powerful tool to discover unconventional optical designs and even uncover new optical phenomena. In this talk, various photonic design approaches as well as emerging material platforms will be discussed showcasting machine-learning-assistedtopology optimization for efficient thermophotovoltaic metasurface designs as well as machine-learning enabled quantum optical measurements. The next steps on merging  photonic optimization with artificial-intelligence-assisted algorithms and materials properties for designing advanced photonic components will be outlined.


Molecular Beam Epitaxy of Mixed Arsenide-Antimonide Alloys for Optoelectronic Applications 

Stephanie Tomasulo, Naval Research Laboratory

Friday, November 22, 2019
11:30am-12:30pm
Lin Hall, 105

 

Mixed arsenide-antimonide (AsSb) materials have many potential applications including photovoltaics and infrared detection as they possess direct bandgaps (Eg) ranging from ~0.5 eV to ~1.8 eV.  However, synthesis of these materials is fairly immature and challenging.  In this presentation, we will explore the molecular beam epitaxy (MBE) of ~1.6 eV InAlAsSb lattice-matched to InP and ~0.04 eV metamorphic InAsSb on GaSb covering both ends of this Egrange.      

As the widest-Eg III-V material lattice-matched to InP, a high-efficiency, wide-Eg InAlAsSb solar cell would be beneficial toward maximizing efficiency of an all-lattice-matched triple-junction solar cell.  However, both the immaturity and mixed group-V nature of this alloy pose significant challenges, requiring in depth investigation. Initial attempts at MBE of InAlAsSb resulted in anomalously low photoluminescence emission energies, compared with energies extracted from variable angle spectroscopic ellipsometry. To further investigate the cause of this discrepancy, we performed a systematic study of the substrate temperature and V/III of In0.26Al0.74As0.88Sb0.22 (expected Eg=1.64 eV) and will report the results in this presentation.  

At the other end of the Eg range, we have metamorphic InAsSb, which possesses the lowest Eg of all the conventional III-V materials, making it attractive for mid-to-long wavelength IR applications.  However, since the composition possessing the lowest Eg is not lattice-matched to existing substrates, compositional graded buffers are required to slowly grade the lattice-constant from that of the substrate to that of the desired composition in order to maintain a low defect density.  Here we will present metamorphic step-graded InAs1-xSbx buffers on GaSb, enabling the study of Sb incorporation as a function of growth conditions over a range of x (~0.1-0.6). We also present investigation of the optimal growth conditions and effect of growth conditions on dislocation dynamics in this low-Eg material system.    

Note special date, time and venue


Spin-helical particles: an enabling platform for quantum matter and quantum technologies

Yong Chen, Purdue University

Thursday, December 5, 2019
1:30pm-2:30pm
Lin Hall, 105

Spin is one of the most fundamental quantum properties of particles.  In this talk I will describe our experimental studies of “spin-helical” particles (analogous to neutrinos with spin locked to the momentum, but for electrons and atoms) as a powerful platform to realize novel quantum matter and enable new applications in quantum technologies --- ranging from quantum information/simulation to, quantum chemistry/energy.    For example the spin-helical electrons on the surface of “topological insulators” (TI) enabled observation of a “topological spin battery” [1] that opens a unique possibility to electrically induce and readout a nuclear and electronic spin polarization. Observations of unusual behaviors in Josephson junctions and SQUIDs made of our TIs [2] that may be relevant for the study of “topological superconductor” and “majorana fermions” with promise for “topologically protected” quantum computing.   As another example, spin-helical bosons in a Bose-Einstein condensate (BEC) of laser-cooled atoms with “synthetic” spin orbit coupling and gauge fields allow us to dynamically control the Hamiltonian and perform various quantum transport, interferometry, chemistry, and even “collider” experiments.  We demonstrate a new “interferometric” approach for quantum control of chemical reactions by preparing reactants in spin superpositions [3]. The system could also be used as a quantum simulator to study phenomena ranging from spin decoherence in interacting systems [4] to novel quantum matter in extra “synthetic” dimensions or curved spaces not easily realized in electronic materials [5].   Time permitting, I may briefly discuss other research programs in my group and Purdue Quantum Science and Engineering Institute (PQSEI), ranging from quantum materials to quantum sensing. 

Refs: [1] J. Tian et al., “On the understanding of current-induced spin polarization of three-dimensional topological insulators”, Nature Comm. 10, 1461 (2019);

[2] M.Kayyalha et al., "Highly skewed current-phase relation in superconductor-topological insulator-superconductor Josephson junctions", arXiv:1812.00499;

[3] D.Blasing et al. "Observation of Quantum Interference and Coherent Control in a Photo-Chemical Reaction", PRL 121, 073202 (2018);

[4] C. Li et al."Spin Current Generation and Relaxation in a Quenched Spin-Orbit Coupled Bose-Einstein Condensate", Nature Comm. 10, 375 (2019);

[5] C.Li et al., "A Bose-Einstein Condensate on a Synthetic Hall Cylinder", arXiv:1809.02122

From Quantum Physics to Quantum Chemistry and Quantum Biology
Vladislav V. Yakovlev, Texas A&M University 

Friday, December 13, 2019
11:30am-12:30pm
Lin Hall, 105

Quantum mechanics provides the most accurate description of the world around us. Quantum effects play important role in developing the next generation of technologies, such as quantum computers and quantum communication. Quantum control ideas, which we developed in early 90’s [1], are now becoming reality and are being implemented for different practical applications.  My current research interests are revolving around imaging and sensing. I am particularly intrigued with precise measurements using quantum properties of molecular systems and quantum states of light which can provide new information with improved sensitivity and specificity. In my presentation I will provide some historical introduction and, after summarizing some of my prior and current work, will attempt to sketch some broader applications of quantum optical imaging and sensing.

[1] B. Kohler, et al "Controlling the future of matter," Accounts of Chemical Research 28, 133-140 (1995).

Spring 2020


Optical Probe of Coherent States in Multi-Functional Materials

Giti Khodaparast, Virginia Tech 

Friday, January 17, 2020
11:30am-12:30pm
Lin Hall, 105

Intense laser pulses can generate carriers, spins, phonons, and magnons far from equilibrium states.  Information about the dynamical behavior of these nonequilibrium states can be elucidated by:  1)the electronic structure, 2)carrier scattering and relaxation mechanisms, including carrier-phonon and carrier-carrier scattering, 3)spin and magnetization dynamics, and 4)dynamical many-body interactions. For example,coherent acoustic phonons which are ultrasonic strain pulses can result in a broad optical spectrum from GHz up to THz.  The possibility of manipulating Coherent Phonons (CP) could lead to develop new techniques such acoustic imaging as well as better understanding and control of electronic and optical properties in devices.  Exploring the interaction of CP with carriers, magnetic impurities, and photons can open new prospective of phononics on nanoscale. For example, the manipulation of spins in semiconductors without the application of magnetic fields opens the door to the next generation of devices, where the electronic computation and magnetic memory can be performed on the same chip.Inthis talk, I will present several time resolved studies including CP generation and control in multifunctional materials such as ferromagnetic semiconductors and mutliferroics. 

Title TBA
Prof. Yi Zho, Shanghai Tech University, China

Friday, February 11, 
1:15-2:15pm
Lin Hall, 105

Cancelled due to travel complications.  

This seminar will be rescheduled at a later date if possible.

APS Conference Talks from Cancelled March Meeting
Various speakers

Friday, March 6, 2020, 
11:30-1:30pm
Lin Hall, 105

Experiment

  • 11:30:  F63.00008 : Hot Carrier Dynamics in Bulk and 2D Perovskites, Shashi Sourabh
  • 11:42:  J21.00005 : Valley Photovoltaics: Experimental Evidence for a Practical Route towards the Realization of the Hot Carrier Solar Cell, Kyle R Dorman
  • 11:54:  J21.00008 : A low-temperature-low-intensity study of flexible CIGS solar cells, Hadi Afshari
  • 12:06:  J21.00011 : Hot carrier dynamics in Quantum Well Solar Cells (Thermal Photon Gain), Brandon Durant

12:18:  Break

Theory:

  • 12:30:  C71.00017 : Topological Effects in Knotted Arrays of One-Dimensional Quantum Rings, Colin Riggert
  • 12:42:  P53.00007 : Applying Machine Learning to Thermal Conductance, Alexander Kerr
  • 12:54:  S56.00013 : Interactions in nodal-line semimetals with quadratic band touching, Geo Jose
  • 1:06:  R15.00003 : Fluid Flow Mechanisms in Shale Organic Nanopores, Felipe Perez Valencia (Petroleum & Geological Engin)

Title Applying quantum Zeno effect to noise sensing and geometrical phase detection
Dr. Hoang Van Do, University of Oklahoma

Friday, March 13, 2020 
11:30am-12:30pm
Lin Hall, 105

Abstract: Dynamical decoupling methods have been introduced to protect a quantum dynamical evolution from decoherence and to infer specific features of the noise spectrum originating from the environment. By measuring the quantum system frequently enough, the system is placed into the so-called quantum Zeno regime. This regime is demonstrated in a Bose-Einstein condensate (BEC) of rubidium-87 atoms on a chip at the 

European Laboratory for Non-Linear Spectroscopy in University of Florence. 

This regime not only provides a robust method for quantum control of populations but also maintains the coherence of the system, the geometric and dynamical phases acquired during evolution in the presence of measurement back-action are evaluated. Furthermore, when a state evolves through a closed loop on the Bloch sphere, it gains a geometric phase factor precisely corresponding to half the solid angle of the closed loop as shown in Phys. Rev. Research 1, 033028 (https://doi.org/10.1103/PhysRevResearch.1.033028). 

Dynamical decoupling methods can be also exploited in sensing technologies. Noise spectroscopy can be carried out by applying a sequence of projective measurements. This procedure induces the loss of atoms in the initial state, with a probability that presents maximal fluctuations when the measurement frequency is resonant with the noise frequency. The noise spectrum can be extracted with $80-90\%$ fidelity. This work is publised in New J. Phys. 21 (https://doi.org/10.1088/1367-2630/ab5740). 

This presentation will also report a collaboration with the Department of Computer Science of Seoul National University. Here, using reinforced--learning methods, we searched for different experimental schemes to produce high--dimensional tripartite entangled states of photons and to assemble inter--level couplings to fabricate quantum logic gates in trapped ions..  

Title:  Quantum quench and nonequilibrium dynamics in lattice-confined spinor Bose-Einstein condensates 

Yingmei Liu, Oklahoma State University

Tuesday, April 7, 2020
1:15pm-2:15pm
Lin Hall, 105

Bose-Einstein condensates (BECs) are ultra-cold gases, in which all atoms have a single collective wavefunction for their spatial degrees of freedom. With an additional spin degree of freedom, spinor BECs constitute a collective quantum system offering an unprecedented degree of control over such parameters as spin, density, temperature, and the dimensionality of the system. Spinor BECs have thus been considered as good quantum simulators for verifying and optimizing condensed matter models. In this talk, I will discuss a novel quantum phase transition realized in our antiferromagnetic spinor BEC system. I will also present our experimental study on nonequilibrium dynamics of a spinor BEC after it is quenched across a superfluid to Mott insulator phase transition in cubic lattices. Intricate few-body dynamics consisting of spin-mixing oscillations at multiple frequencies are observed after distinct quantum quench sequences. We confirm these observed spin-mixing spectra can be utilized to reveal atom number distributions of an inhomogeneous system, to study transitions from two-body to many-body spin dynamics, and to precisely measure two key parameters determining the spinor physics. 

OK-PVRI symposium plenary talk

5:00pm, Nielsen Hall 170

This talk will be the plenary presentation for the OK Photovoltaic Research Institute symposium.  More details will be announced when the schedule is made final.

Title: TBD
Aephraim M. Steinberg, University of Toronto

Tuesday, April 14, 2020
1:15pm-2:15pm
Lin Hall, 105

 

Title: Quantum sensors and their networks as exotic field telescopes in multi-messenger astronomy
Andrei Derevianko,  University of Nevada, Reno

Tuesday, April 21, 2020
1:15pm-2:15pm
Lin Hall, 105

In my talk, I will focus on  exotic bosonic fields potentially sourced by powerful astrophysical events, such as binary neutron star and binary black hole  mergers. Because such hypothetical fields are predicted to feebly interact with standard model particles and fields,  we propose to employ precision quantum sensors to detect potential bursts of such exotic fields. We show that to unambiguously correlate such bursts with gravitational wave triggers, the fields must be ultralight and ultrarelativistic. Moreover, networks of precision sensors are required to resolve the progenitor position in the sky thereby establishing a crucial coincidence with the more conventional, e.g., electromagnetic or gravitational wave, observations of the source.  We show that within certain models,  atomic clocks and magnetometers can be sensitive to intense bursts of exotic fields  from astrophysical sources within the reach of current gravitational wave observatories. This opens an intriguing possibility for a novel, exotic physics, modality in multi-messenger astronomy.

Fall 2020 (virtual Zoom series)

Title: Exciton-polarons in two-dimensional hybrid lead halide perovskites
Ajay Kandada, Wake Forest University

Friday, August 28th, 2020
12:00-1:00pm (Zoom link will be announced)

Excitonic interactions in 2D semiconductors garner considerable attention due to their relevance in quantum opto-electronics and due to the richness of their physics. Quantum-well like derivatives of organic-inorganic perovskites are emerging material systems where strongly bound two-dimensional excitons have been observed even at room temperature [1,2]. These hybrid semiconductors feature complex lattice dynamics due to the ‘softness’ arising from non-covalent bonds between molecular moieties and the inorganic network and due to the ionic character of the crystal [3]. I will discuss the profound and unique consequences of such dynamic structural complexity on the fundamental character of primary photo-excitations. I will present evidence of polaronic effects [4] and multi-body correlations [5,6], both of which are strongly affected by the lattice dynamics, based on various ultrafast optical spectroscopies.

 

References

[1]    S. Neutzner, F. Thouin, D. Cortecchia, A. Petrozza, C. Silva and A. R. S. Kandada, Physical Review Materials (2018), 2, 064605.

[2]    F. Thouin et al, Chemistry of Materials (2019), 31, 7085. 

[3]    F. Thouin et al, Nature Materials (2019), 18, 349-356. 

[4]    A. R. S. Kandada and C. Silva, The Journal of Physical Chemistry Letters (2020), 11, 3173.

[5]    F. Thouin, D. Cortecchia, A. Petrozza, A. R. S. Kandada and C. Silva, Physical Review Research (2019), 1, 032032.

[6]    F. Thouin et al, Physical Review Materials (2018), 2, 034001.

Title: Using photons for quantum information
Elizabeth Goldschmidt, University of Illinois

Friday, September 4th, 2020
12:00-1:00pm (Zoom link will be announced)

I will give an overview of recent, ongoing, and future work using coherent atomic and atom-like optical emitters to build quantum light-matter interfaces. Optical fields play an important role in virtually all schemes for interconnected quantum information systems since only optical photons are well-suited for carrying quantum information at room temperature. I will discuss different physical platforms that can form the basis for quantum light-matter interfaces, different modalities of light-matter entanglement for various applications in quantum information science, and the tradeoffs related to these different systems. I will include recent experimental results efficiently generating high-fidelity single photons, investigating the role of inhomogeneity in ensemble-based quantum memory, and developing a new integrated photonic platform with highly coherent emitters. 

Title: Quantum Techniques for Radar Applications
Alberto Marino, University of Oklahoma

Friday, September 11th, 2020
12:00-1:00pm (Zoom link will be announced)

Quantum resources offer the possibility of enhancing the sensitivity of devices beyond the classical limit.  This has led to the proposal and implementation of a number of different techniques that can take advantage of quantum effects for applications that range from computing to imaging to sensing. Among possible applications, radar has emerged as a candidate for quantum enhancement, with recent proof-of-principle experiments showing the viability of quantum radar. In this talk I will give an overview of quantum techniques that might find their way into radar applications. In particular, I will present the basics for techniques such as quantum illumination, quantum-enhanced positioning, and quantum-enhanced clock synchronization. I will discuss the conditions under which they could lead to a quantum-based enhancement for radar applications and their limitations. Finally, I will give an overview of some recent experimental implementations of quantum radars.

Title:  From mechanical entanglement generation to microwave quantum illumination
Shabir Barzanjeh, Institute for Quantum Science and Technology,
University of Calgary.

Friday, September 18th, 2020 
12:00-1:00pm (Zoom link will be announced)

The recent interest in mechanical quantum systems is driven not only by fundamental tests of quantum gravity but also to develop a new generation of hybrid quantum technologies. Here I confirm the long-standing prediction that a parametrically driven mechanical oscillator can entangle electromagnetic fields. We observe stationary emission of path-entangled microwave radiation from a micro-machined silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 (37) ~ dB below the vacuum level. This entanglement can be used to implement Quantum Illumination. Quantum illumination is a powerful sensing technique that employs entangled photons to boost the detection of low-reflectivity objects in environments with bright thermal noise. The promised advantage over classical strategies is particularly evident at low signal photon flux. This feature makes the protocol an ideal prototype for non-invasive biomedical scanning or low-power short-range radar detection. We experimentally demonstrated quantum illumination at microwave frequencies. We generate entangled fields using a Josephson parametric converter at millikelvin temperatures to illuminate at room-temperature an object at a distance of one meter. These results are experimental proof-of-principle of bistatic radar setup.

Title: Radar: What is it Good for?
Justin Metcalf, University of Oklahoma

Tuesday, September 22nd, 2020
1:15-2:15pm (Zoom link will be announced)

Radar is an active sensing modality exploiting the radio frequency portion of the electromagnetic spectrum, with deployed systems typically operating at center frequencies from 3 MHz to 100 GHz. Radar technology is a diverse ecosystem driven by phenomenology, application, and technology. This talk will give a broad overview to radar technology, including example applications, dominating constraints/tradeoffs, and some current hot research areas. We will also highlight some of the radar technology being developed at the OU Advanced Radar Research Center (ARRC). The goal of this talk is to provide broad background on the motivations underpinning radar applications and technologies in order to stimulate conversation on the benefits quantum technology can offer to improve radar performance. This talk will be primarily oriented from a signal processing perspective, in order to complement the perspective being offered by Dr. Ruyle in a future talk.

Title: Topological Phase Transitions in Hofstadter-Chern Insulators
Luiz Henrique Santos, Emory University

Friday, October 2nd, 2020
12:00-1:00pm (Zoom link will be announced)

Chern bands are the building blocks of the Hofstadter spectrum when a magnetic flux of order h/e penetrates the unit cell of the 2D lattice. They give rise to quantum Hall phases beyond the Landau level paradigm, which have attracted considerable interest in recent years. Furthermore, rapid progress in the fabrication of superlattices with nanometer scale unit cells has recently led to the experimental realization of integer and fractional Hofstadter-Chern insulators, opening remarkable prospects to explore the non-trivial interplay of lattice effects and electronic topology. In this talk, I will present a framework to classify topological phase transitions between integer and fractional Hofstadter-Chern insulators in graphene superlattices, which are tuned by changing hopping parameters in a fixed background uniform magnetic field. Despite the well-known intricacies of the Hofstadter spectrum, I will discuss how certain universal properties of the topological phase transitions can be identified from a simple analytical function, in particular, the emergence of multi-component Dirac fermions that mediate large transfers of Chern number between critical bands. Furthermore, I will discuss a non-trivial relationship between the energy scale of topological phase transitions and the presence of van Hove singularities in the Hofstadter-Chern bands, which provides an understanding for the origin of these topological phase transitions.

 

Title: Designing materials at the nanoscale
Pawel Hawrylak, Chair in Quantum Theory of Materials, Nanostructures and Devices, Department of Physics, University of Ottawa

Tuesday, October 6th, 2020
1:15pm-2:15pm (Zoom link will be announced)

We describe challenges and opportunities in condensed matter and materials physics applied to information and communication, lighting and energy technologies. We show how materials designed at the nanoscale address some of these challenges.  These include quantum circuits based on electron spin [1], synthetic quantum systems hosting macroscopic quantum states [2,3], quantum dots in topological insulators [4], semiconductor nanocrystals [5], graphene and 2D materials quantum dots [6-8] and 2D materials for  valley polarized electron gas [8,9] and laser cooling [10].

  1. C-Y. Hsieh, et al., Rep. Prog. Phys. 75, 114501 (2012).
  2. Blazej Jaworowski et al., Nature Scientific Reports 7, 5529 (2017).
  3. B. Jaworowski et al., ”Quantum bits with macroscopic topologically protected states in semiconductor devices”, Special Issue, Quantum Physical Informatics, D.Ferry, Editor, Applied Science 2019, 9, 474; doi:10.3390/app9030474.
  4. M. Korkusinski, et al., Nature Scientific Reports 4, 4903(2014).
  5. Fengjia Fan, et. al.  Nature 544, 75 (2017).
  6. D.Guclu, et. al. ”Graphene Quantum Dots”, Springer-Verlag (2014).
  7. Y. Saleem, et. al.,  Journal of Physics: Condensed Matter 31 (30), 305503 (2019).
  8. L.Szulakowska, et al, Phys. Rev. B 2020 (submitted).
  9. T. Scrace, et al., Nature Nanotechnology 10, 603 (2015).
  10. J. Jadczak, et al., Nature Comm: DOI/10.1038/s41467-018-07994 (2019).

Title: Quantum sensors and their networks as exotic field telescopes in multi-messenger astronomy
Andrei Derevianko,  University of Nevada, Reno

Friday, October 16th, 2020
12:00pm-1:00pm (Zoom link will be announced)

In my talk, I will focus on  exotic bosonic fields potentially sourced by powerful astrophysical events, such as binary neutron star and binary black hole  mergers. Because such hypothetical fields are predicted to feebly interact with standard model particles and fields,  we propose to employ precision quantum sensors to detect potential bursts of such exotic fields. We show that to unambiguously correlate such bursts with gravitational wave triggers, the fields must be ultralight and ultrarelativistic. Moreover, networks of precision sensors are required to resolve the progenitor position in the sky thereby establishing a crucial coincidence with the more conventional, e.g., electromagnetic or gravitational wave, observations of the source.  We show that within certain models,  atomic clocks and magnetometers can be sensitive to intense bursts of exotic fields  from astrophysical sources within the reach of current gravitational wave observatories. This opens an intriguing possibility for a novel, exotic physics, modality in multi-messenger astronomy.

Title:  TBA 

Derek Meyers, Oklahoma State University

Friday, October 23,  2020
12:00-1:00pm (Zoom link will be announced)

Abstract: TBA

Title: Quantum quench and nonequilibrium dynamics in lattice-confined spinor Bose-Einstein condensates
Yingmei Liu, Oklahoma State University

Friday, November 6th, 2020
12:00-1:00pm (Zoom link will be announced)

Bose-Einstein condensates (BECs) are ultra-cold gases, in which all atoms have a single collective wavefunction for their spatial degrees of freedom. With an additional spin degree of freedom, spinor BECs constitute a collective quantum system offering an unprecedented degree of control over such parameters as spin, density, temperature, and the dimensionality of the system. Spinor BECs have thus been considered as good quantum simulators for verifying and optimizing condensed matter models. In this talk, I will discuss a novel quantum phase transition realized in our antiferromagnetic spinor BEC system. I will also present our experimental study on nonequilibrium dynamics of a spinor BEC after it is quenched across a superfluid to Mott insulator phase transition in cubic lattices. Intricate few-body dynamics consisting of spin-mixing oscillations at multiple frequencies are observed after distinct quantum quench sequences. We confirm these observed spin-mixing spectra can be utilized to reveal atom number distributions of an inhomogeneous system, to study transitions from two-body to many-body spin dynamics, and to precisely measure two key parameters determining the spinor physics. 

Title: Impact of nonparabolic electronic band structure on the optical and transport properties of photovoltaic materials

Lucy Whalley, Northumbria University

Friday, November 13th, 2020
12:00-1:00pm (Zoom link will be announced)

Abstract: The effective mass approximation (EMA) models the response to an external perturbation of an electron in a periodic potential as the response of a free electron with a renormalized mass. For semiconductors used in photovoltaic devices, the EMA allows calculation of important material properties from first-principles calculations, including optical properties (e.g., exciton binding energies), defect properties (e.g., donor and acceptor levels), and transport properties (e.g., polaron radii and carrier mobilities). The conduction and valence bands of semiconductors are commonly approximated as parabolic around their extrema, which gives a simple theoretical description but ignores the complexity of real materials. In this talk I will assess the impact of band nonparabolicity on the optical and transport properties of four thin-film photovoltaic materials (CdTe, GaAs, Cu2ZnSnS4 , CH3NH3PbI3) at temperatures and carrier densities relevant for real-world applications.

 

Title: TBA

Jessica Ruyle, University of Oklahoma

Friday, November 20th, 2020
12:00-1:00pm (Zoom link will be announced)

Abstract: To be announced

Title: TBA

Aephraim M. Steinberg, University of Toronto

Friday, December 11th, 2020
12:00-1:00pm (Zoom link will be announced)

Abstract: To be announced