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Tuesday, March 21, 2023 10:30 am - 11:30 am EDT (GMT -04:00)

IQC Colloquim - Hsin-Yuan (Robert) Huang - California Institute of Technology

Learning in the Quantum Universe

Abstract: I will present recent progress in building a rigorous theory to understand how scientists, machines, and future quantum computers could learn models of our quantum universe. The talk will begin with an experimentally feasible procedure for converting a quantum many-body system into a succinct classical description of the system, its classical shadow. Classical shadows can be applied to efficiently predict many properties of interest, including expectation values of local observables and few-body correlation functions.

I will then build on the classical shadow formalism to answer two fundamental questions at the intersection of machine learning and quantum physics: Can classical machines learn to solve challenging problems in quantum physics? And can quantum machines learn exponentially faster than classical machines?

Bio: Hsin-Yuan (Robert) Huang is a Ph.D. student at Caltech, advised by John Preskill and Thomas Vidick. His research focuses on understanding how the theory of learning can provide new insights into physics, information, and quantum computing. His notable works include classical shadow tomography for learning large-scale quantum systems, provably efficient machine learning algorithms for solving quantum many-body problems, and quantum advantages in learning from experiments.

He has been awarded a Google Ph.D. fellowship, the Quantum Creator Prize, MediaTek research young scholarship, and the Kortschak scholarship.


Follow the link to attend this seminar on Zoom.

Please note: for the passcode, please email Joe Petrik no later than 10 a.m. day of.

Tuesday, March 21, 2023 12:00 pm - 1:00 pm EDT (GMT -04:00)

IQC Student Seminar featuring Aditya Jain

Improved diagnostics and implementation for quantum error correction

Abstract: Fault-tolerant quantum computing will require accurate estimates of the resource overhead, but standard metrics such as gate fidelity and diamond distance have been shown to be poor predictors of logical performance. We present a scalable experimental approach based on Pauli error reconstruction to predict the performance of concatenated codes. Numerical evidence demonstrates that our method significantly outperforms predictions based on standard error metrics for various error models, even with limited data. We illustrate how this method assists in the selection of error correction schemes.
Wednesday, March 22, 2023 2:00 pm - 3:00 pm EDT (GMT -04:00)

Space-Based Quantum Networking at JPL

IQC Special Seminar Featuring Makan Mohageg, NASA's Jet Propulsion Laboratory

JPL has been at the forefront of space-based quantum technologies. Cold Atom Lab is the first orbital experiment exploring the dynamics of Bose-Einstein condensates in micro-gravity. Deep Space Atomic Clock demonstrated that a trapped-Hg+ clock in space provides timing precision and accuracy required for improved spacecraft autonomous navigation.

Monday, March 27, 2023 10:00 am - 11:30 am EDT (GMT -04:00)

Error correction in quantum computers and beyond

IQC Special Seminar Aleksander Kubica, Amazon Web Services Center for Quantum Computing

Quantum computers introduce a radically new paradigm of information processing and revolutionize our thinking about the world. However, designing and building quantum computers that operate properly even when some of their components malfunction and cause errors is a heroic endeavor.

Monday, March 27, 2023 4:00 pm - 5:00 pm EDT (GMT -04:00)

Reactive Conjugated Polymers for Selective Dispersion of Carbon Nanotubes

IQC Colloquium, Alex Adronov McMaster University

Single-Walled Carbon Nanotubes (SWNTs) exhibit a number of unique mechanical, thermal, and electronic properties that render them useful for numerous applications, ranging from molecular electronics to nano-scale construction materials.  However, SWNTs are highly insoluble and are devoid of reactive functionality, posing major limitations to their modification, manipulation, and ...

Tuesday, March 28, 2023 12:00 pm - 1:00 pm EDT (GMT -04:00)

IQC Student Seminar featuring Junan Lin

Characterizing states and measurements: principles and approaches

Abstract: The problem of separately characterizing state preparation and measurement (SPAM) processes has not been frequently discussed in the literature. In this talk, I will first review the theoretical challenge behind SPAM characterization due to a gauge freedom, and then describe two different principles that can be applied to get around it. The first one can be understood as an effective propagation of state preparation noise from the target system to an ancillary qubit, whereas the second one utilizes measurements and post-selection to reduce the state preparation noise and can be interpreted as a form of algorithmic cooling. For the first method, I will present experimental and simulation data obtained from real quantum processors. For the second method, I will analyze its overhead through an upper bound on the expected number of runs to achieve a given error-reduction ratio.
Wednesday, March 29, 2023 2:00 pm - 3:30 pm EDT (GMT -04:00)

Towards a quantum Internet with single atoms in cavities

IQC Special Seminar - Olivier Morin, MAX PLANCK INSTITUTE OF QUANTUM OPTICS

Building a quantum internet requires to develop computing machines but also to connect them at various scales, e.g. via optical fibres. Although it is not yet known which physical platforms are suitable for this challenge, there is a consensus to say that light-matter interface will play an important role. ...

Thursday, March 30, 2023 10:00 am - 11:00 am EDT (GMT -04:00)

Multidimensional Quantum Walks

Math/CS Seminar Featuring Sebastian Zur (CWI, Amsterdam)

While quantum walk frameworks make it easy to design quantum algorithms, as evidenced by their wide application across domains,
the major drawback is that they can achieve at most a quadratic speedup over the best classical algorithm. 

Wednesday, April 5, 2023 11:00 am - 12:00 pm EDT (GMT -04:00)

Quantum Matters Seminar Series: Strange metals from not-so-strange quasiparticles

Brad Ramshaw

Abstract: Strange metals have linear-in-temperature (T-linear) down to low temperature. Strange metals are found in many families of correlated electron materials, leading to the conjecture that a universal bound - the "Planckian" bound - limits the scattering rate of electrons to a value set by fundamental constants. If the Planckian bound exists, it would provide a natural explanation for why a host of seemingly disparate systems, including high-temperature superconductors and twisted bilayer graphene, all have T-linear resistivity. Perhaps more dramatically, T-linear resistivity suggests that electron-electron interactions are so strong that conventional concepts such as quasiparticles and Boltzmann transport do not apply in strange metals. I will present our work on the cuprate Nd-LSCO and the 5-layer superconducting nickelate that shows that conventional quasiparticle transport is alive and well, even in the strange metal regime where the Planckian bound is saturated. This suggests that we may not need to abandon the quasiparticle picture entirely, but that we need to better understand the source of scattering in these materials. 

Wednesday, April 5, 2023 12:00 pm - 1:00 pm EDT (GMT -04:00)

IQC Student Seminar Featuring Xi Dai

Landau-Zener tunneling: from weak to strong environment coupling

Abstract:

Landau-Zener tunneling, which describes the transitions in a two-level system during the passage through an anti-crossing, is a model applicable to a wide range of physical phenomena. Dissipation due to coupling between the system and the environment is an important factor in determining the transition rates. Using a superconducting tunable capacitively shunted flux qubit, we observe the crossover from weak to strong coupling to the environment. The weak coupling limit corresponds to small system-environment coupling and leads to environment-induced thermalization. In the strong coupling limit, environmental polarizations dress the system and transitions occur between the dressed states. Our results confirm previous theoretical studies of dissipative Landau-Zener tunneling in the weak and strong coupling limits, and motivate further work on understanding the intermediate regime. This work is relevant for understanding the role of open system effects in quantum annealing, where Landau-Zener transitions at small gaps, occurring in large scale systems, are important to understand for improving the success probability.

 

This talk is based on the preprint arXiv:2207.02017.