Speaker #1: Alexander Schuckert
Tittle: Fault-tolerant fermionic quantum computation with fermionic atoms
Abstract: Simulating the dynamics of electrons and other fermionic particles is one the most promising applications of fault-tolerant quantum computers. However, the overhead encountered in mapping time evolution under fermionic Hamiltonians to qubit gates renders this endeavour challenging. In this talk, we will show how to remove this overhead by introducing a fault-tolerant quantum computing framework with native fermionic particles, implementing logical fermionic operators. Our scheme yields an exponential improvement in circuit depth from O(N) to O(log(N)) with respect to lattice site number N compared to state-of-the-art qubit-only approaches for simulating time evolution under the kinetic energy term of crystalline materials. We will discuss how to implement all fault-tolerant primitives in neutral atoms. In particular, we require a pairing gate which we show how to implement using photodissociation of molecules. Our work opens the door to qubit-fermion fault-tolerant quantum computation in platforms with native fermions such as neutral atoms, quantum dots and donors in silicon, with applications in quantum chemistry, material science and high-energy physics.
Speaker #2: Mingshu Zhao
Title: Kolmogorov turbulence in 2D atomic Bose-Einstein condensates
Abstract: Turbulence is a fundamental phenomenon in fluid systems. In 1941 Andrey Kolmogorov developed a theory of turbulence for incompressible classical fluids, predicting universal scaling laws that governs energy cascade from large to small scale within a so-called inertial range. This “K41” theory and its later extensions have been widely applied in their original context (e.g. turbulence in water from small tanks to the oceanographic scale), then compressible classical fluids (gas turbulence in wind tunnels to the atmospheric scale), and more recently superfluid Helium, an incompressible quantum fluid. Our study goes beyond this by experimentally verifying Kolmogorov theory predictions in quasi-2D atomic BECs: compressible quantum fluids.
Kolmogorov theory describes the statistical properties of the velocity field of turbulent fluids. A key tool for quantifying turbulence and validating Kolmogorov's scaling laws are velocity structure functions (VSFs), which quantify the spatial properties of velocity field. By analyzing these structure functions, we assess the energy cascade process and detect deviations from K41 theory. Our analysis first confirms K41 scaling for low-order structure functions and finds deviations at higher orders, as predicted by Kolmogorov and Obukhov’s 1962 “KO62” theory. Additionally, we observe fat-tailed velocity increment distributions, suggesting that the probability density function of velocity increments depends on spatial separations: at large separations, increments are uncorrelated and follow Gaussian statistics, while at smaller separations, they become increasingly correlated and non-Gaussian distributed. Taken together, these findings are supported by 2D dissipative Gross-Pitaevskii simulations.
Before this work the velocity field of atomic quantum gases had never been directly observed, this prevented access to the usual predictions of Kolmogorov theory. Our results are enabled by an impurity injection method–analogous to particle image velocimetry in classical fluids–that tracks the motion of these impurities over time to extract the local velocity field.
*You will need to bring your cell phone, so you can sign in using the QR code outside of ATL 2400. You will need to submit your first and last name, email, and affiliation on the form by 11:15am to be able to get lunch after the seminar. Lunch is first come, first served.*