Talks

Floquet Calibration of programmable quantum simulator for ultra-accurate study of energy spectra and persistent current in disordered quantum ring

A promising approach to study quantum materials is to simulate them on an engineered quantum platform. However, achieving the accuracy needed to outperform classical methods has been an outstanding challenge. We will discuss the method of accurate Floquet calibration of multiqubit quantum circuits and its experimental demonstration, using eighteen superconducting qubits. We illustrate the underlying method by reconstructing the single-particle band-structure of a periodically driven quantum wire. We demonstrate nearly complete mitigation of decoherence, readout and systematic errors and arrive at an accuracy in measuring quasi-energy eigenvalues of this wire with a relative error of 1%. Insight into this unprecedented algorithm fidelity is gained by highlighting robust properties of a Fourier transform, including the ability to resolve quasi-energies with a relative error as low as 0.001%. Furthermore, we synthesize magnetic flux and disordered local potentials, two key tenets of a condensed-matter system. When sweeping the magnetic flux, we observe avoided level crossings in the spectrum, a detailed fingerprint of the spatial distribution of local disorder. Combining these methods, we reconstruct electronic properties of the eigenstates where we observe persistent currents and a strong suppression of conductance with added disorder.

Colloquium: Strongly Interacting QCD Matter at Finite Temperature and Density

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Colloquium: A Case for Carbon Dioxide Removal from Air

As a global society we have been burning fossil fuels to meet our energy and transportation needs since the start of the industrial revolution. This has resulted in atmospheric CO2 concentrations much greater than at any other time during the last 650,000 years. That concentration reached a record 415 parts per million in May 2019. The replacement of fossil fuels with renewables, advances in energy efficiency, and carbon capture and storage are among the key strategies required to prevent warming beyond 2°C within this century. But they will not be enough. We need to ramp up our efforts in reducing CO2 emissions, and then we need to do even more. The Earth’s natural systems, such as forests and oceans, are capable of removing roughly half of global CO2 emissions each year, while the rest steadily accumulates in the atmosphere. Until now, our best approach to avoiding the worst impacts of climate change was simply to avoid such emissions in the first place. But because of our failure to act quickly and at a large enough scale, we are now faced with the need to go beyond that strategy—to actually start removing CO2 directly from the air. Trees and oceans already do this, but these systems are overwhelmed. Manufactured or synthetic removal systems are designed to pull CO2 from the atmosphere, and at a much faster rate than natural systems. This talk will review both the promise and pitfalls of this approach.

Colloquium: tba

Colloquium: tba

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Colloquium: tba

Colloquium: tba