Quantum Computing with Imperfect Hardware

Quantum mechanics describes the physical world around us with exquisite precision, with no known violations of the theory. Ironically, this precision comes with some additional baggage: the theory permits the existence of a host of complex, delicate entangled states of the physical world, many of which have yet to be produced or observed. The debate of whether their quantum entanglement really captures the fundamental nature of the physical world and is an engineering resource is reaching a critical moment. Quantum processors with of order 100 qubits based on superconducting circuitry have recently demonstrated computing power on par with the most advanced classical supercomputers for select problems. Current hardware is, however, prone to errors from materials defects, imperfect control systems, and the leakage of quantum information into unwanted modes in the solid-state. I will describe the major decoherence pathways present in state-of-the-art superconducting quantum processors, illustrate techniques to maximize the computing power of imperfect qubits, and highlight recent quantum computations for determining chemical energies, solutions to the transverse-field Ising model, scrambling dynamics in black holes, and nuclear scattering.

Irfan Siddiqi is the Giancoli Professor and Chair of the Physics Department, and a Professor of Electrical Engineering & Computer Science at the University of California, Berkeley. He also holds a faculty scientist position at Lawrence Berkeley National Laboratory (LBNL). Siddiqi is currently the director of the Quantum Nanoelectronics Laboratory at UC Berkeley and the Advanced Quantum Testbed at LBNL. Siddiqi is known for contributions to the fields of superconducting quantum circuits, including dispersive single-shot readout of superconducting quantum bits, quantum feedback, observation of single quantum trajectories, and near-quantum limited microwave frequency amplification. He was awarded the American Physical Society George E. Valley Jr. Prize in 2006 "for the development of the Josephson bifurcation amplifier for ultra-sensitive measurements at the quantum limit" and the 2021 John F. Keithley Award for Advances in Measurement Science. Siddiqi is a fellow of the American Academy of Arts and Sciences, and the American Physical Society. In 2016, he received the UC Berkeley Distinguished Teaching Award, the institution’s highest honor for teaching and commitment to pedagogy.