The Institute for Quantum Information Research and Engineering (INQUIRE) is pleased to welcome Professor Eli Levenson-Falk, University of Southern California, hosted by Professor Prem Kumar.
INQUIRE Seminar
Date: Tuesday, March 24
Time: 11:00am
Location: Ryan 4003 (map | directions)
Title: Amplifying Hamiltonian terms for gate calibration and sensing
Abstract: A common challenge in quantum technology is to measure a repeatable but unknown term in a device's Hamiltonian. This term may be some environmental variable that we are trying to sense, or it may be a coherent error in a gate operation. Accurately measuring terms like these requires suppressing the effects of random, non-repeatable (incoherent) interactions. Accurately interpreting the measurements becomes far easier when a measurement is sensitive only to a single Hamiltonian term. I will discuss two protocols we have developed to perform these measurements.
In the first protocol, we characterize gate errors on a superconducting transmon qubit by repeating pairs of gates that nominally give identity operations. By carefully choosing the initial state and gate sequence, we can isolate frequency and amplitude gate errors along with relaxation and dephasing. This deterministic benchmarking (DB) procedure allows us to create a first-principles effective model for the qubit, including the effect of non-computational levels and environmental couplings. The model accurately predicts behavior due to finite temperature that is typically missed by benchmarking protocols. I will discuss DB's applicability and limitations, and describe how it might be extended to multi-qubit gates.
In the second protocol, we use a continuous, pre-determined drive to stabilize one component of the qubit Bloch vector, protecting it from decoherence. This coherence stabilization protocol allows for a small, constant Hamiltonian term to cause a greater rotation of the state, leading to increased signal. We derive the optimal protocol and show analytically and numerically that it can be used in quantum sensing to give up to a factor of 1.96 greater signal. We demonstrate the protocol with a superconducting transmon qubit, showing a factor of 1.68 increase in signal and a factor of 1.1 increase in signal per root evolution time. I will discuss how the protocol could be applied in quantum sensing and how it might be further improved.
About Prof. Levenson-Falk: Eli Levenson-Falk is an Associate Professor in the Department of Physics & Astronomy and the Ming Hsieh Department of Electrical & Computer Engineering at the University of Southern California, and is the Superconducting Qubits Scientific Lead at Quantum Elements. He runs LFL, an experimental research group that focuses on using superconducting electrical circuits for quantum information applications. He received his PhD from the University of California Berkeley in 2013 and conducted postdoctoral studies at Stanford University.
Hosted by Prem Kumar.
For more information, please contact Keller Paulson at keller.paulson@northwestern.edu.
Keller Paulson
(847) 467-4910
Email