Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G35: Quantum Characterization, Verification, and Validation: Noise and CrossTalkRecordings Available

Hide Abstracts 
Sponsoring Units: DQI Chair: Senrui Chen, University of Chicago Room: McCormick Place W193B 
Tuesday, March 15, 2022 11:30AM  11:42AM 
G35.00001: Characterizing the statistics of the qubit frequency noise Filip A Wudarski, Andre Petukhov, Alexander Korotkov, Yaxing Zhang, Mark I Dykman Measurements of the qubit state brings in randomness, which is superposed on the noise in the qubit parameters. This complicates characterizing the noise. We show that not only the spectrum of the noise, but also its statistics can be revealed using periodically repeated Ramsey measurements. The method is based on studying two and threetime correlators of the measurement outcomes. It allows identifying noise from a periodic frequency modulation and distinguishing a Gaussian from a nonGaussian noise. It also identifies a characteristic footprint of the telegraph noise. We provide analytical expressions for the twoand threetime correlators for different kinds of noise. The results for commonly encountered types of noise, the Gaussian 1/f and exponentially correlated noise, and for a telegraph noise are verified by numerical simulations. 
Tuesday, March 15, 2022 11:42AM  11:54AM 
G35.00002: Modeling of environmental noise in transmon qubit using dynamical decoupling Vinay Tripathi, Huo Chen, Mostafa Khezri, Ka Wa Yip, Eli LevensonFalk, Daniel A Lidar Tackling decoherence is one of the core challenges in the field of quantum computing. For superconducting qubits, coupling to the environment results in several noise channels. A rigorous characterization of the open system dynamics at the circuit Hamiltonian level is essential for a better understanding of these noise processes. Here we model the open quantum system effects for a qubit derived from a transmon circuit Hamiltonian. We use the Redfield master equation with a hybrid bath consisting of both high and low frequency components to model the effects of environment. We develop a fitting procedure using dynamical decoupling to learn the behavior of noise and use it to reproduce the experiments on processors available through IBM Quantum Experience. We test our model with quantum state fidelity experiments for random initial states. We further reproduce the effects of applied timedependent dynamical decoupling pulses. Our model predicts all the experimental results with an average relative error of less than 1%. 
Tuesday, March 15, 2022 11:54AM  12:06PM 
G35.00003: High Fidelity Quantum Gates under random telegraph noise: Machine Learning Approach Jackson C Likens, Sanjay Prabhakar Achieving high fidelity quantum gates under random telegraph noise (RTN) is of great interest for quantum computing. We have generated data for qubit driven by π, CORPSE, SCORPSE, symmetric and asymmetric pulses in presence of RTN and by using traintest model in machine learning algorithm within python environment, we report symmetric pulse provides large fidelity recovery against noise among all the other pulses for large noise correlation time, whereas πpulse has small error among all the other pulses for small noise correlation time. Investigation of high fidelity quantum gate for small energy amplitudes of RTN may be useful for low temperature measurements, whereas large energy amplitudes of RTN may be useful for room temperature measurements of quantum error correction codes. 
Tuesday, March 15, 2022 12:06PM  12:18PM 
G35.00004: Tomographic construction and prediction of superconducting qubit dynamics using the postMarkovian master equation Haimeng Zhang, Bibek B Pokharel, Eli LevensonFalk, Daniel A Lidar

Tuesday, March 15, 2022 12:18PM  12:30PM 
G35.00005: Learning Noise via Dynamical Decoupling of Entangled Qubits Trevor McCourt, Charles J Neill, Kenny Lee, Isaac L Chuang, Vadim Smelyanskiy, Andre Petukhov Arrays of superconducting qubits with frequency tunable couplers are capable of producing interesting quantum behavior. Key to this is the ability to produce highfidelity entangling interactions between qubits. The quality of these interactions is limited by noise caused by systemenvironment interaction. Characterizing noise in entangled systems is difficult not only because of the large numbers of degrees of freedom but also due to the limited and imperfect available control. This makes achieving good correspondence between theory and experiments difficult. By comparing the behavior of isolated and entangled qubits, we establish that the dominating source of noise during our resonant, excitation preserving twoqubit gates is frequency fluctuations of the coupler, not the qubits themselves. We drive pairs of entangled qubits through CPMGinspired pulse sequences and observe steps in the decay curves that cannot be produced by Gaussian noise. Via detailed modeling, we establish that this noise is well described by a few standalone random telegraph fluctuators which interact with the coupler via its flux bias and have a correlation time on the order of 0.1ms. We also explore spatial interqubit correlations in this noise that could be detrimental to multiqubit algorithms. 
Tuesday, March 15, 2022 12:30PM  12:42PM 
G35.00006: Multiqubit Spatially Correlated Noise Characterization Mayra Amezcua, Leigh M Norris, Christopher Watson, Tom Gilliss, Timothy M Sweeney Spatiotemporally correlated noise and its impact on error correcting schemes such as the surface code are of critical interest for quantum information processing research. We propose and validate a quantum noise spectroscopy protocol to measure spatially correlated noise on two qubits. Our scheme reconstructs the real and imaginary part of the power spectrum using two fixed total time pulse sequences and performing single qubit and joint twoqubit measurements to separately resolve spatially correlated noise processes from the individual noise spectra of the participating qubits. We inject noise by using a technique known as Schrodinger Wave Autoregressive Moving Average, developed by our group [1], to generate phase error on the qubit control line. Our results demonstrate that our protocol is a way to characterize spatially correlated noise in a quantum device and inform error correction algorithms. 
Tuesday, March 15, 2022 12:42PM  12:54PM 
G35.00007: DephasingRobust Characterization of TemporallyCorrelated Qubit Control Noise Robert Barr, Yasuo Oda, Colin Trout, Kevin Schultz, Gregory Quiroz, Leigh M Norris, David Clader Precise control of quantum systems is a requirement for quantum technologies spanning fields from quantum metrology to quantum computing. A major factor limiting control fidelity is noise due to fluctuations in control fields. To design optimally robust control sequences, it is first necessary to have a highaccuracy characterization of the statistical properties of control noise. Previous approaches to characterize control noise are limited by their vulnerability to lowfrequency dephasing noise, which can overwhelm the target control noise signal and prevent reliable characterization. In this work, we apply optimized narrowband quantum control sequences to probe fine spectral features of amplitude control noise while simultaneously suppressing dephasing noise. This extends the spectroscopy of control noise to experimentally relevant settings where dephasing is strong relative to control noise, such as superconducting qubits. 
Tuesday, March 15, 2022 12:54PM  1:06PM 
G35.00008: Distinguishing multispin interactions from lower order effects Thomas R Bergamaschi, Tim Menke, William P Banner, Agustin Di Paolo, Cyrus F Hirjibehedin, Steven J Weber, Andrew J Kerman, William D Oliver Multispin interactions can be engineered with artificial quantum spins. However, it is challenging to verify such interactions experimentally. We describe two methods to characterize $n$local coupling of $n$ spins. First, we analyze the variation of the transition energy of the static system as a function of local spin fields. Generally accessible measurement techniques are used to distinguish $n$local interactions between up to five spins from lowerorder contributions in the presence of noise and spurious fields and couplings. Second, we show a detection technique that relies on timedependent driving of the coupling term. Generalizations to larger system sizes are analyzed for both static and dynamic detection methods, and we find that the dynamic method is asymptotically optimal when increasing the system size. The proposed methods enable robust exploration of multispin interactions across a broad range of both coupling strengths and qubit modalities. 
Tuesday, March 15, 2022 1:06PM  1:18PM 
G35.00009: Analysis of Randomized Benchmarking with Realistic Noise Bryan H Fong Recently, a leakagedetecting (“blind”) randomized benchmarking (RB) technique has been employed to characterize overall error and, via interleaving, errors for specific gates, in 6dot arrays of silicon quantum dots operated as exchangeonly qubits [Andrews et al., Nature Nano. 14, 747 (2019)]. Here, we analytically compute functional forms for these RB decays using the group Fourier transform convolutional analysis described in Merkel et al., arXiv:1804.05951. Our analysis includes gatedependent errors caused by composite pulses and control and environmental noise, as well as leakage. The effects of both Markovian and nonMarkovian noise are analyzed, with excellent agreement found between simulations and group Fourier transform theory. We find that, for exchangeonly qubits at least, Markovian and nonMarkovian noiseinduced RB decays are qualitatively similar. 
Tuesday, March 15, 2022 1:18PM  1:30PM 
G35.00010: Measurement efficient automated multilevel qudit pulse optimization on quantum devices Pranav S Mundada, Yuval Baum, Sean Howell, Michael Hush, Michael Biercuk Harnessing the existing higher levels in the cQED qudit can significantly increase the resourcefulness of NISQ era quantum devices. However, increased deviations and complexity in the modeling of higher levels, make it challenging to tune up highfidelity gates on a qudit. We investigate using a modelfree pulse optimization of a U(3) gate. We demonstrate that parameterizing the pulse with Hanning windowed basis functions allows for more efficient optimization, as they reduce the number of parameters required, and ensure strict bandwidth limits. We also simplify the cost function and use only state populations instead of full state tomography, reducing the number of measurements required at each evaluation. Our optimization protocol starts with no prior knowledge about the ideal pulse parameters and obtains a gate error of 2e3 which is primarily coherence limited. Unlike traditional modelbased optimization, this modelfree approach enables optimization of multiqutrit gates and is directly applicable to other qubit architectures including protected qubits. 
Tuesday, March 15, 2022 1:30PM  1:42PM 
G35.00011: Estimating gateset properties from random sequences Jonas Helsen, Marios Ioannou, Ingo Roth, Jonas Kitzinger, Emilio Onorati, Albert H Werner, Jens Eisert With quantum devices for computing and simulation increasing in scale and complexity, there is a growing need for tools that obtain precise diagnostic information about quantum operations. 
Tuesday, March 15, 2022 1:42PM  1:54PM 
G35.00012: Neural Network Based Qubit Environment Characterization Miha Papič, Ines de Vega The exact microscopic structure of the environments that produces $1/f$ noise in superconducting qubits remains largely unknown, hindering our ability to have robust simulations and harness the noise. In this paper we show how it is possible to infer information about such an environment based on a single measurement of the qubit coherence, circumventing any need for separate spectroscopy experiments. Similarly to other spectroscopic techniques, the qubit is used as a probe which interacts with its environment. The complexity of the relationship between the observed qubit dynamics and the impurities in the environment makes this problem ideal for machine learning methods  more specifically neural networks. With our algorithm we are able to reconstruct the parameters of the most prominent impurities in the environment, as well as differentiate between different environment models, paving the way towards a better understanding of $1/f$ noise in superconducting circuits. 
Tuesday, March 15, 2022 1:54PM  2:06PM 
G35.00013: The Learning and Compiled Calibration of Clock Cycle Errors in QuantumComputing Architectures Arnaud CarignanDugas The performance of quantum computers is inhibited by the occurrence of physical errors during computation. 
Tuesday, March 15, 2022 2:06PM  2:18PM 
G35.00014: Flux crosstalk as an optimization problem Xi Dai, Robbyn Trappen, Rui Yang, Rabindra Das, David K Kim, Alexander Melville, Bethany M Niedzielski, Cyrus F Hirjibehedin, Steven J Weber, Jonilyn L Yoder, Joseph M Gibson, Jeffrey A Grover, Steven M Disseler, James I Basham, Sergey Novikov, Adrian Lupascu Flux crosstalk is an important control issue for scaling up quantum computers based on superconducting qubits. The number of measurements required to calibrate crosstalk usually scales at least quadratically with the number of control channels, and becomes worse when the circuit elements interact strongly. Here we propose a new method for calibrating flux crosstalk for superconducting circuits. Using the fundamental property that superconducting circuits respond periodically to external fluxes, crosstalk calibration of N flux channels can be treated as N independent optimization problems, with the optimization metric being the periodicity of a measured signal. We show experimental results on a smallscale quantum annealer, which indicates that the optimization problem is convex given reasonable initial estimates of the crosstalk, and can thus be efficiently solved. 
Tuesday, March 15, 2022 2:18PM  2:30PM 
G35.00015: Optimal Quantum State Tomography with Noisy Gates Violeta N IvanovaRohling, Niklas Rohling, Guido Burkard For limited scenarios, depending on projector rank and system size, optimal measurement schemes for efficient QST are known. In the case of errorless nondegenerate measurements, using mutually unbiased bases yields the optimal QST scheme [1]. Measuring one out of N qubits becomes optimal if the measurement operators project on mutually unbiased subspaces [2]. However, in the general case, the optimal measurement scheme for efficient QST is not known and, oftentimes, it may need to be numerically approximated. This problem can be generalized as a framework for customized efficient QST. Here, we extend this framework to investigate the effect of noise on the optimal QST measurement sets using two noise models: the depolarizing channel, and over and underrotation in twoqubit gates. We demonstrate the benefit of using entangling gates for the efficient QST measurement schemes for two qubits at realistic noise levels, by comparing the fidelity of reconstruction of our optimized QST measurement set to the stateoftheart scheme using only product bases. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2023 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700