Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session R33: Hardware, Software and Techniques for Optimal Quantum ControlLive
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Sponsoring Units: DQI Chair: Jie Luo, UC Berkeley |
Thursday, March 18, 2021 8:00AM - 8:12AM Live |
R33.00001: Quantum Orchestration - Integrated hardware and software for design and execution of complex quantum control protocols, Part 1 Itamar Sivan, Yonatan Cohen, Nissim Ofek, Tal Shani, Ori Weber, Lior Ella, Niv Drucker, Michael Greenbaum, Nir Halay The incredible progress in designing quantum systems, engineering their environment, and controlling them effectively, has led to significant improvements in coherence times, gate fidelities, and the ability to integrate more qubits into a single quantum processor. While the development of quantum processors remains the number one challenge, many bottlenecks exist in the classical control hardware layer as well as the software layer, where optimizations can play a critical role for near term quantum computing. Some examples include (1) feedback for error correction and repeat until success protocols, (2) complex calibrations, and (3) hybrid quantum-classical algorithms. |
Thursday, March 18, 2021 8:12AM - 8:24AM Live |
R33.00002: Quantum Orchestration - Integrated hardware and software for design and execution of complex quantum control protocols, Part 2 Yonatan Cohen, Itamar Sivan, Nissim Ofek, Lior Ella, Niv Drucker, Ori Weber, Tal Shani, Michael Greenbaum, Nir Halay The incredible progress in designing quantum systems, engineering their environment, and controlling them effectively, has led to significant improvements in coherence times, gate fidelities, and the ability to integrate more qubits into a single quantum processor. While the development of quantum processors remains the number one challenge, many bottlenecks exist in the classical control hardware layer as well as the software layer, where optimizations can play a critical role for near term quantum computing. Some examples include (1) feedback for error correction and repeat until success protocols, (2) complex calibrations, and (3) hybrid quantum-classical algorithms. |
Thursday, March 18, 2021 8:24AM - 8:36AM Live |
R33.00003: qopt: A Python Software Package for Quantum Simulation and Optimal Control Julian David Teske, Pascal Cerfontaine, Friederike Butt, Hendrik Bluhm We introduce qopt, a software framework for robust quantum optimal control considering realistic experimental conditions. To this end, we model open and closed qubit systems with a focus on the simulation of noise sources and experimental constraints. Specifically, the influence of noise can be calculated using Monte Carlo methods, effective master equations or with the filter function formalism, enabling the investigation and mitigation of auto-correlated noise. In addition, limitations of control electronics including finite bandwidth effects can be considered. The calculation of gradients based on analytic results is implemented to facilitate the efficient optimization of control pulses. The software is published under an open source license, well tested and features a detailed documentation [1]. |
Thursday, March 18, 2021 8:36AM - 8:48AM Live |
R33.00004: Efficient reverse engineering of robust one-qubit control pulses for broadband noise Ralph Kenneth Colmenar, Jason Kestner We derive an analytical expression for the filter-transfer function of an arbitrary one-qubit gate through the use of dynamical invariant theory and Hamiltonian reverse engineering. We use this result to define a cost functional that provides an efficient way to optimize the filter function for robustness against any specified frequency bands of the noise power spectral density. We demonstrate the utility of our result for the case of purely dephasing noise. We report a set of control parameters for which the normalized filter function can be supressed to ∼10-4 for noise frequencies less than 4π times the inverse gate time. |
Thursday, March 18, 2021 8:48AM - 9:00AM Live |
R33.00005: FPGA-based optimal control for two-qubit gates Sara Sussman, Pranav Mundada, Alexander Place, Anjali Premkumar, Andrew Houck Improved controls for high-coherence superconducting qubits will enable high-fidelity multi-qubit gates. Superconducting qubits made of tantalum were recently found to have lifetimes and coherence times exceeding 0.3 milliseconds. Implementing Field-Programmable Gate Array (FPGA)-based qubit control enables real-time feedback which informs qubit state preparation and allows for careful study of quantum trajectories and decoherence. Implementing classical signal-processing calculations digitally on the FPGA further enhances the quality of control. Here we present the results of these new controls applied in an optimal control scheme for a two-qubit gate. |
Thursday, March 18, 2021 9:00AM - 9:12AM Live |
R33.00006: Control of superconducting qubits using a quantum-based Josephson Arbitrary Waveform Synthesizer Logan Howe, Adam J Sirois, Manuel Castellanos-Beltran, Anna Fox, Paul David Dresselhaus, Samuel P Benz, Peter Hopkins
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Thursday, March 18, 2021 9:12AM - 9:24AM Live |
R33.00007: Clock Synchronization and Data Exchange between FPGA Modules for Superconducting Qubit Control Gang Huang, Yilun Xu, Thorsten Stezelberger, David Ivan Santiago, Irfan Siddiqi Controlling systems for multiple qubit operation can easily exceed the capability of a single FPGA chip. Synchronization among multiple FPGA-based modules is essential for resource-efficient system scale up. We propose and develop a fiber-based clock synchronization and data exchange protocol for inter-module communication using our in-house developed FPGA based RF control system - QubiC. The preliminary test results on this prototype system are presented. |
Thursday, March 18, 2021 9:24AM - 9:36AM Live |
R33.00008: Automatic Two-qubit Gate Calibration with QubiC Yilun Xu, Gang Huang, Ravi K. Naik, Alexis Morvan, Kasra Nowrouzi, Brad Mitchell, David Ivan Santiago, Irfan Siddiqi Two-qubit gate calibration is a complex and time-consuming task. We developed an efficient and systematic method to automatically tune up a CNOT gate with QubiC - a customized FPGA-based Qubit Control system at LBNL. The native cross-resonance (CR) gate time and amplitude were identified by stacking multiple CR pulses. We applied a virtual Z gate on a degenerate prepared state, followed by an X90 gate. By scanning the Z gate phase, we projected the state to any angle in the XY-plane, and spread out the noise among different angles, which enabled us to extract the CNOT parameters from curve fitting. The CNOT finder yielded two sets of parameters for the gate, with a global phase of 90 degrees between them. The CNOT gate found by this method was validated by two-qubit randomized benchmarking (RB). |
Thursday, March 18, 2021 9:36AM - 9:48AM Live |
R33.00009: A low-noise, flexible and scalable control paradigm for quantum computing in the NISQ era Jules C. van Oven, Jordy Gloudemans, Wouter Vlothuizen, Martin Woudstra, Marijn Tiggelman, Callum Attryde, Victor Negirneac, Damien Crielaard, Maxime Hantute, Cornelis Christiaan Bultink In the race towards quantum computers with real-life applications, major challenges have to be overcome: improving the quality of qubits and operations, scaling up the number of qubits, and harnessing algorithms with error mitigation and correction strategies. Crucial to this end is the control stack that orchestrates experiment execution, generates analog control pulses and interprets algorithm outcomes. We battle these challenges by providing hardware stacks that combine low noise and drift, a novel distributed instruction set architecture (ISA) and a scalable infrastructure for low-latency feedback. By enriching our distributed ISA with low-level access to pulse amplitudes, offsets and modulation phases, it allows users to bypass slow communication via external digital interfaces. This creates a system with wide applications in quantum computing and opens up new avenues in quantum error correction and efficient execution of calibration routines and variational quantum algorithms (VQA). |
Thursday, March 18, 2021 9:48AM - 10:00AM Live |
R33.00010: Characterization of the Cross Resonance Effect for Superconducting Transmon Qutrits Merrell Brzeczek, Alexis Morvan, Ravi K. Naik, Brad Mitchell, David Ivan Santiago, Irfan Siddiqi
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Thursday, March 18, 2021 10:00AM - 10:12AM Live |
R33.00011: Arbitrary controlled-phase gate on fluxonium qubits Haonan Xiong, Quentin Ficheux, Konstantin Nesterov, Long B Nguyen, Aaron Somoroff, Chen Wang, Maxim G Vavilov, Vladimir Manucharyan Recent achievements in quantum computing underlined the need of continuous families of two-qubit gates specially tailored for certain class of algorithms currently used on Noisy Intermediate Scale Quantum (NISQ) processors. In this work, we demonstrate the implementation of a continuous set of microwave-activated arbitrary controlled-phase (CPhase) gates on two fluxonium qubits, a promising candidate for quantum computation. We realized fast (110 ns) and precise (99.1% fidelity) CPhase gates by driving off-resonantly higher transitions. We assess the quality of our gates by performing quantum process tomography, interleaved randomized benchmarking and cross-entropy benchmarking. Additionally, we demonstrate that this technique can be used to cancel static ZZ interaction to mitigate quantum cross-talks between qubits. Unlike the equivalent gate on the transmon qubit, our scheme does not require any auxiliary degree of freedom nor parameter matching relieving the burden to scaling this approach to larger systems. We conclude the dominant error source is due to incoherent processes that could be mitigated to reduce errors in the 10^-3 range. |
Thursday, March 18, 2021 10:12AM - 10:24AM Live |
R33.00012: Robust quantum gates for qubit clusters with fixed coupling Nguyen Le, Max Cykiert, Eran Ginossar We design robustness optimal control for implementing a universal set of quantum gates in a finite-size cluster of up to 10 interacting qubits. We find that fidelity higher than 99% can be achieved with smooth pulses varying at less than 5% of the maximum amplitude per time bin. The gates are robust against significant uncertainty, up to 5%, in the qubit-qubit and field-qubit coupling strength. This is useful for large scale quantum computing with solid state devices where fabrication uncertainty is unavoidable, and for systems with slowly fluctuating fields. Transmons are chosen as a concrete example, but the method discussed is platform independent. |
Thursday, March 18, 2021 10:24AM - 10:36AM On Demand |
R33.00013: Control, Calibration and Characterization of a simulated two-transmon chip. Part 1 Federico Roy, Nicolas Wittler, Kevin Pack, Max Werninghaus, Anurag Saha Roy, Daniel Egger, Stefan Filipp, Frank K Wilhelm, Shai Machnes We demonstrate a new integrated open-source tool-set for Control, Calibration and Characterization (C3) [1] by applying it to a simulated example of a two-qubit quantum processor. |
Thursday, March 18, 2021 10:36AM - 10:48AM On Demand |
R33.00014: Control, Calibration and Characterization of a simulated two-transmon chip. Part 2 Nicolas Wittler, Federico Roy, Kevin Pack, Max Werninghaus, Anurag Saha Roy, Daniel Egger, Stefan Filipp, Frank K Wilhelm, Shai Machnes On the road towards high-fidelity quantum computers, it is desirable to obtain a model of the physical system that is detailed enough to understand the limits of gate fidelity. Such a process is arduous and impractical with increasing chip size. |
Thursday, March 18, 2021 10:48AM - 11:00AM On Demand |
R33.00015: Fast, noise-robust pulses for parametric entangling gates in superconducting qubits Christopher Bentley, Andre Carvalho, Michael Biercuk, Michael Hush, Alexander Hill, Nicolas Didier, Glenn Jones
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