Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B35: Quantum Control: Control Hardware and ElectronicsRecordings Available
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Sponsoring Units: DQI Chair: Eric Holland, Keysight Technologies Room: McCormick Place W-193B |
Monday, March 14, 2022 11:30AM - 11:42AM |
B35.00001: Superconducting Qubit Control with Single Flux Quantum Pulses in a Multi-chip Module Andrew L Ballard, Vito M Iaia, Tianna A McBroom, Jaseung Ku, Chuan-Hong Liu, Alexander M Opremcak, Chris D Wilen, Edward M Leonard, Matthew A Beck, Sohair Abdullah, Jonathan L DuBois, David Olaya, John P Biesecker, Adam J Sirois, Dan Schmidt, Joel N Ullom, Samuel P Benz, Peter Hopkins, Robert McDermott, B.L.T Plourde Conventional techniques for controlling superconducting qubits are challenging to extend to large multi-qubit arrays. A promising candidate for scalable control is the Single Flux Quantum (SFQ) digital logic family. In an initial monolithic implementation with qubits and SFQ elements on the same chip, the fidelity of SFQ-based qubit gates was limited by poisoning of the qubit from quasiparticles (QPs) generated by SFQ phase slips. In order to suppress poisoning from QP diffusion and the propagation of phonons generated by QP recombination, we have developed a multi-chip module with an SFQ driver on a classical control chip that is flip-chip coupled to a superconducting transmon qubit on a separate quantum chip. We characterize the QP poisoning in these devices for different qubit geometries, and we compare with earlier measurements on single-chip implementations of SFQ-based qubit control. We also discuss strategies for further mitigation of QP poisoning, including superconductor bandgap engineering. |
Monday, March 14, 2022 11:42AM - 11:54AM Withdrawn |
B35.00002: Distance-Independent Quantum CNOT Operation via Intermediate Measurements Casey Duckering, Jonathan M Baker, Frederic T Chong Quantum computers are fast approaching their potential to solve certain important problems in physics and chemistry. The problem size we can solve accurately, however, is bounded by low qubit coherence time. This time constraint is a major challenge. Consequently, programs are highly optimized to reduce duration and improve accuracy. Computer scientists have made significant progress in these optimization tools, enabling us to solve somewhat larger problems. However, with only optimization, we cannot overcome fundamental barriers. |
Monday, March 14, 2022 11:54AM - 12:06PM |
B35.00003: Towards ultra-high fidelity quantum operations: SQiSW gate as a native two-qubit gate Jiachen Huang, Dawei Ding, Qi Ye, Linghang Kong, Fang Zhang, Feng Wu, Xiaotong Ni, Hui-Hai Zhao, Yaoyun Shi, Jianxin Chen We propose SQiSW, the matrix square root of the standard iSWAP gate, as a native two-qubit gate for superconducting quantum computing. We show numerically that it has potential for an ultra-high fidelity implementation as its gate time is half of that of iSWAP, but at the same time it possesses powerful information processing capabilities in both the compilation of arbitrary two-qubit gates and the generation of large-scale entangled W-like states. Even though it is half of an iSWAP gate, its capabilities surprisingly rival and even surpass that of iSWAP or other incumbent native two-qubit gates such as CNOT. To complete the case for its candidacy, we propose a detailed compilation, calibration and benchmarking framework. In particular, we propose a variant of randomized benchmarking called interleaved fully randomized benchmarking (iFRB) which provides a general and unified solution for benchmarking non-Clifford gates such as SQiSW. For the reasons above, we believe that the SQiSW gate is worth further study and consideration as a native two-qubit gate for both fault-tolerant and noisy intermediate-scale quantum (NISQ) computation. |
Monday, March 14, 2022 12:06PM - 12:18PM |
B35.00004: Gate sequencing approach to reduce calibration and equipment overhead in qubit control Oleksiy Redko, Michael Senatore, Daniel L Campbell, Matthew LaHaye The set of any single pi/2 polar angle rotation on the Bloch sphere together with arbitrary azimuthal rotations (Z gates) allow universal gating on any two computational states. With qubit state sensitive readout, a simple 1D scan of transverse pulse amplitude can identify a candidate pi/2 polar angle gate. With just a single polar angle gate in the universal gate set, non-idealities in the polar angle as a function of pulse amplitude are ignorable. Z gates straightforwardly compensate for any azimuthal rotations accrued during such a pulse. Using this sequencing approach we demonstrate 0.9996(2) single qubit Clifford fidelities on a superconducting transmon qubit without the need for additional compensation for interactions with the second excited state, which reduces calibration overhead. In addition, this high fidelity gate sequencing uses only a single arbitrary waveform generator channel rather than the two that are typically required. Taken together, these attributes yield a simple, efficient, and robust new technique for single-qubit control. |
Monday, March 14, 2022 12:18PM - 12:30PM |
B35.00005: The QICK (Quantum Instrumentation Control Kit): Readout and control for qubits and detectors Sara F Sussman, Leandro Stefanazzi, Ken Treptow, Neal Wilcer, Chris Stoughton, Salvatore Montella, Collin Bradford, Gustavo Cancelo, Shefali Saxena, Horacio Arnaldi, Andrew A Houck, Ankur Agrawal, Helin Zhang, Chunyang Ding, David Schuster We introduce a Xilinx RFSoC-based qubit controller (called the Quantum Instrumentation Control Kit, or QICK for short) which supports the direct synthesis of control pulses with carrier frequencies of up to 6 GHz. The QICK can control multiple qubits or other quantum devices. The QICK consists of a digital board hosting an RFSoC (RF System-on-Chip) FPGA, custom firmware and software and an optional companion custom-designed analog front-end board. We characterize the analog performance of the system, as well as its digital latency, important for quantum error correction and feedback protocols. We benchmark the controller by performing standard characterizations of a transmon qubit. We achieve an average gate fidelity of 99.93%. All of the schematics, firmware, and software are open-source. In this talk we discuss the latest progress and developments on the QICK. |
Monday, March 14, 2022 12:30PM - 12:42PM |
B35.00006: A Customized FPGA-Based Control System for Superconducting Qubits Anastasiia Butko, Yilun Xu, Gang Huang, Thorsten Stezelberger, David I Santiago, Irfan Siddiqi A quantum control system is crucial for precise and reliable quantum computations. Existing off-the-shelf hardware lacks functional flexibility, decision-making speed and is not scalable. We address these limitations by developing custom FPGA control hardware. The system includes the frontend (QUASAR) that acts as an interface between the user software and low-level control electronics, and the backend (QubiC) that hides the complexity of the microwave generation and analog-to-digital conversion of the readout. The key component of the frontend is the control processor that manages quantum program execution. We developed QUASAR to facilitate quantum program execution for high control operation speed and future scalability. QubiC is an LBNL in-house developed open-source backend that provides a full control stack to the low-level hardware. As a result of the close proximity of the control processor and the analog backend, the extended quantum architecture allows us to make control decisions efficiently based on the measurement necessary for fast feedback. We demonstrated our custom control system on a Xilinx FPGA that can be used for a variety of quantum experiments with a superconducting quantum information processor. |
Monday, March 14, 2022 12:42PM - 12:54PM |
B35.00007: Superconducting qubit control with a system of an integrated microwave board and FPGA Makoto Negoro, Kazuhisa Ogawa, Takefumi MIYOSHI, Hidehisa Shiomi, Shinichi Morisaka, Mitsuki Kobachi, Kazuma Moriuchi, Ryohei Niwase, Yuta Kawai, Keisuke Koike, Satoshi Funada, Shuhei Tamate, Yutaka Tabuchi, Yasunobu Nakamura As the number of qubits increases toward the realization of fault-tolerant superconducting quantum computers, current microwave control systems will be limiting factor for the scalability. To address this issue, it is necessary to integrate and miniaturize a large number of microwave control units. As microwave components in C-and X-bands are prone to crosstalk on a board, which is detrimental to the qubit control fidelity, they are often assembled with connectorized milling cases for individual channels, leading to an obstacle to scaling up the system size. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B35.00008: Two-qubit gates for superconducting QC using direct-digital synthesis Riccardo Borgani, Mats Tholen, David B Haviland We describe the implementation of a microwave platform for readout and control of superconducting qubits. This platform, which we name Presto, is based on a radio-frequency system-on-chip (RFSoC) and leverages direct-digital synthesis (DDS). Thanks to DDS, Presto can directly control and readout qubits in the full 4-8 GHz band without the need for external analog mixers and local oscillators, making it a scalable and cost-effective solution for quantum-technology experiments. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B35.00009: Fully-integrated control stacks for quantum computing, part 1: stack overview Marijn Tiggelman, Jordy Gloudemans, Calin Sindile, Rahul Vyas, Jeroen van Straten, Victor Negirneac, Roel van Silfhout, Damien Crielaard, Diogo Valada, Damaz De Jong, Rene Stam, Luis Miguens Fernandez, Callum Attryde, Yemliha Bilal Kalyoncu, Jules van Oven, Cornelis Christiaan Bultink Reaching NISQ applications hinges on improvements in the gate fidelity and qubit number. Qblox supports this with time-efficient, ultralow-noise, and cost-effective control stacks. We introduce the Cluster system which incorporates processors capable of sequencing pulses, their parameters, and measurement operations in real time. This architecture speeds up experiments by orders of magnitude as it avoids the overhead caused by software-controlled loops. This speed-up is realized by multi-parameter real-time pulse modification by on-board data processing (integrating, averaging, binning) of readout signals and storing up to 131072 measurement results per experimental run. The state-of-the-art signal noise level (14 nV/√Hz @ 1 MHz) supports improved gate fidelities and the low gain and offset drift (a few ppm/K) reduces the need for recalibrations. The Cluster supports many qubit platforms with its wide frequency range from DC to 18.5 GHz while occupying less volume than 1 liter per controlled qubit. Quantify -an open-source python framework- manages the hardware stack, which allows hybrid scheduling of gate-level and pulse-level descriptions. This full-stack approach opens a fast track for gate optimizations and scaling efforts towards running NISQ applications. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B35.00010: Fully-integrated control stacks for quantum computing, part 2: step-by-step example experiments Jordy Gloudemans, Yemliha Bilal Kalyoncu, Marijn Tiggelman, Calin Sindile, Rahul Vyas, Jeroen van Straten, Victor Negirneac, Roel van Silfhout, Damien Crielaard, Diogo Valada, Damaz De Jong, Rene Stam, Luis Miguens Fernandez, Callum Attryde, Jules van Oven, Cornelis Christiaan Bultink In this talk, we demonstrate the fully-integrated control stack for quantum computing with two concrete examples: the characterization of transmon qubits and tuneup of quantum dots. For each, we go step-by-step through the stack: 1) We define experiments in the Quantify-Scheduler* as deterministically-timed operations with parameterized amplitude, offset, and modulation. 2) These abstract operations are converted into pulses and readouts which can be examined by the built-in visualization tools. 3) The schedules are compiled to pulse envelopes and hardware-executable programs (Q1 Assembly) which are uploaded to the hardware. 4) The experiment is executed by the Qblox Cluster which directly outputs and inputs all signals. The processed (integrated & averaged) measurement outcomes (up to 131k) are returned to the user. 5) Live plotting and data analysis tools are used for data visualization and interpretation. An extensive set of free and open-source experiment libraries allow for plug&play qubit characterization and save time for further, more sophisticated qubit operations. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B35.00011: In situ Characterization and Compensation of Flux Pulse Distortions at Long Time Scales Christoph Hellings, Richard Boell, Nathan Lacroix, Ants Remm, Johannes Herrmann, Stefania Lazar, Sebastian Krinner, Christian Kraglund Andersen, Francois Swiadek, Graham J Norris, Michael Kerschbaum, Mihai Gabureac, Christopher Eichler, Andreas Wallraff Accurate flux control of superconducting transmon qubits in quantum processors is a key ingredient for achieving high-fidelity two-qubit gates. While controlling nanosecond-scale dynamics is crucial for the fidelity of individual gates, time ranges up to tens of microseconds are relevant for combating memory effects during sequences of gates, and also for enabling flux-pulse-assisted characterization measurements. To accurately compensate flux pulse distortions, the flux line response needs to be characterized in situ, i.e., by using the qubit itself as a measurement device, which guarantees that the flux line configuration is exactly the same as during the later operation of the quantum processor. However, existing in situ methods are limited by the coherence time of the qubits, which makes them inapplicable on long time scales. In this talk, we present an in situ method to characterize linear distortions in the flux line for time ranges going beyond the coherence time of the qubits. Moreover, we present a method to calibrate a higher-order infinite impulse response (IIR) filter based on a single series of measurements, enabling an efficient tune-up of corrections on time scales ranging over three orders of magnitude. We confirm the successful compensation of the long-time distortions in dedicated verification measurements and by measuring two-qubit gate fidelities in long randomized benchmarking sequences. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B35.00012: Quantum optimal control on many-body ground state preparation in Jaynes-Cummings lattices Prabin Parajuli, Lin Tian The ability to engineer the desired quantum many-body state and dynamics is essential for quantum computing. However, due to noises and significant control errors in quantum devices, achieving this goal is extremely challenging. Robust algorithms like adiabatic algorithms often require a long evolution time to maintain a quantum system in a desired many-body state. But long evolution time increases the interaction time between the system and the environment, which leads to decoherence and errors in the system. To overcome this limitation, quantum optimal control (QOC) theory has been developed. QOC is a numerical technique to design fast and robust control pulses to drive the quantum system to the target state under a given set of constraints. Here we use QOC with Chopped-Random Basis (CRAB) algorithm to prepare quantum many-body ground states in Jaynes-Cummings lattices. Our study shows that a high-fidelity many-body ground state can be prepared in a significantly shorter time using the CRAB algorithm than using the adiabatic algorithm. We find the minimal evolution time for achieving fidelity above 0.99 under various parameter constraints. We also analyze the effect of Gaussian noise in the control parameters on the fidelity of prepared states at the optimal evolution time. This study provides insight into the development of fast and efficient quantum algorithms for the many-body ground state preparation in quantum devices. |
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