Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M71: Superconducting Qubit Optimal Control IIFocus
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Sponsoring Units: DQI Chair: Eunjong Kim, Caltech Room: Room 407/408 |
Wednesday, March 8, 2023 8:00AM - 8:12AM |
M71.00001: Optimal control for reduced leakage in superconducting qubits using bichromatic driving Abhishek Chakraborty, Noah J Stevenson, Daniel D Briseno, Trung K Le, Andrew N Jordan, Justin G Dressel, David I Santiago, Irfan Siddiqi We investigate optimal control for reduced leakage in superconducting transmon qubits using microwave drives for both the 0-1 and 1-2 level transitions. We engineer the pulses to minimize the distance to the target unitary, leakage and total energy of the pulse envelope while also tuning the degree of smoothness, for different parametrizations of the control pulse. Weighting these factors differently leads to different optimal pulses, some of which suppress leakage throughout while others utilize higher-level excitations during the gate. We compare our results to single microwave drive DRAG and GRAPE-optimized pulses in terms of leakage and overall gate fidelity. Finally, we extend this optimization technique to the case of two-qubit gates for fixed-frequency and tunable transmon qubits. Our technique is architecture agnostic and we discuss its extension to novel qubits such as fluxonium. |
Wednesday, March 8, 2023 8:12AM - 8:24AM |
M71.00002: High fidelity, universal gates on a noise-decoupled, coherence enhanced flux-tunable transmon Michael Senatore, Daniel L Campbell, Matthew LaHaye Flux tunable superconducting qubits often have decay-limited coherence at flux sweet spots but may suffer from high pure-dephasing while they are flux biased away from that sweet spot. We present the results of our experiment, performing fast, high fidelity, universal single-qubit gates, on a noise-decoupled flux-tunable transmon qubit that is biased far away from its flux sweet spot. Under these conditions, the noise-decoupled transmon benefits from a factor of 10 enhancement of coherence. This technique can expand operational ranges of qubits, broadening the selection of viable qubit operational regimes by making qubits in otherwise low-coherence configurations operable with high coherence. The efficacy of this technique is not limited to the superconducting circuits. |
Wednesday, March 8, 2023 8:24AM - 8:36AM |
M71.00003: Learning-based Calibration of Flux Crosstalk in a Transmon Qubit Array Cora N Barrett, Amir H Karamlou, Sarah E Muschinske, Ilan T Rosen, Alexander Melville, Bethany M Niedzielski, Jonilyn L Yoder, Mollie E Schwartz, Jeffrey A Grover, William D Oliver Flux-tunable transmon qubit arrays are a promising platform for quantum computation and simulation. A challenge in scaling this platform, however, is the flux crosstalk in the system. In order to exercise precise control, we need to measure this flux crosstalk, and compensate for it. Brute force approaches to flux crosstalk calibration scale quadratically with the number of qubits in the array. As we strive towards chips with hundreds of qubits, we need an extensible approach. We propose an iterative learning-based procedure to calibrate flux crosstalk. Based on statistical tests on simulated data, we have demonstrated our calibration protocol to be accurate (less than 1 MHz mean frequency error for qubits with a maximum frequency of 5 GHz) and to scale approximately linearly with array size. We have experimentally implemented this calibration protocol on planar and 3D integrated flip-chip devices, enabling precise control of qubit frequencies with an approach that will extend naturally as we fabricate larger qubit arrays. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M71.00004: Power-efficient all-microwave manipulation of superconducting qubits with a fixed-frequency transmon coupler Shotaro Shirai, Yuta Okubo, Kohei Matsuura, Alto Osada, Yasunobu Nakamura, Atsushi Noguchi The fixed-frequency transmon system is a promising candidate for practical quantum processor thanks to its long coherence time and low wiring cost. However, such architecture requires all-microwave entangling gates enabled with precise qubit-frequency allocation, which is a significant burden on design and fabrication. To address this issue, we propose and experimentally demonstrate a novel power-efficient all-microwave entangling gate using a fixed-frequency transmon coupler. This scheme, which tolerates relatively large frequency variations of qubits, executes a controlled-Z gate with 97.7(2)% average fidelity and eliminates residual ZZ interaction. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M71.00005: Error budget of parametric-resonance gates using a tunable coupler Vinay Tripathi, Shobhan Kulshreshtha, Amy F Brown, Simon Devitt, Mark J Hodson, Jerome Lenssen, Arshpreet S Maan, Kevin Obenland, Alexandru Paler, David R Perez, Nariman Sadantman, Yuval R Sanders, Phattharaporn Singkanipa, Eyob A Sete, Josh Y Mutus, Daniel A Lidar We study the parametric-resonance gate activated in a system of two transmons coupled via a tunable coupler. Entangling gates such as iSWAP, CZ and fsim can be enacted by modulating one of the qubits through a flux control and using the resulting central band. We employ numerical simulations based on multilevel systems to analyze the performance of the gates as a function of gate duration. We systematically study the error budget of the gate, which is mainly dominated by leakage, ZZ coupling and the decoherence time of the qubits. We explore the dependence of the gate fidelity on several other parameters, such as pulse shape, and coupler flux controls. Other optimal control techniques are also used to design pulses for both the coupler and the qubits, resulting in higher-fidelity gates. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M71.00006: Controlling ultrahigh-quality microwave resonators with noisy nonlinear circuits Ondrej Cernotik, Iivari Pietikäinen, Radim Filip, Steven M Girvin Three-dimensional microwave cavity resonators can reach lifetimes of the order of a second by maximizing the cavity volume relative to its surface. Such cavities represent an ideal platform for quantum computing with bosonic qubits but their efficient control remains an outstanding problem since the large mode volume results in inefficient coupling to nonlinear elements used for their control. Moreover, this coupling introduces additional cavity decay via the inverse Purcell effect which can easily destroy the advantage of long intrinsic lifetime. In this talk, we will discuss conditions on, and protocols for, efficient control of these ultrahigh-quality microwave cavities using conventional nonlinear circuits. We will compare various schemes based on resonant and dispersive interactions of the cavity with the control element and strategies for enhancing these interactions using suitable pumping of the cavity and control circuit. Our work thus explores a potentially viable roadmap towards using ultrahigh-quality microwave cavity resonators for storing and processing information encoded in bosonic qubits. |
Wednesday, March 8, 2023 9:12AM - 9:48AM |
M71.00007: Optimized control of superconducting qubits Invited Speaker: Stefan Filipp To enhance the capabilities of today’s quantum processors not only the coherence of qubits, but also the preparation of complex quantum states via optimized control signals needs further improvement. For quantum processors based on superconducting qubits it is of particular importance to avoid leakage out of the computational subspace, which is facilitated by the low anharmonicity of transmon-type qubits. This can be achieved by optimizing the shape of the control pulses utilizing closed-loop optimization methods to tailor the microwave pulses towards short and high-fidelity gates. Using a piecewise-constant pulse parameterization we demonstrate single-qubit pulses as short as 4ns with low leakage out of the computational subspace. For the rapid calibration and optimization of single-qubit operations we employ a ‘restless’ measurement protocol that uses the outcome of a projective measurement as the initial state of the next operation. Along with an efficient analysis that compensates for distortions in the signal due to SPAM errors this allows for data collection at a high rate of the order of 100 kHz, which is not limited by the decay time of the qubits. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M71.00008: Cloaking a qubit in a cavity Cristóbal Lledó, Rémy Dassonneville, Adrien Moulinas, Joachim Cohen, Ross Shillito, Audrey Bienfait, Benjamin Huard, Alexandre Blais Cavity and circuit quantum electrodynamics (QED) explore light-matter interaction at its most fundamental level, providing the tools to control the dynamical evolution of single atoms and photons in a deterministic fashion. In this work, we introduce a simple approach to engineer a situation where, in the presence of a cavity drive, an atom decouples from the classical part of the cavity field, perceiving the resonator as if it was in the vacuum state. In this situation, the atom and the cavity undergo Rabi oscillations in the strong coupling regime even when the resonator is loaded with photons, while in the dispersive regime, the atom experiences no ac-Stark frequency shift nor photon-induced dephasing. Since the qubit feels an empty cavity, its manipulation remains unperturbed, maintaining constant gates fidelities in the presence of cavity photons. Exploiting this latter effect, we will show how to accelerate dispersive qubit readout. We will theoretically introduce this approach and then provide an experimental demonstration of the concept using a superconducting transmon qubit. This adds a new element to the toolbox of cavity/circuit QED. |
Wednesday, March 8, 2023 10:00AM - 10:12AM Author not Attending |
M71.00009: Demolition measurement of superconducting qubits Ashutosh Mishra, Shai Machnes, Frank Wilhelm-Mauch Qubit initialization, state preparation, and measurement are some of the core components of quantum computation using superconducting qubits. Traditional methods to initialize the state of the qubit rely on waiting a few T1 times for the qubit to decay into the ground state. But, with better qubit designs (increased coherence time) initialization by this method would lead to longer wait times. Additionally, algorithms like quantum error correction require the qubits to be re-initialized quickly. This necessitates the need for an active reset protocol. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M71.00010: Optimized qubit reset in a multimode superconducting circuit Marc-Antoine Lemonde, Valentin Kasper, Dany Lachance-Quirion, Jean Olivier Simoneau, Sara Turcotte, Julien Camirand Lemyre, Philippe St-Jean Having the ability to efficiently reset a qubit in its ground state is essential for performing fast and reliable quantum computation. Recently, a fast and unconditional all-microwave reset of a superconducting qubit via a lossy cavity has been successfully implemented; allowing to perform this operation without the use of active feedback [1]. The reset is also a key element for autonomous stabilization of Gottesman-Kitaev-Preskill (GKP) states with the added complexity of having the qubit coupled to an additional, long-lived, cavity mode. In this setup, the unconditionality of the qubit reset is more challenging and the back-action of the controls further detrimental. Our work explores optimal quantum control in open systems to design feasible and efficient microwave pulse sequences that maximize the gate efficiency and minimize its impact on the logical lifetime of the GKP states. We compare the experimental implementation of the pulse sequence proposed in ref. [1] with optimized protocols and comment on the practical benefits of using optimized pulse sequences. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M71.00011: Quantum-circuit refrigerator for reset of superconducting qubits Mikko Möttönen, Timm F Mörstedt, Vasilii Sevriuk, Matti Silveri, Gianluigi Catelani, Hao Hsu, Louis Lattier, Maaria Tiiri, Tapio Ala-Nissila, Arto Viitanen, Máté Jenei, Leif Grönberg, Wei Liu, Jami Rönkkö, Fabian Marxer, Matti Partanen, Jukka Räbinä, Johannes Heinsoo, Tianyi Li, Jani Tuorila, Vasilii Vadimov, Juha Hassel, Kuan Y Tan Quantum-circuit refrigerator (QCR) [1] is an active on-chip component which can change the dissipation rate in superconducting microwave devices in-situ by orders of magnitude. The dissipation channels can be turned on and off by applying a dc or rf voltage, or both [2]. Such an additional energy input together with an energy quantum from the refrigerated quantum circuit promotes photon-assisted quasiparticle tunneling through a normal-metal–insulator–superconductor junction. Previously, we have experimentally demonstrated that a QCR can change the quality factor of a superconducting microwave resonator by several orders of magnitude also giving rise to an effective Lamb shift of the resonator frequency [3] and that the dissipation can be turned on or off in a few nanoseconds [4]. We have also demonstrated that a superconducting qubit can be reset with a QCR from 100% to a few percent population in less than 100 ns. However, we observed non-exponential decay of the population rendering the optimization of the qubit reset involved. Here, we introduce a single-junction QCR [5] which simplifies the optimal control pulses, removes non-idealities related to junction asymmetry, increases the physical distance between the QCR and the qubit, and provides opportunities for optimizing the coupling strength for inimal spurious dissipation. We report on the first experiments of the single-junction QCR coupled to a transmon qubit and provide evidence supporting these claims. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M71.00012: Control of superconducting qubits using a superconducting circuit at 3K. Manuel A Castellanos-Beltran, Adam J Sirois, Logan Howe, David Olaya, John P Biesecker, Paul D Dresselhaus, Samuel P Benz, Peter Hopkins In superconducting qubit technology, the control, monitoring, and feedback are typically accomplished using commercial off-the-shelf, and therefore large-footprint room-temperature electronics. Even as more custom electronics are used with larger scale systems, the size, power dissipation, and complexity associated with these classical components of QI systems are not scalable to the large numbers of qubits projected for a fault-tolerant quantum computer. Integration of control/readout electronics at cryogenic temperatures offers an attractive solution to these challenges and benefits from reduced latency feedback via proximity with the quantum hardware. In this talk, I will describe our use of a Josephson pulse generator (JPG) at the 3 K stage of a dilution refrigerator to digitally control a transmon qubit. I will show that we achieve comparable qubit control using both our JPG and traditional semiconductor-based control electronics. Finally, I will discuss our efforts to improve upon these results by incorporating a new JPG design that is compatible with traditional Single-Flux-Quantum logic circuits and includes a memory element for storing pulse-sequenced digital gates at cryogenic temperatures. |
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