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 Q72: Superconducting and Semiconductor Qubits: I/O, Packaging, and 3D Integration II |
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Sponsoring Units: DQI Chair: Matthias Mergenthaler, IBM Research Europe - Zurich Room: Room 406 |
Wednesday, March 8, 2023 3:00PM - 3:12PM |
Q72.00001: Time-division multiplexed superconducting qubit control using ultra-low-power, base-temperature cryo-CMOS multiplexer Rohith Acharya, Steven Brebels, Alexander Grill, Jeroen Verjauw, Tsvetan Ivanov, Daniel Perez Lozano, Danny Wan, Jacques Van Damme, A. M. Vadiraj, Massimo Mongillo, Bogdan Govoreanu, Jan Craninckx, Iuliana P Radu, Georges Gielen, Francky Catthoor, Anton Potocnik, Kristiaan De Greve Large-scale superconducting quantum computing systems entail high-fidelity control and readout of large numbers of qubits at millikelvin temperatures. State-of-the-art control architectures use dedicated control lines for each qubit, thereby resulting in a massive input-output bottleneck. The hardware cost and wiring complexity for large-scale systems can be significantly reduced by functionally multiplexing the qubit control lines at the base temperature stage of a dilution refrigerator. In this talk, we demonstrate the feasibility to perform functional time-division multiplexing of qubit control signals using a custom-designed, ultra-low power (<1 µW), fast switching (~2 ns) cryo-CMOS multiplexer operating at the base temperature stage of a dilution refrigerator, with port-to-port signal crosstalk suppressed by greater than 30 dB. We employ this capability to demonstrate novel two-qubit operations using a single qubit control line in a tunable-coupler based two-qubit device. Finally, we discuss the limitations and the scalability of the multiplexer for large-scale systems. Our results pave the way for a viable path to address the wiring bottleneck for large-scale quantum processor control and quantum error correction protocols. |
Wednesday, March 8, 2023 3:12PM - 3:24PM |
Q72.00002: Vector microwave signal modulators using high kinetic inductance superconductors M. Pushp1, N. D. Johnson1, and A. J. Sigillito11Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA Mridul Pushp, Noah D Johnson, Anthony Sigillito Conventional microwave mixers are unsuitable at cryogenic temperatures owing to their large insertion loss and high power dissipation. As quantum computing systems are scaled-up, to reduce cabling overheads in the dilution refrigerators there is an advantage to integrating the classical control electronics on chip at cryogenic temperatures. Here, we describe a fully-superconducting phase and amplitude modulator based on high kinetic inductance transmission lines offering a bias current tuneable impedance. We describe device geometries designed to offer amplitude and phase modulation as well as frequency up-conversion at millikelvin temperatures. Device performance and a route towards ultra-low-loss multiplexing will be discussed. Although designed to scale up control of quantum dot spin qubits, these modulators are expected to be useful for other quantum computing architectures utilizing microwave control. |
Wednesday, March 8, 2023 3:24PM - 3:36PM |
Q72.00003: Control-Signal Crosstalk in Flip-Chip Superconducting Quantum Processors Sandoko Kosen, Hang-Xi Li, Andreas Nylander, Marcus Rommel, Marco Caputo, Kestutis Grigoras, Leif Grönberg, Robert Rehammar, Liangyu Chen, Christian Križan, Christopher Warren, Giovanna Tancredi, Janka Biznárová, Amr Osman, Anita F Roudsari, Alexey Zadorozhko, Miroslav Dobsicek, Tahereh Abad, Jorge Fernández-Pendás, Göran Johansson, Anton F Kockum, Per Delsing, Joonas Govenius, Jonas Bylander We present recent results on the crosstalk performance of our multi-qubit processors. The processors are fabricated based on the quantum-compatible flip-chip technology demonstrated in Ref.[1]. The choice of device architecture (fixed-frequency transmons, frequency-tunable couplers) requires multiple control lines, carrying both DC and/or RF signals, routed in proximity to each other and in a way that is scalable to larger processors. For such a routing scheme to be scalable, the total crosstalk has to be low enough. We will discuss how far we are from this goal and what we have done to reach our level of performance. |
Wednesday, March 8, 2023 3:36PM - 3:48PM |
Q72.00004: Scalable Flexible Coaxial Ribbon Cables for High-Density Quantum Wiring (Part I) Jenny Smith, Tucker Vana, Kyle Thompson, Alirio Boaventura, Johanna Zultak, Benjamin Mazin Superconducting electronics often require high-density microwave interconnects capable of transporting signals between temperature stages with minimal loss, cross talk, and heat conduction. We report improvements on the design and fabrication of superconducting 53 wt% Nb-47 wt% Ti (Nb47Ti) FLexible coAXial ribbon cables (FLAX). The cables are designed to operate up to 20 GHz and use G3PO coaxial push-on connectors. 3D E&M simulations were performed to optimize the connector transition, predict the cable characteristic impedance, and inform manufacturing decisions. The design improvements are being incorporated into a roll-to-roll manufacturing system by Maybell Quantum Industries in preparation for offering the cables commercially. The presentation will detail improvements to the design and provide updated performance metrics in comparison with existing commercial solutions. |
Wednesday, March 8, 2023 3:48PM - 4:00PM |
Q72.00005: Scalable Flexible Coaxial Ribbon Cables for High-Density Quantum Wiring (Part II) Kyle Thompson, Tucker Vana, Jennifer Smith, Alirio Boaventura, Johanna Zultak, Ben Mazin As quantum processors increase in complexity, fitting sufficient high-quality input/output (I/O) and RF data cables and connectors into the limited footprint of a dilution refrigerator is becoming increasingly complex. Traditional semi-rigid RF cables have a large footprint, thermal load, and stiffness. A novel Ribbon Cable has been developed on-scale which offers high density, low attenuation, low crosstalk, low heat load, and low production costs. In this presentation we share progress on the cable production system using a custom laser welding technique to produce a low-cost, high-performance quantum I/O solution. Cable properties, including heat load, pitch density, and contact resistance between the cables and connectors have been calculated and measured at 300K, 4K, and 100mK for superconducting and non-superconducting FLEX lines are reported and show the cable's suitability as a high-density cable solution. |
Wednesday, March 8, 2023 4:00PM - 4:12PM |
Q72.00006: Optical Interfaces for Superconducting Microwave Circuits Matthew J Weaver, Robert Stockill, Frederick Hijazi, Thierry van Thiel, Martin Zemlicka, Simon Groeblacher Quantum computers will soon exceed the space and thermal cooling capacity of single cryogenic systems. One of the biggest bottlenecks is microwave lines going into and out of dilution refrigerators. Recent experiments have demonstrated optical readout of superconducting qubits [1,2] and high fidelity control and readout pulse generation [3] via an optical fiber. In order to scale these approaches to meet the size and fidelity requirements of state-of-the-art quantum processors a number of improvements are required, including microwave and optical multiplexing. We discuss active and passive heat loads and the efficiency and added noise requirements for optical to microwave and microwave to optical subsystems. We outline how these technologies could support quantum computers with sufficient qubit numbers for practical applications. |
Wednesday, March 8, 2023 4:12PM - 4:24PM |
Q72.00007: Temperature Performance of Magnetic Shielding for Multi-Qubit Chip Carrier Soren Andresen, Patrick Paluch, Alexander Zilz, Ioan-Mihai Pop, Wolfgang Wernsdorfer Quantum error correction for fault tolerant quantum computing will require dense one- and two-qubit gate sequences with minimal generation of noise and heating effects. Flux-tunable superconducting qubits have recently been implemented in a surface-code-inspired geometry [1], utilizing frequency tuning and short gate operations at the cost of increased flux-bias noise [2]. Overall, microwave and magnetic shielding is considered crucial for achieving high coherence and fidelity in a wide variety of superconducting qubit experiments. |
Wednesday, March 8, 2023 4:24PM - 4:36PM |
Q72.00008: Surface Acustic Wave filters for superconducting qubits David Eslava, Eloi Guerrero, Lluis Acosta, Paul Jamet, Yifei Chen, Joel Pérez, Chris Hensel, Albert Solana, Daniel Szombati, Ramiro Sagastizabal, Pedro de Paco, Pol Forn-Díaz In an open system, the dynamical evolution of a qubit state is non-deterministic due to the stochastic noise, leading to qubit state decoherence. In the case of the qubit readout circuit, even when the readout resonator is far off-resonance, the qubit is still damped to some degree. By using a Purcell filter, qubit loss is reduced by several orders of magnitude. |
Wednesday, March 8, 2023 4:36PM - 4:48PM |
Q72.00009: Cryogenic Thermal Modeling for Scalable High Density Signaling Naomi E Raicu, Tom Hogan, Thomas Douglas, David P Pappas, Xian Wu, David Snow, Mark Field, Matthew Hollister Upscaling quantum computers based on superconducting qubits necessitates the addition of many microwave signal lines to a dilution refrigerator without overwhelming the available cooling power at each stage with heat loads. As each signal line is composed of several different materials, calculating these heat loads requires models of the thermal conductivities versus temperature for the static load of each material component in addition to models of the electrical resistances as a function of temperature for the Ohmic losses associated with each component. While comprehensive thermal conductivity models exist for various grades of copper and aluminum, models for other materials, such as alloys like cupronickel, remain to be synthesized. |
Wednesday, March 8, 2023 4:48PM - 5:00PM |
Q72.00010: Characterization of Chip Packaging for Multi-Qubit Quantum Processors Merlin von Soosten, Slawomir Simbierowicz, Volodymyr Monarkha, Soren Andresen, Russell E Lake Noisy Intermediate-Scale Quantum (NISQ) superconducting hardware are nowadays widely used to demonstrate surface codes algorithm as well as quantum simulators implementation [1,2]. However, despite having achieved single and two-qubit gates with fidelity above the surface code threshold limit [3], further improvement is required to reduce the number of physical qubits that will be required to operate a fault-tolerant quantum computer. |
Wednesday, March 8, 2023 5:00PM - 5:12PM |
Q72.00011: Quantifying the power radiated to a qubit through its control lines Slawomir Simbierowicz, Volodymyr Monarkha, Nurul Huda, Russell E Lake We report measurements of the power radiated from a qubit drive line to a quantum device within a dilution refrigerator. The measurements were recorded using an in situ hot electron microwave nanobolometer with a designed-50- Ω absorber [1] that is coupled to a coaxial input. First, the nanobolometer was calibrated by connecting a temperature-controlled blackbody source spanning the range 0.1 K –0.5 K [2]. Second, applying a microwave tone at 5.8 GHz, we measure the background radiated power and attenuation from the passive components in the drive line. Finally, we obtain the thermal latencies of those components. Our measurement results are crucial for understanding and suppressing qubit dephasing due to photon shot noise [3]. |
Wednesday, March 8, 2023 5:12PM - 5:24PM |
Q72.00012: Noise and signal distortions in qubit wiring Russell E Lake, Md Nurul Huda, Volodymyr Monarkha, Slawomir Simbierowicz, Antti P Vaaranta In this talk we highlight recent measurements to accurately characterize cryogenic qubit control and readout lines at microwave frequencies. Through combined theoretical and experimental studies, we quantify the qubit-gate errors that arise due to signal distortions and present direct measurements of the S-parameters of qubit control line components in situ [1]. We also demonstrate a cryogenic variable temperature noise source [2] to determine noise temperature of readout lines that use three-wave mixing parametric amplifiers. In addition, temperature-calibrated added noise can be used as a diagnostic resource to quantify thermalization requirements for qubit wiring [3]. Taken together our results provide a methodology for extrapolating system-level performance metrics for the i/o of large-scale quantum computers based on individual wiring components. [1] S. Simbierowicz, V. Y. Monarkha, S. Singh, N. Messaoudi, P. Krantz, R. E. Lake, "Microwave calibration of qubit drive line components at millikelvin temperatures", Appl. Phys. Lett. 120, 054004 (2022); [2] S. Simbierowicz, V. Vesterinen, J. Milem, A. Lintunen, M. Oksanen, L. Roschier, L. Grönberg, J. Hassel, D. Gunnarsson, R. E. Lake, "Characterizing cryogenic amplifiers with a matched temperature-variable noise source", Rev. Sci. Instr. 92, 034708 (2021); [3] A. Vaaranta, M. Cattaneo, R. E. Lake “Dynamics of a dispersively coupled transmon qubit in the presence of a noise source embedded in the control line” Phys. Rev. A 106, 042605 (2022) |
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