Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J07: Superconducting Qubits: Josephson Junction-based Amplifiers and Parametric Devices I |
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Sponsoring Units: DQI Chair: Archana Kamal Room: 102 |
Tuesday, March 3, 2020 2:30PM - 2:42PM |
J07.00001: Design and Fabrication of Impedance Matched Parametric Amplifiers for Quantum Applications Joel Grebel, Audrey Bienfait, Hung-Shen Chang, Ming-Han Chou, Christopher R Conner, Etienne Dumur, Gregory Peairs, Rhys G Povey, Youpeng Zhong, Andrew Cleland Josephson parametric amplifiers (JPAs) are an important resource for the single-shot readout of superconducting qubits. Being able to amplify signals at the quantum limit, with noise approaching 1/2-photon for phase-independent gain [1], enables high fidelity measurements of single as well as multiplexed qubits. We will describe the circuit designs and fabrication process for on-chip impedance matched lumped-element JPAs ([2], [3]) operated in both three-wave and four-wave mixing modes. We will present data on the devices’ gain, saturation power, and bandwidth. Key improvements from the previous year’s design will be discussed as well as practical advice for ensuring reliable performance in the cryogenic environment. |
Tuesday, March 3, 2020 2:42PM - 2:54PM |
J07.00002: Josephson Array Mode Parametric Amplifier Volodymyr Sivak, Shyam Shankar, Gangqiang Liu, Jose Aumentado, Michel H. Devoret We introduce a novel near-quantum-limited amplifier with a large tunable bandwidth and high dynamic range – the Josephson Array Mode Parametric Amplifier (JAMPA). The signal and idler modes involved in the amplification process are realized by the array modes of a chain of 1000 flux tunable, Josephson-junction-based, nonlinear elements. The frequency spacing between array modes is comparable to the flux tunability of the modes, ensuring that any desired frequency can be occupied by a resonant mode, which can further be pumped to produce high gain. We experimentally demonstrate that the device can be operated as a nearly quantum-limited parametric amplifier with 20dB of gain at almost any frequency within (4−12)GHz band. On average, it has a 3dB bandwidth of 11MHz and input 1dB compression power of −108dBm, which can go as high as −93dBm. We envision the application of such a device to the time- and frequency-multiplexed readout of multiple qubits, as well as to the generation of continuous-variable cluster states. |
Tuesday, March 3, 2020 2:54PM - 3:06PM |
J07.00003: Frequency Tunable Josephson Traveling Wave Parametric Amplifier with Nondegenerate Pump Phase Matching Kaidong Peng, Mahdi Naghiloo, Kevin O'Brien Resonantly phase-matched Josephson traveling wave parametric amplifiers (JTWPAs) with gigahertz of bandwidth and near-quantum limited noise performance are now widely used in superconducting quantum computing experiments. For such conventional single-pump JTWPAs, resonators are critical to cancel phase mismatch from both the normal group velocity dispersion and the nonlinear phase modulations. However, these resonators make up half of the device footprint, require high fabrication uniformity, and fix the device operating frequency. Here we develop a resonator-free, dual-pump JTWPA with a reduced footprint, wider bandwidth, but comparable gain, dynamic range, and noise performance. In contrast to the resonant phase matching technique, our dual-pump scheme generates a linear phase mismatch which naturally compensates the nonlinear phase mismatch. In addition to their larger fabrication tolerance, these dual-pump JTWPAs have dynamically reconfigurable frequency bands controlled by the frequency detuning of the two pumps. These devices will open up new possibilities for tunable amplification, both phase sensitive and preserving, applicable to cQED and higher-frequency cosmological applications. |
Tuesday, March 3, 2020 3:06PM - 3:18PM |
J07.00004: Minimal manifestation of Kerr-mediated frequency combs in superconducting circuits Pinlei Lu, Saeed Khan, Tzu-Chiao Chien, Xi Cao, Hakan Tureci, Michael Jonathan Hatridge In this presentation, we present an experimental realization of a coherently driven, Kerr-mediated, microwave frequency comb. Our device consists of two superconducting modes: a mode with modest Kerr-nonlinearity strongly coupled to a second, linear mode. We explore the phase space of the two-mode system, including the transition from a stable regime to a region where the system settles into limit cycle dynamics exhibiting a frequency comb [1]. Temporal correlation function measurements reveal it is highly coherent, with a phase coherence as 30 μs, significantly exceeding the bare mode decay times of 15 ns. Additionally, in contrast to standard optical comb devices the comb’s coherence is strongly influenced by quantum fluctuations due to the intrinsic Kerr nonlinearity of the system. This result is further supported by excellent agreement of comb coherence and dynamics measurements with a microscopic quantum theory of the two-mode system. The combination of strong and engineerable interactions in our system makes it a promising platform for engineering spectrally broader and denser microwave frequency combs, and also a good testbed for studying complex quantum nonlinear dynamics. |
Tuesday, March 3, 2020 3:18PM - 3:30PM |
J07.00005: Impedance-matched Josephson parametric amplifier using open stubs as shunt capacitance Yoshiro Urade, Kun Zuo, Kunihiro Inomata, Zhirong Lin, Tsuyoshi Yamamoto, Yasunobu Nakamura Broadband Josephson parametric amplifiers (JPAs) are essential devices for frequency-multiplexed readout of integrated superconducting qubits towards large-scale quantum computers. Lumped capacitors such as parallel-plate capacitors are often used for such broadband JPAs to bring LC resonance with Josephson inductances to the GHz frequency region. Fabricating insulating layers of the parallel-plate capacitors makes fabrication process complex and causes additional dielectric losses. |
Tuesday, March 3, 2020 3:30PM - 3:42PM |
J07.00006: Four-port directional parametric amplifier Vidul Joshi, Gangqiang Liu, Andrew Lingenfelter, Shyam Shankar, Michel H. Devoret Quantum limited parametric amplifiers based on Josephson junctions are important for measurement of superconducting qubits. Traditionally, these are reflection amplifiers which need external non-reciprocal elements to separate the input from the output. It is possible however, to make multi-mode circuits and drive multiple parametric processes together to achieve non-reciprocity. Three-mode devices based on these techniques that have been made so far have either lacked output matching or provide unity reverse gain, thus relying on perfectly well matched and thermalized output lines. Adding a fourth mode can solve these issues and can help us build a fully directional parametric amplifier. We present the design and experimental progress towards realizing such a four-mode device which under appropriate drive conditions would act like an amplifier which has appreciable forward gain, has perfect isolation, is input- and output-matched and has an auxiliary port which acts as the cold load. |
Tuesday, March 3, 2020 3:42PM - 3:54PM |
J07.00007: Pump-power-efficient 3-wave mixing Josephson parametric amplifier Wei Dai, Volodymyr Sivak, Gangqiang Liu, Shyam Shankar, Michel H. Devoret Josephson Parametric Amplifiers (JPAs) are commonly used in superconducting quantum information processing. In linear amplification regime, a JPA typically requires pump that is orders of magnitude stronger than its output power. Larger signal power handling of a JPA would require application of even stronger pump. However, maximum pump power delivered to a JPA, which is proportional to power dissipated in attenuators, is limited by cooling power of dilution fridges. To address this limitation, we apply on-chip impedance engineering to enable strong coupling of the off-resonance pump to a 3-wave-mixing JPA. Compared to similar JPAs with a capacitively coupled pump port or mutual-inductively coupled flux-pumping, this design requires at least an order of magnitude less pump power, while achieving theoretically quantum-limited amplification with state-of-the-art dynamic range. Preliminary experimental results will be shown. |
Tuesday, March 3, 2020 3:54PM - 4:06PM |
J07.00008: Optimizing Josephson-Ring-Modulator-based Josephson Parametric Amplifiers via full Hamiltonian control Chenxu Liu, Tzu-Chiao Chien, Michael Jonathan Hatridge, David Pekker A Josephson Parametric Amplifier (JPA) with a large saturation power is an essential ingredient to achieve efficient quantum sensing and qubit readout in superconducting quantum computing circuits. In a previous work, we showed that the saturation power of JPAs is not limited by pump depletion, but instead by the strong nonlinearity of Josephson junctions, the nonlinear circuit elements that enables amplification in JPAs [1]. Here, we present a systematic study of the nonlinearities in JPAs, we show which nonlinearities limit the saturation power, and present a strategy for optimizing the circuit parameters for achieving the best possible JPA. For concreteness, we focus on JPAs that are constructed around a Josephson Ring Modulator (JRM). We show that by tuning the external and shunt inductors, we should be able to take the best experimentally available JPAs and improve their saturation power by ~ 15dB. Finally, we argue that our methods and qualitative results are applicable to a broad range of JPAs with few-Josephson junctions like SNAILs. |
Tuesday, March 3, 2020 4:06PM - 4:18PM |
J07.00009: Dependence of Kerr nonlinearity on junction array size in Josephson parametric amplifiers Gangqiang Liu, Volodymyr Sivak, Shyam Shankar, Luigi Frunzio, Michel H. Devoret Josephson parametric amplifiers have become indispensable components of superconducting quantum computing devices. However, their gain saturation power, which is limited by Kerr nonlinearity of Josephson junctions, is still too low for large scale readout.One way to suppress the Kerr nonlinearity, therefore improving the gain saturation power, is to replace the single Josephson element with an array of such elements. We investigate the dependence of Kerr nonlinearity on the array size under realistic fabrication constraints. We find the suppression of Kerr nonlinearity is sub-linear in array size for amplifiers with tens to hundreds Josephson element. We believe such a weak dependence accounts for the fact that arraying has not yet brought significant improvement of the dynamic |
Tuesday, March 3, 2020 4:18PM - 4:30PM |
J07.00010: A quantum state router based on parametrically driven photon exchange Chao Zhou, Pinlei Lu, Matthieu Praquin, Xi Cao, Ryan Kaufman, Roger Mong, David Pekker, Michael Jonathan Hatridge Precisely controlled couplings between qubits are a vital part of all quantum information processing. For superconducting qubits, most efforts seek to implement a “surface code” architecture, which only couples nearest-neighbor qubits. However, longer range couplings are very desirable as they reduce the overhead of interactions between distant qubits. We present a design that can realize long range couplings between qubits through a modular quantum router. The design contains a 3D superconducting waveguide ‘trunk’ of microwave modes and a Superconducting Nonlinear Asymmetric Inductive eLement (SNAIL) to generate parametric photon exchange couplings between each pair of modes. We couple individual modules via a communication cavity deliberately detuned from a corresponding waveguide mode, with resulting (weaker) parametric couplings directly from module to module. Quantum information is exchanged between modules by driving the SNAIL at the difference of the communication modes’ frequencies. We will present a theory treatment of our router’s performance, as well as experimental results from our realization in an aluminum waveguide prototype. |
Tuesday, March 3, 2020 4:30PM - 4:42PM |
J07.00011: Superconducting Parametric Cavities as an “Optical” Quantum Computation Platform Jimmy Shih-Chun Hung, Chung Wai Sandbo Chang, A.M. Vadiraj, Ibrahim Nsanzineza, C.M. Wilson Quantum information may be encoded into systems of discrete variables (DV) or continuous variables (CV). CV quantum computation has typically been studied at optical frequencies using linear quantum optics to realize Gaussian operations. To achieve universal computation, however, non-Gaussian resources such as the photon number measurements or the cubic phase state are necessary. In superconducting circuits, DV quantum computation is dominant. Here, we propose and study the superconducting parametric cavity for optical quantum computation using microwave photons. At optical frequencies, the qumodes are often separated spatial modes. Here we use the orthogonal frequency modes of the cavity. Gaussian operations between the modes are achieved via standard parametric interactions. In addition, the recent realization of three-photon spontaneous parametric downconversion in this system provides access to both a non-Gaussian gate and resource state, which provides a path to universality. We will present preliminary results towards the development of the parametric cavity for optical quantum computation starting with demonstrations of simple algorithms. One such algorithm is a quantum machine learning algorithm called Quantum Kitchen Sinks. |
Tuesday, March 3, 2020 4:42PM - 4:54PM |
J07.00012: In-cavity parametric amplification for qubit readout in 3D circuit QED architecture Zhixin Wang, Volodymyr Sivak, Shantanu O Mundhada, Shyam Shankar, Michel H. Devoret High-efficiency qubit readout is essential for implementing quantum feedback and remote entanglement schemes as well as studying the basic physics related to quantum measurement processes. In circuit quantum electrodynamics (QED) systems, one typically reads out superconducting qubits by monitoring the qubit-state-dependent phase shift of a microwave tone, which is first amplified by a quantum-limited parametric amplifier before being processed by classical electronics. In this configuration, readout efficiency is mainly limited by the loss between the readout microwave resonator and the parametric amplifier. The optimized arrangement is therefore to place the latter inside the former. Here we introduce a design that uses two coupled transmon artificial atoms housed in a 3D readout cavity/waveguide to perform quantum-limited amplification within the circuit QED module. Compatible with 3D cold cavity attenuators, this layout minimizes the qubit dephasing induced by residual thermal photons and can potentially achieve the single-shot readout for qubits with long coherence times. Preliminary results will be presented. |
Tuesday, March 3, 2020 4:54PM - 5:06PM |
J07.00013: Amplification with an array of lumped Josephson Parametric Converters Olivia Lanes, Tzu-Chiao Chien, Chenxu Liu, Anja Metelmann, David Pekker, Michael Jonathan Hatridge Josephson Parametric Amplifiers, although nearly quantum-limited, suffer from lack of directionality, low saturation powers, and a fixed gain-bandwidth product. We have recently shown that when extremely strong, carefully imbalanced gain and conversion processes (GCI) are combined between a pair of modes, we produce an amplifier that has broadband, bi-directional gain in transmission and is matched at both ports. This latter feature opens the possibility of chaining GCI amplifiers together in series. We have realized an amplifier series array by chaining two Josephson Parametric Converters (JPCs) together in such a way that signal ports form the chain’s input and output and the two idlers are matched in frequency and capacitively coupled. The signal modes have deliberately different frequencies so that all parametric processes may be individually controlled. As the dynamic range of JPCs typically fall faster than linearly with gain, we can distribute gain unequally among the array elements to enhance the array’s overall saturation power. We will also use our array as a platform for studying new combinations of parametric couplings, with a particular focus on pump schemes which provide directional amplification. |
Tuesday, March 3, 2020 5:06PM - 5:18PM |
J07.00014: Experimental violation of the standard quantum limit for parametric amplification of broadband signals Michael Renger, Kirill Fedorov, Stefan Pogorzalek, Qi-Ming Chen, Yuki Nojiri, Matti Partanen, Achim Marx, Frank Deppe, Rudolf Gross Phase-preserving amplification of weak signals is a crucial part of many protocols in microwave quantum information processing, such as quantum teleportation, remote state preparation, or dispersive qubit readout. Flux-driven Josephson parametric amplifiers (JPAs) allow amplification close to the standard quantum limit (SQL), implying a fundamental bound of 1/2 for the maximal quantum efficiency η for amplification of narrowband input signals. We demonstrate that the SQL does not hold for broadband input signals and experimentally find η = 70% with an amplification chain consisting of a JPA and a cryogenic HEMT amplifier. We show that η can reach 100% and experimentally is limited by the Poissonian fluctuations in the JPA pump line. This result can be exploited for multiple applications such as high-efficiency parity measurements of superconducting qubits. |
Tuesday, March 3, 2020 5:18PM - 5:30PM |
J07.00015: Nonreciprocal amplification via Hamiltonian Engineering Tzu-Chiao Chien, Chenxu Liu, Pinlei Lu, Olivia Lanes, Xi Cao, Ryan Kaufman, David Pekker, Michael Jonathan Hatridge In superconducting quantum information processing, we realize high fidelity measurements by using quantum-limited parametric processes. However, cavity-based amplifiers have limited bandwidth, saturation power, and operate in reflection, and so must be operated with external lossy microwave commercial components such as circulators. Many of these limitations can be circumvented by combining multiple parametric processes in a few-mode device. By combining multiple instances of imbalanced gain and conversion processes between three modes[1], we can realize an amplifier with non-reciprocal, transmission-only amplification, matched ports, and large, gain-independent bandwidth. We have realized this scheme in a Lumped, single-ended version of the Josephson Parametric Converter (LJPC) whose inductance is dominated by the central Josephson Ring Modulator. We avoid the use of hybrids by integrating the LJPC and superconducting bandpass filters on a single chip. The resulting device is small, relatively simple to fabricate and thus an excellent candidate for direct integration into superconducting quantum computers. |
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