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 Y32: Spin Qubit Readout and AmplifiersFocus Session Live
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Sponsoring Units: DQI Chair: Ted White, Google |
Friday, March 19, 2021 11:30AM - 11:42AM Live |
Y32.00001: Bolometer operating at the threshold for circuit quantum electrodynamics Roope Kokkoniemi, Jean-Philippe Girard, Dibyendu Hazra, Antti Laitinen, Joonas Govenius, Russell Lake, Iiro Sallinen, Visa Vesterinen, Matti Partanen, J. Y. Tan, Kok Wai Chan, Kuan Yen Tan, Pertti Juhani Hakonen, Mikko Möttönen Bolometers operating at low temperatures are promising for detection of itinerant microwave photons and qubit readout. They benefit from a broad detection bandwidth and low dissipation. However, single-microwave-photon sensitivity has not been achieved yet. To address this issue, we experimentally demonstrate an ultrafast bolometer based on a graphene Josephson junction and operating at the threshold of circuit quantum electrodynamics [1]. Graphene, with its unusual thermal properties, offers the opportunity to reach the single-microwave-photon regime. Our device yields a noise equivalent power of 30 zW/rtHz at a thermal time constant of 500 ns and an extracted energy resolution of h×30 GHz. |
Friday, March 19, 2021 11:42AM - 11:54AM Live |
Y32.00002: Improving the Quantum Efficiency of Josephson Traveling Wave Parametric Amplifiers Kaidong Peng, Mahdi Naghiloo, Jennifer Wang, Yufeng Ye, Kevin O'Brien Josephson traveling wave parametric amplifiers (JTWPAs) with gigahertz of simultaneous bandwidth and near-quantum-limited noise performance have become workhorse amplifiers for a wide variety of microwave superconducting quantum experiments. However, the best reported intrinsic quantum efficiency of such amplifiers remains at least 20% below that of an ideal phase-preserving amplifier. Here, we systematically analyze the quantum efficiency of a standard resonantly phase-matched JTWPA using a multi-mode input-output theory framework. We identify the higher order sidebands as a significant noise source that prevents the JTWPA from attaining quantum limited performance. Finally, we report our progress towards designing JTWPAs which mitigate these noise mechanisms. Such devices may advance applications such as continuous quantum error correction, measurement-based quantum feedback protocols, and dark matter detection. |
Friday, March 19, 2021 11:54AM - 12:06PM Live |
Y32.00003: Power-efficient 3-wave mixing Josephson parametric amplifier Wei Dai, Volodymyr Sivak, Gangqiang Liu, Shyam Shankar, Michel Devoret Josephson Parametric Amplifiers (JPAs) are commonly used in superconducting quantum information processing. A JPA is powered by an rf pump, which typically is orders of magnitude stronger than its output signal. Increasing signal power handling of JPAs would generally require stronger pump. However, the maximum pump power we are able to deliver is limited by the thermalization of the wiring linking the amplifier to room temperature. To address this limitation, we have engineered strong coupling of the off-resonance pump in a 3-wave mixing JPA. Compared to similar JPAs with a capacitively coupled pump port or mutual-inductively coupled flux-pumping, this technique improves power efficiency by at least an order of magnitude without lowering dynamic range and noise performance. Preliminary experimental results will be shown. |
Friday, March 19, 2021 12:06PM - 12:18PM Live |
Y32.00004: The kinetic inductance traveling-wave amplifier: an alternative to high electron mobility transistors Maxime Malnou, michael R. vissers, Jordan D. Wheeler, Jose Aumentado, Johannes Hubmayr, Joel N Ullom, Jiansong Gao High electron mobility transistors (HEMTs) are widely used in quantum computing as a second amplifier, because of their wideband, high saturation power, and relatively low noise performance. However, they typically require milliwatts of power, which will limit the development of quantum computers, as they scale up to hundreds or thousands of qubits. We propose to use kinetic inductance traveling-wave amplifiers (KITs) at 4K as an alternative to HEMTs. KITs consume three orders of magnitude less power than HEMTs, and have enough power-handling to read thousands of qubits or cryogenic sensors simultaneously, while having enough gain to replace HEMTs in the amplification chain. Furthermore, they have recently been shown to be near-quantum-limited over several gigahertz of bandwidth when operated at mK temperatures [1]. We present the characterization of an amplification chain where a KIT at 4K replaces a HEMT, and in particular will discuss its noise performance as well as its suitability for qubit readout. |
Friday, March 19, 2021 12:18PM - 12:30PM Live |
Y32.00005: Niobium-based lumped element SNAIL parametric amplifiers with improved power handling capacity Vidul Joshi, Gangqiang Liu, Maxime Malnou, Volodymyr Sivak, Nicholas Frattini, Gene C Hilton, Leila Vale, Joel N Ullom, Michel Devoret Parametric amplifiers based on Josephson junctions play a crucial role in superconducting quantum information processing. Resonator-based amplifiers, such as the Josephson parametric amplifier (JPA), the Josephson Parametric Converter (JPC) and the SNAIL parametric amplifier (SPA), are widely used due to their ease of operation and near quantum-limited noise performance. It has been shown that the compression power of these amplifiers, an increasingly desirable feature, increases quadratically with the resonator linewidth and inversely with the fourth-order non-linearity (Kerr) of their Josephson elements. In this talk, we present SPAs with lumped element resonators fabricated by niobium tri-layer technology. In these new devices, the Kerr nonlinearity is reduced while the junction participation ratio is increased, compared to the devices fabricated with single layer, aluminum technology. This resulted in a 10 dB improvement in compression power and more than twice larger bandwidth. We also discuss further improvement of these devices which, in the long run, would service most of the needs of the superconducting quantum circuits community. |
Friday, March 19, 2021 12:30PM - 12:42PM Live |
Y32.00006: Full control of Josephson nonlinear processes in a Gradiometric SNAIL Parametric Amplifier Alessandro Miano, Gangqiang Liu, Volodymyr Sivak, Luigi Frunzio, Vidul Joshi, Wei Dai, Nicholas Frattini, Michel Devoret Superconducting parametric amplifiers rely on nonlinear processes in order to coherently amplify readout photons with the addition of a minimal amount of noise limited just by Quantum Mechanics principles. A precise tuning of these processes is required to achieve 20dB gain at the readout tone frequency and, simultaneously, obtain a Kerr-free operation in order to reduce undesired effects as gain compression. State-of-the-art parametric amplifiers are capable of Kerr-free operation at a single frequency only, depending on the design parameters of the device. In this work, we present experimental results on the Gradiometric SNAIL Parametric Amplifier (GSPA), a device biased by two independent on-chip magnetic fluxes that allow to independently tune even and odd Josephson nonlinearities. Such a device is capable of 20dB Kerr-free amplification over a continuous range of frequency, providing a shortcut towards the development of a precision and universal parametric amplifier for optimal readout of many-qubit platforms. |
Friday, March 19, 2021 12:42PM - 12:54PM Live |
Y32.00007: Minimal construction of fully directional parametric amplifier Gangqiang Liu, Vidul Josh, Andrew Lingenfelter, Nicholas Frattini, Shyam Shankar, Michel Devoret Quantum-limited parametric amplifiers based on Josephson junctions are indispensable components of superconducting quantum information processing machines. Traditionally, these are reflection amplifiers which need external non-reciprocal elements to separate the input from the output. It is possible however, to achieve non-reciprocal amplification in a multi-mode device by interfering multiple signal pathways between the input and the output mode. However, directional amplifiers based on this technique have lacked either output matching or adequate reverse isolation. In this talk, we present a new design for a fully directional parametric amplifier whose input and output ports are matched, and whose reverse transmission is much smaller than the inverse of the forward gain. We show that at least four modes and six parametric couplings are required to implement these amplifiers with Josephson-junction-only circuits. We further show that under realistic operating conditions, these devices can generate 20 dB forward gain and less than -20 dB reverse transmission, therefore enabling high efficiency quantum measurements and on-chip integration with qubit-cavity system. |
Friday, March 19, 2021 12:54PM - 1:06PM Live |
Y32.00008: Efficient and low-backaction quantum measurement using a chip-scale detector Eric Rosenthal, Christian M. F. Schneider, Maxime Malnou, Ziyi Zhao, Felix Leditzky, Benjamin Chapman, Waltraut Wustmann, Xizheng Ma, Daniel A Palken, Maximilian Zanner, Leila Vale, Gene C Hilton, Jiansong Gao, Graeme Smith, Gerhard Kirchmair, Konrad Lehnert Superconducting qubits are a leading platform for scalable quantum computing and quantum error correction. One feature of this platform is the ability to perform projective measurements orders of magnitude more quickly than qubit decoherence times. Such measurements are enabled by the use of quantum-limited parametric amplifiers in conjunction with ferrite circulators-magnetic devices which provide isolation from noise and decoherence due to amplifier backaction. Because these non-reciprocal elements have limited performance and are not easily integrated on-chip, it has been a longstanding goal to replace them with a scalable alternative. Here, we demonstrate a solution to this problem by using a superconducting switch to control the coupling between a qubit and amplifier. Doing so, we measure a transmon qubit using a single, chip-scale device to provide both parametric amplification and isolation from the bulk of amplifier backaction. This measurement is also fast, high fidelity, and has 70% efficiency, comparable to the best that has been reported in any superconducting qubit measurement. As such, this work constitutes a high-quality platform for the scalable measurement of superconducting qubits. |
Friday, March 19, 2021 1:06PM - 1:42PM Live |
Y32.00009: Rapid gate-based readout of spins in silicon using an on-chip resonator Invited Speaker: Guoji Zheng Over the past decade tremendous progress has been made on spin qubits based on electron spins in silicon gate-defined quantum dots. As with any qubit implementation, a critical requirement is the ability to read out the qubit rapidly, with high fidelity, and in a scalable manner. Much attention has been focused on improving single-electron transistors embedded in radio-frequency reflectometry circuits as charge detectors to detect, in conjunction with a spin-to-charge conversion scheme, electron spin states. While they are the most sensitive detectors to date, additional resources are required that take up valuable space near the quantum dots (gate electrodes, electron reservoirs), which makes scaling up to two-dimensional spin qubit arrays difficult. More efficiently, readout can be performed with the gates that are already in place for defining quantum dots by connecting those gates to resonant circuits. This promising method of gate-based sensing has been developed for quantum dots with off-chip resonators, and recently achieved the sensitivity necessary for single-shot readout [1]. In this talk, we describe the use of an on-chip superconducting microwave resonator instead to improve the sensitivity, aided by its high quality factor and high impedance. Using Pauli Spin Blockade as the spin-to-charge conversion scheme, we demonstrate the gate-based readout of a two-electron spin state in a single shot with an average fidelity of 98% in 6 microseconds [2]. Furthermore, on-chip resonators can potentially couple distant spin qubits. We briefly present our latest work in direction, which includes on-chip gate filters to preserve the resonator’s quality factor in the presence of quantum dot gate electrodes [3] and long-distance spin-spin interaction. |
Friday, March 19, 2021 1:42PM - 1:54PM Live |
Y32.00010: A Quantum measurement induced ground-state transition Michael S Ferguson, Leon Camenzind, Clemens Müller, Daniel E. F. Biesinger, Christian Scheller, Bernd H. Braunecker, Dominik Zumbuhl, Oded Zilberberg The act of measurement is necessarily invasive as the observer and the system become entangled. We show that already weak (non-projective) measurements with a sensor dot can drive a ground-state transition in the adjacent double quantum dot [arXiv:2010.04635]. The experiment operates close to the (1,0)-(0,1) charge degeneracy line where an electron resides in the left and right dot with equal probabilities. With increasing measurement strength (sensor bias), the line deforms into an S-shaped curve. The area enclosed between S-shape and line hosts a new measurement induced ground-state. Here, the system prepared in the (1,0) ground state with an electron in the left dot, occupies the (0,1) state while being measured. We have developed a model that quantitatively accounts for the experiment. Each electron passing the sensor induces a capacitive shift in the adjacent quantum dot level. The resulting level-broadening enhances charge transfer with the reservoir, allowing the system to populate an energetically unfavorable state. Changing the nature of a many-body state simply by observing it is a major shift in how we understand the act of measurement and poses new challenges for quantum technologies. |
Friday, March 19, 2021 1:54PM - 2:06PM Live |
Y32.00011: Detecting spins with a microwave photon counter Emanuele Albertinale, Léo Balembois, Eric Billaud, Vishal Ranjan, Daniel Flanigan, Thomas Schenkel, Daniel Esteve, Denis Vion, Patrice Bertet, Emmanuel Flurin Operational single photon counters at microwave frequencies have been developed recently. Here we plug such a single microwave photon counter [R. Lescanne et al., PRX 10, 021038, 2020] to the output of a superconducting micro-resonator, itself coupled to an ensemble of bismuth donor electron spins in silicon at millikelvin temperatures in the Purcell regime [A. Bienfait et al., Nature, vol. 531, pp. 74 – 77, 2016]. We report the direct observation of the microwave photons emitted by the spins, during their energy relaxation following a pi pulse. Moreover by changing the area of the exciting pulse we were able to measured Rabi oscillations in the variation of the total number of detected photons. Finally we report the direct observation of the photons emitted from the spin ensemble in a Hahn echo experiment. |
Friday, March 19, 2021 2:06PM - 2:18PM Live |
Y32.00012: Fast RF-only tuneup of quantum dot systems using multiplexed GHz CPW resonators Christian Prosko, Damaz De Jong, Daan Waardenburg, Lin Han, Filip Malinowski, Nejc Blaznik, Peter Krogstrup, Jonne Koski, Leo Kouwenhoven, Wolfgang Pfaff Radio-Frequency (RF) sensing is a fast and scalable tool for measuring mesoscopic semiconductor and hybrid devices. We implement a combination of capacitively and galvanically coupled Co-Planar Waveguide (CPW) resonators in a multi-quantum-dot InAs nanowire device and characterize it without the aid of DC measurement. Notably, we extract high frequency conductance without calibration from DC data. Furthermore, we demonstrate multiplexed measurement of a charge stability diagram using this resonator and resonators capacitively coupled to two dots. These resonators are optimized for visibility of dispersive shifts imparted by electron charge transitions, leading to signal-to-noise ratios exceeding 10 for 1 microsecond integration times. |
Friday, March 19, 2021 2:18PM - 2:30PM Live |
Y32.00013: Accurate theory for drive-activated nonlinear processes in the SNAIL parametric amplifier Alexandru Petrescu, Baptiste Royer, Alexandre Blais The presence of spurious nonlinear interactions in parametric amplifiers often leads to detrimental effects such as gain saturation. In this talk, we present a perturbative approach aimed at analytically characterizing unwanted interactions and predicting parameter regimes in which their effect is minimized, and apply it to a specific degenerate parametric amplifier. We derive for arbitrary pump strengths the effective Hamiltonian, accounting for drive-induced renormalizations of its energy scales. In particular, this theory captures the nonlinear AC Stark shift, drive-activated Kerr nonlinearity and a collection of other terms ensuing from the expansion of the Josephson potential. Our predictions agree qualitatively with recent experimental results on the SNAIL parametric amplifier [N. Frattini et al., Phys. Rev. Appl. 10, 054020 (2018); V. Sivak et al., ibid. 11, 054060 (2019)]. |
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