Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Z37: Quantum AcousticsFocus Recordings Available
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Sponsoring Units: DQI Chair: Yiwen Chu, ETH Zurich Room: McCormick Place W-194B |
Friday, March 18, 2022 11:30AM - 11:42AM |
Z37.00001: Non-demolition tomography of quantum states in a mechanical oscillator Agnetta Y Cleland, Edward A Wollack, Rachel G Gruenke, Zhaoyou Wang, Patricio Arrangoiz-Arriola, Amir Safavi-Naeini Nanomechanical oscillators display many useful properties for technological applications, motivating their integration into the domain of quantum information science. In the field of quantum acoustics, one important effort is to leverage the strong nonlinearity and established control techniques of superconducting qubits to prepare and characterize quantum states of motion in mechanical oscillators. Studies of nonclassical mechanical states have been conducted in recent experiments using surface acoustic waves [1] and bulk acoustic waves [2] through a resonant qubit-mechanics interaction. In this talk, we present a quantum non-demolition approach to performing Wigner tomography on a mechanical oscillator, which leverages strong dispersive coupling between a superconducting transmon qubit and a thin-film phononic crystal resonator. We use the qubit to prepare quantum states of phonons in the resonator, and perform full quantum state tomography on the mechanical mode through a Ramsey measurement. We present experimental results and show that our measured state fidelities are in good agreement with numerical models that include energy dissipation in the mechanical oscillator. |
Friday, March 18, 2022 11:42AM - 11:54AM |
Z37.00002: Joint tomography and quantum entanglement of a pair of nanomechanical oscillators Edward A Wollack, Agnetta Y Cleland The field of quantum acoustics combines the advantages of nanomechanical resonators with the established techniques of circuit QED to achieve quantum control of mechanical systems. These hybrid acoustic devices have been proposed as promising platforms for quantum random access memories and biased-error cat qubits [2-4], but current devices have not demonstrated control of multiple mechanical oscillators with a single qubit. In this talk, we present a small quantum acoustic processor used to synthesize and characterize quantum entanglement between two nanomechanical resonators [1]. The device is composed of two thin-film phononic crystal resonators coupled to a superconducting transmon qubit, which we use to manipulate the quantum states of the joint mechanical system. After preparing the mechanical resonators in a Bell-state, we perform full joint quantum state tomography using a non-demolition measurement where the qubit is dispersively coupled to both resonators simultaneously. The reconstructed quantum states for the joint mechanical system show good agreement with numerical simulations, suggesting that the measured state fidelities are limited by decoherence mechanisms in the mechanical resonators. |
Friday, March 18, 2022 11:54AM - 12:06PM |
Z37.00003: Experimental study of two-level system loss in surface acoustic wave resonators Rachel G Gruenke Progress in quantum acoustics suggests that truly powerful quantum technologies for computation and sensing may be within reach. However, fabricated devices are often limited by internal loss that can be modeled as a bath of two level systems (TLS) coupled to the resonator. Here I present a study of TLS sources in Lithium Niobate and Lithium Tantalate using 600-900 MHz surface acoustic wave resonators (SAW). TLS due to a variety of sources, including crystal defects and organics that lie on the substrate surface, make SAW resonators a good probe of these dissipation channels. SAW devices at these frequencies are made with a one mask photolithography process, meaning that fabrication is minimally destructive and easily iterated. TLS loss is characterized by studying changes in the internal quality factor and resonant frequency shifts as a function of resonator temperature. Several resonators with differing surface treatments of the piezoelectric substrate done prior to SAW deposition were measured and compared for TLS loss. Finally, I compare cryogenic measurement results with studies using X-ray photon spectroscopy on the same samples to better understand the effects of different chemical composition between the substrate surfaces. |
Friday, March 18, 2022 12:06PM - 12:18PM |
Z37.00004: Enhancement and inhibition of acoustic spontaneous emission from a superconducting qubit: Part I Design and characterization Vijay Jain, Yanni D Dahmani, Chan U Lei, Taekwan Yoon, Leonid Glazman, Luigi Frunzio, Peter T Rakich, Robert J Schoelkopf Recent experiments in quantum acoustics have demonstrated quantum coherent control of individual phonons. However, in the presence of piezoelectric materials, transmon lifetimes have been orders of magnitude lower than the state of the art. The excess loss may be attributed to parasitic loss channels introduced through electro-mechanical coupling in piezoelectric materials. Through careful microwave design and systematic testing, we have designed a qubit architecture that both suppresses acoustic spontaneous emission and increases the electro-mechanical cooperativity. |
Friday, March 18, 2022 12:18PM - 12:30PM |
Z37.00005: Enhancement and inhibition of acoustic spontaneous emission from a superconducting qubit: Part II Coherent control and dispersive measurement Yanni D Dahmani, Vijay Jain, Taekwan Yoon, Luigi Frunzio, Leonid Glazman, Peter T Rakich, Robert J Schoelkopf Hybrid platforms based on superconducting circuits and bulk acoustic wave resonators provide a compact, multi-mode geometry for bosonic control owing to the slow velocity of sound in comparison to that of light. Our experimental platform, described in the first talk, is based on thin-film Aluminum Nitride on Sapphire coupled in a flip-chip geometry to a transmon superconducting qubit. Here, we characterize the strong dispersive coupling between the transmon and bulk acoustic waves in Sapphire. |
Friday, March 18, 2022 12:30PM - 12:42PM |
Z37.00006: Experimental verification of minimally-diffracting quartz for quantum acoustodynamics Alec L Emser, Brendon C Rose, Lucas R Sletten, Pablo Aramburu Sanchez, Konrad Lehnert Acoustic systems offer quantum technologies a favorable combination of long on-chip delays, competitive coherence times, and the ability to connect disparate quantum systems. In particular, surface acoustic wave (SAW) resonators can be integrated with superconducting qubits to investigate quantum acoustodynamics in the multi-mode, strong dispersive regime. These experiments have required a compromise between the anharmonicity of the qubit and the acoustic aperture of the SAW device, resulting in significant diffraction loss as the aperture is reduced in typical flat-flat SAW cavity designs. Although previous work has identified an orientation of quartz which minimizes SAW diffraction loss at room temperature [1], this orientation is unsuitable for ultra-low temperature applications. Through finite-element simulations we find an orientation of quartz which minimizes SAW diffraction at millikelvin temperatures while maintaining a near-zero beam-steering angle. Using this orientation of quartz we demonstrate 500MHz highly-coherent (Q > 3x105 ) flat-flat SAW resonators with narrow apertures (10λ). |
Friday, March 18, 2022 12:42PM - 12:54PM |
Z37.00007: Quantum acoustodynamics with a fluxonium qubit Brendon C Rose, Lucas R Sletten, Alec L Emser, Pablo Aramburu Sanchez, Konrad Lehnert Quantum states of mechanical motion offer the potential to realize long lived multimodal quantum memories as well as quantum transduction between disparate quantum systems. Surface acoustic wave (SAW) devices in particular provide customizable long-on chip delays for realizing a multimodal system. Most previous quantum acoustic SAW devices have utilized a transmon qubit, necessitating operation at several gigahertz where the qubit has significant anharmonicity. Here, we integrate a 500 MHz SAW resonator with a fluxonium superconducting qubit. This design provides a large anharmonicity at low frequency and long lived acoustic modes due to decreased bulk scattering losses at low frequency. We demonstrate acoustic modes with linewidths of 1.5 kHz. Our design uses flip chip indium bump bonding, intended to increase qubit performance by removing the fluxonium qubit from the piezoelectric quartz medium and instead placing it on sapphire. This device is positioned to investigate quantum acoustodynamics in the multi-mode, strong dispersive regime. |
Friday, March 18, 2022 12:54PM - 1:06PM |
Z37.00008: Capacitively Mediated Quantum Acoustic Strong Coupling in a Hybrid SAW-Qubit System Joe M Kitzman, Justin R Lane, Niyaz Beysengulov, Camille A Mikolas, Liangji Zhang, Kater W Murch, Johannes Pollanen Piezoelectric surface acoustic wave (SAW) devices can be integrated with superconducting qubits in a framework similar to circuit quantum electrodynamics known as circuit quantum acoustodynamics (cQAD). In these hybrid systems the intrinsic non-linearity of the superconducting qubit is leveraged to access new regimes of circuit quantum optics using GHz-frequency piezophonons. Here we present a cQAD architecture based on a purely capacitive coupling between a superconducting transmon qubit and a SAW resonator housed in a three-dimensional microwave cavity. This system achieves the strong coupling regime of cQAD with a coupling on the order of 10 MHz. The properties of the SAW resonator, as well as its impact on the transmon lifetime, are well-described by the coupling-of-modes formalism of SAW devices. Higher power microwave measurements reveal the presence of strongly non-linear (and non-classical) features of the spectroscopic response of the coupled system. |
Friday, March 18, 2022 1:06PM - 1:18PM |
Z37.00009: Off-Resonant, Free-Space Launching of High-Frequency Surface Acoustic Waves Camille A Mikolas, Joe M Kitzman, Justin R Lane, Niyaz Beysengulov, Liangji Zhang, Johannes Pollanen Piezoelectric surface acoustic wave (SAW) devices operating in the GHz-frequency range find application in a wide variety of classical microwave telecom circuits including, SAW filters, resonators, and sensors. SAWs have also been of increasing interest in the development of hybrid quantum systems containing superconducting circuits and qubits, providing insight into the regime of circuit quantum acoustodynamics (cQAD). Here we report on experiments demonstrating the off-resonant free-space coupling between the dipole moment of a SAW resonator and a mode of a three-dimensional (3D) microwave cavity that is detuned by approximately 0.4 GHz from the main SAW resonance. We find that this response is well described by a coupling of modes modeling of the SAW resonator. These results reveal how the intrinsically large impedance mismatch between the SAW and electromagnetic resonators can be overcome via the fabrication of large antenna pads on a strong piezoelectric substrate (lithium niobate) and how these devices can be incorporated into novel cQAD systems. |
Friday, March 18, 2022 1:18PM - 1:30PM |
Z37.00010: Squeezing and multimode entanglement of surface acoustic wave phonons Gustav Andersson, Shan W Jolin, Marco Scigliuzzo, Riccardo Borgani, Mats O Tholén, Juan Carlos Rivera Hernández, Vitaly Shumeiko, David B Haviland, Per Delsing Exploiting multiple modes in a quantum acoustic device could enable applications in quantum information in a hardware-efficient setup, including quantum simulation in a synthetic dimension and continuous-variable quantum computing with cluster states. We develop a multimode surface acoustic wave (SAW) resonator with a superconducting quantum interference device (SQUID) integrated in one of the Bragg reflectors. The interaction with the SQUID-shunted reflector gives rise to parametric coupling between the resonator modes. We exploit this coupling to demonstrate two-mode squeezing of SAW phonons, as well as four-mode multipartite entanglement. Our results open avenues for continuous-variable quantum computing in a compact hybrid quantum system. |
Friday, March 18, 2022 1:30PM - 1:42PM |
Z37.00011: Parity measurement in the strong dispersive regime of circuit quantum acoustodynamics (Part I) Uwe von Lüpke, Marius Bild, Yu Yang, Laurent Michaud, Matteo Fadel, Yiwen Chu Mechanical resonators are emerging as an important new platform for quantum science and technologies. By interfacing mechanical resonators with superconducting circuits, circuit quantum acoustodynamics (cQAD) can make a variety of important tools available for manipulating and measuring motional quantum states. We demonstrate direct measurements of the phonon number distribution and parity of non-classical mechanical states, which are useful for a variety of protocols such as quantum state preparation and error correction. In this talk, we present the design and characterization of a cQAD device operating in the strong dispersive regime, consisting of a superconducting qubit and a phonon mode in a bulk acoustic wave resonator. We show qubit spectroscopy measurements that resolve the phonon number distribution in classical and quantum states of the mechanical mode. |
Friday, March 18, 2022 1:42PM - 1:54PM |
Z37.00012: Parity measurement in the strong dispersive regime of circuit quantum acoustodynamics (Part II) Marius Bild, Uwe von Lüpke, Yu Yang, Laurent Michaud, Matteo Fadel, Yiwen Chu Mechanical resonators are emerging as an important new platform for quantum science and technologies. |
Friday, March 18, 2022 1:54PM - 2:06PM |
Z37.00013: Persistent spectral hole burning and atomic frequency comb at microwave frequency in Er3+:CaWO4 Zhiren Wang, Zhiren Wang, Marianne Le Dantec, Milos Rancic, Emmanuel Flurin, Denis Vion, Daniel Esteve, Patrice Bertet, Philippe Goldner, Thierry Chaneliere, Sylvain Bertaina, Sen Lin, Renbao Liu, Alban Ferrier The interaction of electron spins with neighboring nuclear spins in a host crystal leads to rich physics and dynamics, as observed in semiconducting quantum dots, color centers in diamond and donors in silicon. Here, we report a new phenomenon, using a crystal of CaWO4 containing Erbium ions, at millikelvin temperature. Erbium has a doublet ground state with a large magnetic moment behaving as an effective electron spin-1/2. In CaWO4, Er3+ couple to the magnetic moment of neighboring 183W nuclear spins (14% abundance). Under a field of 450mT, the Erbium spin is brought in resonance with a superconducting resonator at 7.8GHz used for detection. By applying a microwave tone, we observe spectral holes created in the absorption of Er and these holes exist over 20 hours, which is much longer than the Er3+:CaWO4 spin-lattice relaxation time (0.2s). We interpret the holes as being caused by dynamic nuclear polarization of the nearby W nuclear spin leading to an Overhauser field seen by the Er3+, while its persistent existence demonstrates the stability of polarization within W nuclear spins at low temperature. Furthermore, by applying repeated double-pulse sequence, we are able to generate an atomic frequency comb in the spin ensemble, which persists for at least 120 hours at 10mK. |
Friday, March 18, 2022 2:06PM - 2:18PM |
Z37.00014: In-situ Tuning of the Electric-Dipole Strength of a Double Dot Charge Qubit: Charge Noise Protection and Ultra Strong Coupling Pasquale Scarlino, Jann H Ungerer, David J Van Woerkom, Peter Stano, Clemens Muller, Andreas Landig, Jonne V Koski, Christian Reichl, Werner Wegscheider, Thomas Ihn, Klaus Ensslin, Andreas Wallraff Semiconductor quantum dots (QDs) are promising building blocks for semiconductor-based quantum technology. Here, we investigate double-QD (DQD) charge qubits in GaAs, capacitively coupled to high-impedance SQUID array and Josephson junction array resonators. We tune the strength of the electric-dipole interaction between the qubit and the resonator in-situ using surface gates. We characterize the qubit-resonator coupling strength, qubit decoherence, and detuning noise affecting the charge qubit for different electrostatic DQD configurations. We find that all quantities can be tuned systematically over more than one order of magnitude, resulting in reproducible decoherence rates < 5 MHz in the limit of high inter-dot capacitance. Conversely, by reducing the inter-dot capacitance, we can increase the DQD electric-dipole strength, and therefore its coupling to the resonator. By employing a Josephson junction array resonator with an impedance of 4 kOhm and a resonance frequency of 5.6 GHz, we observe a coupling strength of 630 MHz, demonstrating the possibility to achieve the ultrastrong coupling regime (USC) for electrons hosted in a semiconductor DQD. These results are essential for further increasing the coherence of QD-based qubits and investigating USC physics in semiconducting QDs. |
Friday, March 18, 2022 2:18PM - 2:30PM |
Z37.00015: Si hole qubits in a cQED architecture Cécile Yu, Simon Zihlmann, Benoit Bertrand, Romain Maurand With the recent development of spin-orbit qubit based on holes in silicon and in germanium, it is nowadays conceivable to use a microwave photon as a « quantum bus » for long distance spin-orbit qubits interaction. The strong spin/photon coupling has been achieved using an engineered spin-orbit interaction with electron spins in silicon and long-range microwave mediated interactions have also been demonstrated recently. Our goal here is to use the intrinsic spin-orbit term in the valence band of silicon to achieve this coherent spin/photon coupling. |
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