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 S67: Hybrid Quantum Systems IV |
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Sponsoring Units: DQI Chair: Susanne Yelin, Harvard University Room: Room 412 |
Thursday, March 9, 2023 8:00AM - 8:12AM |
S67.00001: Spin-split Andreev levels in a quantum dot with superconducting leads: microwave spectroscopy Arno Bargerbos, Marta Pita-Vidal, Rok Zitko, Lukas Johannes Splitthoff, Lukas Grunhaupt, Jaap J Wesdorp, Yu Liu, Leo P Kouwenhoven, Ramon Aguado, Christian K Andersen, Angela Kou, Bernard Van Heck We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2 ground state with an unpaired quasiparticle. Due to spin-orbit coupling, we resolve two flux-sensitive branches in the transmon spectrum, depending on the spin of the quasi-particle. A finite magnetic field shifts the two branches in energy, favoring one spin state and resulting in the anomalous Josephson effect. We demonstrate the excitation of the direct spin-flip transition using all-electrical control. Manipulation and control of the spin-flip transition allow for the implementation of charging energy protected Andreev spin qubits. |
Thursday, March 9, 2023 8:12AM - 8:24AM |
S67.00002: Spin-split Andreev levels in a quantum dot with superconducting leads: Andreev spin qubit Marta Pita-Vidal, Arno Bargerbos, Rok Zitko, Lukas Johannes Splitthoff, Lukas Gruenhaupt, Jaap J Wesdorp, Yu Liu, Leo P Kouwenhoven, Ramon Aguado, Bernard Van Heck, Angela Kou, Christian K Andersen Spin qubits in semiconductors are currently one of the most promising architectures for quantum computing. However, they face challenges in realizing multi-qubit interactions over extended distances. Superconducting spin qubits provide a promising alternative by encoding a qubit in the spin degree of freedom of an Andreev level. Such an Andreev spin qubit could leverage the advantages of circuit quantum electrodynamic, enabled by an intrinsic spin-supercurrent coupling. The first realization of an Andreev spin qubit encoded the qubit in the excited states of a semiconducting weak-link, leading to frequent decay out of the computational subspace. Additionally, rapid qubit manipulation was hindered by the need for indirect Raman transitions. Here, we exploit a different qubit subspace, using the spin-split doublet ground state of an electrostatically-defined quantum dot Josephson junction with large charging energy. Additionally, we use a magnetic field to enable direct spin manipulation over a frequency range of 10 GHz. Using an all-electric microwave drive we achieve Rabi frequencies exceeding 200 MHz. We furthermore embed the Andreev spin qubit in a superconducting transmon qubit, demonstrating strong coherent qubit-qubit coupling. These results are a crucial step towards a hybrid architecture that combines the beneficial aspects of both superconducting and semiconductor qubits. |
Thursday, March 9, 2023 8:24AM - 8:36AM |
S67.00003: Decoherence mechanisms in Andreev spin qubits Silas Hoffman We theoretically study the dephasing of an Andreev spin qubit interacting with nuclear spins. Using a tight-binding model, we calculate the Andreev states formed in a Josephson junction mediated by a semiconductor with large strong spin-orbit interaction. Because of both the spin-orbit interaction and the superconducting boundary, the local spin of these states varies as a function of the phase difference between the superconducting leads. Consequently, coupling to fluctuations of the magnetic environment is renormalized which informs the rate of dephasing. We qualitative predict the dependence of dephasing on the nature of the environment and phase difference between the junction. |
Thursday, March 9, 2023 8:36AM - 8:48AM |
S67.00004: Engineering Flat-Band Lattices with Superconducting Circuits Jeronimo G Martinez, Christie S Chiu, Basil M Smitham, Sara F Sussman, Andrew A Houck Many strongly interacting many-body phenomena may be intimately related to the presence of flat electronic bands. Engineering lattices with such bands, however, requires precise and accurate control over lattice site connectivity along with minimal disorder. Superconducting circuits provide a flexible architecture to realize tight-binding Hamiltonians with flat bands by placing qubits in near-arbitrary lattice configurations. The qubit nonlinearity provides effective on-site interactions between photons to access the strongly interacting many-body regime. We present our experimental realization and characterization of a single plaquette of the rhombus chain flat-band lattice and introduce an artificial gauge field to realize a plaquette of an all-flat-band lattice. |
Thursday, March 9, 2023 8:48AM - 9:00AM |
S67.00005: Scattering solution of interacting Hamiltonian for electronic control of molecular spin qubits Christian Bunker, Silas Hoffman, Jie-Xiang Yu, Xiaoguang Zhang, Hai-Ping Cheng We theoretically study how a scattered electron can entangle molecular spin qubits (MSQs). This requires solving the inelastic transport of a single electron through a scattering region described by a tight-binding interacting Hamiltonian. We accomplish this using a Green's function solution. We can model realistic physical implementations of MSQs by parameterizing the tight-binding Hamiltonian with first-principles descriptions of magnetic anisotropy and exchange interactions. We find that for two-MSQ systems with inversion symmetry, the spin degree of freedom of the scattered electron offers probabilistic control of the degree of entanglement between the MSQs. |
Thursday, March 9, 2023 9:00AM - 9:12AM |
S67.00006: Polarized electrons in a low-energy spin-transparent storage ring as a quantum computer Matt Grau, Riad S Suleiman, Vasiliy S Morozov Electrons in spin-transparent storage rings can exhibit a spin-coherence time of several hours, presenting a compelling platform for quantum computing. Spin-polarized electrons are generated by shining circularly-polarized light onto a photocathode, and then injected into the storage ring. Then, single-qubit rotations can be implemented by a pulsed solenoid, and readout of the spin is done using a Mott polarimeter. However, a significant question of the viability of storage rings as a quantum computing platform remains: to date, there is no demonstration of a two-qubit gate. In this talk, I will explore the possibility of using an entangled train of light pulses impinging on a photocathode to produce electrons with entangled spins. These spin-entangled electrons could then be used as a resource in a measurement-based scheme to perform multi-qubit gates in the storage ring. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S67.00007: Progress Towards the Sensing of Short Wavelength Spin Waves In Yttrium Iron Garnet Using Nitrogen Vacancy Spin Qubits Shantam M Ravan, Johannes Cremer, Daniel Fernandez, Ilya Esterlis, Eugene Demler, Ronald L Walsworth, Amir Yacoby Spin waves are coherent magnetic excitations that can exist in ferromagnets. The state of the art host material for these spin waves is yttrium iron garnet (YIG) due to its low dissipation [1]. Recent experiments have demonstrated the coupling between spin waves in YIG and nitrogen vacancy (NV) spin quibits in diamond, which are well established quantum sensors of magnetic fields. Using NVs, experiments have been able to directly image spin waves in YIG down to around 600 nm [2-3]. Due to the potential of YIG spin waves to be used in magnetic scattering and spintronic applications, it is of interest to image shorter wavelengths of magnons. However, this can be difficult due to the presence of thermal magnetic noise from the YIG, reducing NV coherence properties [4-5]. Here we present techniques to improve the coherence properties of NV centers close to YIG films. These will enhance the sensitivity of future NV/YIG studies opening the possibility to observe short wavelength magnons. |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S67.00008: Using cQED techniques to study of superconductivity in monolayer WTe2 Pat Gumann, Charlotte Boettcher, Amir Yacoby, Robert Cava Superconductivity in two-dimensional materials remains in many aspects still an unexplored territory. There have been numerous theoretical proposals describing the formation of a superconducting state in 2D-systems. However, conventional techniques fall short in probing the underlying pairing symmetry in those small-scaled materials. In this talk, we explore methods commonly used in circuit quantum electrodynamics (cQED), particularly superconducting qubits to probe the voltage-tunable superconducting state of monolayer tungsten ditelluride (mono-WTe2). By in-situ fabrication of superconducting contacts, we examine the properties of a hybrid NbN-WTe2 resonator. As a result of direct tuning of the gate voltage and temperature we observed anomalous changes in the resonator frequency, suggesting a presents of competing phases at low temperatures. |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S67.00009: Localized infrared light source of quasiparticles in transmon qubits Rodrigo d Benevides, Maxwell Drimmer, Giacomo Bisson, Francesco Adinolfi, Yiwen Chu Improving the capabilities of superconducting circuits as quantum processors relies on furthering our understanding of their decoherence mechanisms. For example, high energy radiation can break Cooper pairs and create so-called Bogoliubov quasiparticles, which can lead to relaxation and decoherence of quantum states. In general, it is believed that the decoherence of a superconducting qubit is proportional to the density of quasiparticles in the device, motivating efforts to avoid any sources of stray electromagnetic radiation that could induce these excitations. Here we present an experiment that takes the opposite approach and controllably introduces infrared light in the vicinity of a 3D aluminum transmon. We use a pulsed telecom band laser as a spatially and temporally localized source of quasiparticles. We show how the absorption of light modifies the lifetime of the transmon and demonstrate a typical recovery time for the qubit that is one order of magnitude faster than in previous experiments with microwave-induced quasiparticles [1]. Our results also have useful implications for the transduction of quantum information between the microwave and telecom domains. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S67.00010: Single electron spin resonance by microwave photon counting Zhiren Wang, Léo Balembois, Milos Rancic, Eric Billaud, Marianne Le Dantec, Alban Ferrier, Philippe Goldner, Sylvain Bertaina, Thierry Chaneliere, Daniel Esteve, Denis Vion, Patrice Bertet, Emmanuel Flurin Electron spin resonance (ESR) with single spin addressability is an approach to characterize paramagnetic species and gives coherent manipulation of the spins. This goal has been reached in various systems or techniques, such as gate-defined quantum dots, spin-dependent photoluminescence and scanning-probe techniques. However, these approaches require specific systems or restrict themselves to small detection volume. Therefore, operational and universal single spin detection remains a challenge. Here, we demonstrate single electron spin resonance by spin fluorescence detection with a superconducting-qubit-based single microwave photon detector at cryogenic temperature. We couple individual paramagnetic erbium ions in a scheelite crystal to a high-quality factor superconducting resonator to enhance their radiative decay rate. By counting the spontaneously emitted photons from ions, we resolve their ESR spectrum down to single impurity level. In one second integration time of the detection, we reach a signal-to-noise ratio of 1.45. The observed photon anti-bunching in the emission proves that the fluorescence signal comes from single emitters. Our results pave the way for practical ESR spectroscopy of arbitrary paramagnetic species with single spin resolution and it may also find potential applications for quantum computing. |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S67.00011: Continuous-Wave Room-Temperature Masers, using NV-Centers in Diamond Christoph W Zollitsch, Stefan Ruloff, Yan Fett, Jonathan D Breeze, Christopher W Kay The concepts of microwave amplification by stimulated emission of radiation (MASER) were developed in the late 1950s, in conjunction with its optical counterpart the laser. While the Laser found applications in many fields, ranging from fundamental science to industry and everyday life, the applications of the maser were highly specialized e.g., for deep-space communications and astronomy. This was due to the extreme operating conditions of the first masers, requiring cryogenic temperatures and high vacuum environments. However, the maser’s excellent low-noise microwave amplification properties still make it an attractive candidate for a broad range of microwave applications. To this end, the recent realization of a continuous-wave room temperature maser, using NV-centers in diamond, invigorated the Maser as an intriguing platform for microwave research and development [1]. |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S67.00012: Transitions in the learnability of global charges from local measurements. Utkarsh Agrawal, Romain Vasseur, Sarang Gopalakrishnan, Andrew C Potter, Fergus Barratt We consider monitored quantum systems with a global conserved charge, and ask how efficiently an observer ("eavesdropper") can learn the global charge of such systems from local projective measurements. We find phase transitions as a function of the measurement rate, depending on how much information about the quantum dynamics the eavesdropper has access to. For random unitary circuits with U(1) symmetry, we present an optimal classical classifier to reconstruct the global charge from local measurement outcomes only. We demonstrate the existence of phase transitions in the performance of this classifier in the thermodynamic limit. We also study numerically improved classifiers by including some knowledge about the unitary gates pattern. |
Thursday, March 9, 2023 10:24AM - 10:36AM |
S67.00013: Measurement-induced entanglement transition in a two-dimensional shallow circuit Hanchen Liu, Tianci Zhou, Xiao Chen We prepare two-dimensional states generated by shallow circuits composed of (1) one layer of the two-qubit controlled-Z (CZ) gate or (2) a few layers of the two-qubit random Clifford gate. After measuring all of the bulk qubits, we study the entanglement structure of the remaining qubits on the one-dimensional boundary. In the first model, we observe that the competition between the bulk X and Z measurements can lead to an entanglement phase transition between an entangled volume law phase and a disentangled area law phase. We numerically evaluate the critical exponents and generalize this idea to other qudit systems with a local Hilbert space dimension larger than 2. In the second model, we observe the entanglement transition by varying the density of the two-qubit gate in each layer. We give an interpretation of this transition in terms of the random bond Ising model in a similar shallow circuit composed of random Haar gates. |
Thursday, March 9, 2023 10:36AM - 10:48AM Author not Attending |
S67.00014: Stabilizer simulations of measurement- and feedback-induced entanglement transition in the probabilistic control of chaos Justin H Wilson, Conner LeMaire, Thomas Iadecola, Sriram Ganeshan, Jed Pixley In recent work on measurement-induced phase transitions, measurements interspersed with unitary evolution leads to a dynamical phase transition where entanglement is volume-law for low rates of measurements and area-law for high measurement rates. However, naive post-selection arguments estimate that viewing the transition experimentally requires more than the lifetime of the universe. Inspired by a classical model in the theory of chaotic dynamics in which a system's dynamics can be "controlled" (a classical dynamic phase transition), we construct dynamics within stabilizer circuits that experience control onto a specific state while also experiencing a similar entanglement transition. In this "quantum Bernoulli map," the transition into the phase in which entanglement is lost is heralded by an operator that acts as an order parameter for the transition. As such, an experiment could probe this transition without post-selection. We present data on larger system sizes than can be accomplished with exact methods, building on our previous work on a similar model. |
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