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 G74: Novel Spin Qubit Materials and Technologies IFocus
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Sponsoring Units: DQI Chair: J. Carlos Egues, University of Basel Room: Room 403/404 |
Tuesday, March 7, 2023 11:30AM - 12:06PM |
G74.00001: Quantum links for large-scale spin qubit architecturesAndre Saraiva Invited Speaker: Andre Saraiva Provably useful quantum computations require tens of millions of qubits to be operated with high fidelity in order to implement quantum error correction. Wiring qubits individually will not be scalable, such that it will be necessary to combine some in loco control electronics near the qubits and some control signals that can be shared among multiple qubits, using a wordline/bitline scheme. This creates a requirement for reducing the density of qubits to allow room for this interspersed electronics. |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G74.00002: Towards High-Dimensional Quantum States in Trilayer WSe2 Quantum Dots Pengcheng Luan, Nicholas Mazzucca, Kenji Watanabe, Takashi Taniguchi, Fan Zhang, Marc Bockrath As the unit for building quantum circuits, qubits have been broadly studied for quantum information processing. Recently, quantum states with higher dimensions, also known as qudits, are attracting more attention due to their potential advantages, including simplifying quantum computation. Experimentally, quantum dots can be used to build qubits, but their applications for qudits are limited. Here we use trilayer WSe2, which has 6 inequivalent valleys inside the 1st Brillouin zone [1], to make quantum dot devices. Several electrodes are used as electrostatic gates to define a dot region in the device. Preliminary data from the first generation of devices shows Coulomb blockade features, indicating the presence of a quantum dot [2]. By shrinking the dot region and applying electric and magnetic fields, better manipulation of 3- or 6-fold nearly degenerate quantum states can be achieved [3]. Our latest results will be discussed. |
Tuesday, March 7, 2023 12:18PM - 12:30PM |
G74.00003: Towards quantum-confined spin-qubits in monolayer, semiconducting WSe2 Eleanor C Nichols, Carola M Purser, Michael Pitts, Andrea C Ferrari, Mete Atatüre, Dhiren Kara Monolayer transition metal dichalcogenides provide a promising platform for quantum communications due in large part to their 2D nature. Interface-free emission from the monolayer results in efficient light extraction. Meanwhile, large exciton binding energies ~100 meV due to low screening and confinement in the 2D plane are suitable for operation at elevated temperatures. Strong optical selection rules arising from the symmetry of the 2D lattice enable optical excitation of excitons at distinct valleys through control over the polarisation of optical excitation. Establishing a spin in the ground state with spin-dependent optical selection rules would enable an efficient mechanism for photon entanglement. Such a spin ground state is expected to have long coherence lifetimes (~40 ms) from the dilute nuclear spin bath and reduced dimensionality of the material. However, a local spin ground state has yet to be identified for these quantum emitters. Here, we present our on-going efforts to introduce a quantum emitter with a spin ground state in fully encapsulated, monolayer WSe2. Establishing a local spin qubit with optical selection rules will pave the way towards a coherent spin-photon interface in 2D materials. |
Tuesday, March 7, 2023 12:30PM - 12:42PM |
G74.00004: Probing the optical coherence of quantum emitters in a WSe2 monolayer Carola Purser, Eleanor C Nichols, Michael Pitts, Evgeny Alexeev, Andrea C Ferrari, Dhiren Kara, Mete Atatüre Quantum emitters in monolayer transition-metal dichalcogenides are a promising platform for quantum communication in a direct-bandgap, semiconducting light-matter interface. However, demonstrating the optical coherence of these emitters remains an outstanding challenge, thus limiting their application as sources of entangled photons. Here, we probe the quality of single-photon emitters in WSe2 monolayers as a function of dielectric environment and excitation energy and determine the effects on spectral wander, purity, and brightness. We further report on our on-going efforts to directly measure the optical coherence of these emitters. |
Tuesday, March 7, 2023 12:42PM - 12:54PM |
G74.00005: Coherent Dynamics of Strongly Interacting Electronic Spin Defects in Hexagonal Boron Nitride Ruotian Gong, Guanghui He, Xingyu Gao, Peng Ju, Zhongyuan Liu, Bingtian Ye, Erik Henriksen, Tongcang Li, Chong Zu Optically active spin defects in van der Waals materials are promising platforms for modern quantum technologies. We investigate the coherent dynamics of strongly interacting ensembles of negatively charged boron-vacancy (VB-) centers in hexagonal boron nitride (hBN) with varying defect density. By employing advanced dynamical decoupling sequences to selectively isolate different dephasing sources, we observe more than 5-fold improvement in the measured coherence times across all hBN samples. Crucially, we identify that the many-body interaction within the VB- ensemble plays a substantial role in the coherent dynamics, which is then used to directly determine the precise concentration of VB-. We find that at high ion implantation dosage, only less than 5 % of the created boron vacancy defects are in the desired negatively charged state. Finally, we investigate the spin response of VB- to the local charged defects induced electric field signals, and estimate its transverse electric field susceptibility of VB-. Our results provide new insights on the spin and charge properties of VB-, which are important for future use of defects in hBN as quantum sensors and simulators. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G74.00006: Thickness-dependent properties of color centers in hexagonal boron nitride: a first principles study Sai Krishna Narayanan, Pratibha Dev Since the discovery of quantum emission from hexagonal boron nitride (hBN) in 2016, a significant research effort has been directed to determine the chemical identities of the color centers responsible for the observed quantum emission. In the process, works have shown that properties of the as-yet unidentified color centers, such as their photo-stability and luminosity, are affected by: (i) the number of hBN layers, (ii) the presence of a substrate and (iii) even the twist angle between the layers. In addition, experiments show a wide spread in emission frequencies of the color centers. However, the mechanisms that result in the observed changes in properties have not been identified, although there is some indication that the strain in the hBN layers may be playing a role [Phys. Rev. Research 2, 022050(R) (2020)]. In this work, we used density functional theory to explore whether the presence of multiple layers is a source of strain due to “interlayer-friction”. We also determine the size of the thickness-dependent changes in excited state properties, and show how it contributes towards the spreads in quantum emission frequencies that have been observed in experiment. |
Tuesday, March 7, 2023 1:06PM - 1:18PM |
G74.00007: Integrated system of an optical cryostat and single-photon detectors for applications in near infrared spectroscopy of quantum emitters Victoria A Norman, Sridhar Majety, Pranta Saha, Pietra Curro, Marina Radulaski Historically, optical cryostats have not been able to reliably achieve temperatures below 4 K, a temperature that is higher than the operating threshold for many single photon detector designs. Instead, when performing single photon detection experiments, groups frequently require a secondary, fiber-coupled cryostat to hold the single photon detectors at their operating temperature. This is expensive in terms of purchasing equipment, space required, and upkeep costs. |
Tuesday, March 7, 2023 1:18PM - 1:30PM |
G74.00008: Coherent spin dynamics of hyperfine-coupled vanadium impurities in silicon carbide Joop Hendriks, Carmem Gilardoni, Chris Adambukulam, Arne Laucht, Caspar Van der Wal Spin-active optical defects in silicon carbide (SiC) are promising contenders for applications in quantum technology. The vanadium defect is of particular technological interest, as it combines emission at a telecom wavelength with a host material that is compatible with industrial semiconductor processing methods [1-2]. Compared to defects such as the NV center in diamond or the divacancy in SiC, its spin-orbit and hyperfine coupling are much stronger, but how this affects their spin coherence is little explored [3]. Here we show coherent spin dynamics of an ensemble of vanadium defects, of which a part is strongly coupled to neighboring nuclear spins and a part is isolated from it, around a clock transition. We find spin dephasing times up to 7.2 μs, and coherence times that can be extended well beyond tens of microseconds by applying a Hahn spin-echo . We demonstrate that strong coupling to neighboring nuclear spins does not compromise the coherence of the central vanadium spin. These findings indicate the potential of this system for use as a coherent spin register, and helps with understanding a wide class of defects with similar energy scales and crystal symmetries that are currently explored in diamond, silicon carbide, and hexagonal boron nitride. |
Tuesday, March 7, 2023 1:30PM - 1:42PM |
G74.00009: Neutral shallow donors in ZnO: Contributions to the optical linewidth of the donor - bound excitonic transition Vasileios Niaouris, Samuel H D'Ambrosia, Christian Zimmermann, Michael Titze, Edward S Bielejec, Ethan Hansen, Xingyi Wang, Simon P Watkins, Kai-Mei C Fu Neutral shallow donors (D0) in ZnO such as In, Ga, and Al substituting for Zn are promising solid-state spin qubits for quantum technologies. The D0 are optically coupled to donor bound excitons (D0X). Studying donor ensembles, we have demonstrated long spin relaxation times (up to 0.48 sec at 1.75 T) [1], spin initialization via optical pumping [2], Hahn-spin-echo time of 50 μs [2], and all-optical coherent control [3]. In almost every quantum application, including remote entanglement generation, linear optics quantum computing, and quantum memories, a key figure of merit is the ratio of the optical transition linewidth to the Fourier-transformed limited linewidth. In this contribution, we present an experimental and theoretical study on the D0 /D0X optical linewidth properties of donor ensembles. In micro-PL measurements, we observed inhomogeneous linewidths as narrow as 6.5 GHz, only one order of magnitude broader than the expected lifetime-limited linewidth (~0.5 GHz). Temperature dependent linewidth studies are consistent with a one-phonon broadening mechanism based on population relaxation to an excited D0X state. At 2 K, the phonon contribution to the linewidth is negligible. Transient reverse spectral hole burning spectroscopy reveal a 4.3 GHz anti-hole that is similar to the inhomogeneous linewidth, suggesting a spectral diffusion mechanism. Finally, we propose that the linewidth is partially inhomogeneously broadened due to the isotope mass environment variation between disparate emitters in the ensemble. |
Tuesday, March 7, 2023 1:42PM - 1:54PM |
G74.00010: Coherent control of Er in Si Ian R Berkman, Alexey Lyasota, Gabriele G de Boo, John G Bartholomew, Brett C Johnson, Jeffrey C McCallum, Bin-Bin Xu, Shouyi Xie, Rose L Ahlefeldt, Matthew J Sellars, Chunming Yin, Sven Rogge Rare-earth ions in solid-state hosts exhibit low homogeneous broadening and long spin coherence at cryogenic temperatures, thus making them a promising candidate for optical-spin interfaces to achieve long-distance spin-spin coupling. Here, we present the electron spin properties of Er ensembles in Si accessed via resonant photoluminescence excitation. Samples were positioned directly on top of dedicatedly fabricated superconducting single photon detectors and resonantly excited using fiber optics. We investigated Si samples with different O doping levels and Er densities between 1016 cm-3 to 1018 cm-3 implanted using ion beam. The samples with an Er doping level of 1018 cm-3 showed an inhomogeneous linewidth of less than 400 MHz and an upper bound of 350 kHz on the homogeneous broadening. |
Tuesday, March 7, 2023 1:54PM - 2:06PM |
G74.00011: Heralded Entanglement of Single Rare-Earth Ion Qubits Andrei Ruskuc, Chun-Ju Wu, Joonhee Choi, Sophie Hermans, Andrei Faraon Photon-based entanglement distribution is a critical requirement for quantum networking, enabling secure communication and distributed quantum computing. Solid-state defects have emerged as leading candidates for network nodes due to their compatibility with scalable device engineering and the presence of nuclear spins for local quantum processing. Recently we have demonstrated key milestones toward this application using single 171Yb ions in YVO4, coupled to a nanophotonic cavity. These include coherent optical and spin control, long-term quantum information storage, single-shot readout and a nuclear ancilla qubit. |
Tuesday, March 7, 2023 2:06PM - 2:18PM |
G74.00012: Decoherence-free subspace of nuclear spins coupled to a rare-earth ion qubit Chun-Ju Wu, Andrei Ruskuc, Joonhee Choi, Andrei Faraon Nuclear spins surrounding solid-state qubits are a crucial resource for quantum information processing and storage. However, initialization, readout and control of the primary qubit usually lead to decoherence of the nuclear spin state. Encoding information into decoherence-free subspaces allows the independent operation of these two quantum subsystems. |
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