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 G50: Quantum Simulations of Coherent States of MatterInvited
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Sponsoring Units: DCOMP Chair: Kade Head-Marsden, Washington University in St. Louis Room: Room 320 |
Tuesday, March 7, 2023 11:30AM - 12:06PM |
G50.00001: Decoherence of qubits in spinless and spinful semiconductors Invited Speaker: Viktor Ivady Spin defects in semiconductors provide a versatile material platform for quantum information processing, quantum sensing, and quantum computing with unprecedented high temperature capabilities. Magnetic field fluctuations due to various parasitic spin defects in the host material as well as interaction with lattice phonons cause decoherence and spin relaxation of spin qubits that limit current applications. It therefore of fundamental importance to study material related disturbances and develop mitigation strategies. In recent years, significant advances have been achieved on the theriacal characterization of decoherence [1-3] and spin relaxation [4,5] of spin qubits in semiconductors. The developed first principles methods led to new understanding of decoherence in various materials [6-8]. In my talk, I will present our latest computational results on various spin defects in silicon carbide (SiC) and hexagonal boron nitride (hBN). More specifically, I will discuss the spin state lifetime of divacancy and silicon vacancy qubits in a bath of electron and nuclear spins in SiC. [9,10] Furthermore, I will demonstrate that isotope purification may lead to unexpected enhancement of electron spin relaxation rates and magnetic field fluctuations due to the residual electron spin bath that may limit the lifetime and coherence time of spin qubits in materials. [11] By taking into account all the relevant effects, I will shed light on the interplay of the electron and nuclear spin bath and discuss the complex nuclear spin abundance dependence of the coherence time in isotope engineered host materials. In addition, I will present our latest results on the coherence of boron vacancy center in hBN.[8,12] |
Tuesday, March 7, 2023 12:06PM - 12:42PM |
G50.00002: Spin Relaxation and Dephasing in Solids from Ab Initio Density-matrix Dynamics Invited Speaker: Yuan Ping Designing new quantum materials with long-lived electron spin states is in urgent need of a general theoretical formalism and computational technique to reliably predict spin lifetimes. We present a new, universal first-principles methodology based on density matrix (DM) dynamics for open quantum systems to calculate the spin relaxation and decoherence time of solids with arbitrary spin mixing and crystal symmetry. In particular, this method describes contributions of the Elliott-Yatfet (EY) and D’yakonov-Perel (DP) mechanisms to spin relaxation, on an equal footing[1]. Our ab initio predictions are in excellent agreement with experimental spin lifetime for a broad range of materials, such as Si, bcc Fe, MoS2, graphene as well as GaAs. |
Tuesday, March 7, 2023 12:42PM - 1:18PM |
G50.00003: Interactions of Electron Spin with Phonons: Spin Relaxation and Decoherence in Condensed Matter from First Principles Invited Speaker: Marco Bernardi Combining density functional theory with many-body approaches has enabled quantitative studies of electron interactions and dynamics in materials. Yet, treating the electron spin with these first-principles methods remains challenging. Spin interactions with atomic vibrations (phonons) are particularly important as they set an intrinsic limit to the performance of spintronic and spin-based quantum devices. |
Tuesday, March 7, 2023 1:18PM - 1:54PM |
G50.00004: Understanding the Magnetic Environment of Spin Defects from First Principles Invited Speaker: Mykyta Onizhuk The magnetic environment of spin defects plays a key role in the applications of these systems in quantum information. For example, while the nuclear spin bath of material acts as a source of noise for an electronic spin defect, the spin-possessing nuclei can also be used as auxiliary qubits. They provide an excellent platform for long-term quantum information storage due to their low coupling to the magnetic environment. |
Tuesday, March 7, 2023 1:54PM - 2:30PM |
G50.00005: First-principles investigation of optically active quantum defects in hexagonal boron nitride Invited Speaker: Hosung Seo Two-dimensional materials (TDMs) have been recently found to host a variety of quantum point defects [1] that are potentially useful for advancing quantum information science and technology. Among a growing suite of the TDMs, hexagonal boron nitride (h-BN) has emerged as a host of bright single-photon emitters (SPEs) and optically active spin qubits operating at room temperature. However, there are several challenges to be addressed for realizing h-BN-based quantum applications. In this talk, we summarize our recent efforts to predict and understand optically active quantum defects in h-BN using density functional theory (DFT) and cluster correlation expansion theory (CCE). In the first part of the talk, we discuss the property of SPEs in terms of their coupling behavior to lattice strain and how engineered lattice strain could be used to understand the structural and optical properties of SPEs. For spin qubits in h-BN, we discuss the issue of the short spin coherence time of the boron vacancy spin in h-BN in the presence of the intrinsic dense nuclear spin bath. To address these issues, we combine CCE and DFT to predict that the spin coherence time in h-BN can be significantly increased by six times larger than its intrinsic limit in natural h-BN by employing isotopic enrichment and strain engineering. Our results strengthened the potential of h-BN quantum spin defects as materials platforms to realize TDM-based quantum sensors and integrated quantum photonics. |
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