Computational Materials Insights Into Solid-State Multiqubit Systems
20 Sep 2021-Vol. 2, Iss: 3, pp 030102
TL;DR: A path to bridge the gap between ab initio materials calculations and the model Hamiltonians used to discover and develop scalable quantum systems is presented in this paper, where the authors propose a method to discover a scalable quantum system.
Abstract: A path to bridge the gap between ab initio materials calculations and the model Hamiltonians used to discover and develop scalable quantum systems is presented.
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Journal Article•
TL;DR: This work presents a list of physical criteria that deep center defects and their hosts should meet and explains how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems.
Abstract: Identifying and designing physical systems for use as qubits, the basic units of quantum information, are critical steps in the development of a quantum computer. Among the possibilities in the solid state, a defect in diamond known as the nitrogen-vacancy (NV-1) center stands out for its robustness—its quantum state can be initialized, manipulated, and measured with high fidelity at room temperature. Here we describe how to systematically identify other deep center defects with similar quantum-mechanical properties. We present a list of physical criteria that these centers and their hosts should meet and explain how these requirements can be used in conjunction with electronic structure theory to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare electronic structure calculations of the NV-1 center in diamond with those of several deep centers in 4H silicon carbide (SiC). We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.
421 citations
Posted Content•
TL;DR: In this article, the Kadanoff-Baym equation is solved using time propagation for the non-equilibrium Green function for atoms and molecules, by solving it within a conserving self-energy approximation.
Abstract: We have implemented time-propagation of the non-equilibrium Green function for atoms and molecules, by solving the Kadanoff-Baym equations within a conserving self-energy approximation. We here demonstrate the usefulnes of time-propagation for calculating spectral functions and for describing the correlated electron dynamics in a non-perturbative electric field. We also demonstrate the use of time-propagation as a method for calculating charge-neutral excitation energies, equivalent to highly advanced solutions of the Bethe-Salpeter equation.
76 citations
Journal Article•
TL;DR: In this article, the authors investigate the polarization selection rules of sharp zero-phonon lines (ZPLs) from isolated defects in hexagonal boron nitride (HBN) and compare their findings with the predictions of a Huang-Rhys model involving two electronic states.
Abstract: We investigate the polarization selection rules of sharp zero-phonon lines (ZPLs) from isolated defects in hexagonal boron nitride (HBN) and compare our findings with the predictions of a Huang-Rhys model involving two electronic states. Our survey, which spans the spectral range $\ensuremath{\sim}550--740\text{ }\text{ }\mathrm{nm}$, reveals that, in disagreement with a two-level model, the absorption and emission dipoles are often misaligned. We relate the dipole misalignment angle ($\mathrm{\ensuremath{\Delta}}\ensuremath{\theta}$) of a ZPL to its energy shift from the excitation energy ($\mathrm{\ensuremath{\Delta}}E$) and find that $\mathrm{\ensuremath{\Delta}}\ensuremath{\theta}\ensuremath{\approx}0\ifmmode^\circ\else\textdegree\fi{}$ when $\mathrm{\ensuremath{\Delta}}E$ corresponds to an allowed HBN phonon frequency and that $0\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}\mathrm{\ensuremath{\Delta}}\ensuremath{\theta}\ensuremath{\le}90\ifmmode^\circ\else\textdegree\fi{}$ when $\mathrm{\ensuremath{\Delta}}E$ exceeds the maximum allowed HBN phonon frequency. Consequently, a two-level Huang-Rhys model succeeds at describing excitations mediated by the creation of one optical phonon but fails at describing excitations that require the creation of multiple phonons. We propose that direct excitations requiring the creation of multiple phonons are inefficient due to the low Huang-Rhys factors in HBN and that these ZPLs are instead excited indirectly via an intermediate electronic state. This hypothesis is corroborated by polarization measurements of an individual ZPL excited with two distinct wavelengths that indicate a single ZPL may be excited by multiple mechanisms. These findings provide new insight on the nature of the optical cycle of novel defect-based single-photon sources in HBN.
65 citations
TL;DR: It is demonstrated that electron-photon correlation is fundamental to describe intermolecular interactions in strong light-matter coupling and proposed optical cavities as a novel tool to manipulate and control ground state properties, solvent effects, and intermolescular interactions for molecules and materials.
Abstract: Intermolecular bonds are weak compared to covalent bonds, but they are strong enough to influence the properties of large molecular systems. In this work, we investigate how strong light-matter coupling inside an optical cavity can modify these intermolecular forces. We perform a detailed comparison between currently available ab initio electron-photon methodologies. The electromagnetic field inside the cavity can modulate the ground state properties of weakly bound complexes. Controlling the field polarization, the interactions can be stabilized or destabilized, and electron densities, dipole moments, and polarizabilities can be altered. We demonstrate that electron-photon correlation is fundamental to describe intermolecular interactions in strong light-matter coupling. This work proposes optical cavities as a novel tool to manipulate and control ground state properties, solvent effects, and intermolecular interactions for molecules and materials.
47 citations
Journal Article•
TL;DR: The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks.
Abstract: Quantum entanglement is among the most fascinating aspects of quantum theory. Entangled optical photons are now widely used for fundamental tests of quantum mechanics and applications such as quantum cryptography. Several recent experiments demonstrated entanglement of optical photons with trapped ions, atoms and atomic ensembles, which are then used to connect remote long-term memory nodes in distributed quantum networks. Here we realize quantum entanglement between the polarization of a single optical photon and a solid-state qubit associated with the single electronic spin of a nitrogen vacancy centre in diamond. Our experimental entanglement verification uses the quantum eraser technique, and demonstrates that a high degree of control over interactions between a solid-state qubit and the quantum light field can be achieved. The reported entanglement source can be used in studies of fundamental quantum phenomena and provides a key building block for the solid-state realization of quantum optical networks.
38 citations
References
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TL;DR: In this paper, the Hartree and Hartree-Fock equations are applied to a uniform electron gas, where the exchange and correlation portions of the chemical potential of the gas are used as additional effective potentials.
Abstract: From a theory of Hohenberg and Kohn, approximation methods for treating an inhomogeneous system of interacting electrons are developed. These methods are exact for systems of slowly varying or high density. For the ground state, they lead to self-consistent equations analogous to the Hartree and Hartree-Fock equations, respectively. In these equations the exchange and correlation portions of the chemical potential of a uniform electron gas appear as additional effective potentials. (The exchange portion of our effective potential differs from that due to Slater by a factor of $\frac{2}{3}$.) Electronic systems at finite temperatures and in magnetic fields are also treated by similar methods. An appendix deals with a further correction for systems with short-wavelength density oscillations.
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TL;DR: In this paper, the authors proposed a method for quantum interconnects, which convert quantum states from one physical system to those of another in a reversible manner, allowing the distribution of entanglement across the network and teleportation of quantum states between nodes.
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5,003 citations