Bibliographies thématiques / Molecular qubits

Littérature scientifique sur le sujet « Molecular qubits »

Auteur : Grafiati

Publié le 10 mars 2023

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Articles de revues sur le sujet "Molecular qubits"

Yamamoto, Satoru, Shigeaki Nakazawa, Kenji Sugisaki, Kazunobu Sato, Kazuo Toyota, Daisuke Shiomi et Takeji Takui. « Adiabatic quantum computing with spin qubits hosted by molecules ». Physical Chemistry Chemical Physics 17, n^o 4 (2015) : 2742–49. http://dx.doi.org/10.1039/c4cp04744c.

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CAO, WEN-ZHEN, LI-JIE TIAN, HUI-JUAN JIANG et CHONG LI. « SINGLE QUBIT MANIPULATION IN HETERONUCLEAR DIATOMIC MOLECULAR SYSTEM ». International Journal of Quantum Information 06, n^o 06 (décembre 2008) : 1223–30. http://dx.doi.org/10.1142/s0219749908004390.

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We propose a scenario to realize quantum computers utilizing heteronuclear diatomic rovibrational states as qubits. We focused on rovibrational qubits created by simple transform limited infrared laser pulse instead of using chirped pulse. Numerical calculations show that single qubit gate operation in the electronic ground state of LiH molecule can be obtained. We also discuss the effect of temperature on the initially rotational states, and a suitable experiment condition is indicated.

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Hastings, Matthew B., et Jeongwan Haah. « Dynamically Generated Logical Qubits ». Quantum 5 (19 octobre 2021) : 564. http://dx.doi.org/10.22331/q-2021-10-19-564.

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We present a quantum error correcting code with dynamically generated logical qubits. When viewed as a subsystem code, the code has no logical qubits. Nevertheless, our measurement patterns generate logical qubits, allowing the code to act as a fault-tolerant quantum memory. Our particular code gives a model very similar to the two-dimensional toric code, but each measurement is a two-qubit Pauli measurement.

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Tahan, Charles. « Opinion : Democratizing Spin Qubits ». Quantum 5 (18 novembre 2021) : 584. http://dx.doi.org/10.22331/q-2021-11-18-584.

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I've been building Powerpoint-based quantum computers with electron spins in silicon for 20 years. Unfortunately, real-life-based quantum dot quantum computers are harder to implement. Materials, fabrication, and control challenges still impede progress. The way to accelerate discovery is to make and measure more qubits. Here I discuss separating the qubit realization and testing circuitry from the materials science and on-chip fabrication that will ultimately be necessary. This approach should allow us, in the shorter term, to characterize wafers non-invasively for their qubit-relevant properties, to make small qubit systems on various different materials with little extra cost, and even to test spin-qubit to superconducting cavity entanglement protocols where the best possible cavity quality is preserved. Such a testbed can advance the materials science of semiconductor quantum information devices and enable small quantum computers. This article may also be useful as a light and light-hearted introduction to quantum dot spin qubits.

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Mani, Tomoyasu. « Molecular qubits based on photogenerated spin-correlated radical pairs for quantum sensing ». Chemical Physics Reviews 3, n^o 2 (juin 2022) : 021301. http://dx.doi.org/10.1063/5.0084072.

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Photogenerated spin-correlated radical pairs (SCRPs) in electron donor–bridge–acceptor (D–B–A) molecules can act as molecular qubits and inherently spin qubit pairs. SCRPs can take singlet and triplet spin states, comprising the quantum superposition state. Their synthetic accessibility and well-defined structures, together with their ability to be prepared in an initially pure, entangled spin state and optical addressability, make them one of the promising avenues for advancing quantum information science. Coherence between two spin states and spin selective electron transfer reactions form the foundation of using SCRPs as qubits for sensing. We can exploit the unique sensitivity of the spin dynamics of SCRPs to external magnetic fields for sensing applications including resolution-enhanced imaging, magnetometers, and magnetic switch. Molecular quantum sensors, if realized, can provide new technological developments beyond what is possible with classical counterparts. While the community of spin chemistry has actively investigated magnetic field effects on chemical reactions via SCRPs for several decades, we have not yet fully exploited the synthetic tunability of molecular systems to our advantage. This review offers an introduction to the photogenerated SCRPs-based molecular qubits for quantum sensing, aiming to lay the foundation for researchers new to the field and provide a basic reference for researchers active in the field. We focus on the basic principles necessary to construct molecular qubits based on SCRPs and the examples in quantum sensing explored to date from the perspective of the experimentalist.

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Xue, Xiao, Maximilian Russ, Nodar Samkharadze, Brennan Undseth, Amir Sammak, Giordano Scappucci et Lieven M. K. Vandersypen. « Quantum logic with spin qubits crossing the surface code threshold ». Nature 601, n^o 7893 (19 janvier 2022) : 343–47. http://dx.doi.org/10.1038/s41586-021-04273-w.

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AbstractHigh-fidelity control of quantum bits is paramount for the reliable execution of quantum algorithms and for achieving fault tolerance—the ability to correct errors faster than they occur1. The central requirement for fault tolerance is expressed in terms of an error threshold. Whereas the actual threshold depends on many details, a common target is the approximately 1% error threshold of the well-known surface code2,3. Reaching two-qubit gate fidelities above 99% has been a long-standing major goal for semiconductor spin qubits. These qubits are promising for scaling, as they can leverage advanced semiconductor technology4. Here we report a spin-based quantum processor in silicon with single-qubit and two-qubit gate fidelities, all of which are above 99.5%, extracted from gate-set tomography. The average single-qubit gate fidelities remain above 99% when including crosstalk and idling errors on the neighbouring qubit. Using this high-fidelity gate set, we execute the demanding task of calculating molecular ground-state energies using a variational quantum eigensolver algorithm5. Having surpassed the 99% barrier for the two-qubit gate fidelity, semiconductor qubits are well positioned on the path to fault tolerance and to possible applications in the era of noisy intermediate-scale quantum devices.

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Gidney, Craig, Michael Newman et Matt McEwen. « Benchmarking the Planar Honeycomb Code ». Quantum 6 (21 septembre 2022) : 813. http://dx.doi.org/10.22331/q-2022-09-21-813.

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We improve the planar honeycomb code by describing boundaries that need no additional physical connectivity, and by optimizing the shape of the qubit patch. We then benchmark the code using Monte Carlo sampling to estimate logical error rates and derive metrics including thresholds, lambdas, and teraquop qubit counts. We determine that the planar honeycomb code can create a logical qubit with one-in-a-trillion logical error rates using 7000 physical qubits at a 0.1% gate-level error rate (or 900 physical qubits given native two-qubit parity measurements). Our results cement the honeycomb code as a promising candidate for two-dimensional qubit architectures with sparse connectivity.

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Bravyi, Sergey, Ruslan Shaydulin, Shaohan Hu et Dmitri Maslov. « Clifford Circuit Optimization with Templates and Symbolic Pauli Gates ». Quantum 5 (16 novembre 2021) : 580. http://dx.doi.org/10.22331/q-2021-11-16-580.

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The Clifford group is a finite subgroup of the unitary group generated by the Hadamard, the CNOT, and the Phase gates. This group plays a prominent role in quantum error correction, randomized benchmarking protocols, and the study of entanglement. Here we consider the problem of finding a short quantum circuit implementing a given Clifford group element. Our methods aim to minimize the entangling gate count assuming all-to-all qubit connectivity. First, we consider circuit optimization based on template matching and design Clifford-specific templates that leverage the ability to factor out Pauli and SWAP gates. Second, we introduce a symbolic peephole optimization method. It works by projecting the full circuit onto a small subset of qubits and optimally recompiling the projected subcircuit via dynamic programming. CNOT gates coupling the chosen subset of qubits with the remaining qubits are expressed using symbolic Pauli gates. Software implementation of these methods finds circuits that are only 0.2% away from optimal for 6 qubits and reduces the two-qubit gate count in circuits with up to 64 qubits by 64.7% on average, compared with the Aaronson-Gottesman canonical form.

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Bahari, Iskandar, Timothy P. Spiller, Shane Dooley, Anthony Hayes et Francis McCrossan. « Collapse and revival of entanglement between qubits coupled to a spin coherent state ». International Journal of Quantum Information 16, n^o 02 (mars 2018) : 1850017. http://dx.doi.org/10.1142/s021974991850017x.

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We extend the study of the Jayne–Cummings (JC) model involving a pair of identical two-level atoms (or qubits) interacting with a single mode quantized field. We investigate the effects of replacing the radiation field mode with a composite spin, comprising [Formula: see text] qubits, or spin-1/2 particles. This model is relevant for physical implementations in superconducting circuit QED, ion trap and molecular systems. For the case of the composite spin prepared in a spin coherent state, we demonstrate the similarities of this set-up to the qubits-field model in terms of the time evolution, attractor states and in particular the collapse and revival of the entanglement between the two qubits. We extend our analysis by taking into account an effect due to qubit imperfections. We consider a difference (or “mismatch”) in the dipole interaction strengths of the two qubits, for both the field mode and composite spin cases. To address decoherence due to this mismatch, we then average over this coupling strength difference with distributions of varying width. We demonstrate in both the field mode and the composite spin scenarios that increasing the width of the “error” distribution increases suppression of the coherent dynamics of the coupled system, including the collapse and revival of the entanglement between the qubits.

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Koiller, Belita, Xuedong Hu, Rodrigo B. Capaz, Adriano S. Martins et Sankar Das Sarma. « Silicon-based spin and charge quantum computation ». Anais da Academia Brasileira de Ciências 77, n^o 2 (juin 2005) : 201–22. http://dx.doi.org/10.1590/s0001-37652005000200002.

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Silicon-based quantum-computer architectures have attracted attention because of their promise for scalability and their potential for synergetically utilizing the available resources associated with the existing Si technology infrastructure. Electronic and nuclear spins of shallow donors (e.g. phosphorus) in Si are ideal candidates for qubits in such proposals due to the relatively long spin coherence times. For these spin qubits, donor electron charge manipulation by external gates is a key ingredient for control and read-out of single-qubit operations, while shallow donor exchange gates are frequently invoked to perform two-qubit operations. More recently, charge qubits based on tunnel coupling in P+2 substitutional molecular ions in Si have also been proposed. We discuss the feasibility of the building blocks involved in shallow donor quantum computation in silicon, taking into account the peculiarities of silicon electronic structure, in particular the six degenerate states at the conduction band edge. We show that quantum interference among these states does not significantly affect operations involving a single donor, but leads to fast oscillations in electron exchange coupling and on tunnel-coupling strength when the donor pair relative position is changed on a lattice-parameter scale. These studies illustrate the considerable potential as well as the tremendous challenges posed by donor spin and charge as candidates for qubits in silicon.

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Thèses sur le sujet "Molecular qubits"

Plant, Simon Richard. « Molecular engineering with endohedral fullerenes : towards solid-state molecular qubits ». Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:84f12a03-5b1d-4e04-82d5-5b28ca92e56c.

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Information processors that harness quantum mechanics may be able to outperform their classical counterparts at certain tasks. Quantum information processing (QIP) can utilize the quantum mechanical phenomenon of entanglement to implement quantum algorithms. Endohedral fullerenes, where atoms, ions or clusters are trapped in a carbon cage, are a class of nanomaterials that show great promise as the basis for a solid-state QIP architecture. Some endohedral fullerenes are spin–active, and offer the potential to encode information in their spin-states. This thesis addresses the challenges of how to engineer the components of a scalable QIP architecture based on endohedral fullerenes. It focuses on the synthesis and characterization of molecules which may, in the future, permit the demonstration of entanglement; the optical read-out of quantum states; and the creation of quasi-one-dimensional molecular arrays. Due to its long spin decoherence time, N@C₆₀ is the selected as the basic molecular unit for ‘coupled’ fullerene pairs, molecular systems for which it may be possible to demonstrate entanglement. To this end, isolated fullerene pairs, in the form of spin-bearing fullerene dimers, are created. This begins with the processing of N@C₆₀ at the macroscale and leads towards the synthesis of ¹⁵N@C₆₀-¹⁵N@C₆₀ dimers at the microscale. High throughput processing is introduced as the most efficient technique to obtain high purity N@C₆₀ on a reasonable timescale. A scheme to produce symmetric and asymmetric fullerene dimers is also demonstrated. EPR spectroscopy of the dimers in the solid-state confirms derivatization, whilst permitting the modelling of spin–spin interactions for 'coupled' fullerene pairs. This suggests that the optimum inter–spin separation for which to observe spin–spin coupling in powders is circa 3 nm. Motivated by the properties of the trivalent erbium ion for the optical detection of quantum states, optically–active erbium–doped fullerenes are also investigated. These erbium metallofullerenes are synthesized and isolated as individual isomers. They are characterized by low temperature photoluminescence spectroscopy, emitting in the infra- red at a wavelength of 1.5 μm. The luminescence is markedly different where a C₂ cluster is trapped alongside the erbium ions in the fullerene cage. Er₂C₂@C₈₂ (isomer I) exhibits emission linewidths that are comparable to those observed for Er³⁺ in crystals. Finally, the discovery of a novel praseodymium-doped fullerene is reported. The balance of evidence favours the structure being assigned as Pr₂@C₇₂. This novel endohedral fullerene forms quasi-one-dimensional arrays in carbon nanotubes, which is a useful proof-of-principle of how a scaled fullerene-based architecture may be achieved.

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Dhungana, Daya Sagar. « Growth of InAs and Bi1-xSBx nanowires on silicon for nanoelectronics and topological qubits by molecular beam epitaxy ». Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30150/document.

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Grâce à leur propriétés uniques, les nanofils d'InAs et de Bi1-xSbx sont important pour les domaines de la nanoélectronique et de l'informatique quantique. Alors que la mobilité électronique de l'InAs est intéressante pour les nanoélectroniques; l'aspect isolant topologique du Bi1-xSbx peut être utilisé pour la réalisation de Qubits basés sur les fermions de Majorana. Dans les deux cas, l'amélioration de la qualité du matériau est obligatoire et ceci est l'objectif principal cette thèse ou` nous étudions l'intégration des nanofils InAs sur silicium (compatibles CMOS) et où nous développons un nouvel isolant topologique nanométrique: le Bi1-xSbx. Pour une compatibilité CMOS complète, la croissance d'InAs sur Silicium nécessite d'être auto- catalysée, entièrement verticale et uniforme sans dépasser la limite thermique de 450 ° C. Ces normes CMOS, combineés à la différence de paramètre de maille entre l'InAs et le silicium, ont empêché l'intégration de nanofils InAs pour les dispositifs nanoélectroniques. Dans cette thèse, deux nouvelles préparations de surface du Si ont été étudiées impliquant des traitements Hydrogène in situ et conduisant à la croissance verticale et auto-catalysée de nanofils InAs compatible avec les limitations CMOS. Les différents mécanismes de croissance résultant de ces préparations de surface sont discutés en détail et un passage du mécanisme Vapor-Solid (VS) au mécanisme Vapor- Liquid-Solid (VLS) est rapporté. Les rapports d'aspect très élevé des nanofils d'InAs sont obtenus en condition VLS: jusqu'à 50 nm de diamètre et 3 microns de longueur. D'autre part, le Bi1-xSbx est le premier isolant topologique 3D confirmé expérimentalement. Dans ces nouveaux matériaux, la présence d'états surfacique conducteurs, entourant le coeur isolant, peut héberger les fermions de Majorana utilisés comme Qubits. Cependant, la composition du Bi1-xSbx doit être comprise entre 0,08 et 0,24 pour que le matériau se comporte comme un isolant topologique. Nous rapportons pour la première fois la croissance de nanofils Bi1-xSbx sans défaut et à composition contrôlée sur Si. Différentes morphologies sont obtenues, y compris des nanofils, des nanorubans et des nanoflakes. Leur diamètre peut être de 20 nm pour plus de 10 microns de long, ce qui en fait des candidats idéaux pour des dispositifs quantiques. Le rôle clé du flux Bi, du flux de Sb et de la température de croissance sur la densité, la composition et la géométrie des structures à l'échelle nanométrique est étudié et discuté en détail
InAs and Bi1-xSbx nanowires with their distinct material properites hold promises for nanoelec- tronics and quantum computing. While the high electron mobility of InAs is interesting for na- noelectronics applications, the 3D topological insulator behaviour of Bi1-xSbx can be used for the realization of Majorana Fermions based qubit devices. In both the cases improving the quality of the nanoscale material is mandatory and is the primary goal of the thesis, where we study CMOS compatible InAs nanowire integration on Silicon and where we develop a new nanoscale topological insulator. For a full CMOS compatiblity, the growth of InAs on Silicon requires to be self-catalyzed, fully vertical and uniform without crossing the thermal budge of 450 °C. These CMOS standards, combined with the high lattice mismatch of InAs with Silicon, prevented the integration of InAs nanowires for nanoelectronics devices. In this thesis, two new surface preparations of the Silicon were studied involving in-situ Hydrogen gas and in-situ Hydrogen plasma treatments and leading to the growth of fully vertical and self-catalyzed InAs nanowires compatible with the CMOS limitations. The different growth mechanisms resulting from these surface preparations are discussed in detail and a switch from Vapor-Solid (VS) to Vapor- Liquid-Solid (VLS) mechanism is reported. Very high aspect ratio InAs nanowires are obtained in VLS condition: upto 50 nm in diameter and 3 microns in length. On the other hand, Bi1-xSbx is the first experimentally confirmed 3D topololgical insulator. In this new material, the presence of robust 2D conducting states, surrounding the 3D insulating bulk can be engineered to host Majorana fermions used as Qubits. However, the compostion of Bi1-xSbx should be in the range of 0.08 to 0.24 for the material to behave as a topological insula- tor. We report growth of defect free and composition controlled Bi1-xSbx nanowires on Si for the first time. Different nanoscale morphologies are obtained including nanowires, nanoribbons and nanoflakes. Their diameter can be 20 nm thick for more than 10 microns in length, making them ideal candidates for quantum devices. The key role of the Bi flux, the Sb flux and the growth tem- perature on the density, the composition and the geometry of nanoscale structures is investigated and discussed in detail

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Brown, Richard Matthew. « Coherent transfer between electron and nuclear spin qubits and their decoherence properties ». Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:21e043b7-3b72-44d7-8095-74308a6827dd.

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Conventional computing faces a huge technical challenge as traditional transistors will soon reach their size limitations. This will halt progress in reaching faster processing speeds and to overcome this problem, require an entirely new approach. Quantum computing (QC) is a natural solution oﬀering a route to miniaturisation by, for example, storing information in electron or nuclear spin states, whilst harnessing the power of quantum physics to perform certain calculations exponentially faster than its classical counterpart. However, QCs face many diﬃculties, such as, protecting the quantum-bit (qubit) from the environment and its irreversible loss through the process of decoherence. Hybrid systems provide a route to harnessing the beneﬁts of multiple degrees of freedom through the coherent transfer of quantum information between them. In this thesis I show coherent qubit transfer between electron and nuclear spin states in a ¹⁵N@C₆₀ molecular system (comprising a nitrogen atom encapsulated in a carbon cage) and a solid state system, using phosphorous donors in silicon (Si:P). The propagation uses a series of resonant mi- crowave and radiofrequency pulses and is shown with a two-way ﬁdelity of around 90% for an arbitrary qubit state. The transfer allows quantum information to be held in the nuclear spin for up to 3 orders of magnitude longer than in the electron spin, producing a ¹⁵N@C₆₀ and Si:P ‘quantum memory’ of up to 130 ms and 1.75 s, respectively. I show electron and nuclear spin relaxation (T₁), in both systems, is dominated by a two-phonon process resonant with an excited state, with a constant electron/nuclear T₁ ratio. The thesis further investigates the decoherence and relaxation properties of metal atoms encapsulated in a carbon cage, termed metallofullerenes, discovering that exceptionally long electron spin decoherence times are possible, such that these can be considered a viable QC candidate.

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Rolon, Soto Juan Enrique. « Coherent Exciton Phenomena in Quantum Dot Molecules ». Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1314742055.

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Amoza, Dávila Martín. « Anisotropía Magnética en Imanes Moleculares y Qubits con Complejos Metálicos de Espín ½ ». Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667860.

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Esta tesis presenta una serie de estudios computacionales basados en métodos de estructura electrónica en los que se analizan la anisotropía magnética y las propiedades derivadas de esta en complejos magnéticos candidatos a imán molecular y bit cuántico con la particularidad de tener un espín total S = ½. En los primeros tres capítulos de esta tesis se estudian complejos de metales de transición. Por otro lado, el cuarto y último capítulo se centra en analizar complejos de lantánidos, concretamente de YbIII. En el primer capítulo se incluye un trabajo a través del cual se relaciona la configuración electrónica y la geometría de coordinación de un compuesto con su anisotropía magnética, en la forma del tensor g. Se puede establecer dicha conexión gracias a la dependencia del tensor g con la energía de los orbitales d. Esta energía se obtiene mediante cálculos ab initio analizados con el modelo de AILFT. Estos se realizan a partir de la función de onda obtenida en cálculos NEVPT2 realizados en modelos sencillos [MIILn], siendo MII el correspondiente metal divalente de la primera serie de transición con S = ½, L ligandos NH3 Cl- y n un número de coordinación entre 2 y 8. La observación de una anisotropía magnética de eje fácil fuerte indicar la presencia de un posible imán unimolecular mientras que una anisotropía débil es adecuada para presentar comportamiento de bit cuántico. El segundo capítulo realizado en colaboración con el grupo de “Molecular Magnetism and Quantum Computing” dirigido por el Dr. Alejandro Gaita Ariño del Institut de Ciència Molecular de Valencia (ICMol), se centra en el estudio del acoplamiento espín-fonón en tres bits cuánticos de VIV: [VOPc], [VO(dmit)2]2- y [V(dmit)3]2- donde Pc es el ligando ftalocianina y dmit es el ligando 2-tioxo-1,3-ditiol-4,5-ditiolato. A través de la variación que se produce en la anisotropía magnética al deformarmse las distintas moléculas debido al movimiento de cada modo vibracional, se calculó la fuerza del acoplamiento espín-fonón correspondiente a los distintos estados vibracionales, mediante cálculos a nivel NEVPT2/AILFT. Esta magnitud se utilizó para entender las diferencias en los tiempos de coherencia para los distintos sistemas estudiados. El tercer capítulo, finalizando el bloque dedicado a metales de transición, recopila una serie de colaboraciones con distintos grupos experimentales. Se realizó un análisis computacional similar al delos capítulos anteriores para cada compuesto en concreto: estudio de la estructura electrónica mediante cálculos NEVPT2/AILFT, anisotropía magnética en base a los orbitales d de cada compuesto, y comparación de las distintas propiedades magnéticas calculadas con las medidas experimentales. Además, se realizó el ajuste de los tiempos de relajación del espín, examinando los distintos mecanismos de relajación posibles en cada caso. En el último capítulo se analizó el caso del YbIII, un lantánido con S = ½, haciendo uso de cálculos CASPT2+RASSI con el programa MOLCAS. Dichos cálculos de estructura electrónica se realizaron en una serie de modelos [Yb(H2O)n]3+ y [Yb(OH)3(H2O)n-3], utilizando geometrías ideales para números de coordinación entre 2 y 10. Estos cálculos muestran el efecto de la geometría de coordinación y la distribución de carga de los ligandos sobre propiedades fundamentales como la energía de los distintos estados electrónicos, la anisotropía magnética del estado fundamental, o las probabilidades para los distintos mecanismos de relajación. A partir de estos resultados se explican las propiedades como imanes unimoleculares de los sistemas de YbIII encontrados en la bibliografía y se propusieron una serie de geometrías adecuadas para el fenómeno de imán unimolecular en estos sistemas.
This thesis presents a series of theoretical studies based on electronic structure methods to analyze the magnetic anisotropy and other related properties of magnetic complexes with total spin S = ½. The first three chapters are devoted to transition metal complexes while the fourth one addresses lanthanides systems, specifically YbIII. The first chapter determines a relationship between the d orbitals occupation and the coordination geometry of S = ½ transition metal complexes with their magnetic anisotropy, through its g-tensor. This connection is possible due to the relationship between the g-tensor and the splitting of the d manyfold. These energies were obtained using NEVPT2/AILFT calculation on [MIILn] models, screening for different MII metals, coordination numbers (n) and geometries, and ligand nature (L = NH3 or Cl-). The second chapter is a study carried out in collaboration with Dr. Gaita Ariño’s group from the molecular Science Institute of Valencia (ICMol) analyzing the spin-phonon coupling in three VIV qubits: [VOPc], [VO(dmit)2]2- y [V(dmit)3]2-, being Pc = Phthalocyanine and dmit = 1,3-dithiole-2-thione-4,5-dithiolate. In order to analyze the spin-phonon coupling we examined the variation of the magnetic anisotropy using NEVPT2/AILFT calculations for each vibrational mode. The spin-phonon coupling constants obtained for the vibrational modes in the three complexes were used to rationalize their different decoherence times. The third chapter, the last one dedicated to transition metal complexes, compiles a series of collaborations with experimental groups. In these studies, using the same methods as in the previous chapters, we analyzed the electronic structure and magnetic properties of the compounds, explaining experimental results through theoretical calculations. Also, we fitted the spin relaxation times considering the all possible spin relaxation mechanisms. Finally, the fourth chapter explores the magnetic anisotropy and electronic structure of YbIII compounds on the basis of theoretical calculations in a series of [Yb(H2O)n]3+ y [Yb(OH)3(H2O)n-3] model using ideal geometries corresponding to coordination numbers between 2 and 10. These calculations explain the properties of the YbIII single-molecule

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Hakimi, Shirin. « Theory and Modeling of Electrical Control of Chiral Qubit in Spin-Frustrated Molecular Triangle ». Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-84587.

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Spin-frustrated molecular triangles have four low-lying energy states, so called chiral states, which can be employed as the unit of information, qubit, in a quantum computer. The fact that the chiral states are characterized by two quantum numbers chirality and spin allows the control of the magnetization of the molecule by an electric ﬁeld due to the spin-electric interaction. Unlike a magnetic ﬁeld, electric ﬁelds can be applied spatially and temporally on the scale of single molecules, as an electric impulse by using a scanning tunneling microscope (STM) tip. In this thesis, I report on, i. Theoretical description of spin-frustrated molecular triangles based on sym-metry group theory, ii. Modeling of the system by using an extended Hubbard Hamiltonian includ-ing spin-orbit coupling and an external magnetic ﬁeld. iii. Modeling of the spin-electric interaction for a spin-frustrated molecular tri-angle. iv. Studying the chiral states by performing numerical calculations based on exact diagonalization of the Hubbard Hamiltonian. v. Investigating the electrical control of the chiral qubits through numerical calculation.

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Tuorila, J. (Jani). « Spectroscopy of artificial atoms and molecules ». Doctoral thesis, Oulun yliopisto, 2010. http://urn.fi/urn:isbn:9789514262135.

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Abstract Elementary experiments of atomic physics and quantum optics can be reproduced on a circuit board using elements built of superconducting materials. Such systems can show discrete energy levels similar to those of atoms. With respect to their natural cousins, the enhanced controllability of these ‘artificial atoms’ allows the testing of the laws of physics in a novel range of parameters. Also, the study of such systems is important for their proposed use as the quantum bits (qubits) of the foreseen quantum computer. In this thesis, we have studied an artificial atom coupled with a harmonic oscillator formed by an LC-resonator. At the quantum limit, the interaction between the two can be shown to mimic that of ordinary matter and light. The properties of the system were studied by measuring the reflected signal in a capacitively coupled transmission line. In atomic physics, this has an analogy with the absorption spectrum of electromagnetic radiation. To simulate such measurements, we have derived the corresponding equations of motion using the quantum network theory and the semi-classical approximation. The calculated absorption spectrum shows a good agreement with the experimental data. By extracting the power consumption in different parts of the circuit, we have calculated the energy flow between the atom and the oscillator. It shows that, in a certain parameter range, the absorption spectrum obeys the Franck-Condon principle, and can be interpreted in terms of vibronic transitions of a diatomic molecule. A coupling with a radiation field shifts the spectral lines of an atom. In our system, the interaction between the atom and the field is nonlinear, and we have shown that a strong monochromatic driving results in energy shifts unforeseen in natural or, even, other artificial atoms. We have used the Floquet method to calculate the quasienergies of the coupled system of atom and field. The oscillator was treated as a small perturbation probing the quasienergies, and the resulting absorption spectrum agrees with the reflection measurement.

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Navickas, Tomas. « Towards high-fidelity microwave driven multi-qubit gates on microfabricated surface ion traps ». Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/79060/.

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Leslie, Nathaniel. « Maximal LELM Distinguishability of Qubit and Qutrit Bell States using Projective and Non-Projective Measurements ». Scholarship @ Claremont, 2017. http://scholarship.claremont.edu/hmc_theses/108.

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Many quantum information tasks require measurements to distinguish between different quantum-mechanically entangled states (Bell states) of a particle pair. In practice, measurements are often limited to linear evolution and local measurement (LELM) of the particles. We investigate LELM distinguishability of the Bell states of two qubits (two-state particles) and qutrits (three-state particles), via standard projective measurement and via generalized measurement, which allows detection channels beyond the number of orthogonal single-particle states. Projective LELM can only distinguish 3 of 4 qubit Bell states; we show that generalized measurement does no better. We show that projective LELM can distinguish only 3 of 9 qutrit Bell states that generalized LELM allows at most 5 of 9. We have also made progress on distinguishing qubit $\times$ qutrit hyperentangled Bell states, which are made up of tensor products of the qubit Bell states and the qutrit Bell states, showing that the maximum number distinguishable with projective LELM measurements is between 9 and 11.

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Krajňák, Tomáš. « Depozice velkých organických molekul v UHV ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402579.

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In this thesis, large organic molecules (DM15N, DM18N, Cu(dbm)2) were deposited. These molecules are cannot be deposited by thermal sublimation due the fact that they decompose at lower temperature than they sublime. The employed molecules to single molecular magnets, which can be potentially used as quantum bites (qubit). The new method of deposition atomic layer injection made by Bihur Crystal company was introduced and tested. The method uses liquid solution with molecules which is driven by argon gas through pulse valve to the sample placed in ultra-high vacuum chamber. During the deposition, droplets of solution are formed on the sample surface. The solvent can be removed by light annealing or by keeping the sample in the vacuum for couple of days. The molecules were investigated by x-ray photoelectron spectroscopy and by scanning electron microscopy to determine fragmentation of the molecules, to study topography of the resultant surface and homogeneity of the deposited layer. We found conditions at which the intact molecules are deposited on the sample surfaces and form molecular nano- and micro- crystals.

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Livres sur le sujet "Molecular qubits"

Martínez Pérez, María José. μSQUID susceptometry of molecular qubits. Prensas Universitarias de la Universidad de Zaragoza, 2011. http://dx.doi.org/10.26754/uz.978-84-15274-82-7.

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Chapitres de livres sur le sujet "Molecular qubits"

Santini, Paolo, Stefano Carretta et Giuseppe Amoretti. « Magnetic Molecules as Spin Qubits ». Dans Molecular Magnetic Materials, 103–29. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2016. http://dx.doi.org/10.1002/9783527694228.ch5.

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Nakazawa, Shigeaki, Shinsuke Nishida, Kazunobu Sato, Kazuo Toyota, Daisuke Shiomi, Yasushi Morita, Kenji Sugisaki et al. « Molecular Spin Qubits : Molecular Optimization of Synthetic Spin Qubits, Molecular Spin AQC and Ensemble Spin Manipulation Technology ». Dans Principles and Methods of Quantum Information Technologies, 605–24. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-55756-2_28.

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Aromí, Guillem, Fernando Luis et Olivier Roubeau. « Lanthanide Complexes as Realizations of Qubits and Qugates for Quantum Computing ». Dans Lanthanides and Actinides in Molecular Magnetism, 185–222. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2015. http://dx.doi.org/10.1002/9783527673476.ch7.

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Clemente-Juan, Juan M., Eugenio Coronado et Alejandro Gaita-Ariño. « Mononuclear Lanthanide Complexes : Use of the Crystal Field Theory to Design Single-Ion Magnets and Spin Qubits ». Dans Lanthanides and Actinides in Molecular Magnetism, 27–60. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2015. http://dx.doi.org/10.1002/9783527673476.ch2.

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Mur-Petit, J., J. Pérez-Ríos, J. Campos-Martínez, M. I. Hernández, S. Willitsch et J. J. García-Ripoll. « Toward a Molecular Ion Qubit ». Dans Architecture and Design of Molecule Logic Gates and Atom Circuits, 267–77. Berlin, Heidelberg : Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-33137-4_20.

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Moreno-Pineda, Eufemio, Daniel O. T. A. Martins et Floriana Tuna. « Molecules as qubits, qudits and quantum gates ». Dans Electron Paramagnetic Resonance, 146–87. Cambridge : Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/9781839162534-00146.

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Baldoví, J. J., S. Cardona-Serra, A. Gaita-Ariño et E. Coronado. « Design of Magnetic Polyoxometalates for Molecular Spintronics and as Spin Qubits ». Dans Advances in Inorganic Chemistry, 213–49. Elsevier, 2017. http://dx.doi.org/10.1016/bs.adioch.2016.12.003.

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Flarend, Alice, et Bob Hilborn. « More Quantum Algorithms ». Dans Quantum Computing : From Alice to Bob, 182–212. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780192857972.003.0012.

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This chapter explores in detail the Grover search algorithm, which finds a basis state that has been “tagged” by making its amplitude negative, while the amplitudes of all the other basis states are positive. The analysis provides answers to important questions: How many steps are needed to find the tagged state? What is the probability of identifying the tagged state after a specified number of steps? The answers to those questions show the advantages of the quantum algorithm over the corresponding classical one. Alice and Bob introduce quantum error correction, which is needed for practical QCs because qubits interact with their environments in uncontrollable ways. It is important to detect when those “errors” occur and to correct them. The chapter concludes with an introduction to computational chemistry, algorithms used to find the energy and structures of molecular configurations. This application is likely to revolutionize materials science and the discovery of new drugs, to mention just two examples.

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Vallone, Giuseppe, et Paolo Mataloni. « Generation and Applications of n-Qubit Hyperentangled Photon States ». Dans Advances In Atomic, Molecular, and Optical Physics, 291–314. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-12-385508-4.00006-1.

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Rau, Jochen. « Computation ». Dans Quantum Theory, 168–222. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192896308.003.0004.

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This chapter introduces the basic building blocks of quantum computing and a variety of specific algorithms. It begins with a brief review of classical computing and discusses how its key elements – bits, gates, circuits – carry over to the quantum realm. It highlights crucial differences to the classical case, such as the impossibility of copying a qubit. The quantum circuit model is shown to be universal, and a peculiar variant of quantum computing, based on measurements only, is illustrated. That a quantum computer can perform some calculations more efficiently than a classical computer, at least in principle, is exemplified with the Deutsch-Jozsa algorithm. Other examples covered in this chapter are the variational quantum eigensolver, which can be applied to the study of molecules and classical optimization problems; quantum simulation; and entanglement-assisted metrology.

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Actes de conférences sur le sujet "Molecular qubits"

Goswami, Debabrata, Tapas Goswami, S. K. Karthick Kumar, Dipak K. Das, Dipankar Home, Guruprasad Kar et Archan S. Majumda. « Towards Using Molecular States as Qubits ». Dans 75 YEARS OF QUANTUM ENTANGLEMENT : FOUNDATIONS AND INFORMATION THEORETIC APPLICATIONS : S. N. Bose National Centre for Basic Sciences Silver Jubilee Symposium. AIP, 2011. http://dx.doi.org/10.1063/1.3635869.

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NISKANEN, ANTTI O. « FLUX QUBITS, TUNABLE COUPLING AND BEYOND ». Dans Molecular Realizations of Quantum Computing 2007. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812838681_0002.

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SILLANPÄÄ, MIKA A. « JOSEPHSON PHASE QUBITS, AND QUANTUM COMMUNICATION VIA A RESONANT CAVITY ». Dans Molecular Realizations of Quantum Computing 2007. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812838681_0003.

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Sato, Kazuo, Shigeki Nakazawa, Robabeh D. Rahimi, Shinsuke Nishida, Tomoaki Ise, Daisuke Shimoi, Kazuo Toyota et al. « QUANTUM COMPUTING USING PULSE-BASED ELECTRON-NUCLEAR DOUBLE RESONANCE (ENDOR) : MOLECULAR SPIN-QUBITS ». Dans Molecular Realizations of Quantum Computing 2007. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812838681_0004.

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Bashkirov, Eugene K. « Entanglement between two qubits with two-photon transitions interacting with a slightly detuned thermal field ». Dans Laser Physics, Photonic Technologies, and Molecular Modeling, sous la direction de Vladimir L. Derbov. SPIE, 2021. http://dx.doi.org/10.1117/12.2588674.

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Albert, Victor V., Jacob P. Covey et John Preskill. « Encoding a qubit in a molecule ». Dans Conference on Coherence and Quantum Optics. Washington, D.C. : OSA, 2019. http://dx.doi.org/10.1364/cqo.2019.m5a.11.

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Ide, Toshiki. « CONTINUOUS–VARIABLE TELEPORTATION OF SINGLE–PHOTON STATES AND AN ACCIDENTAL CLONING OF A PHOTONIC QUBIT IN TWO–CHANNEL TELEPORTATION ». Dans Molecular Realizations of Quantum Computing 2007. WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812838681_0009.

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Das, S., S. Faez et A. S. Sørensen. « Quantum information with optical photons in hybrid molecule-superconducting qubit system ». Dans SPIE Photonics Europe, sous la direction de Benjamin J. Eggleton, Alexander L. Gaeta, Neil G. R. Broderick, Alexander V. Sergienko, Arno Rauschenbeutel et Thomas Durt. SPIE, 2014. http://dx.doi.org/10.1117/12.2057790.

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Wang, H., et G. Iyanu. « Prospects of Creating Qubit with Ultracold RbCs Molecules in Lowest Quantum States ». Dans Conference on Coherence and Quantum Optics. Washington, D.C. : OSA, 2007. http://dx.doi.org/10.1364/cqo.2007.csua11.

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Chow, Colin, Zhexuan Gong, Luming Duan et Duncan G. Steel. « Proposal for a Universal Two-Qubit Quantum Gate in Self-Assembled InAs/GaAs Quantum Dot Molecules with Intensity-Modulated CW Laser ». Dans Laser Science. Washington, D.C. : OSA, 2013. http://dx.doi.org/10.1364/ls.2013.lth1g.1.

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