Bibliographies thématiques / Molecular qubit

Littérature scientifique sur le sujet « Molecular qubit »

Auteur : Grafiati

Publié le 10 mars 2023

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Articles de revues sur le sujet "Molecular qubit"

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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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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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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Yirka, Justin, et Yiğit Subaşı. « Qubit-efficient entanglement spectroscopy using qubit resets ». Quantum 5 (2 septembre 2021) : 535. http://dx.doi.org/10.22331/q-2021-09-02-535.

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One strategy to fit larger problems on NISQ devices is to exploit a tradeoff between circuit width and circuit depth. Unfortunately, this tradeoff still limits the size of tractable problems since the increased depth is often not realizable before noise dominates. Here, we develop qubit-efficient quantum algorithms for entanglement spectroscopy which avoid this tradeoff. In particular, we develop algorithms for computing the trace of the n-th power of the density operator of a quantum system, Tr(ρn), (related to the Rényi entropy of order n) that use fewer qubits than any previous efficient algorithm while achieving similar performance in the presence of noise, thus enabling spectroscopy of larger quantum systems on NISQ devices. Our algorithms, which require a number of qubits independent of n, are variants of previous algorithms with width proportional to n, an asymptotic difference. The crucial ingredient in these new algorithms is the ability to measure and reinitialize subsets of qubits in the course of the computation, allowing us to reuse qubits and increase the circuit depth without suffering the usual noisy consequences. We also introduce the notion of effective circuit depth as a generalization of standard circuit depth suitable for circuits with qubit resets. This tool helps explain the noise-resilience of our qubit-efficient algorithms and should aid in designing future algorithms. We perform numerical simulations to compare our algorithms to the original variants and show they perform similarly when subjected to noise. Additionally, we experimentally implement one of our qubit-efficient algorithms on the Honeywell System Model H0, estimating Tr(ρn) for larger n than possible with previous algorithms.

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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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Moreno-Pineda, Eufemio, Clément Godfrin, Franck Balestro, Wolfgang Wernsdorfer et Mario Ruben. « Molecular spin qudits for quantum algorithms ». Chemical Society Reviews 47, n^o 2 (2018) : 501–13. http://dx.doi.org/10.1039/c5cs00933b.

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Molecules are promising building blocks for Quantum information processing. Herein we describe how a molecular multilevel nuclear spin qubit (or qudit, where d = 4), known as TbPc₂, showing all necessary requirements to perform as a molecular hardware platform with a first generation of molecular devices enabling even quantum algorithm operations.

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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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Johnson, Alexander I., Fhokrul Islam, C. M. Canali et Mark R. Pederson. « A multiferroic molecular magnetic qubit ». Journal of Chemical Physics 151, n^o 17 (7 novembre 2019) : 174105. http://dx.doi.org/10.1063/1.5127956.

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Lao, Lingling, Alexander Korotkov, Zhang Jiang, Wojciech Mruczkiewicz, Thomas E. O'Brien et Dan E. Browne. « Software mitigation of coherent two-qubit gate errors ». Quantum Science and Technology 7, n^o 2 (15 mars 2022) : 025021. http://dx.doi.org/10.1088/2058-9565/ac57f1.

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Abstract Two-qubit gates are important components of quantum computing. However, unwanted interactions between qubits (so-called parasitic gates) can be particularly problematic and degrade the performance of quantum applications. In this work, we present two software methods to mitigate parasitic two-qubit gate errors. The first approach is built upon the Cartan’s KAK decomposition and keeps the original unitary decomposition for the error-free native two-qubit gate. It counteracts a parasitic two-qubit gate by only applying single-qubit rotations and therefore has no two-qubit gate overhead. We show the optimal choice of single-qubit mitigation gates. The second approach applies a numerical optimisation algorithm to re-compile a target unitary into the error-parasitic two-qubit gate plus single-qubit gates. We demonstrate these approaches on the CPhase-parasitic iSWAP-like gates. The KAK-based approach helps decrease unitary infidelity by a factor of 3 compared to the noisy implementation without error mitigation. When arbitrary single-qubit rotations are allowed, recompilation could completely mitigate the effect of parasitic errors but may require more native gates than the KAK-based approach. We also compare their average gate fidelity under realistic noise models, including relaxation and depolarising errors. Numerical results suggest that different approaches are advantageous in different error regimes, providing error mitigation guidance for near-term quantum computers.

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Abu-Nada, Ali. « Quantum computing simulation of the hydrogen molecular ground-state energies with limited resources ». Open Physics 19, n^o 1 (1 janvier 2021) : 628–33. http://dx.doi.org/10.1515/phys-2021-0071.

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Abstract In this article, the hydrogen molecular ground-state energies using our algorithm based on quantum variational principle are calculated. They are calculated through a simulator since the system of the present study (i.e., the hydrogen molecule) is relatively small and hence the ground-state energies for this molecule are efficiently classically simulable using a simulator. Complete details of this algorithm are elucidated. For this, a full description on the fermions–qubits and the molecular Hamiltonian–qubit Hamiltonian transformations, is given. The authors search for qubit system parameters ( θ 0 {\theta }_{0} and θ 1 {\theta }_{1} ) that yield the minimum energies for the system and also study the ground state energies as a function of the molecular bond length. Proposed circuit is humble and does not include many parameters compared with that of Kandala et al., the authors control only two parameters ( θ 0 {\theta }_{0} and θ 1 {\theta }_{1} ).

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Thèses sur le sujet "Molecular qubit"

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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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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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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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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Godfrin, Clément. « Quantum information processing using a molecular magnet single nuclear spin qudit ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY015/document.

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La physique quantique appliquée à la théorie de l’information se révèle être pleine de promesses pour notre société. Conscients de ce potentiel, des groupes de scientifiques du monde entier ont pour objectif commun de créer un ordinateur utilisant les principes de la mécanique quantique. La premières étape de cet ambitieux cheminement menant à l’ordinateur quantique est la réalisation du bloc de base de l’encodage quantique de l’information, le qubit. Dans le large choix de qubits existants, ceux utilisant un spin sont très attrayants puisqu’ilspeuvent être lus et manipulés de façon cohérente uniquement en utilisant des champs électriques. Enfin, plus un système est isolé, plus son comportement demeure quantique, ce qui fait du spin nucléaire un sérieux candidat dans la course aux long temps de cohérence et donc aux grands nombres d’opérations quantiques.Dans ce contexte, j’ai étudié un transistor de spin moléculaire. Ce dispositif, placé dans un réfrigérateur à dilution assurant des mesures à 40mK, est composé d’une molécule magnétique TbPc2 couplée à des électrodes (source, drain et grille) et à une antenne hyperfréquence. Il nous a permis de lire à l’aide d’une mesure de conductance, à la fois l’état de spin électronique et nucléaire de l’ion Terbium. Ma thèse se focalise sur l’étude de la dynamique de ces spins et plus particulièrement celle du spin nucléaire 3/2 sous l’influence d’un champ micro-onde. La première étape consiste à mesurer la différence d’énergie entreces quatre états de spin nucléaire pour ensuite parvenir à manipuler de façon cohérente ses trois transitions en utilisant uniquement un champ électrique. Pour caractériser davantage les processus de décohérence à l’origine de la perte de phase des états quantique, j’ai réalisé des mesures Ramsey et Hahn-echo révélant des temps de cohérence de l’ordre de 0.3ms. Ces résultats préliminaires montrent que nous sommes en présence de 3 qubits ayant une figure de mérite supérieure à deux milles, répondant ainsi aux attentes suscitées par l’utilisation d’un spin nucléaire comme bloc de base de l’information quantique.Plus que démontrer expérimentalement la dynamique de trois qubits, ces mesures nous prouvent qu’un spin nucléaire intégré dans une géométrie de type transistor à aimant moléculaire est un système à quatre états contrôlé de façon cohérente. Des propositions théoriques démontrent qu’un traitement quantique de l’information, telle que l’application de portes quantiques et la réalisation d’algorithmes, peuvent être implémentées sur un tel système. Je me suis concentré sur un algorithme de recherche. Il s’agit de la succession d’une porteHadamard, qui crée une superposition cohérente de tous les états de spin nucléaire, et une évolution unitaire qui amplifie l’amplitude d’un état désiré. Il permet une accélération quadratique de la recherche d’un élément dans une liste non ordonnée comparée à un algorithme classique. Pendant ma thèse, j’ai apporté la preuve expérimentale de la faisabilité de cet algorithme de Grover sur un système à plusieurs niveaux. La première étape a été de créer une superposition cohérente de 2, 3 et 4 états par l’application d’un pulsation radio-fréquence. Enfin, j’ai mesuré une oscillation cohérente entre une superposition de trois états et un état sélectionné qui est la signature de l’implémentation de l’algorithme de recherche.En résumé, cette thèse expose la première implémentation d’un algorithme quantique de recherche sur un qudit de type aimant moléculaire. Ces résultats, combinés à la grande polyvalence des molécules magnétiques, sont autant de promesses pour la suite de ce défi scientifique qu’est la construction d’un ordinateur quantique moléculaire
The application of quantum physics to the information theory turns out to be full of promises for our information society. Aware of this potential, groups of scientists all around the world have this common goal to create the quantum version of the computer. The first step of this ambitious project is the realization of the basic block that encodes the quantum information, the qubit. Among all existing qubits, spin based devices are very attractive since they reveal electrical read-out and coherent manipulation. Beyond this, the more isolated a system is, the longer its quantum behaviour remains, making of the nuclear spin a serious candidate for exhibiting long coherence time and consequently high numbers of quantum operation.In this context I worked on a molecular spin transistor consisting of a TbPc2 singlemolecule magnet coupled to electrodes (source, drain and gate) and a microwave antenna. This setup enabled us to read-out electrically both the electronic and the nuclear spin states and to coherently manipulate the nuclear spin of the Terbium ion. I focus during my Ph.D. on the study of the spins dynamic and mainly the 3/2 nuclear spin under the influence of a microwave pulse. The first step was to measure the energy difference between these statesleading in a second time to the coherent manipulation of the three nuclear spin transitions using only a microwave electric field. To further characterize the decoherence processes that break the phase of the nuclear spin states, I performed Ramsey and Hahn-echo measurements. These preliminary results show that we were in presence of three qubits with figure of merit higher than two thousands, thus meeting the expectations aroused by the use of a nuclearspin as the basic block of quantum information.More than demonstrating the qubit dynamic, I demonstrated that a nuclear spin embedded in the molecular magnet transistor is a four quantum states system that can be fully controlled, a qudit. Theoretical proposal demonstrated that quantum information processing such as quantum gates and algorithms could be implemented using a 3/2 spin. I focused on a research algorithm which is a succession of an Hadamard gate, that creates a coherent superposition of all the nuclear spin sates, and an unitary evolution, that amplified the amplitude of a desired state. It allows a quadratic speed-up to find an element in an unordered list compared to classical algorithm. During my Ph.D., I demonstrated the experimental proof of feasibility of this Grover like algorithm applied to a multi-levels system. The first step was to experimentally create coherent superposition of 2, 3 and 4 states. Then I measured coherent oscillations inbetween a 3 state superposition and a selected state which is the signature of the research algorithm implementation.In summary, this Ph.D. exposed the first quantum search algorithm on a single-molecule magnet based qudit. These results combined to the great versatility of molecular magnet holds a lot of promises for the next challenge: building up a scalable molecular based quantum computer

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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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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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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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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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Livres sur le sujet "Molecular qubit"

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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Majumdar, Sumit K. History and Background. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199641994.003.0003.

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The chapter summarizes details of political and institutional contexts for post-independence growth. India was severely impoverished in the period from 1900 to 1947, and per-capita growth rates were almost zero. Growth was ten times larger after independence, relative to before independence. Growth was conditioned by the institutional climate defining capitalism practiced in India. In the 1940s, the Second World War, the Quit India movement, the Bengal Famine, and the “Bombay Plan” were important growth-related contingencies. The background to policy making had been the Indian Industrial Commission report of 1918. M. Visevesvaraya’s and Ardeshir Dalal’s suggestions for India’s industrial and economic development are discussed. How India’s unique structure of industrial capitalism, consisting of private, State, and molecular sectors came about is highlighted, and how the founding policy makers’ ideas were translated into actual industrial policy, with a national capabilities development process simultaneously engendered, is described.

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Chapitres de livres sur le sujet "Molecular qubit"

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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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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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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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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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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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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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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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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Actes de conférences sur le sujet "Molecular qubit"

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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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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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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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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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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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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