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FILIPPO TROIANI

DIPENDENTE ALTRO ENTE DI RICERCA
Dipartimento di Scienze Fisiche, Informatiche e Matematiche sede ex-Fisica

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Pubblicazioni

2023 - Quantum estimation and remote charge sensing with a hole-spin qubit in silicon [Articolo su rivista]
Forghieri, Gaia; Secchi, Andrea; Bertoni, Andrea; Bordone, Paolo; Troiani, Filippo
abstract

Hole-spin qubits in semiconductors represent a mature platform for quantum technological applications. Here we consider their use as quantum sensors, and specifically for inferring the presence and estimating the distance from the qubit of a remote charge. Different approaches are considered, based on the use of single or double quantum dots, ground and out-of-equilibrium states, Rabi and Ramsey measurements, and comparatively analyzed by means of the discrimination probability, and of the classical and quantum Fisher information. Detailed quantitative aspects result from the multiband character of the hole states, which we account for by means of the Luttinger-Kohn Hamiltonian. Furthermore, general conclusions can be drawn on the relative efficiency of the above options, and analytical expressions are derived for the Fisher information of a generic qubit within the Rabi and Ramsey schemes.

2022 - Unveiling Vibronic Coupling within the Q-bands of a Freebase Porphyrin [Relazione in Atti di Convegno]
Petropoulos, V.; Russo, M.; Rukin, P.; Quintela, F.; Moretti, L.; Moore, A.; Moore, T.; Gust, D.; Prezzi, D.; Scholes, G.; Molinari, E.; Troiani, F.; Cerullo, G.; Rozzi, C.; Maiuri, M.
abstract

Multidimensional spectroscopies unveil the presence of vibronic coupling within the Q-states in a free-base porphyrin. High-frequency coupling and tuning modes drive the ultrafast internal conversion and track the excited state structural evolution.

2021 - Roadmap on bio-nano-photonics [Articolo su rivista]
Herkert, E.; Slesiona, N.; Recchia, M. E.; Deckert, T.; Garcia-Parajo, M. F.; Fantuzzi, E. M.; Pruccoli, A.; Ragupathy, I. C.; Gudavicius, D.; Rigneault, H.; Majer, J.; Zumbusch, A.; Munger, E.; Brasselet, S.; Jones, A. T.; Watson, P.; Boppart, S. A.; Singh, V.; Borkar, S.; Quintela Rodriguez, F. E.; Langbein, W.; Petropoulos, V.; van Hulst, N. F.; Maiuri, M.; Cerullo, G.; Brida, D.; Troiani, F.; Rozzi, C. A.; Molinari, E.; Vengris, M.; Borri, P.
abstract

In the quest to decipher the chain of life from molecules to cells, the biological and biophysical questions being asked increasingly demand techniques that are capable of identifying specific biomolecules in their native environment, and can measure biomolecular interactions quantitatively, at the smallest possible scale in space and time, without perturbing the system under observation. The interaction of light with biomolecules offers a wealth of phenomena and tools that can be exploited to drive this progress. This Roadmap is written collectively by prominent researchers and encompasses selected aspects of bio-nano-photonics, spanning from the development of optical micro/nano-spectroscopy technologies for quantitative bioimaging and biosensing to the fundamental understanding of light–matter interaction phenomena with biomolecules at the nanoscale. It will be of interest to a wide cross-disciplinary audience in the physical sciences and life sciences.

2021 - Toward Hole-Spin Qubits in Si p -MOSFETs within a Planar CMOS Foundry Technology [Articolo su rivista]
Bellentani, L.; Bina, M.; Bonen, S.; Secchi, A.; Bertoni, A.; Voinigescu, S. P.; Padovani, A.; Larcher, L.; Troiani, F.
abstract

Hole spins in semiconductor quantum dots represent a viable route for the implementation of electrically controlled qubits. In particular, the qubit implementation based on Si p-MOSFETs offers great potentialities in terms of integration with the control electronics and long-term scalability. Moreover, the future down scaling of these devices will possibly improve the performance of both the classical (control) and quantum components of such monolithically integrated circuits. Here, we use a multiscale approach to simulate a hole-spin qubit in a down-scaled Si-channel p-MOSFET, the structure of which is based on a commercial 22-nm fully depleted silicon-on-insulator device. Our calculations show the formation of well-defined hole quantum dots within the Si channel and the possibility of a general electrical control, with Rabi frequencies of the order of 100MHz for realistic field values. A crucial role of the channel aspect ratio is also demonstrated, as well as the presence of a favorable parameter range for the qubit manipulation.

2020 - Efficient molecule discrimination in electron microscopy through an optimized orbital angular momentum sorter [Articolo su rivista]
Troiani, F.; Rotunno, E.; Frabboni, S.; Ravelli, R. B. G.; Peters, P. J.; Karimi, E.; Grillo, V.
abstract

We reformulate the single-molecule analysis in an electron microscope in terms of a quantum-state discrimination problem, and discuss its implementation through electron-beam shaping. Our approach relies on the use of new electron-optical elements to efficiently extract the "which-molecule"information from the state of each electron. The optimal observables are formally derived, and subsequently implemented by suitably designed phase elements in a generalized orbital angular momentum sorter. As a representative example, we simulate the discrimination between model proteins and benchmark the performance of the sorter against that of the best known real-space approach.

2020 - How the observation in a new custom basis based on orbital angular momentum space could improve our dose effective reconstruction of the protein structure [Articolo su rivista]
Troiani, F.; Rotunno, E.; Frabboni, S.; Ravelli, R.; Peters, P.; Karimi, E.; Grillo, V.
abstract

2018 - Microwave dual-mode resonators for coherent spin-photon coupling [Articolo su rivista]
Bonizzoni, C.; Troiani, F.; Ghirri, A.; Affronte, M.
abstract

We implement superconducting Yttrium barium copper oxide planar resonators with two fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate good tunability in the resonant microwave frequencies and in their interplay, as emerges from the dependence of the transmission spectra on the device geometry. We then investigate the magnetic coupling of the resonant modes with bulk samples of 2,2-diphenyl-1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low temperature shows that the coherent spin-photon coupling regime with the spin ensembles can be achieved by each of the resonator modes. The analysis of the results within the framework of the input-output formalism and by means of entropic measures demonstrates coherent mixing of the degrees of freedom corresponding to two remote spin ensembles and, with a suitable choice of the geometry, the approaching of a regime with spin-induced mixing of the two photon modes.

2018 - Quantum metrology at level anticrossing [Articolo su rivista]
Ghirardi, Luca; Siloi, Ilaria; Bordone, Paolo; Troiani, Filippo; Paris, Matteo G. A.
abstract

We address parameter estimation in two-level systems exhibiting level anticrossing and prove that universally optimal strategies for parameter estimation may be designed. In fact, we find a parameter-independent measurement scheme, leading to the ultimate quantum precision, independently of the value of the parameter of interest. Optimal estimationmay be achieved also at high temperature, depending on the structure of the two-level Hamiltonian. Finally, we discuss parameter estimation based on dynamical strategies, and a number of specific applications.

2016 - Coherent ultrafast polaron pair formation in a conjugated polymer at room temperature [Relazione in Atti di Convegno]
De Sio, A; Sommer, E; Troiani, F; Rehault, J; Maiuri, M; Molinari, E; Cerullo, G; Lienau, C
abstract

Ultrafast 2D optical spectroscopy with 10-fs-time-resolution, complemented by density matrix simulations, show that coherent vibronic coupling accelerates polaron-pair formation and results in strongly correlated exciton and polaron-pair dynamics in polythiophene thin films at room temperature.

2016 - Coherent vibronic coupling in a conjugated polymer at room temperature [Relazione in Atti di Convegno]
De Sio, Antonietta; Sommer, Ephraim; Troiani, Filippo; Maiuri, Margherita; Rehault, Julien; Lim, James; Huelga, Susana F.; Plenio, Martin B.; Molinari, Elisa; Cerullo, Giulio; Lienau, Christoph
abstract

Two-dimensional electronic spectroscopy with sub-10-fs time resolution shows that coherent vibronic coupling promotes charge delocalization and results in long-lasting coherent oscillatory dynamics of strongly coupled excitons and polaron-pairs in a conjugated polymer thin film at room temperature.

2016 - Coherently coupling distinct spin ensembles through a high-Tc superconducting resonator [Articolo su rivista]
Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Buccheri, N.; Beverina, L.; Cassinese, A.; Affronte, Marco
abstract

The problem of coupling multiple spin ensembles through cavity photons is revisited by using (3,5-dichloro-4- pyridyl)bis(2,4,6-trichlorophenyl) methyl (PyBTM) organic radicals and a high-T-c superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the g factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures.

2016 - Tracking the coherent generation of polaron pairs in conjugated polymers [Articolo su rivista]
De Sio, Antonietta; Troiani, Filippo; Maiuri, Margherita; Réhault, Julien; Sommer, Ephraim; Lim, James; Huelga, Susana F.; Plenio, Martin B.; Rozzi, Carlo Andrea; Cerullo, Giulio; Molinari, Elisa; Lienau, Christoph
abstract

The optical excitation of organic semiconductors not only generates charge-neutral electron-hole pairs (excitons), but also charge-separated polaron pairs with high yield. The microscopic mechanisms underlying this charge separation have been debated for many years. Here we use ultrafast two-dimensional electronic spectroscopy to study the dynamics of polaron pair formation in a prototypical polymer thin film on a sub-20-fs time scale. We observe multi-period peak oscillations persisting for up to about 1 ps as distinct signatures of vibronic quantum coherence at room temperature. The measured two-dimensional spectra show pronounced peak splittings revealing that the elementary optical excitations of this polymer are hybridized exciton-polaron-pairs, strongly coupled to a dominant underdamped vibrational mode. Coherent vibronic coupling induces ultrafast polaron pair formation, accelerates the charge separation dynamics and makes it insensitive to disorder. These findings open up new perspectives for tailoring light-to-current conversion in organic materials.

2015 - Magnetic interplay between two different lanthanides in a tris-phthalocyaninato complex: a viable synthetic route and detailed investigation in the bulk and on the surface [Articolo su rivista]
Lan, Yanhua; Klyatskaya, Svetlana; Ruben, Mario; Fuhr, Olaf; Wernsdorfer, Wolfgang; Candini, Andrea; Corradini, Valdis; LODI RIZZINI, Alberto; DEL PENNINO, Umberto; Troiani, Filippo; Joly, Loïc; Klar, David; Wende, Heiko; Affronte, Marco
abstract

Future applications of molecular units in quantum information technologies require a fine control at the single molecule level. This includes the choice of each functional element, the intramolecular interaction and the robustness of molecules when dispersed on a substrate. Keeping these goals in mind, we designed and synthesized a heterometallic phthalocyaninato-complex including two different lanthanides in each moiety, namely [PcDyPcTbPc*] (Pc being phthalocyanines; and Pc* being 2,3,9,10,16,17,23,24- octahexyl-substituted phthalocyanines). Full magnetic characterization was performed down to the mK temperature range on bulk microcrystals by means of AC susceptibility, DC magnetization (including microSQUID) and specific heat measurements. A weak, yet sizeable, interaction between the two lanthanides is clearly detected by different techniques, altering the magnetic behavior of the single lanthanide as observed in the parent [LnPc2] complexes. Isolated [PcDyPcTbPc*] molecules dispersed on HOPG and the Au surface by liquid phase deposition are proven to maintain their main chemical and magnetic features by combined XPS, XAS and XMCD analysis and to lie with one Pc ligand flat to the surface. Opening of a small but sizable hysteresis loop at 1.8 K is directly observed on both Tb and Dy sites proving the retention of magnetization at the single molecule level.

2015 - Quantum Computation with Molecular Nanomagnets: Achievements, Challenges, and New Trends [Capitolo/Saggio]
Ghirri, Alberto; Troiani, Filippo; Affronte, Marco
abstract

Molecular nanomagnets exhibit quanto-mechanical properties that can be nicely tailored at synthetic level: superposition and entanglement of quantum states can be created with molecular spins whose manipulation can be done in a timescale shorter than their decoherence time, if the molecular environment is controlled in a proper way. The challenge of quantum computation is to exploit the similarities between the coherent manipulation of molecular spins and algorithms used to process data and solve problems. In this chapter we shall firstly introduce basic concepts, stressing analogies between the physics and the chemistry of molecular nanomagnets and the science of computing. Then we shall review main achievements obtained in the first decade of this field and present challenges for the next future. In particular we shall focus on two emerging topics: quantum simulators and hybrid systems made by resonant cavities and molecular nanomagnets.

2014 - DFT Study of the Cr8 Molecular Magnet Within Chain-Model Approximations [Relazione in Atti di Convegno]
Bellini, Valerio; Daria, M. Tomecka; Brzostowski, Bartosz; Wojciechowski, Michał; Troiani, Filippo; Manghi, Franca; Affronte, Marco
abstract

We present a density functional theory (DFT) study of the electronic and magnetic properties of the Cr8 molecular ring. The allelectron linearized augmented plane wave method (LAPW) implemented in the Wien2k package and pseudopotential method implemented in SIESTA package are used to calculate the electronic states, exchange coupling parameters of an infinite chain model system of Cr8.We demonstrate how, under opportune modifications to the ring cycle structure, different one-dimensional chain models can be devised, with the capability of mimicking with good approximation the electronic and magnetic properties of the original Cr8 molecule. Such models offer an unique opportunity, in virtue of the reduced computational effort, to carry out extensive investigations of a whole set of molecules belonging to the Crbased molecular rings family.

2009 - The role of exciton-exciton interaction on nonlinearities in GaN microdisks [Relazione in Atti di Convegno]
Shojaei, S.; Troiani, F.; Asgari, A.; Kalafi, M.; Goldoni, G.
abstract

Large built-in piezoelectric fields in nitride nanostructures, because of their wurtzite structure, induce a spatial seperation between confined electrons and holes and lead to formation of electric dipoles. This paper investigates the effects of exciton-exciton interaction as a dipolar interaction in a GaN/AlxGa1-xN microdisk. We show how this interaction result in biexciton binding energies in the meV energy range. Also we study the effect of disk radius on exciton binding energy. Results show that the exciton binding energy in smaller disks, is larger than the bigger one. © 2009 SPIE.

2007 - Molecular spin clusters for quantum computation [Articolo su rivista]
Affronte, M.; Troiani, F.; Ghirri, A.; Carretta, S.; Santini, P.; Schuecker, R.; Timco, G.; Winpenny, R. E. P.
abstract

We present our recent progresses on the implementation of qubits with molecular-spin clusters. Here, we focus on molecular linkers, made of Ru dimers with different electronic states and designed to couple two Cr7Ni molecular rings with spin S = 1 / 2 as ground state. © 2006 Elsevier B.V. All rights reserved.

2007 - Single molecule magnets for quantum computation [Articolo su rivista]
Affronte, Marco; Troiani, Filippo; Ghirri, Alberto; Candini, Andrea; M., Evangelisti; Corradini, Valdis; S., Carretta; P., Santini; G., Amoretti; F., Tuna; G., Timco; R. E. P., Winpenny
abstract

We present recent achievements and perspectives for the encoding of qubitswith molecular spin clusters.

2007 - Spin triangles as optimal units for molecule-based quantum gates [Articolo su rivista]
S., Carretta; P., Santini; G., Amoretti; Troiani, Filippo; Affronte, Marco
abstract

We show that isosceles antiferromagnetic spin triangles constitute simple and very advantageous units forimplementing quantum gates with magnetic molecules. Indeed, the spin structure of their low-energy wavefunctions enables switchable effective interqubit couplings even in the presence of permanent microscopicinteractions. The great advantage of the proposed hardware is that no fine tuning of microscopic intermolecularinteractions is required. This significantly increases the robustness with respect to disorder of both the local andglobal manipulation approaches.

2005 - AntiFerromagnetic molecular rings for quantum computation. [Relazione in Atti di Convegno]
Affronte, Marco; Troiani, Filippo; Ghirri, Alberto; S., Carretta; P., Santini; G., Amoretti; S., Piligkos; G., Timco; R. E. P., Winpenny
abstract

Molecular magnets have been recently proposed as possible building blocks for a solid-state quantum computer. In order to substantiateand develop such a proposal, one needs to identify those molecules that are best suited for the qubit encoding and manipulation.Here, we focus on a heterometallic molecular ring, namely Cr7Ni, where the substitution of one Cr3+(S = 3/2) withNi2+(S = 1) provides an extra spin to the otherwise compensated molecule. We show that its ground state consists in an S = 1/2doublet, energetically well separated (D0/kB 13 K at zero magnetic field) from the first excited multiplet. This relatively large valueof D0, together with the reduced mixing of the subspaces corresponding to different values of the total spin S, enables a safe encodingof the |0æ and |1æ states with the ground-state doublet, and allows to coherently rotate the effective S = 1/2 spin, while keeping thepopulation loss to the excited states negligible. A further, intriguing challenge is represented by the implementation of the conditionaldynamics (two-qubit gates). We present here preliminary characterization of molecular ‘‘Cr7Ni-dimers’’, i.e., derivatives inwhich two Cr7Ni rings are linked with each other by means of delocalized aromatic amines. The resulting intercluster couplingsare estimated to be 61 K and are expected to be permanent, i.e., not tuneable during gating, as required by the standard approachto quantum computation. We discuss a computational scheme that allows in principle to overcome this limitation. The most relevantdecoherence mechanisms for Cr7Ni and possible ways to reduce their effects are discussed as well.

2005 - Biexcitons in artificial molecules with in-plane magnetic field [Articolo su rivista]
Bellucci, D.; Troiani, Filippo; Goldoni, Guido; Molinari, Elisa
abstract

We theoretically investigate the effect of a magnetic field perpendicular to the tunneling direction on the ground-state properties of biexcitons in coupled quantum dots. The single-particle states are computed by numerically solving the 3D Scrodinger equation. The biexciton states are obtained by means of a configuration-interaction approach, which fully accounts for the intra- and inter-dot Coulomb correlations. We show that the biexciton ground state undergoes nontrivial transitions as a function of the applied magnetic field, which can be traced back to unexpected carrier localizations. (C) 2004 Elsevier B.V. All rights reserved.

2005 - Interacting electrons in artificial molecules with magnetic field of arbitrary direction [Articolo su rivista]
Bellucci, D.; Troiani, Filippo; Goldoni, Guido; Molinari, Elisa
abstract

We theoretically investigate the mechanisms for the magnetic field-induced singlet-triplet transition of two electrons in vertically coupled quantum dots, as a function of the field strength and direction. Our numerical approach is based on a real-space description of single-particle states in realistic samples and exact diagonalization of carrier-carrier Coulomb interaction. The three-electron system is also discussed, and we show that the magnetic field drives non-trivial transitions in the ground and excited states. (C) 2004 Elsevier B.V. All rights reserved.

2005 - Proposal for quantum gates in permanently coupled antiferromagnetic spin rings without need of local fields [Articolo su rivista]
Troiani, F.; Affronte, M.; Carretta, S.; Santini, P.; Amoretti, G.
abstract

We propose a scheme for the implementation of quantum gates which is based on the qubit encoding inantiferromagnetic molecular rings.We show that a proper engineering of the intercluster link would resultin an effective coupling that vanishes as far as the system is kept in the computational space, while it isturned on by a selective excitation of specific auxiliary states. These are also shown to allow theperforming of single-qubit and two-qubit gates without an individual addressing of the rings by meansof local magnetic fields.

2004 - Competing mechanisms for singlet-triplet transition in artificial molecules [Articolo su rivista]
Bellucci, D.; Rontani, Massimo; Troiani, Filippo; Goldoni, Guido; Molinari, Elisa
abstract

We study the magnetic field induced singlet/triplet transition for two electrons in vertically-coupled quantum dots by exact diagonalization of the Coulomb interaction. We identify the different mechanisms occurring in the transition, involving either in-plane correlations or localization in opposite dots, depending on the field direction. Therefore, both spin and orbital degrees of freedom can be manipulated by field strength and direction. The phase diagram of realistic devices is determined.

2004 - Field-controlled suppression of phonon-induced transitions in coupled quantum dots [Articolo su rivista]
Bertoni, Andrea; Rontani, Massimo; Goldoni, Guido; Troiani, Filippo; Molinari, Elisa
abstract

We suggest that order-of-magnitude reduction of the longitudinal-acoustic phonon scattering rate, the dominant decoherence mechanism in quantum dots, can be achieved in coupled structures by the application of an external electric or magnetic field. Modulation of the scattering rate is traced to the relation between the wavelength of the emitted phonon and the length scale of delocalized electron wave functions. Explicit calculations for realistic devices, performed with a Fermi golden rule approach and a fully three-dimensional description of the electronic quantum states, show that the lifetime of specific states can achieve tens of microseconds. Our findings extend the feasibility basis of many proposals for quantum gates based on coupled quantum dots. (C) 2004 American Institute of Physics.

2004 - High-finesse optical quantum gates for electron spins in artificial molecules [Articolo su rivista]
Troiani, Filippo; Hohenester, U; Molinari, Elisa
abstract

We propose the storage of the quantum information (qubit) in the spin of an excess electron in two vertically coupled quantum dots and its all-optical manipulation through ps-laser pulses. The auxiliary levels of the artificial molecule allow the implementation of the logical gates solely by means of stimulated Raman adiabatic passages, and the consequent suppression of the environment losses. The mapping of the spin states onto the orbital degrees of freedom results in the switch on of the dipole-dipole interaction between neighbouring qubits and thus allows the conditional dynamics (two-qubit gates) to be performed.

2004 - Neutral and charged electron-hole complexes in artificial molecules: quantum transitions induced by the in-plane magnetic field [Articolo su rivista]
Bellucci, D.; Troiani, Filippo; Goldoni, Guido; Molinari, Elisa
abstract

We theoretically investigate the properties of neutral and charged excitons and of the biexciton in vertically coupled quantum dots, as a function of the in-plane magnetic field B-parallel to. The main effect of the field consists in the suppression of the bonding-antibonding splitting, and in the resulting enhancement of the interdot correlations. As a consequence, the excitons form with the additional carrier a bound or an unbound complex depending on the sign of the charging, whereas the biexciton undergoes a transition between different quantum states with increasing B-parallel to. The discussed behaviors and transitions show up in the field dependence of experimentally accessible quantities, such as the charged-exciton and biexciton binding energies.

2003 - High-Finesse Optical Quantum Gates for Electron Spins in Artificial Molecules [Articolo su rivista]
Troiani, Filippo; U., Hohenester; Molinari, Elisa
abstract

A doped semiconductor double-quantum-dot molecule is proposed as a qubit realization. The quantum information is encoded in the electron spin, thus benefiting from the long relevant decoherence times; the enhanced flexibility of the molecular structure allows one to map the spin degrees of freedom onto the orbital ones and vice versa and opens the possibility for high-finesse (conditional and unconditional) quantum gates by means of stimulated Raman adiabatic passages.

2002 - Dominance of Charged Excitons in Single Quantum Dot Photoluminescence Spectra [Articolo su rivista]
M., Lomascolo; A., Vergine; T. K., Johal; R., Rinaldi; A., Passaseo; R., Cingolani; S., Patanè; M., Lombardi; M., Allegroni; Troiani, Filippo; Molinari, Elisa
abstract

Single InxGa1-xAs/GaAs quantum dot photoluminescence spectra, obtained by low-temperature near-field scanning optical microscopy, are compared with theoretically derived optical spectra. The spectra show shell filling as well as few-particle fine structure associated with neutral and charged multiexcitons, in good agreement with the many-body calculations. There appears to be a greater tendency to charged-exciton formation, which is discussed in terms of the high diffusivity of photogenerated electrons.

2002 - Electron-Hole Localization in Coupled Quantum Dots [Articolo su rivista]
Troiani, Filippo; U., Hohenester; Molinari, Elisa
abstract

We theoretically investigate correlated electron-hole states in vertically coupled quantum dots. Employing a prototypical double-dot confinement and a configuration-interaction description for the electron-hole states, it is shown that the few-particle ground state undergoes transitions between different quantum states as a function of the interdot distance, resulting in unexpected spatial correlations among carriers and in electron-hole localization. Such transitions provide direct manifestations of inter- and intradot correlations, which can be directly monitored in experiments.

2001 - Quantum phases in artificial molecules [Articolo su rivista]
Rontani, Massimo; Troiani, Filippo; Hohenester, U; Molinari, Elisa
abstract

The few-particle state of carriers confined in a quantum dot is controlled by the balance between their kinetic energy and their Coulomb correlation. In coupled quantum dots, both can be tuned by varying the inter-dot tunneling and interactions. Using a theoretical approach based on the diagonalization of the exact Hamiltonian, we show that the transitions between different quantum phases can be induced through the inter-dot coupling both for a system of few electrons (or holes) and for aggregates of electrons and holes. We discuss their manifestations, in addition energy spectra (accessible through capacitance or transport experiments) and optical spectra. (C) 2001 Elsevier Science Ltd. All rights reserved.

2001 - Quantum-information processing in semiconductor quantum dots [Articolo su rivista]
Troiani, Filippo; Hohenester, U; Molinari, Elisa
abstract

We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, where electron-hole excitations (excitons) serve ve as the computational degrees of freedom (qubits). The strong dot confinement leads to a strong renormalization of excitonic states, which, in analogy to NMR:based implementations of quantum-information processing, can be exploited for performing conditional and unconditional qubit operations.

2000 - Coherent population transfer in coupled semiconductor quantum dots [Articolo su rivista]
Hohenester, U; Troiani, Filippo; Molinari, Elisa; Panzarini, G; Macchiavello, C.
abstract

We propose a solid-state implementation of stimulated Raman adiabatic passage in two coupled semiconductor quantum dots. Proper combination of two pulsed laser fields allows the coherent carrier transfer between the two nanostructures without suffering significant losses due to environment coupling. By use of a general solution scheme for the carrier states in the double-dot structure, we identify the pertinent dot and laser parameters. (C) 2000 American Institute of Physics. [S0003-6951(00)05338-9].

2000 - Exploiting exciton-exciton interactions in semiconductor quantum dots for quantum-information processing [Articolo su rivista]
Troiani, Filippo; Hohenester, U; Molinari, Elisa
abstract

We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, when electron-hole excitations (excitons) serve as the computational degrees of freedom (qubits). We show that the strong dot confinement leads to an overall enhancement of Coulomb correlations and to a strong renormalization of the excitonic states, which can be exploited for performing conditional and unconditional qubit operations.