Search results for "QUBIT"

Molecular spin qubits based on lanthanide ions encapsulated in cubic polyoxopalladates: design criteria to enhance quantum coherence

2015

The family of cubic polyoxopalladates encapsulating lanthanide ions [LnPd12(AsPh)8O32]5− where Ln = Tb, Dy, Ho, Er and Tm, is magnetically characterised and theoretically described by the Radial Effective Charge (REC) model and a phenomenological crystal-field approach using the full-hamiltonian, in the SIMPRE and CONDON packages respectively. The lack of anisotropy generates an extraordinarily rich energy level structure at low temperatures, which allows us to study how such a structure is affected by lifting the strict cubic symmetry and/or by applying an external magnetic field. In particular, we will explore the possibility of using these cubic Ln complexes as spin-qubits. We will focus…

Mononuclear Lanthanide Complexes: Use of the Crystal Field Theory to Design Single-Ion Magnets and Spin Qubits

2015

Electron-nuclear decoupling at a spin clock transition

2023

The ability to design quantum systems that decouple from environmental noise sources is highly desirable for development of quantum technologies with optimal coherence. The chemical tunability of electronic states in magnetic molecules combined with advanced electron spin resonance techniques provides excellent opportunities to address this problem. Indeed, so-called clock transitions have been shown to protect molecular spin qubits from magnetic noise, giving rise to significantly enhanced coherence. Here we conduct a spectroscopic and computational investigation of this physics, focusing on the role of the nuclear bath. Away from the clock transition, linear coupling to the nuclear degree…

Molecular magnetism: from chemical design to spin control in molecules, materials and devices

2019

The field of molecular magnetism is rapidly evolving towards the use of magnetic molecules and molecule-based magnetic materials in physics-driven and nanotechnology-driven fields, in particular molecular spintronics, quantum technologies, metal–organic frameworks (MOFs) and 2D materials. In molecular spintronics, the goal is the development of a new generation of spintronic devices based on molecular materials or, in the longer term, on one or a few molecules. In the area of quantum technologies, the milestones reached in the design of molecular spin qubits with long quantum coherence times and in the implementation of quantum operations have raised expectations for the use of molecular sp…

Entanglement control via reservoir engineering in ultracold atomic gases

2013

We study the entanglement of two impurity qubits immersed in a Bose-Einstein condensate (BEC) reservoir. This open quantum system is particularly interesting because the reservoir and system parameters are easily controllable and the reduced dynamics is highly non-Markovian. We show how the model allows for interpolation between a common dephasing scenario and an independent dephasing scenario by simply modifying the wavelength of the superlattice superposed to the BEC, and how this influences the dynamical properties of the impurities. We demonstrate the existence of very rich entanglement dynamics correspondent to different values of reservoir parameters, including phenomena such as entan…

Entanglement dynamics and relaxation in a few-qubit system interacting with random collisions

2008

The dynamics of a single qubit interacting by a sequence of pairwise collisions with an environment consisting of just two more qubits is analyzed. Each collision is modeled in terms of a random unitary operator with a uniform probability distribution described by the uniform Haar measure. We show that the purity of the system qubit as well as the bipartite and the tripartite entanglement reach time averaged equilibrium values characterized by large instantaneous fluctuations.These equilibrium values are independent of the order of collision among the qubits. The relaxation to equilibrium is analyzed also in terms of an ensemble average of random collision histories. Such average allows for…

Effects of Indistinguishability in a System of Three Identical Qubits

2019

Quantum correlations of identical particles are important for quantum-enhanced technologies. The recently introduced non-standard approach to treat identical particles [G. Compagno et al., Phil. Trans. R. Soc. A 376, 20170317 (2018)] is here exploited to show the effect of particle indistinguishability on the characterization of entanglement of three identical qubits. We show that, by spatially localized measurements in separated regions, three independently-prepared separated qubits in a pure elementary state behave as distinguishable ones, as expected. On the other hand, delocalized measurements make it emerge a measurement-induced entanglement. We then find that three independently-prepa…

Quantum information processing on spin degrees of freedom in QDs placed in diluted magnetic semiconductor

2006

The spin degrees of freedom in quantum dot (QD) embedded in a diluted magnetic semiconductor (DMS) medium are considered in a model of a qubit and a gate for quantum information processing (QIP). The qubit is defined as a singlet and triplet pair of states of two electrons in a He-type QD in the DMS medium with strongly enhanced gyromagnetic factor. Methods of qubit rotation (Rabi oscillations) as well as two-qubit operations are suggested and analyzed. Moreover, decoherence related to spin waves (magnon-induced dephasing) in this new system (QD in DMS) is studied, and the relevant time-scale is estimated in accordance with preliminary experimental results. (© 2006 WILEY-VCH Verlag GmbH & C…

Accelerated stabilization of coherent photon states

2018

| openaire: EC/H2020/681311/EU//QUESS Control and utilization of coherent states of microwave photons is a ubiquitous requirement for the present and near-future implementations of solid-state quantum computers. The rate at which the photon state responds to external driving is limited by the relaxation rate of the storage resonator, which poses a trade-off between fast control and long storage time. Here, we present a control scheme that is designed to drive an unknown photon state to a desired coherent state much faster than the resonator decay rate. Our method utilizes a tunable environment which acts on an ancillary qubit coupled to the resonator. By periodically resetting the qubit and…

Ultrafast Fault-Tolerant Long-Distance Quantum Communication with Static Linear Optics

2017

We present an in-depth analysis regarding the error resistance and optimization of our all-optical Bell measurement and ultrafast long-distance quantum communication scheme proposed in [arXiv:1503.06777]. In order to promote our previous proposal from loss- to fault-tolerance, we introduce a general and compact formalism that can also be applied to other related schemes (including non-all-optical ones such as [PRL 112, 250501]). With the help of this new representation we show that our communication protocol does not only counteract the inevitable photon loss during channel transmission, but is also able to resist common experimental errors such as Pauli-type errors (bit- and phase-flips) a…