scholarly journals When Molecular Magnetism Meets Supramolecular Chemistry: Multifunctional and Multiresponsive Dicopper(II) Metallacyclophanes as Proof-of-Concept for Single-Molecule Spintronics and Quantum Computing Technologies?

2020 ◽  
Vol 6 (4) ◽  
pp. 69
Author(s):  
Renato Rabelo ◽  
Salah-Eddine Stiriba ◽  
Danielle Cangussu ◽  
Cynthia L. M. Pereira ◽  
Nicolás Moliner ◽  
...  
Keyword(s):  
Quantum Computing ◽  
Single Molecule ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Research Work ◽  
Theoretical Models ◽  
Magnetic Interactions ◽  
Molecular Magnetism ◽  
Special Focus ◽  
Dinuclear Metal Complexes

Molecular magnetism has made a long journey, from the fundamental studies on through-ligand electron exchange magnetic interactions in dinuclear metal complexes with extended organic bridges to the more recent exploration of their electron spin transport and quantum coherence properties. Such a field has witnessed a renaissance of dinuclear metallacyclic systems as new experimental and theoretical models for single-molecule spintronics and quantum computing, due to the intercrossing between molecular magnetism and metallosupramolecular chemistry. The present review reports a state-of-the-art overview as well as future perspectives on the use of oxamato-based dicopper(II) metallacyclophanes as promising candidates to make multifunctional and multiresponsive, single-molecule magnetic (nano)devices for the physical implementation of quantum information processing (QIP). They incorporate molecular magnetic couplers, transformers, and wires, controlling and facilitating the spin communication, as well as molecular magnetic rectifiers, transistors, and switches, exhibiting a bistable (ON/OFF) spin behavior under external stimuli (chemical, electronic, or photonic). Special focus is placed on the extensive research work done by Professor Francesc Lloret, an outstanding chemist, excellent teacher, best friend, and colleague, in recognition of his invaluable contributions to molecular magnetism on the occasion of his 65th birthday.

scholarly journals Enhanced quantum coherence in exchange coupled spins via singlet-triplet transitions

2018 ◽  
Vol 4 (11) ◽  
pp. eaau4159 ◽  
Author(s):  
Y. Bae ◽  
K. Yang ◽  
P. Willke ◽  
T. Choi ◽  
A. J. Heinrich ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Magnetic Interactions ◽  
Single Atom ◽  
Quantum Decoherence ◽  
Scanning Tunneling ◽  
Spin States ◽  
Spin Coherence ◽  
Spin Structures

Manipulation of spin states at the single-atom scale underlies spin-based quantum information processing and spintronic devices. These applications require protection of the spin states against quantum decoherence due to interactions with the environment. While a single spin is easily disrupted, a coupled-spin system can resist decoherence by using a subspace of states that is immune to magnetic field fluctuations. Here, we engineered the magnetic interactions between the electron spins of two spin-1/2 atoms to create a “clock transition” and thus enhance their spin coherence. To construct and electrically access the desired spin structures, we use atom manipulation combined with electron spin resonance (ESR) in a scanning tunneling microscope. We show that a two-level system composed of a singlet state and a triplet state is insensitive to local and global magnetic field noise, resulting in much longer spin coherence times compared with individual atoms. Moreover, the spin decoherence resulting from the interaction with tunneling electrons is markedly reduced by a homodyne readout of ESR. These results demonstrate that atomically precise spin structures can be designed and assembled to yield enhanced quantum coherence.

Engineering Electronic Structure to Protect Phase Memory in Molecular Qubits by Minimising Orbital Angular Momentum

2018 ◽  
Author(s):  
Ana Maria Ariciu ◽  
David H. Woen ◽  
Daniel N. Huh ◽  
Lydia Nodaraki ◽  
Andreas Kostopoulos ◽  
...  
Keyword(s):  
Electron Spin ◽  
Quantum Coherence ◽  
Quantum Information Processing ◽  
Pulse Sequences ◽  
Grover Algorithm ◽  
Ligand Shell ◽  
Information Strategies ◽  
Spin Qubit ◽  
Molecular Spin ◽  
The Impact

Using electron spins within molecules for quantum information processing (QIP) was first proposed by Leuenberger and Loss (1), who showed how the Grover algorithm could be mapped onto a Mn12 cage (2). Since then several groups have examined two-level (S = ½) molecular spin systems as possible qubits (3-12). There has also been a report of the implementation of the Grover algorithm in a four-level molecular qudit (13). A major challenge is to protect the spin qubit from noise that causes loss of phase information; strategies to minimize the impact of noise on qubits can be categorized as corrective, reductive, or protective. Corrective approaches allow noise and correct for its impact on the qubit using advanced microwave pulse sequences (3). Reductive approaches reduce the noise by minimising the number of nearby nuclear spins (7-11), and increasing the rigidity of molecules to minimise the effect of vibrations (which can cause a fluctuating magnetic field via spin-orbit coupling) (9,11); this is essentially engineering the ligand shell surrounding the electron spin. A protective approach would seek to make the qubit less sensitive to noise: an example of the protective approach is the use of clock transitions to render spin states immune to magnetic fields at first order (12). Here we present a further protective method that would complement reductive and corrective approaches to enhancing quantum coherence in molecular qubits. The target is a molecular spin qubit with an effective 2S ground state: we achieve this with a family of divalent rare-earth molecules that have negligible magnetic anisotropy such that the isotropic nature of the electron spin renders the qubit markedly less sensitive to magnetic noise, allowing coherent spin manipulations even at room temperature. If combined with the other strategies, we believe this could lead to molecular qubits with substantial advantages over competing qubit proposals.<br>

On the classical character of control fields in quantum information processing

2002 ◽  
Vol 2 (1) ◽  
pp. 1-13
Author(s):  
S.J. van Enk ◽  
H.J. Kimble
Keyword(s):  
Quantum Computing ◽  
Information Processing ◽  
Quantum Information ◽  
Laser Beam ◽  
Quantum State ◽  
Quantum Communication ◽  
Quantum Information Processing ◽  
Laser Fields ◽  
Undesirable Property

Control fields in quantum information processing are almost by definition assumed to be classical. In reality, however, when such a field is used to manipulate the quantum state of qubits, the qubits always become slightly entangled with the field. For quantum information processing this is an undesirable property, as it precludes perfect quantum computing and quantum communication. Here we consider the interaction of atomic qubits with laser fields and quantify atom-field entanglement in various cases of interest. We find that the entanglement decreases with the average number of photons \bar{n} in a laser beam as $E\propto\log_2 \bar{n}/\bar{n}$ for $\bar{n}\rightarrow\infty$.

Recent advances in lanthanide coordination polymers and clusters with magnetocaloric effect or single-molecule magnet behavior

2021 ◽  
Author(s):  
Jun-Jie Hu ◽  
Yan Peng ◽  
Sui-Jun Liu ◽  
He-Rui Wen
Keyword(s):  
Quantum Computing ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Coordination Polymers ◽  
Single Molecule ◽  
Information Storage ◽  
Lanthanide Ions ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Lanthanide Coordination Polymers

The molecular magnetorefrigerant materials for low-temperature magnetic refrigeration and single-molecule magnets for high-density information storage and quantum computing have received extensive attention from chemists and magnetic experts. Lanthanide ions with...

scholarly journals Special Focus: The Use of Emerging Technologies on the Internet of Everything

2017 ◽  
Vol 11 (5) ◽  
pp. 4
Author(s):  
Alberto Cardoso ◽  
Maria Teresa Restivo ◽  
Hélia Guerra ◽  
Luís Brito Palma
Keyword(s):  
Emerging Technologies ◽  
International Workshop ◽  
Research Work ◽  
Mobile Technologies ◽  
The Internet ◽  
Special Focus ◽  
Application Development ◽  
Internet Of Everything ◽  
Technology Applications ◽  
Interdisciplinary Concept

The Internet of Everything is an interdisciplinary concept that involves technology, applications and people in a framework where emerging technologies can give a relevant contribute in education and in different application areas, namely in the scope of the interactive mobile technologies. This Special Issue collects a set of contributions to this topic resulting from the works presented in the Experiment@ International Workshop 2016 “The Emerging Technologies on the Internet of Everything” – ETIoE’16, held at University of the Azores (Ponta Delgada, Azores, Portugal). These articles comprise different perspectives in this field from research work and application development to case studies.

THE TRAPPED-ION QUBIT: COHERENT CONTROL IN INFINITE-DIMENSIONAL QUANTUM SYSTEMS

2009 ◽  
Vol 24 (32) ◽  
pp. 2565-2578
Author(s):  
C. RANGAN
Keyword(s):  
Quantum Computing ◽  
Quantum System ◽  
Quantum Control ◽  
Coherent Control ◽  
Quantum Information Processing ◽  
Quantum Systems ◽  
Infinite Dimensional ◽  
Trapped Ion ◽  
Rich Variety ◽  
Control Research

Theories of quantum control have, until recently, made the assumption that the Hilbert space of a quantum system can be truncated to finite dimensions. Such truncations, which can be achieved for most quantum systems via bandwidth restrictions, have enabled the development of a rich variety of quantum control and optimal control schemes. Recent studies in quantum information processing have addressed the control of infinite-dimensional quantum systems such as the quantum states of a trapped-ion. Controllability in an infinite-dimensional quantum system is hard to prove with conventional methods, and infinite-dimensional systems provide unique challenges in designing control fields. In this paper, we will discuss the control of a popular system for quantum computing the trapped-ion qubit. This system, modeled by a spin-half particle coupled to a quantized harmonic oscillator, is an example for a surprisingly rich variety of control problems. We will show how this infinite-dimensional quantum system can be examined via the lens of the Finite Controllability Theorem, two-color STIRAP, the generalized Heisenberg system, etc. These results are important from the viewpoint of developing more efficient quantum control protocols, particularly in quantum computing systems. This work shows how one can expand the scope of quantum control research to beyond that of finite-dimensional quantum systems.

scholarly journals Microscopic quantum coherence in a photosynthetic-light-harvesting antenna

2012 ◽  
Vol 370 (1972) ◽  
pp. 3672-3691 ◽  
Author(s):  
Jahan M. Dawlaty ◽  
Akihito Ishizaki ◽  
Arijit K. De ◽  
Graham R. Fleming
Keyword(s):  
Single Molecule ◽  
Quantum Coherence ◽  
Energy Transport ◽  
Light Harvesting ◽  
Electronic Spectroscopy ◽  
Coherent Motion ◽  
Quantum Beats ◽  
Ensemble Averaging ◽  
Light Harvesting Antenna

We briefly review the coherent quantum beats observed in recent two-dimensional electronic spectroscopy experiments in a photosynthetic-light-harvesting antenna. We emphasize that the decay of the quantum beats in these experiments is limited by ensemble averaging. The in vivo dynamics of energy transport depends upon the local fluctuations of a single photosynthetic complex during the energy transfer time (a few picoseconds). Recent analyses suggest that it remains possible that the quantum-coherent motion may be robust under individual realizations of the environment-induced fluctuations contrary to intuition obtained from condensed phase spectroscopic measurements and reduced density matrices. This result indicates that the decay of the observed quantum coherence can be understood as ensemble dephasing. We propose a fluorescence-detected single-molecule experiment with phase-locked excitation pulses to investigate the coherent dynamics at the level of a single molecule without hindrance by ensemble averaging. We discuss the advantages and limitations of this method. We report our initial results on bulk fluorescence-detected coherent spectroscopy of the Fenna–Mathews–Olson complex.

Statistical Analyses and Theoretical Models of Single-Molecule Enzymatic Dynamics

1999 ◽  
Vol 103 (49) ◽  
pp. 10477-10488 ◽  
Author(s):  
Gregory K. Schenter ◽  
H. Peter Lu ◽  
X. Sunney Xie
Keyword(s):  
Single Molecule ◽  
Theoretical Models ◽  
Statistical Analyses

Three-state molecular potentiometer based on a non-symmetrically positioned in-backbone linker

2021 ◽  
Author(s):  
Lucia Palomino-Ruiz ◽  
Pablo Reiné ◽  
Irene R. Marquez ◽  
Luis Alvarez de Cienfuegos ◽  
Nicolas Agrait ◽  
...  
Keyword(s):  
Single Molecule ◽  
Theoretical Models ◽  
Phenylene Ethynylene ◽  
Conductance States

We report on the synthesis and single-molecule conductance of a para-oligo(phenylene)ethynylene (p-OPE) derivative with three well-defined conductance states. Employing theoretical models and comparing to reference compounds we show that this...

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