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Perylenebisimide (PBI)–anthracene (AN) donor–acceptor dyads/triad were prepared to investigate spin–orbit charge‐transfer intersystem crossing (SOCT‐ISC). Molecular conformation was controlled by connecting PBI units to the 2‐ or 9‐position of the AN moiety. Steady‐state, time‐resolved transient absorption and emission spectroscopy revealed that chromophore orientation, electronic coupling, and dihedral angle between donor and acceptor exert a significant effect on the photophysical property. The dyad PBI‐9‐AN with orthogonal geometry shows weak ground‐state coupling and efficient intersystem crossing (ISC, ΦΔ=86 %) as compared with PBI‐2‐AN (ΦΔ=57 %), which has a more coplanar geometry. By nanosecond transient absorption spectroscopy, a long‐lived PBI localized triplet state was observed (τT=139 μs). Time‐resolved EPR spectroscopy demonstrated that the electron spin polarization pattern of the triplet state is sensitive to the geometry and number of AN units attached to PBI. Reversible and stepwise generation of near‐IR‐absorbing PBI radical anion (PBI−⋅) and dianion (PBI2−) was observed on photoexcitation in the presence of triethanolamine, and it was confirmed that selective photoexcitation at the near‐IR absorption bands of PBI.− is unable to produce PBI2−. [ABSTRACT FROM AUTHOR]

We study the spin distillation of spinor gases of bosonic atoms and find two different mechanisms in 52 Cr and 23 Na atoms, both of which can cool effectively. The first mechanism involves dipolar scattering into initially unoccupied spin states and cools only above a threshold magnetic field. The second proceeds via equilibrium relaxation of the thermal cloud into empty spin states, reducing its proportion in the initial component. It cools only below a threshold magnetic field. The technique was initially demonstrated experimentally for a chromium dipolar gas (Naylor et al. in Phys Rev Lett 115:243002, 2015), whereas here we develop the concept further and provide an in-depth understanding of the required physics and limitations involved. Through numerical simulations, we reveal the mechanisms involved and demonstrate that the spin distillation cycle can be repeated several times, each time resulting in a significant additional reduction of the thermal atom fraction. Threshold values of magnetic field and predictions for the achievable temperature are also identified. [ABSTRACT FROM AUTHOR]

The quadratic low-temperature dependence of resistance in ordinary metals is determined by the momentum relaxation due to electron–electron scattering in the presence Umklapp processes and scattering on impurities. In metals without inversion center spin–orbit interaction of electrons with crystal lattice lifts spin degeneracy of electron states and splits each band on two bands. The temperature dependence of electron–electron collisions scattering rate is found using the matrix kinetic equation including the electron-impurity and electron–electron intra and inter band scattering. It is shown that in clean enough case when the energy of band splitting exceeds the electron-impurity scattering rate but at the same time it is much smaller than the Fermi energy the square low-temperature dependence of resistivity is still valid. [ABSTRACT FROM AUTHOR]

Magnetism of pure electrons is fundamental for understanding diverse magnetic phenomena in condensed matters but has not been fully investigated in experiments due to the lack of a tractable model system. Such an exotic material necessitates an exclusive magnetic interaction of electrons being devoid of orbital and lattice degrees of freedom. Here, we report the two-dimensional mixed-cation [YGdC]2+∙2e− electride, showing ferrimagnetic nature from the direct exchange interaction of magnetic interstitial electrons in interlayer space. We identify that magnetic interstitial electrons are periodically localized in octahedral and tetrahedral cavities between 2D cationic Y2−xGdx arrays. The mixed configuration of non-magnetic and magnetic cations in cavities induces divergent spin states and interactions of magnetic interstitial electrons, in which their direct exchange interaction overwhelms the interactions with magnetic cations, triggering the ferrimagnetic spin-alignment. This discovery facilitates further exploration of magnetic electrides and nurtures the study of two-dimensional magnetism of layered crystals and electron phases. [ABSTRACT FROM AUTHOR]

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The variational quantum eigensolver (VQE) algorithm, designed to calculate the energy of molecular ground states on near‐term quantum computers, requires specification of symmetries that describe the system, for example, spin state and number of electrons. This opens the possibility of using VQE to obtain excited states as the lowest‐energy solutions of a given set of symmetries. In this paper, the performances of various unitary coupled cluster (UCC) ansätze applied to VQE calculations on excited states are investigated using quantum circuits designed to represent single reference and multireference wavefunctions to calculate energy curves with respect to variations in the molecular geometry. These ansätze include standard Unitary Coupled Cluster Singles and Doubles (UCCSD), as well as modified versions of Unitary Coupled Cluster Generalized Singles and Doubles (UCCGSD) and k‐UpCCGSD, which are engineered to tackle excited states without undesired spin symmetry crossover to lower states during VQE optimization. These studies are carried out on a range of systems, including H2, H3, H4, NH, OH+, CH2, and NH2+, covering examples of spin singlet, doublet, and triplet molecular ground states with single and multireference excited states. In most cases, our calculations are in excellent agreement with results from full‐configuration interaction calculations on classical machines, thus showing that the VQE algorithm is capable of calculating the lowest excited state at a certain symmetry, including multireference closed‐ and open‐shell states, by setting appropriate restrictions on the excitations considered in the cluster operator and appropriate constraints in the qubit register encoding the starting mean field state. [ABSTRACT FROM AUTHOR]

Optimal population transfer is of critical importance for quantum information processing. Here an efficient scheme is proposed for implementing controllable and shortcut-based population transfers with a nitrogen-vacancy (NV) electron spin and cavity photons. The electron spin is placed inside a setup of circuit quantum electrodynamics (QED). Under a suitable magnetic field bias, the ground state of electron spin constitutes an effective triplet. By means of the quantized cavity field and classical drivings, we obtain a Δ -configuration interaction within a composite three-state system. Based on the adjustable Rabi couplings, the shortcut-based population transfers can be performed controllably. Moreover, compared with the adiabatic counterparts, the operations assisted by counter-diabatic drivings need much shorter times and then are less susceptible to decoherence effects. Our scheme provides a promising avenue toward optimized transfer operations on NV center electron spins in circuit QED. [ABSTRACT FROM AUTHOR]

The possibility to switch the damping rate for a one-electron oscillator is demonstrated for an electron that oscillates along the magnetic field axis in a Penning trap. Strong axial damping can be switched on to allow this oscillation to be used for quantum nondemolition detection of the cyclotron and spin quantum state of the electron. Weak axial damping can be switched on to circumvent the backaction of the detection motion that has limited past measurements. The newly developed switch will reduce the linewidth of the cyclotron transition of one-electron by two orders of magnitude. [ABSTRACT FROM AUTHOR]

Monolayers of chiral molecules can preferentially transmit electrons with a specific spin orientation, introducing chiral molecules as efficient spin filters. This phenomenon is established as chirality‐induced spin selectivity (CISS) and was demonstrated directly for the first time in self‐assembled monolayers (SAMs) of double‐stranded DNA (dsDNA)1. Here, we discuss SAMs of double‐stranded peptide nucleic acid (dsPNA) as a system which allows for systematic investigations of the influence of various molecular properties on CISS. In photoemission studies, SAMs of chiral, γ‐modified PNA show significant spin filtering of up to P = (24.4 ± 4.3)% spin polarization. The polarization values found in PNA lacking chiral monomers are considerably lower at about P = 12%. The results confirm that the preferred spin orientation is directly linked to the molecular handedness and indicate that the spin filtering capacity of the dsPNA helices might be enhanced by introduction of chiral centers in the constituting peptide monomers. [ABSTRACT FROM AUTHOR]

We have found a stable spin-structure of N = 3 system in which three spin-3 atoms are trapped and coupled to total spin S = 3. We have proved that a pair of this structure is nearly an exact solution for N = 6 systems in a very broad district in the parameter-space. Comparing with the well-known singlet pairs, this pair is a more promising candidate to serve as a building block for large N systems with spin-3 atoms. This is because the spin-structure of the latter can be modified depending on the interactions to reduce the energy while the singlet pairs can not. In fact, we have proved that, for a specific set of strengths (a point in the parameter-space) the product state based on this pair is an exact solution of the N-body Hamiltonian. Thus, in the neighborhood of this point, the product state will appear as an approximate solution. However, how broad this neighborhood would be remains to be clarified. [ABSTRACT FROM AUTHOR]

We present a system for facilitated sample vitrification, melting, and transfer in dissolution dynamic nuclear polarization (DDNP) experiments. In DDNP, a sample is typically hyperpolarized at cryogenic temperatures before dissolution with hot solvent and transfer to a nuclear magnetic resonance (NMR) spectrometer for detection in the liquid state. The resulting signal enhancements can exceed 4 orders of magnitude. However, the sudden temperature jump from cryogenic temperatures close to 1K to ambient conditions imposes a particular challenge. It is necessary to rapidly melt the sample to avoid a prohibitively fast decay of hyperpolarization. Here, we demonstrate a sample dissolution method that facilitates the temperature jump by eliminating the need to open the cryostat used to cool the sample. This is achieved by inserting the sample through an airlock in combination with a dedicated dissolution system that is inserted through the same airlock shortly before the melting event. The advantages are threefold: (1) the cryostat can be operated continuously at low temperatures. (2) The melting process is rapid as no pressurization steps of the cryostat are required. (3) Blockages of the dissolution system due to freezing of solvents during melting and transfer are minimized. [ABSTRACT FROM AUTHOR]

The signal of magnetic resonance imaging (MRI) can be enhanced by several orders of magnitude using hyperpolarization. In comparison to a broadly used dynamic nuclear polarization (DNP) technique that is already used in clinical trials, the parahydrogen (pH2)-based hyperpolarization approaches are less cost-intensive, are scalable, and offer high throughput. However, a pH2 generator is necessary. Available commercial pH2 generators are relatively expensive (EUR 10 000-150 000). To facilitate the spread of pH2-based hyperpolarization studies, here we provide the blueprints and 3D models as open-source for a low-cost (EUR< 3000) 50-bar liquid-nitrogen-cooled pH2 generator. [ABSTRACT FROM AUTHOR]

We report studies of k -dependent Landé g-factor, performed by both continuous media approximation k · p method, and atomistic tight-binding sp 3 d 5 s ∗ approach. We propose an effective, mesoscopic model for InAs that we are able to successfully compare with atomistic calculations, for both very small and very large nanostructures, with a number of atoms reaching over 60 million. Finally, for nanostructure dimensions corresponding to near-zero g-factor we report electron spin states anti-crossing as a function of system size, despite no shape-anisotropy nor strain effects included, and merely due to breaking of atomistic symmetry of cation/anion planes constituting the system. [ABSTRACT FROM AUTHOR]

Coherent electron displacement is a conventional strategy for processing quantum information, as it enables to interconnect distinct sites in a network of atoms. The efficiency of the processing relies on the precise control of the mechanism, which has yet to be established. Here, we theoretically demonstrate a new route to drive the electron displacement on a timescale faster than that of the dynamical distortion of the electron wavepacket by utilizing attosecond single-cycle pulses. The characteristic feature of these pulses relies on a vast momentum transfer to an electron, leading to its displacement following a unidirectional path. The scenario is illustrated by revealing the spatiotemporal nature of the displaced wavepacket encoding a quantum superposition state. We map out the associated phase information and retrieve it over long distances from the origin. Moreover, we show that a sequence of such pulses applied to a chain of ions enables attosecond control of the directionality of the coherent motion of the electron wavepacket back and forth between the neighbouring sites. An extension to a two-electron spin state demonstrates the versatility of the use of these pulses. Our findings establish a promising route for advanced control of quantum states using attosecond single-cycle pulses, which pave the way towards ultrafast processing of quantum information as well as imaging. [ABSTRACT FROM AUTHOR]

We represent the mutual swapping of two unknown states using bidirectional quantum teleportation (BQT) while transferring a single photon. In our BQT scheme, two users (Alice and Bob) can mutually teleport their two unknown states of the electron-spin in quantum dots (QDs) embedded in single-sided cavities. For this BQT scheme, we employ the interactions of a photonic spin (photon) and an electron-spin (excess electron) of QDs confined in a single-sided cavity, which is feasible in practice. The previous BQT scheme which used cross-Kerr nonlinearities (XKNLs) and X-homodyne detection was inevitable the decoherence effect in optical fibers. Consequently, the proposed BQT scheme can enhance an experimental implementation with the use of QD-cavity systems under the decoherence effect and this can also be realized with current technology, compared with the previous BQT scheme based on XKNLs. [ABSTRACT FROM AUTHOR]

A three‐dimensional (3D) quantum printing technique is proposed that uses electron spin cloud projections generated by microring‐embedded gold grating. A dark soliton pulse with a center wavelength of 1.50 μm excites the gold grating, leading to electron cloud oscillations. By using suitable parameters, the whispering gallery mode is obtained, which is the result of trapping light (electrons) inside the silicon microring. The plasma wave frequency is generated at the Bragg wavelength at which the electron density is obtained. The electron spin‐down and spin‐up forms the x‐axis and y‐axis along the propagation z‐axis. In this proposal, the propagation wave axis is applied to increase the printing resolution. The printing points are formed by the spin‐down, spin‐up, and no spin associated with [x, y, z] as [1, 0, −]. The electron spins are distinguished by the time sequence and by modulating with the Gaussian pulse of 1.30, 1.10, and 0.80 μm, from which the spin states of the electron can be detected and characterized. The shortest space‐time paradox gap is around 50 fs, which is the limitation of all measurements (observations). The electron transport spin projection is achieved with respect to the time function in which the 3D image is printed with a resolution of 50 fs (10−15 s). In application, the trapped electron densities within the circuit are made possible via wireless connection for long‐distance transmission. [ABSTRACT FROM AUTHOR]

To boost the performance for various applications, a rational bottom‐up design on materials is necessary. The defect engineering on nanoparticle at the atomic level can efficiently tune the electronic behavior, which offers great opportunities in enhancing the catalytic performance. In this paper, we optimized the surface oxygen vacancy concentration and created the lattice distortion in rare‐earth‐based perovskite oxide through gradient replacement of the B site with valence alternated element. The dual defects make the electron spin state transit from low spin state to high spin state, thus decreasing the charge transport resistance. Furthermore, assembly the modified nanoparticle subunits into the micro‐sized hollow multishelled structures can provide porous shells, abundant interior space and effective contact, which enables an enhanced mass transfer and a shorter charge transport path. As a result, the systemic design in the electronic and nano‐micro structures for catalyst has brought an excellent oxygen evolution performance. [ABSTRACT FROM AUTHOR]

In the present work, available experimental data up to high-spin states of $^{119-126}$ Sn isotopes with different seniority ($v$), including $v = 4$ , 5, 6, and 7, are interpreted with the shell model, by performing shell-model calculations in the 50–82 valence shell composed of $1g_{7/2}$ , $2d_{5/2}$ , $1h_{11/2}$ , $3s_{1/2}$ , and $2d_{3/2}$ orbitals. The results are compared with the available experimental data. These states are described in terms of broken neutron pairs occupying the $h_{11/2}$ orbital. Possible configurations of seniority isomers in these nuclei are discussed. The breaking of three neutron pairs is responsible for generating high-spin states. The isomeric states $5^-$ , $7^-$ , $10^+$ , and $15^-$ of even Sn isotopes, and isomeric states $19/2^+$ , $23/2^+$ , $27/2^-$ , and $35/2^+$ of odd Sn isotopes, are described in terms of different seniority. For even Sn isotopes, the isomeric states $5^-$ , $7^-$ , and $10^+$ are due to seniority $v = 2$ ; the isomeric state $15^-$ is due to seniority $v = 4$ , and, in the case of odd Sn isotopes, the isomeric states $19/2^+$ , $23/2^+$ , and $27/2^-$ are due to seniority $v = 3$ , and the isomeric state $35/2^+$ in $^{123}$ Sn is due to seniority $v = 5$. These are maximally aligned spins, which involve successive pair breakings in the $\nu (h_{11/2})$ orbital. [ABSTRACT FROM AUTHOR]

The transfer of the inherent bistability of spin crossover compounds to surfaces has attracted considerable interest in recent years. The deposition of the complexes on surfaces allows investigating them individually and to further understand the microscopic mechanisms at play. Moreover, it offers the prospect of engineering switchable functional surfaces. We review recent progress in the field with a particular focus on the challenges and limits associated with the dominant experimental techniques used, namely near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and scanning tunneling microscopy (STM). One of the main difficulties in NEXAFS-based experiments is to ascertain that the complexes are in direct contact with the surfaces. We show that molecular coverage determination based on the amplitude of the edge-jump of interest is challenging because the latter quantity depends on the substrate. Furthermore, NEXAFS averages the signals of a large number of molecules, which may be in different states. In particular, we highlight that the signal of fragmented molecules is difficult to distinguish from that of intact and functional ones. In contrast, STM allows investigating individual complexes, but the identification of the spin states is at best done indirectly. As quite some of the limits of the techniques are becoming apparent as the field is gaining maturity, their detailed descriptions will be useful for future investigations and for taking a fresh look at earlier reports. [ABSTRACT FROM AUTHOR]

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (3CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the 3NI* state. Then the slow secondary CS (125 ns) gives the long‐lived 3CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1NI*→1CT→3NI*→3CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory. [ABSTRACT FROM AUTHOR]

Fe‐Al‐bearing bridgmanite may be the dominant host for ferric iron in Earth's lower mantle. Here we report the synthesis of (Mg0.5Fe3+0.5)(Al0.5Si0.5)O3 bridgmanite (FA50) with the highest Fe3+‐Al3+ coupled substitution known to date. X‐ray diffraction measurements showed that at ambient conditions, the FA50 adopted the LiNbO3 structure. Upon compression at room temperature to 18 GPa, it transformed back into the bridgmanite structure, which remained stable up to 102 GPa and 2,600 K. Fitting Birch‐Murnaghan equation of state of FA50 bridgmanite yields V0 = 172.1(4) Å3, K0 = 229(4) GPa with K0′ = 4(fixed). The calculated bulk sound velocity of the FA50 bridgmanite is ~7.7% lower than MgSiO3 bridgmanite, mainly because the presence of ferric iron increases the unit‐cell mass by 15.5%. This difference likely represents the upper limit of sound velocity anomaly introduced by Fe3+‐Al3+ substitution. X‐ray emission and synchrotron Mössbauer spectroscopy measurements showed that after laser annealing, ~6% of Fe3+ cations exchanged with Al3+ and underwent the high‐ to low‐spin transition at 59 GPa. The low‐spin proportion of Fe3+ increased gradually with pressure and reached 17–31% at 80 GPa. Since the cation exchange and spin transition in this Fe3+‐Al3+‐enriched bridgmanite do not cause resolvable unit‐cell volume reduction, and the increase of low‐spin Fe3+ fraction with pressure occurs gradually, the spin transition would not produce a distinct seismic signature in the lower mantle. However, it may influence iron partitioning and isotopic fractionation, thus introducing chemical heterogeneity in the lower mantle. Plain Language Summary: Fe‐Al‐bearing bridgmanite may be the dominant mineral in the lower mantle, which occupies more than half of Earth's volume. A subject of much debate is whether spin transition of Fe in bridgmanite produces an observable influence on the physics and chemistry of the lower mantle. In this study, we synthesized a new (Mg0.5Fe3+0.5)(Al0.5Si0.5)O3 bridgmanite with the highest Fe3+‐Al3+ coupled substitution known to date. We studied its structure, elasticity, and spin state by multiple experimental and theoretical methods. The high Fe content allowed us to better resolve a pressure‐induced spin transition of Fe3+ caused by Fe‐Al cation exchange at high temperature. Our results suggest that the spin transition is enabled by cation exchange but has a minor effect on the seismic velocity, although it may introduce chemical heterogeneity in the lower mantle. Our study helps resolve existing discrepancies on the nature of spin transition of Fe‐Al bridgmanite and its influence on the physics and chemistry of the lower mantle. Key Points: Bridgmanite may contain 50% trivalent cations through Fe3+‐Al3+ coupled substitutionThe bulk sound velocity of (Mg0.5Fe3+0.5)(Al0.5Si0.5)O3 bridgmanite is 7.7% lower than MgSiO3Through Fe‐Al cation exchange, Fe3+ in (Mg0.5Fe3+0.5)(Al0.5Si0.5)O3 bridgmanite undergoes gradual spin transition at lower mantle conditions [ABSTRACT FROM AUTHOR]

A theoretical framework is proposed to describe the spin dynamics driven by coherent spin mixing at level anti-crossings (LACs). We briefly introduce the LAC concept and propose to describe the spin dynamics using a vector of populations of the diabatic eigenstates. In this description, each LAC gives rise to a pairwise redistribution of eigenstate populations, allowing one to construct the total evolution operator of the spin system. Additionally, we take into account that in the course of spin evolution a "rotation" of the eigenstate basis case take place. The approach is illustrated by a number of examples, dealing with magnetic field inversion, crosspolarization, singlet-state nuclear magnetic resonance and parahydrogen-induced polarization. [ABSTRACT FROM AUTHOR]

The high-speed implementation and robustness against of non-adiabatic holonomic quantum computation provide a new idea for overcoming the difficulty of the quantum system interacting with the environment easily decoherence, which realizing large-scale quantum computer construction. Here, we show that high-fidelity quantum gates to implement non-adiabatic holonomic quantum computation under electron spin states in Nitrogen-Vacancy(NV) centers, providing an extensible experimental platform that has the potential for room-temperature quantum computing, which has increased attention recent years. Compared with the previous method, we can implement both the one- and two-qubit gates by varying the amplitude and phase of the microwave pulse applied to control the non-Abelian geometric phase acquired by NV centers. We also found that our proposed scheme may be implemented in the current experiment to discuss the gate fidelity with the experimental parameters. Therefore, the scheme adopts a new method to achieve high-fidelity non-adiabatic holonomic quantum computation. [ABSTRACT FROM AUTHOR]

As shown, taking into account the centrifugal energy in the Hamiltonian of an exciton with spatially separated electron and hole (the hole moves in the germanium quantum dot, and the electron is localized over the spherical interface of the silicon matrix–quantum dot) leads to the appearance of quasistationary states in the zone of surface exciton states, which transform into stationary states with increasing quantum dot radius. As determined, the absorption spectra of the nanosystem interband consist of energy bands, which are formed by electron transitions between quasi-stationary and stationary states, and the intraband absorption spectra consist of zones formed by electron transitions between stationary states. [ABSTRACT FROM AUTHOR]

A novel method for reading out the electron spin state of the negatively charged nitrogen‐vacancy (NV) point defect in diamond, based on photoelectric detection of NV magnetic resonances (PDMR), is reviewed. As a convenient way to measure the spin state of qubits, the presented technique is anticipated to lead to a vast range of applications in the field of quantum technologies. It has been demonstrated that this method can be used both in continuous‐wave mode and for the pulse readout of coherently manipulated NV− spins. The PDMR technique presents interesting advantages over the commonly used optical detection of magnetic resonances (ODMR) and was recently downscaled to the reading out of a single NV− spin qubit. The principles, current developments, advantages, and drawbacks of PDMR are presented in this progress report. A complete to‐date methodology of NV photoelectric readout is described and PDMR is compared to ODMR. Future developments and possible improvements of the technique are mentioned. The results of the latest studies, aiming at overcoming limitations in the PDMR contrast through a better understanding of NV photo‐physics and of charge exchanges between NV centers and other electrically active defects, are discussed. [ABSTRACT FROM AUTHOR]

Among the different platforms for quantum information processing, individual electron spins in semiconductor quantum dots stand out for their long coherence times and potential for scalable fabrication. The past years have witnessed substantial progress in the capabilities of spin qubits. However, coupling between distant electron spins, which is required for quantum error correction, presents a challenge, and this goal remains the focus of intense research. Quantum teleportation is a canonical method to transmit qubit states, but it has not been implemented in quantum-dot spin qubits. Here, we present evidence for quantum teleportation of electron spin qubits in semiconductor quantum dots. Although we have not performed quantum state tomography to definitively assess the teleportation fidelity, our data are consistent with conditional teleportation of spin eigenstates, entanglement swapping, and gate teleportation. Such evidence for all-matter spin-state teleportation underscores the capabilities of exchange-coupled spin qubits for quantum-information transfer. Despite recent demonstrations of coherent spin-state transfer in arrays of spin qubits via exchange interaction, all-matter spin-state teleportation is still out of reach. Here the authors provide evidence for conditional teleportation of quantum-dot spin states, entanglement swapping, and gate teleportation. [ABSTRACT FROM AUTHOR]

Designing new quantum materials with long-lived electron spin states urgently requires a general theoretical formalism and computational technique to reliably predict intrinsic spin relaxation times. We present a new, accurate and universal first-principles methodology based on Lindbladian dynamics of density matrices to calculate spin-phonon relaxation time of solids with arbitrary spin mixing and crystal symmetry. This method describes contributions of Elliott-Yafet and D'yakonov-Perel' mechanisms to spin relaxation for systems with and without inversion symmetry on an equal footing. We show that intrinsic spin and momentum relaxation times both decrease with increasing temperature; however, for the D'yakonov-Perel' mechanism, spin relaxation time varies inversely with extrinsic scattering time. We predict large anisotropy of spin lifetime in transition metal dichalcogenides. The excellent agreement with experiments for a broad range of materials underscores the predictive capability of our method for properties critical to quantum information science. First-principles calculations can help design and understand the behaviour of quantum technologies, but this requires the development of accurate methods to predict material properties. Here the authors present a method for calculating the spin-phonon relaxation time of general systems, a key quantity for spintronic devices. [ABSTRACT FROM AUTHOR]

We present a detailed analysis about the changes of the orbital electron-correlation effects in one quantum-dot circuit, by considering finite couplings between the quantum dots and Majorana zero modes (MZMs). It is found that the dot-MZM couplings complicate the orbital-Kondo effect, because the orbital correlation occurs between the localized states in the quantum dots and the continuum hybridized states induced by the indirect metal-MZM couplings. When two of such correlation exist in pair, they have an opportunity to induce a long-range RKKY correlation, which is related to the MZMs. Further investigation shows that this RKKY interaction leads to the anomalous fractional Josephson effect. Our work can be helpful in clarifying the influence of MZM on the orbital electron correlation effects. [ABSTRACT FROM AUTHOR]

For the recently proposed exactly solvable two-chain correlated electron model with the anisotropic spin-spin interaction between electrons and the spin-orbit interaction the ground state persistent currents are calculated. The model describes the quasi-one-dimensional type II superconductor. It is shown, that the spin-orbit coupling determines the initial phase of oscillations of charge and spin persistent currents, related to unbound electron states. On the other hand, Cooper-like singlet pairs define oscillations of only charge persistent currents with the period, characteristic to pairs. Depending on the value of the external magnetic field and the band filling, the system can reveal the complicated picture of the interference of several kinds of oscillations. [ABSTRACT FROM AUTHOR]

We find that in the ferromagnetic semiconductor EuS, near its Curie temperature, a single band edge photon generates a spin polaron (SP), whose magnetic moment approaches 20 000 Bohr magnetons. This is much larger than the supergiant photoinduced SPs in antiferromagnetic europium chalcogenides, reported previously. The larger SP in ferromagnetic EuS, and still larger expected for EuO, is explained by a larger Bohr radius of the photoexcited electron state, which encircles and polarizes a greater number of lattice spins. However, because the wave function of the photoexcited electron spreads over a greater volume, the photoexcited electron's exchange interaction with individual lattice spins weakens, which makes the SP more easily quenched thermally. [ABSTRACT FROM AUTHOR]

The structural parameters of Eu@C60 isomers and the squared electron spin <Ŝ2> have been calculated using the quantum-chemical DFT (U)PBE0 method with variable quantum numbers MS. The (C2v) isomer (MS = 7/2, <Ŝ2> = 15.76 a. u.) includes a triatomic EuC2 fragment with a degraded C=C bond (2.565 Å), common for two 6-atom cycles. Two (C3v) isomers (MS = 7/2±1, <Ŝ2> = 17.76±7.01 a. u.) include the hexagonal pyramid EuC6. The energies of the isomers differ by no more than 0.046 eV. The energy barriers allow pseudo-rotation of the molecule. The Eu endo atom increases the reactivity of the carbon shell of C60 and stabilizes the (Eu@C60)2 nano-dumbbell. The <Ŝ2> values are 56 and 90 a. u. for the structures of similar energy, (Ci)-(Eu@η2-C60)2 and (Ci)-(Eu@η6-C60)2, with Eu∙∙∙Eu distances of 10.35 and 10.08 Å, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this article is to answer the question of how symmetry helps us to investigate and understand the properties of nanoscopic magnetic clusters with complex structures. The systems of choice will be the three types of polyoxometalates (POMs): (1) POMs containing localised spins; (2) reduced mixed-valence (MV) POMs; (3) partially delocalised POMs in which localised and delocalised subunits coexist and interact. The theoretical tools based on various kinds of symmetry are the following: (1) irreducible tensor operator (ITO) approach based on the so-called "spin-symmetry" and MAGPACK program; (2) group-theoretical assignment of the exchange multiplets based on spin- and point symmetries; (3) group-theoretical classification of the delocalised electronic and electron-vibrational states of MV POMs; (4) general approach (based on spin symmetry) to evaluate the energy levels of large MV clusters and the corresponding MVPACK program; (5) computational approach (employing point symmetry) to solve multidimensional non-adiabatic vibronic problems in the nanoscopic systems realized as VIBPACK software. We made it our goal to avoid a conventional deductive style of presentation. On the contrary, we first consider specially selected complex POMs and then show by what methods and in what way the theoretical problems arising in the description of the properties of these molecules can be properly solved. [ABSTRACT FROM AUTHOR]

In this paper, the influence of dispersion and polarization on the electronic probability density, the transition frequency and the longitudinal optical (LO) phonon spontaneous emission rate in the two-parameter asymmetric Gaussian confinement (AGC) potential two-level system with the electric field are studied by using the Pekar-type variational method. Numerical results show that the selecting the two-parameter AGC potential to describe the restricted effects of electron in quantum dot can more accurately reveal the quantization characteristics of of the wave property of electronic states, the statistical regularity of electron motion and LO phonons spontaneous emission rate. The influence of the electric field, dispersion and electron -phonon coupling of materials on the probability distribution, transition frequency and LO spontaneous emission rate in the two-level system cannot be ignored. [ABSTRACT FROM AUTHOR]

The electronic structure of benzene is a battleground for competing viewpoints of electronic structure, with valence bond theory localising electrons within superimposed resonance structures, and molecular orbital theory describing delocalised electrons. But, the interpretation of electronic structure in terms of orbitals ignores that the wavefunction is anti-symmetric upon interchange of like-spins. Furthermore, molecular orbitals do not provide an intuitive description of electron correlation. Here we show that the 126-dimensional electronic wavefunction of benzene can be partitioned into tiles related by permutation of like-spins. Employing correlated wavefunctions, these tiles are projected onto the three dimensions of each electron to reveal the superposition of Kekulé structures. But, opposing spins favour the occupancy of alternate Kekulé structures. This result succinctly describes the principal effect of electron correlation in benzene and underlines that electrons will not be spatially paired when it is energetically advantageous to avoid one another. The electronic structure of benzene has been a test bed for competing theories along the years. Here the authors show via quantum chemistry calculations that the wavefunction of benzene can be partitioned into tiles which show that the two electron spins exhibit staggered Kekulé structures. [ABSTRACT FROM AUTHOR]

Herein, the tunnel current in double planar tunnel junctions, consisting of ferromagnetic external electrodes and a central ferromagnetic layer separated by ferroelectric barriers, is analyzed. Different orientations of magnetic moments in the electrodes and electric polarization in the barriers are considered. The influence of the thickness of the central layer, the spin splitting of the electron bands, and the Thomas–Fermi screening length in the electrodes and the central layer on the obtained results is analyzed. The modification of the results caused by the change of the width and electric polarization of the barriers is also discussed. The influence of the change of the ferroelectric configuration on the magnitude of the tunnel current can be enhanced in the junctions with different Thomas–Fermi screening lengths in the central layer and external electrodes as well as in the junctions in which the resonant states in the central layer are located near the Fermi level in the source electrode or near the band edge for electrons of minority spin in the drain electrode. It is possible to find the junctions in which electron transport is sensitive to both ferroelectric and magnetic configurations, which can be used as multibit memories. [ABSTRACT FROM AUTHOR]

Cryptochromes are highly conserved blue light-absorbing flavoproteins which function as photoreceptors during plant development and in the entrainment of the circadian clock in animals. They have been linked to perception of electromagnetic fields in many organisms including plants, flies, and humans. The mechanism of magnetic field perception by cryptochromes is suggested to occur by the so-called radical pair mechanism, whereby the electron spins of radical pairs formed in the course of cryptochrome activation can be manipulated by external magnetic fields. However, the identity of the magnetosensitive step and of the magnetically sensitive radical pairs remains a matter of debate. Here we investigate the effect of a static magnetic field of 500 μT (10× earth's magnetic field) which was applied in the course of a series of iterated 5 min blue light/10 min dark pulses. Under the identical pulsed light conditions, cryptochrome responses were enhanced by a magnetic field even when exposure was provided exclusively in the 10 min dark intervals. However, when the magnetic stimulus was given exclusively during the 5 min light interval, no magnetic sensitivity could be detected. This result eliminates the possibility that magnetic field sensitivity could occur during forward electron transfer to the flavin in the course of the cryptochrome photocycle. By contrast, radical pair formation during cryptochrome flavin reoxidation would occur independently of light, and continue for minutes after the cessation of illumination. Our results therefore provide evidence that a magnetically sensitive reaction is entwined with dark-state processes following the cryptochrome photoreduction step. [ABSTRACT FROM AUTHOR]

The CuA center is a paradigm for the study of long-range biological electron transfer. This metal center is an essential cofactor for terminal oxidases like cytochrome c oxidase, the enzymatic complex responsible for cellular respiration in eukaryotes and in most bacteria. CuA acts as an electron hub by transferring electrons from reduced cytochrome c to the catalytic site of the enzyme where dioxygen reduction takes place. Different electron transfer pathways have been proposed involving a weak axial methionine ligand residue, conserved in all CuA sites. This hypothesis has been challenged by theoretical calculations indicating the lack of electron spin density in this ligand. Here we report an NMR study with selectively labeled methionine in a native CuA. NMR spectroscopy discloses the presence of net electron spin density in the methionine axial ligand in the two alternative ground states of this metal center. Similar spin delocalization observed on two second sphere mutants further supports this evidence. These data provide a novel view of the electronic structure of CuA centers and support previously neglected electron transfer pathways. [ABSTRACT FROM AUTHOR]

We show that enantioselective reactions can be induced by the electron spin itself and that it is possible to replace a conventional enantiopure chemical reagent by spin‐polarized electrons that provide the chiral bias for enantioselective reactions. Three examples of enantioselective chemistry resulting from electron‐spin polarization are presented. One demonstrates the enantioselective association of a chiral molecule with an achiral self‐assembled monolayer film that is spin‐polarized, while the other two show that the chiral bias provided by the electron helicity can drive both reduction and oxidation in enantiospecific electrochemical reactions. In each case, the enantioselectivity does not result from enantiospecific interactions of the molecule with the ferromagnetic electrode but from the polarized spin that crosses the interface between the substrate and the molecule. Furthermore, the direction of the electron‐spin polarization defines the handedness of the enantioselectivity. This work demonstrates a new mechanism for realizing enantioselective chemistry. [ABSTRACT FROM AUTHOR]

Four salts of the dissymmetric TTF-derivative 4-cyanobenzene-ethylenedithio-tetrathiafulvalene (4-CNB-EDT-TTF) with different anions, namely (4-CNB-EDT-TTF)A with A = ClO4 (1), BF4 (2) and (4-CNB-EDT-TTF)2[M(mnt)2] with M = Ni (3) and Au (4), were obtained by electrocrystallization and characterized by single-crystal X-ray diffraction, magnetic susceptibility and electrical conductivity measurements in comparison with the analogues based on the donor 5-CNB-EDT-TTF. All the compounds present dimerization of the donor units. Compounds 1 and 2 are isomorphous with a crystal structure characterized by slipped head to tail donor dimer stacks segregated from anion columns. Compounds 3 and 4 are isostructural with a crystal structure characterized by alternated stacks of head to tail donor dimers and acceptors. In spite of the different structural types and stoichiometries, all of these compounds have C≡N⋯H pairing interactions associated with R 22 (8), R 24 (8), R 22 (10), and R 24 (10) synthons between donors in nearby dimers. 3 and 4 are semiconductors, and their magnetic susceptibility exhibits a behaviour typical of antiferromagnetically coupled spin chains with magnetic exchange values J/k = −149.9 and −60.1 K, respectively, and in the case of 3, a Curie–Weiss contribution from the paramagnetic anions [Ni(mnt)2]−. [ABSTRACT FROM AUTHOR]

Searching two-dimensional (2D) magnetic materials with high spin polarization is important for the development and application of next-generation spintronic devices. Here, based on spin-polarized density functional theory calculations, the stability, electronic structure and magnetic properties of Mn-doped and Mn–NM (NM = B, C, N and S) co-doped monolayer WSe2 are investigated in detail. The results indicate that the Mn–S co-doped MoSe2 configuration has the lowest formation energy in the whole chemical potential range and easily spontaneously forms under thermodynamic equilibrium conditions. Obviously, the Mn-doped WSe2 configuration exhibits magnetic half-metallicity characters with a completely spin polarization at the Femi level (E F) , which can be attributed to that the electrons partially occupy the bonding states consisting of Mn a 1 states at the E F . For the Mn–C and Mn–S co-doped configurations, the Mn d x y and d z 2 orbitals strongly hybridize with the C or S spin-up p z orbital at the E F , which induces strong spin exchange splitting and eventually gives rise to the magnetic semiconductor character. However, the Mn–B and Mn–N co-doped configurations exhibit completely symmetrical spin-up and spin-down channel of a 1 , a 2 , a 3 and a 4 states due to the effective charge compensation between Mn and B or N atoms. These studies provide a new class of 2D magnetic materials for future spintronics devices. [ABSTRACT FROM AUTHOR]

Magnetoresistance and thermopower of crossed NiCr and CoCr nanowire networks have been measured as a function of temperature and chromium content in dilute alloys. At low temperatures, it is found that the impurity effect leads to negative anisotropic magnetoresistance, an observation that even persists until room temperature in diluted CoCr alloy nanowires. The addition of a small amount of Cr in nickel nanowires also abruptly reverses the sign of the thermopower from −20 μV/K for pure Ni up to +18 μV/K for the dilute alloys, implying the switching from n- to p-type conduction. These results are consistent with pronounced changes in the density of states for the majority spin electrons. The high room-temperature power factors of these magnetic nanowire networks (in the range of 1–10 mW/K2 m) provide interesting perspectives for designing n- and p-type legs for flexible spin thermoelectric devices. [ABSTRACT FROM AUTHOR]

In this paper, we study spin transport properties of silicene structures such as ribbons and superlattices with the Kane–Mele model. We investigate the effects of ferromagnetic and antiferromagnetic exchange fields, vertical and transverse electric fields and defects on the band structure, density of states, as well as conductance of the system. Our calculated results indicate that by applying a vertical electric field and/or an antiferromagnetic exchange field, metal–semimetal and also metal–semiconductor quantum phase transitions occur. We show that a zigzag silicene ribbon, when exposed to a transverse electric field in combination with an antiferromagnetic exchange field, behaves as a half-metal that allows one spin state electrons to move. Furthermore, under a vertical electric field and in the simultaneous presence of ferromagnetic and antiferromagnetic exchange fields applied to two half-widths of the ribbon, we observe the half-metallic phase. Our results help to control spin currents and to have new applications in silicene spintronics. [ABSTRACT FROM AUTHOR]

Thiocarbohydrazones (TCHs) and structurally related molecules are versatile organic compounds which exert antioxidant, anticancer, and other beneficial health effects. The combination of UV/Vis, NMR spectroscopy, and quantum chemical calculations was used to rationalize the experimentally observed increase in the radical scavenging activity upon the addition of water in DMSO solution of TCHs. Mono- and bis(salicylaldehyde) TCHs (compounds 1 and 2) undergo water-induced E-to-Z isomerization which is followed by disruption of intramolecular hydrogen bond, ground state destabilization, and 11 kcal/mol decrease in the bond dissociation enthalpy (BDE). Electron spin delocalization is more pronounced in Z-isomers of 1 and 2. On the other hand, 2-acetylpyridine TCHs (compounds 3 and 4) undergo thione-to-thiol tautomerism which also decreases the BDE and facilitates the hydrogen atom transfer to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH∙). The appearance of thiolic –SH group as another reactive site toward free radicals improves the antioxidant activity of 3 and 4. The spin density of 3- and 4-thiol radicals is delocalized over the entire thiocarbohydrazide moiety compared to more localized spin of thione radicals. Additional stabilization of thiol radicals corroborates with the increased antioxidant activity. This study provides the new insights on the solution structure of TCHs, and also highlights the importance of solution structure determination when studying the structure-antioxidant relationships of isomerizable compounds. [ABSTRACT FROM AUTHOR]

The nitrogen-vacancy (NV) color center in diamond has rapidly emerged as an important solid-state system for quantum information processing. Whereas individual spin registers have been used to implement small-scale diamond quantum computing, the realization of a large-scale device requires the development of an on-chip quantum bus for transporting information between distant qubits. Here, we propose a method for coherent quantum transport of an electron and its spin state between distant NV centers. Transport is achieved by the implementation of spatial stimulated adiabatic Raman passage through the optical control of the NV center charge states and the confined conduction states of a diamond nanostructure. Our models show that, for two NV centers in a diamond nanowire, high-fidelity transport can be achieved over distances of order hundreds of nanometers in timescales of order hundreds of nanoseconds. Spatial adiabatic passage is therefore a promising option for realizing an on-chip spin quantum bus. [ABSTRACT FROM AUTHOR]

Spectra of magnetosonic waves are studied by taking account of spin-up and spin-down electrons as two different fluids. It is found that the electron spin effect modifies the dispersions of the perpendicular and obliquely propagating magnetosonic waves even without considering the magnetization current effect. It may be noted that previously the spin effect in these dispersions appeared only due to magnetization. Furthermore, the consideration of separate spin evolution gives rise to the existence of a new spin dependent mode, i.e., spin magnetoacoustic mode along with fast and slow magnetosonic modes. It is also noted that spin polarization reduces the wave frequency of spin magnetoacoustic waves and fast magnetosonic waves while the frequency of the slow mode was slightly affected by these effects. The relevance of the present investigation in the dense astrophysical environments is also pointed out. [ABSTRACT FROM AUTHOR]

In recent years, photoexcited molecular triplet states became increasingly popular in magnetic resonance, e.g. as spin probes to measure distances relative to other electron-paramagnetic species or as moieties that transfer light-generated electron–spin polarisation of the triplet state to surrounding magnetic nuclei. In this study, the triplet states of three commercially available dyes, Erythrosin B, Rose Bengal and Atto Thio 12, all typically utilised as fluorophores in optical spectroscopies and microscopies, are investigated in aqueous solutions by using transient absorption spectroscopy and transient electron paramagnetic resonance (EPR). From these methods, the triplet-state lifetimes as well as their zero-field splitting parameters, D and E, which reflect the electronic structures of the triplet state wavefunctions, were obtained. Atto Thio 12 exhibits much smaller D and E values as compared to Rose Bengal and Erythrosin B. On the basis of density functional theory calculations of the triplets' energy splittings at zero magnetic field, these findings were rationalised. As a proof of concept for applications, the triplet-state properties of Atto Thio 12 bound to an aptamer were also determined and the results are discussed. [ABSTRACT FROM AUTHOR]

A theoretical approach to Optical Nuclear Polarisation (ONP) is described, which is based on the analysis of Level Anti-Crossings (LACs) in triplet states. Here we consider ONP formed in molecular crystals doped with suitable guest molecules and ONP generated in diamond crystals containing negatively charged nitrogen-vacancy (NV–) centres. In both cases, electron spin polarisation of triplet states generated by light excitation is transferred to nuclei giving rise to ONP. Polarisation transfer is most efficient at LACs; for this reason, we consider in detail crossings of electron–nuclear energy levels and the role of different perturbation terms (coming from isotropic and anisotropic hyperfine coupling, zero-field splitting and sample orientation), which turn these crossings into LACs and give rise to ONP. Analytical results are supported by numerical calculations of the ONP field dependences. Thus, the outlined LAC analysis is a useful approach for interpreting the ONP magnetic field dependence. [ABSTRACT FROM AUTHOR]