The successful development of a quantum computer would change the world, and current internet encryption methods would cease to function. However, no working quantum computer that even begins to rival conventional computers has been developed yet, which is due to the lack of suitable quantum bits. A key characteristic of a quantum bit is the coherence time. Transition metal complexes are very promising quantum bits, owing to their facile surface deposition and their chemical tunability. However, reported quantum coherence times have been unimpressive. Here we report very long quantum coherence times for a transition metal complex of 68 μs at low temperature (qubit figure of merit QM=3,400) and 1 μs at room temperature, much higher than previously reported values for such systems. We show that this achievement is because of the rigidity of the lattice as well as removal of nuclear spins from the vicinity of the magnetic ion.

Room temperature quantum coherence in a potential molecular qubit.

This review serves as a brief introduction to phospholes and discusses their unique favorable properties for application in organic electronic materials. Over the past several years, π-conjugated phospholes have been slowly making their way into devices. We report here the mode of synthesis of these π-conjugated phospholes as well as discuss the performances of the devices.

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π-Conjugated phospholes and their incorporation into devices: components with a great deal of potential

In the search for long-lived quantum coherence in spin systems, vanadium(IV) complexes have shown record phase memory times among molecular systems. When nuclear spin-free ligands are employed, vanadium(IV) complexes can show at low temperature sufficiently long quantum coherence times, Tm, to perform quantum operations, but their use in real devices operating at room temperature is still hampered by the rapid decrease of T1 caused by the efficient spin–phonon coupling. In this work we have investigated the effect of different coordination environments on the magnetization dynamics and the quantum coherence of two vanadium(IV)-based potential molecular spin qubits in the solid state by introducing a unique structural difference, i.e., an oxovanadium(IV) in a square pyramidal versus a vanadium(IV) in an octahedral environment featuring the same coordinating ligand, namely, the 1,3-dithiole-2-thione-4,5-dithiolate. This investigation, performed by a combined approach of alternate current (ac) susceptibility...

Quantum Coherence Times Enhancement in Vanadium(IV)-based Potential Molecular Qubits: the Key Role of the Vanadyl Moiety

The mononuclear Co(II) complex dmphCoBr (dmph = 2,9-dimethyl-1,10-phenanthroline) was obtained and X-ray structurally characterized as a distorted tetrahedron environment that is responsible for the moderately strong positive anisotropy of high spin Co(II). In combination with variable-field magnetic susceptibility data at low temperature, high-field electron paramagnetic resonance (HF-EPR) spectroscopy reveals the presence of easy-plane anisotropy (D > 0) in complex dmphCoBr. Slow magnetic relaxation effects were observed for dmphCoBr in the presence of a dc magnetic field. At very low temperatures, ac magnetic susceptibility data show the magnetic relaxation time, τ, to be temperature-independent, while above 2.4 K thermally activated Arrhenius behavior is dominated with Ueff = 22.8(8) cm−1 and τ0 = 3.7(5) × 10−10 s. Upon dilution of the complex within a matrix of the isomorphous compound dmphZnBr, ac susceptibility data reveal the individual molecular nature of the slow magnetic relaxation and indicate that the quantum tunneling pathway observed at low temperatures is likely mediated by intermolecular dipolar interactions.

Field-induced slow relaxation of magnetization in a tetrahedral Co(II) complex with easy plane anisotropy

https://iopscience.iop.org/article/10.1070/RCR4795/pdf

Organofluorine chemistry: promising growth areas and challenges

Phospholes – Development and Recent Advances

Major tendencies in modern chemistry of alkali and transition metal phospholides (phosphacyclopentadienides) are systematized, analyzed and generalized. Basic methods of synthesis of these compounds are presented. Their chemical properties are considered with a special focus on their complexing ability. Potential applications of phospholides and their derivatives are discussed. The bibliography includes 184 references.

https://iopscience.iop.org/article/10.1070/RC2014v083n06ABEH004442/pdf

Alkali and transition metal phospholides

Cycloaddition Reactions of 1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-dienes

We investigate a possibility to enhance the coherence time of electron spins in magnetic molecular complexes by application of the Carr-Purcell-Meiboom-Gill (CPMG) multiple microwave pulse sequence. Our theoretical analysis shows that the CPMG sequence can efficiently suppress the spin decoherence channel arising due to spectral diffusion induced by a random modulation of the hyperfine interaction which is an important source of the spin dephasing in molecular magnets. We confirm this by employing the CPMG protocol in pulse electron spin resonance experiments on model binuclear 1,2-diphosphacyclopentadienyl manganese complexes. We show that, compared to the standardly used two-pulse primary spin-echo technique, the CPMG experiment can boost the phase memory time up to one order of magnitude, bringing it to above 10 μs at low temperatures. This finding may be important for the implementation of quantum computation protocols on molecular magnets. We discuss a possible interesting analogy with the Zeno’s paradox in quantum theory (the Zeno quantum effect), which could be implicit in the CPMG experiment. DOI: 10.1103/PhysRevB.88.094418

Boosting the electron spin coherence in binuclear Mn complexes by multiple microwave pulses

Reactions of sodium 3,4,5-triphenyl-1,2-diphosphacyclopentadienide with primary alkyl bromides, secondary alkyl iodides, and silicon and tin chlorides gave stable 1-substituted 1,2-diphospholes. In a solution of 3,4,5-triphenyl-1-trimethylstannyl-1,2-diphosphacyclopenta-2,4-diene, the Me3Sn group migrates between two phosphorus atoms.

Ilya Bezkishko

Papers

Phospholes – Development and Recent Advances

Alkali and transition metal phospholides

Cycloaddition Reactions of 1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-dienes

Boosting the electron spin coherence in binuclear Mn complexes by multiple microwave pulses

Reactions of sodium 3,4,5-triphenyl-1,2-diphosphacyclopentadienide with alkyl halides and silicon and tin chlorides