Single-Crystal Study of a Low Spin Co(II) Molecular Qubit: Observation of Anisotropic Rabi Cycles

Abstract

A mononuclear low spin (S = 1/2) Co­(II) molecule crystallized in a 4-fold symmetry is fully investigated by CW and pulsed EPR on a single crystal sample. The quantum phase memory time of the molecule around 1 μs at 5 K is direction-independent, while the Rabi oscillation frequency is anisotropic. The spin Hamiltonian analyses reveal that the anisotropic Landé factor and hyperfine tensor do not influence the anisotropy apparently when the microwave magnetic field is applied along a certain direction. It is considered that the possibly involved nuclear spin forbidden transitions may be responsible for the small distinction of Rabi frequencies in two directions.

Manipulation of Molecular Qubits by Isotope Effect on Spin Dynamics

“…However, no ligand was located in the d z 2 orbital, avoiding the vibration which accelerates the spin decoherence. Furthermore, Xu et al 43 reported a similar structural low-spin Co(II) qubit with high symmetry (C 4h ), demonstrating spin echo in the temperature range from 5 to 25 K. And the spin life at 5 K can reach 900 ns, which is much longer than our complexes. This suggests that the symmetry of molecular structure plays an important role in quantum coherence.…”

Relevance of Dzyaloshinskii–Moriya spectral broadenings in promoting spin decoherence: a comparative pulsed-EPR study of two structurally related iron(iii) and chromium(iii) spin-triangle molecular qubits

“…In assessing the mechanisms through which decoherence occurs in the temperature-independent regime, comparisons between the two complexes are helpful. The main source of decoherence are the hyperfine interactions with the surrounding magnetic nuclei; 11,67 since in terms of 1 H and 2 H content the two complexes are identical, their differences in T M times should be sought in alternative decoherence pathways.…”

Symmetry-Induced Emergence of a Pseudo-Qutrit in the Dipolar Coupling of Two Qubits

“…A similar route has recently been used to investigate the dynamics of a pair [ 25 , 26 , 27 , 28 , 29 , 30 , 31 ] or a chain [ 32 , 33 ] of coupled spins (also greater than ) subjected to time-independent and time-dependent [ 34 , 35 , 36 ] external magnetic fields. Symmetry arguments have also been exploited to elegantly bring to light intriguing dynamic features of physical systems living in Hilbert spaces of infinite dimensions [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ]. In Section 4 it is demonstrated that the time evolution of the two dipolarly coupled spins nests a qutrit subdynamics governed by a Hamiltonian model that is explicitly derived.…”