Electron spin coherence near room temperature in magnetic quantum dots

Abstract

We report on an example of confined magnetic ions with long spin coherence near room temperature. This was achieved by confining single Mn2+ spins in colloidal semiconductor quantum dots (QDs) and by dispersing the QDs in a proton-spin free matrix. The controlled suppression of Mn–Mn interactions and minimization of Mn–nuclear spin dipolar interactions result in unprecedentedly long phase memory (TM ~ 8 μs) and spin–lattice relaxation (T1 ~ 10 ms) time constants for Mn2+ ions at T = 4.5 K, and in electron spin coherence observable near room temperature (TM ~ 1 μs).

Persuasive Evidence for Electron–Nuclear Coupling in Diluted Magnetic Colloidal Nanoplatelets Using Optically Detected Magnetic Resonance Spectroscopy

“…Spin decoherence via interaction with nuclear spins was widely discussed in semiconductors, governed by paramagnetic isotopes of the materials' constituents, 86 and was also shown to take place in colloidal quantum dots via coupling to organic ligand nuclei. 94,36,95 In summary, the ODMR method in combination with magneto-PL spectroscopy supplied a thorough information about trapping a photogenerated electron at a core/shell interface in undoped and doped CdSe/CdS platelets. In particular, the experiment afforded the opportunity to monitor individual carrier−dopant interactions, and the present study followed the electron−dopant coupling.…”

Realization of Universal Quantum Gates with Spin‐Qudits in Colloidal Quantum Dots

“…allowed ESR transitions, Δ m s = ±1, Δ m I = 0) within the m s = |±1/2〉 spin multiplet. The broad wings beside the central narrow hyperfine lines are ascribed to the contribution of forth order zero field splitting (ZFS) terms due to Mn ions that experience distortions of the PbS cubic lattice near the QD surface . The m s = |+1/2〉 and m s = |−1/2〉 states are chosen for the definition of the qubit / qudit states because their hyperfine lines are isotropic and are not broadened by the orientation distribution and strain of the ZFS parameters.…”

“…Mn, Fe) and rare earth (e.g. Gd, Tb) ions embedded in solid state, in molecular systems, and QDs . The hyperfine interaction between electrons on 3d or 4f orbitals and the nuclear spin creates a multilevel system, and hence a qudit , which could encode and store information .…”

“…Mn) with concentration down to a single impurity per QD17c,20 and flexibility in the manipulation of the QD surface and environment enable the minimization of the major sources of Mn spin qubit decoherence (i.e. Mn–Mn spin interactions, protons of the QD surface capping ligands and nuclear spins) and to observe long quantum coherence near room temperature 18,21,17a. Furthermore, these narrow band gap nanocrystals offer opportunities for optical control of exciton‐Mn entangled states by ultrafast optical pulses and integration with other low‐dimensional semiconductors, such as graphene, to construct new hybrid functional devices …”

Coordination Mechanism in Dopamine Neurons of the <em>Substantia Nigra Pars Compacta</em> and Norepinephrine Neurons of the <em>Locus Coeruleus</em>

“…Ferritin is a magnetic nanoparticle (Fittipaldi et al, 2011) and includes iron in a form that is antiferromagnetic at room temperature (Kaur, 2009). Antiferromagnetism has been shown to extend coherence lifetimes in QDs under certain conditions (Tackeuchi et al, 2006;Papaefthymiou, 2010;Cole and Hollenberg, 2009;Moro et al, 2015;Caram et al, 2015). Ferritin has both direct and indirect electron band gaps, meaning that it can generate excitons either due only to an electric field and in the absence of photons or as a function of photon energy.…”