Room-temperature coherence boosting of molecular graphenoids by environmental spectral decomposition

Abstract

We explore the usage of pulse sequence optimization to boost the quantum properties of topological defects in molecular graphenoids at high temperatures. We reach spin-lattice relaxation times on the same order as those of the best quantum devices in the literature, ∼1 ms at room temperature. The coherence time is shown to be heavily affected by the hyperfine interaction and by the high concentration of hydrogen atoms in particular. We test and compare the applicability and performance of different decoupling sequences in enhancing the coherence, identifying the best-performing sequences for the purposes of robust state initialization and coherence optimization. Coherence times up to 30 μs are reached, and we provide insight into the system-environment interaction mechanisms, with a semiclassical model that considers the nuclear bath as a source of a classical random noise and the dynamical decoupling as a filter function. Full deconvolution of the noise spectrum of the bath is obtained, and we show the noise density has a Lorentzian shape whose parameters describe the nuclear-bath dynamics.

Stable organic radical qubits and their applications in quantum information science

“… 54 The CPMG pulse sequence applies a train of spin-locking π pulses that further suppresses spectral diffusion and improve coherence by filtering out environmental noise efficiently. 146 , 147 , 148 , 149 Thus, T m generally increases with an increasing number of π pulses applied— ( Figure 5 E). 139 For example, for radicals trapped on chemically modified carbon nanotubes, Hahn echo gives rise to a T m = 1.2 μs at 5 K, whereas CPMG significantly improves T m , reaching 8.2 μs with 32 π pulses ( Figure 5 F).…”

Cyclohepta[def]fluorene as a bistable molecule: first principles studies on its electronic structure and the effects of benzo-extension, substitution and solvation

“…Non-alternant hydrocarbons are intensely studied due to possible technological applications such as in optical components [1][2][3] or in quantum devices. [4][5][6] In a quantum technological context, we want to note that unpaired electrons can be localized at certain carbon centres by engineering the molecular topology 4 and that corresponding quantum devices are predicted to be suited for room temperature applications. 5 Another useful property of some non-alternant hydrocarbons is bistability.…”

“…[4][5][6] In a quantum technological context, we want to note that unpaired electrons can be localized at certain carbon centres by engineering the molecular topology 4 and that corresponding quantum devices are predicted to be suited for room temperature applications. 5 Another useful property of some non-alternant hydrocarbons is bistability. This means that two electronic states with distinct properties compete for the ground state.…”