Hamiltonian simulation of quantum beats in radical pairs undergoing thermal relaxation on near-term quantum computers.

Quantum dynamics of the radical pair mechanism is a major driving force in quantum biology, materials science, and spin chemistry. The rich quantum physical underpinnings of the mechanism are determined by a coherent oscillation (quantum beats) between the singlet and triplet spin states and their interactions with the environment, which is challenging to experimentally explore and computationally simulate. In this work, we take advantage of quantum computers to simulate the Hamiltonian evolution and thermal relaxation of two radical pair systems undergoing the quantum beats phenomenon. We study radical pair systems with nontrivial hyperfine coupling interactions, namely, 9,10-octalin+/p-terphenyl-d14 (PTP)- and 2,3-dimethylbutane (DMB)+/p-terphenyl-d14 (PTP)- with one and two groups of magnetically equivalent nuclei, respectively. Thermal relaxation dynamics in these systems are simulated using three methods: Kraus channel representations, noise models on Qiskit Aer and the inherent qubit noise present on the near-term quantum hardware. By leveraging the inherent qubit noise, we are able to simulate the noisy quantum beats in the two radical pair systems better than with any classical approximation or quantum simulator. While classical simulations of paramagnetic relaxation grow errors and uncertainties as a function of time, near-term quantum computers can match the experimental data throughout its time evolution, showcasing their unique suitability and future promise in simulating open quantum systems in chemistry.

Oxidation reactions of a nucleophilic palladium carbene: mono and bi-radical carbenes.

Palladium(ii) cationic carbene radical and neutral bi-radical complexes were synthesized from a previously reported Pd(ii) carbene in the presence of one and two electron oxidants. When [{PC(sp2)P}tBuPd(PMe3)] (1, [PC(sp2)P]tBu = (bis[2-(di-iso-propylphosphino)-4-tertbutylphenyl]methylene)) was treated with [Cp2Fe][X] (X = BArF4, ArF = 3,5-(CF3)2C6H3, or PF6), the corresponding radical cationic complexes [{PC˙(sp2)P}tBuPd(PMe3)][X] (2: X = BArF4, 3: PF6) were isolated and characterized. Magnetic moment measurements and EPR spectroscopy indicated the presence of a ligand centered unpaired electron. In the presence of two electron oxidants such as 1,8-naphthylene disulfide or 9,10-anthracenedione, 1 converts to [{PC˙(sp2)P}tBuPdS(C10H6)SPd{PC˙(sp2)P}tBu] (4) or [{PC˙(sp2)P}tBuPdO(C14H10)OPd{PC˙(sp2)P}tBu] (5), respectively. Single crystal X-ray diffraction and EPR spectroscopy confirmed the bi-radical nature of 4 and 5.

Heterobimetallic Pd-K carbene complexes via one-electron reductions of palladium radical carbenes.

Heterobimetallic Pd-K carbenes featuring Pd-Ccarbene-K moieties were synthesized via an unprecedented sequential substitution/reduction reaction from a radical precursor, [{PC˙(sp2)P} tBuPdI] ([PC(sp2)P] tBu = bis[2-(di-iso-propylphosphino)-4-tert-butylphenyl]methylene). Polymeric structures were observed in the solid state for the heterobimetallic compounds that can be interrupted in the presence of a donor solvent.

Comparison of acid generation in EUV lithography films of poly(4-hydroxystyrene) (PHS) and noria adamantyl ester (Noria-AD(50)).

The mechanism for acid production in phenolic extreme ultraviolet (EUV) lithography films containing triphenylsulfonium triflate (Ph(3)S(+)TfO(-)) acid generator has been investigated by electron paramagnetic resonance (EPR) spectroscopy and by use of the acid indicator coumarin 6 (C6). Gamma radiolysis was substituted for the EUV radiation with the assumption that the chemistry generated by ionization of the matrix does not depend on the ionization source. Poly(4-hydroxystyrene) (PHS) was first investigated as a well-studied standard, after which the water-wheel-like cyclic oligomer derivative containing pendant adamantyl ester groups, noria-AD(50), was investigated. EPR measurements confirm that the dominant free radical product is a phenoxyl derivative (PHS-O(•) or noria-O(•)) that exhibits quite slow stretched exponential recombination kinetics at room temperature. Also observed at 77 K was the presence of a significant hydrogen atom product of radiolysis. The G value or yield of acid production in thin lithography films was measured with the C6 indicator on a fused silica substrate. It was found that a significant amount of acid is generated via energy transfer from the irradiated fused-silica substrate to the Ph(3)S(+)TfO(-) in the films. By varying the film thickness on the substrates, the substrate effect on the acid yield was quantitatively determined. After subtraction of the contribution from the substrates, the acid yield G value in the PHS film with 10 wt % Ph(3)S(+)TfO(-) and 5 wt % C6 was determined to be 2.5 ± 0.3 protons per 100 eV of radiation. The acid yield of noria-AD(50) films was found to be 3.2 ± 0.3 protons per 100 eV.