Triplet-radical spin entanglement: potential of molecular materials for high-temperature quantum information processing

Abstract

Recently, spin-bearing molecules have been experimentally demonstrated to have great potential as building blocks for quantum information processing due to their substantial advantages including tunability, portability, and scalability. Here, we propose a theoretical model based on the theory of open quantum systems for spin dynamics in a molecule containing one radical, which can interact with the triplet state arising from another part of the molecule owing to optical excitation and intersystem crossing. With the initial state being a classical mixture of a radical $$\frac{1}{2}$$ 1 2 -spin, the exchange interaction between the radical and the triplet produces a spin coherent state, which could potentially be used for a qubit-qutrit quantum entangling gate. Our calculations for the time-resolved electron paramagnetic resonance spectra showed good qualitative agreement with the related experimental results for radical-bearing molecules at high temperature (~77 K, the boiling point of liquid nitrogen). This work therefore lays a solid theoretical cornerstone for optically driven quantum gate operations in radical-bearing molecular materials, aiming toward high-temperature quantum information processing.

A quantum circuit architecture based on the integration of nanophotonic devices and two-dimensional molecular network

“…On the other hand, in molecular materials, inter-system crossing is a well-know phenomenon, in which a singlet excited state can transform to a triplet state via spin-orbit interaction. 22 Many useful molecules such as thermally assisted delayed fluorenscence molecules explore the small gap between the excited singlet and triplet for the application of more efficient organic light emitting diodes. 23 Recently optical excitation and exploration of inter-system crossing have been proposed for high-temperature quantum gate operations.…”

“…Similar to the idea in Ref., 20 the authors proposed a mechanism exploring triplet mediating the interaction between organic radicals. 22,24,25 This is promising particularly due to the huge potential of molecular engineering, in addition to the advantages mentioned in the section for qubit technology. We therefore speculate that the network formed by spin-bearing molecules and 'control' molecules is particularly promising for scaling up quantum computing architecture and high-temperature quantum gate operations.…”

“…One recent proposal is to integrate such type of nanophotonic devices with two-dimensional molecular network, taking advantages from inter-system crossing-mediated exchange interactions. 22,25 Figure.2 shows the essential mechanism to realize such idea based on single molecules, whereas we show the two-dimensional molecular design with nanophotonics in Figure .3. The photonic devices that can be programmed are also important to realise specific quantum gate operations in hybrid photonics.…”

Designing thermally activated delayed fluorescence emitters with through-space charge transfer: a theoretical study

“…[1][2][3][4][5][6][7][8][9] The photophysical performance of organic molecules depends highly on their excited state properties. [10][11][12] By designing TADF molecules with twisted donor (D) and acceptor (A) configurations, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) can be effectively separated, leading to a reduction in the singlet-triplet energy gap (DE ST ) and an increase in the reverse intersystem crossing rate (K RISC ). [13][14][15][16] For instance, a group of D-A-D type TADF emitters employing 10-(pyridin-2-yl)-acridin-9(10H)-one and substituted carbazoles can achieve a high K RISC of 10 5 s À1 .…”

Molecular Control of Triplet-Pair Spin Polarization and Its Optoelectronic Magnetic Resonance Probes

“…There are at least four photochemical pathways toward the vision articulated above: photoinitiated radical ion pairs, ,,, ligand-field state engineering, photoexcited triplets derived from intersystem crossing, , and singlet fission (SF). − ,,− Our work has focused on the last of these pathways due to its unique and potentially powerful properties, including ultrafast (sub-nanosecond) state preparation, the possibility of controlling spin evolution through both the inter- and intramolecular structure, and the demonstrated optical and electrical pathways toward ultrasensitive spin readout.…”