Quantum Teleportation of an Electron Spin State Mediated by a Photodriven Electron Transfer Reaction

Rugg, Brandon Kenneth

doi:https://doi.org/10.21985/n2-15wf-tz96

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Quantum Teleportation of an Electron Spin State Mediated by a Photodriven Electron Transfer Reaction

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This thesis describes a novel demonstration of quantum teleportation, a protocol within the broader field of quantum information science, carried out by an electron transfer reaction within a molecular system. As described in Chapter 1, quantum information science has potential impacts in computation, communication, and cryptography. This field relies on the manipulation of qubits, or “quantum bits”, which provide advantages over their classical counterparts as they can exhibit quantum phenomena such as coherent superposition states and entanglement. Molecular electron spins have potential use in quantum information processing schemes due to their long coherence times and the synthetic tunability of their environment. Additionally, photo-driven electron transfer in organic systems is known to create an entangled radical qubit pair. Utilizing this entanglement, we have demonstrated the quantum teleportation of a spin state prepared on a stable radical (R•) utilizing the radical pair generated by photoexcitation of a covalent donor-acceptor-radical triad (D-A-R•). Prior to demonstrating teleportation, transient absorption spectroscopy of a D-A-R• triad was used to analyze the kinetics of electron transfer to R•. This process is described in Chapter 2. Photoexcitation of the molecule resulted in D•+-A•--R•, which rapidly formed the desired species D•+-A-R-. The spin states of A•- and R• were also observed to affect the yield of this electron transfer, in a manner that was consistent with the electron transfer event acting as the Bell state measurement step in the quantum teleportation scheme. In the observed case, it would be expected that D•+ in D•+-A-R- would inherit the exact spin state of R• at the time of its reduction. The final chapter describes the confirmation of this result by electron paramagnetic resonance spectroscopy, in which the quantum teleportation protocol is tested using an unbiased sample of six different quantum states. Each of these states was prepared on R•, electron transfer to form D•+-A-R- was initiated by photoexcitation, and then the spin state of D•+ was characterized using selective microwave pulse sequences. Comparison of the prepared states to the corresponding teleported states indicated an average fidelity of 89%, exceeding the limit of 60% that can be achieved without quantum teleportation. This experiment serves as the first instance of quantum teleportation utilizing a chemical reaction.

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