Understanding chiral-induced
spin selectivity (CISS), resulting
from charge transport through helical systems, has recently inspired
many experimental and theoretical efforts but is still the object
of intense debate. In order to assess the nature of CISS, we propose
to focus on electron-transfer processes occurring at the single-molecule
level. We design simple magnetic resonance experiments, exploiting
a qubit as a highly sensitive and coherent magnetic sensor, to provide
clear signatures of the acceptor polarization. Moreover, we show that
information could even be obtained from time-resolved electron paramagnetic
resonance experiments on a randomly oriented solution of molecules.
The proposed experiments will unveil the role of chiral linkers in
electron transfer and could also be exploited for quantum computing
applications.
We pinpoint the key ingredients ruling decoherence in
multispin
clusters, and we engineer the system Hamiltonian to design optimal
molecules embedding quantum error correction. These are antiferromagnetically
coupled systems with competing exchange interactions, characterized
by many low-energy states in which decoherence is dramatically suppressed
and does not increase with the system size. This feature allows us
to derive optimized code words, enhancing the power of the quantum
error correction code by orders of magnitude. We demonstrate this
by a complete simulation of the system dynamics, including the effect
of decoherence driven by a nuclear spin bath and the full sequence
of pulses to implement error correction and logical gates between
protected states.
Magnetic molecules are prototypical systems to investigate peculiar quantum mechanical phenomena. As such, simulating their static and dynamical behavior is intrinsically difficult for a classical computer, due to the exponential increase of required resources with the system size. Quantum computers solve this issue by providing an inherently quantum platform, suited to describe these magnetic systems. Here, we show that both the ground state properties and the spin dynamics of magnetic molecules can be simulated on prototype quantum computers, based on superconducting qubits. In particular, we study small-size anti-ferromagnetic spin chains and rings, which are ideal test-beds for these pioneering devices. We use the variational quantum eigensolver algorithm to determine the ground state wave-function with targeted ansatzes fulfilling the spin symmetries of the investigated models. The coherent spin dynamics are simulated by computing dynamical correlation functions, an essential ingredient to extract many experimentally accessible properties, such as the inelastic neutron cross-section.
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