Engineering the coupling between molecular spin qubits by coordination chemistry

Abstract

The ability to assemble weakly interacting subsystems is a prerequisite for implementing quantum information processing and generating controlled entanglement. In recent years, molecular nanomagnets have been proposed as suitable candidates for qubit encoding and manipulation. In particular, antiferromagnetic Cr7Ni rings behave as effective spin-1/2 systems at low temperature and show long decoherence times. Here, we show that these rings can be chemically linked to each other and that the coupling between their spins can be tuned by choosing the linker. We also present calculations that demonstrate how realistic microwave pulse sequences could be used to generate maximally entangled states in such molecules.

Spin in density‐functional theory

“…(4). A consequence of these four-dimensional operators is that the Dirac Hamiltonianĥ D is a 4Â4 matrix operator with a four-component eigenvector w(r,t), the so-called 4-spinor.…”

“…In fact, the electronic spin gives rise to a magnetic moment that makes such molecular systems functional for various purposes. For instance, organic radicals can be used as spin probes in biomolecules [1] and are of interest as building blocks for molecular spintronics devices, [2,3] single-molecule magnets have the potential to act as molecular qubits for quantum information processing, [4] and open-shell transition metal compounds serve as catalytic centers in (bio-)inorganic chemistry, [5][6][7][8] where a change in the spin state can be an essential step in the catalytic cycle. [9] Consequently, a first-principles theory that is useful for descriptive and analytic purposes and that has the potential to be a predictive tool in theoretical studies on such chemical systems must consider the spin properties of the electronic structure.…”

Exploiting Structured Environments for Efficient Energy Transfer: The Phonon Antenna Mechanism

“…These effects have been neglected here for simplicity, but exploring these effects in the context of the phonon antenna mechanism could lead to an even more sophisticated principle, involving transient, broadband sampling of the spectral function and evolving exciton spectra and localisation lengths which could, potentially, activate or deactivate relaxation pathways dynamically. Finally, the concept of using coherent interactions to alter the sampling of a (fixed) environmental spectral function could be readily achieved in a variety of atomic and condensed matter systems [33,37], and could also be used as a sensitive probe for measuring spectral functions by measuring transport rates as functions of a controllable coupling parameter.…”

Spin dynamics of molecular nanomagnets unravelled at atomic scale by four-dimensional inelastic neutron scattering

“…Shells of organic ligands provide magnetic separation between adjacent magnetic cores, which behave as identical and independent zero-dimensional units [1]. The magnetic dynamics are characterized by strong quantum fluctuations and this makes MNMs of great interest in quantum magnetism as model systems to investigate a range of phenomena, such as quantum-tunnelling of the magnetization [2][3][4], Néel-vector tunnelling (NVT) [5,6], quantum information processing [7][8][9], quantum entanglement [10][11][12][13] or decoherence [14][15][16]. Besides their fundamental interest, MNMs are also the focus of intense research for the potential technological applications as classical or quantum bits [1,[7][8][9]17] and as magnetocaloric refrigerants [18].…”