Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 29: Quantum information systems

MA 29.3: Talk

Wednesday, April 3, 2019, 10:00–10:15, H53

Investigation of intrinsic decoherence in different closed quantum spin systems — •Patrick Vorndamme and Jürgen Schnack — Universität Bielefeld, PF 100131, D-33501 Bielefeld

Not only in spintronic devices, but also as constituents of quantum simulators or quantum computers, magnetic molecules have many potential applications. At low temperatures the magnetic levels of molecular nanomagnets enable the use as qubits. For such an application the investigation and understanding of decoherence caused by external and internal effects is very important. For now, we work with a pure spin Hamiltonian which contains both, the qubits of interest and bath spins. Both together form our closed system of which we perform time evolutions numerically. We interpret decoherence as entanglement of the qubits with the bath spins, resulting in a mixed reduced density matrix of the qubits. With our spin Hamiltonian we can treat isotropic exchange couplings and anisotropic effects, such as dipolar interactions and easy magnetization axes caused by spin orbit coupling. Our goal is to find qubit states that are insensitive to decoherence. For this purpose we examine clock transitions as well as the stability of ground states with nonzero toroidal moment and zero magnetic moment in different spin constructs, such as spin-frustrated triangular nanomagnets (like Cu₃) with strong antiferromagnetic coupling and weak spin orbit coupling. In fact, there are several ways to realize toroidal moments with both a strong spin orbit coupling and a weak one. In a quantum computer such moments could be conveniently manipulated with a spin-polarized current.